Dietary protein and blood pressure: a systematic review

Plant protein and animal proteins: do they differentially affect cardiovascular disease risk?

Proteins from plant-based compared with animal-based food sources may have different effects on cardiovascular disease (CVD) risk factors. Numerous epidemiologic and intervention studies have evaluated their respective health benefits; however, it is difficult to isolate the role of plant or animal protein on CVD risk. This review evaluates the current evidence from observational and intervention studies, focusing on the specific protein-providing foods and populations studied. Dietary protein is derived from many food sources, and each provides a different composite of nonprotein compounds that can also affect CVD risk factors. Increasing the consumption of protein-rich foods also typically results in lower intakes of other nutrients, which may simultaneously influence outcomes. Given these complexities, blanket statements about plant or animal protein may be too general, and greater consideration of the specific protein food sources and the background diet is required. The potential mechanisms responsible for any specific effects of plant and animal protein are similarly multifaceted and include the amino acid content of particular foods, contributions from other nonprotein compounds provided concomitantly by the whole food, and interactions with the gut microbiome. Evidence to date is inconclusive, and additional studies are needed to further advance our understanding of the complexity of plant protein vs. animal protein comparisons. Nonetheless, current evidence supports the idea that CVD risk can be reduced by a dietary pattern that provides more plant sources of protein compared with the typical American diet and also includes animal-based protein foods that are unprocessed and low in saturated fat.

Protein intake in early childhood and cardiometabolic health at school age: the Generation R Study

Purpose

High protein intake in infancy has been linked to obesity. We aimed to examine the associations of protein intake in early childhood with cardiovascular and metabolic outcomes at school age.

Methods

This study was performed in 2965 children participating in a population-based prospective cohort study. Protein intake at 1 year was assessed with a food frequency questionnaire and was adjusted for energy intake. At the children’s age of 6 years, we measured their body fat percentage (BF%), blood pressure (BP), and insulin, HDL cholesterol, and triglyceride serum levels. These measures were incorporated into a cardiometabolic risk factor score, using age- and sex-specific SD scores.

Results

In covariate-adjusted models, higher protein intake was associated with a higher BF%, lower diastolic BP, and lower triglyceride levels. We observed a significant interaction of protein intake with child sex on metabolic outcomes. Stratified analyses showed that protein intake was positively associated with BF% [0.07 SD (95 % CI 0.02; 0.13) per 10 g/day] and insulin levels in girls, but not in boys. In boys, but not in girls, higher protein intake was associated with lower triglyceride levels [−0.12 SD (95 % CI −0.20; −0.04) per 10 g/day] and a lower cardiometabolic risk factor score. Protein intake was not consistently associated with systolic BP or HDL cholesterol levels.

Conclusion

Protein intake in early childhood was associated with a higher BF% and higher insulin levels at 6 years in girls and with lower triglyceride levels in boys. Further studies are needed to explore these sex differences and to investigate whether the observed changes persist into adulthood.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-015-1026-7) contains supplementary material, which is available to authorized users.

Protective Effects of the Mediterranean Diet on Type 2 Diabetes and Metabolic Syndrome

Several studies provide evidence supporting a beneficial effect from the traditional Mediterranean diet (MedDiet) on the risk of type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS). This review summarizes the current scientific evidence from epidemiologic studies and clinical trials on the relation between the MedDiet and T2DM and MetS and the possible mechanisms underlying the reported associations. A recent meta-analysis of prospective cohort studies showed that greater adherence to the MedDiet was associated with a significant reduction in the risk of diabetes. The MedDiet has also been found to be beneficial in the prevention of gestational diabetes. Four large prospective studies have observed inverse associations between the MedDiet and MetS or its components. Few randomized controlled trials (RCTs) have evaluated the effect of the MedDiet on T2DM and MetS. Results from the landmark PREvención con DIeta MEDiterránea (PREDIMED) nutrition intervention trial showed that participants assigned to the MedDiet had a significant 30% reduction in the risk of T2DM and that it also promoted the reversion of MetS and its components, hyperglycemia and central obesity. In addition, 5 RCTs showed the beneficial effects of the MedDiet compared with other dietary patterns on glycemic control in patients with T2DM. A recent meta-analysis of RCTs revealed that, compared with a variety of control diets, the MedDiet was associated with beneficial effects on all MetS components. Bioactive components of the MedDiet synergize to affect various metabolic pathways, leading to a reduced cardiometabolic disease risk. The abundance of healthy, nutrient-dense foods that make up the plant-based MedDiet predicts its bioactivity and potential to beneficially influence metabolic pathways that lead to MetS and T2DM, as well as other chronic conditions. Abundant epidemiologic and clinical trial evidence supports the role of the MedDiet on the prevention and management of T2DM and MetS.

Nutraceuticals and Blood Pressure Control: Results from Clinical Trials and Meta-Analyses

Beyond the well-known effects on blood pressure (BP) of the dietary approaches to stop hypertension (DASH) and the Mediterranean diets, a large number of studies has investigated the possible BP lowering effect of different dietary supplements and nutraceuticals, the most part of them being antioxidant agents with a high tolerability and safety profile. In particular relatively large body of evidence support the use of potassium, L-arginine, vitamin C, cocoa flavonoids, beetroot juice, coenzyme Q10, controlled-release melatonin, and aged garlic extract. However there is a need for data about the long-term safety of a large part of the above discussed products. Moreover further clinical research is advisable to identify between the available active nutraceuticals those with the best cost-effectiveness and risk-benefit ratio for a large use in general population with low-added cardiovascular risk related to uncomplicated hypertension.

Increased protein intake is associated with uncontrolled blood pressure by 24-hour ambulatory blood pressure monitoring in patients with type 2 diabetes

OBJECTIVE

To analyze possible associations of dietary components, especially protein intake, with blood pressure (BP) during ambulatory BP monitoring (ABPM) in patients with type 2 diabetes.

METHODS

In this cross-sectional study, BP of outpatients with type 2 diabetes was evaluated by 24-hour ABPM (Spacelabs 90207) and usual diet by 3-day weighed diet records. Patients were divided into 2 groups according to their daytime ABPM: uncontrolled BP (systolic BP ≥ 135 mmHg or diastolic BP ≥ 85 mmHg) and controlled BP (systolic BP < 135 mmHg and diastolic BP < 85 mmHg). Logistic regression models unadjusted and adjusted for possible confounders (covariates) were used to analyze the association of protein and uncontrolled BP.

RESULTS

A total of 121 patients with type 2 diabetes aged 62.3 years, 54.5% of whom were women, were studied. The uncontrolled BP group had higher glycated hemoglobin (HbA1C) values (8.4 ± 2.0 vs 7.6 ± 1.3%; p = 0.04) and consumed more protein (20.0 ± 3.8 vs 18.2 ± 3.6% of energy; p = 0.01) and meat, (2.6 [1.45, 2.95] vs 2.0 [1.49, 2.90] g/kg weight; p = 0.04) than the controlled BP group. In a multivariate analysis, protein intake (% of energy) increased the chance for uncontrolled BP (odds ratio [OR] = 1.16; 95% confidence interval [CI], 1.02, 1.30; p = 0.02), adjusted for body mass index (BMI), HbA1C, low-density lipoprotein (LDL) cholesterol, number of antihypertensive medications, and ethnicity. Meat consumption higher than 3.08 g/kg weight/day more than doubled the chance for uncontrolled BP (OR = 2.53; 95% CI, 1.01, 7.60; p = 0.03).

CONCLUSION

High protein intake and meat consumption were associated with high daytime ABPM values in patients with type 2 diabetes. Reducing meat intake might represent an additional dietary intervention in hypertensive patients with type 2 diabetes.

Diets higher in protein predict lower high blood pressure risk in Framingham Offspring Study adults

BACKGROUND

Short-term clinical trials suggest that dietary protein lowers blood pressure (BP); however, long-term effects of total, animal, and plant proteins are less clear. Our goal was to evaluate effects of these dietary proteins on mean systolic BP (SBP) and diastolic BP (DBP) and incident high BP (HBP) risk among middle-aged adults in the Framingham Offspring Study.

METHODS

Men and women (aged 30-54 years) without prevalent HBP, cardiovascular disease, or diabetes with 3-day dietary records from exams 3 or 5 (n = 1,361) were included and followed for a mean of 11.3 years for development of HBP. Protein intakes adjusted for body size were derived using the residual method. Analysis of covariance and Cox proportional hazard's models were used to adjust for age, sex, education, height, activity, smoking, fat calories, diet quality, and body mass index.

RESULTS

Higher protein intakes were associated with lower mean SBP and DBP. Both animal and plant proteins lowered BP and led to statistically significant reductions in HBP risk (hazard ratios of 0.68 and 0.51, respectively). Participants in the highest tertile of total protein intake had 40% less risk (95% confidence interval [CI], 0.45-0.78) of developing HBP. Beneficial effects of protein were apparent for men and women and for normal-weight and overweight individuals. Higher protein diets also characterized by higher fiber intakes led to a 59% reduction (95% CI, 0.37-0.66) in HBP risk.

CONCLUSIONS

Adults consuming more dietary protein from either plant or animal sources had lower long-term risks of HBP.

Estimated dietary acid load is not associated with blood pressure or hypertension incidence in men who are approximately 70 years old

BACKGROUND

Dietary acid load affects acid-base homeostasis, which may be associated with blood pressure (BP). Previous research on dietary acid load and BP in the community has provided conflicting results, which may be confounded by underlying kidney function with inability to eliminate acid excess.

OBJECTIVE

The objective of this study was to determine whether dietary acid load is associated with blood pressure or the incidence of hypertension in older men taking into account each individual's kidney function.

METHODS

We included 673 men aged 70-71 y and not receiving antihypertensive medication from the Uppsala Longitudinal Study of Adult Men. Of those, 378 men were re-examined after 7 y. Dietary acid load was estimated at baseline by potential renal acid load (PRAL) and net endogenous acid production (NEAP), based on nutrient intake assessed by 7-d food records at baseline. Ambulatory blood pressure monitoring (ABPM) was performed at both visits. Cystatin C-estimated kidney function allowed identification of underlying chronic kidney disease.

RESULTS

Median estimated PRAL and NEAP were 3.3 and 40.7 mEq/d, respectively. In cross-section, PRAL was in general not associated with ABPM measurements (all P > 0.05, except for the 24-h diastolic BP). During follow-up, PRAL did not predict ABPM changes (all P > 0.05). When individuals with baseline hypertension (ABPM ≥ 130/80 mm Hg) or nondippers (with nighttime-to-daytime systolic BP ratio > 0.9) were excluded, PRAL was not a predictor of incident cases (P > 0.30). Kidney function did not modify these null relations. Similar findings were obtained with the use of NEAP as the exposure.

CONCLUSION

Our analyses linking estimated dietary acid load with BP outcome measurements both cross-sectionally and after 7 y in community-based older Swedish men of similar age did not reveal an association between dietary acid load and BP.

Reconstruction and analysis of correlation networks based on GC-MS metabolomics data for young hypertensive men

The awareness, treatment, and control rates of hypertension for young adults are much lower than average. It is urgently needed to explore the variances of metabolic profiles for early diagnosis and treatment of hypertension. In current study, we applied a GC-MS based metabolomics platform coupled with a network approach to analyze plasma samples from young hypertensive men and age-matched healthy controls. Our findings confirmed distinct metabolic footprints of young hypertensive men. The significantly altered metabolites between two groups were enriched for the biological module of amino acids biosynthesis. The correlations of GC-MS metabolomics data were then visualized as networks based on Pearson correlation coefficient (threshold=0.6). The plasma metabolites identified by GC-MS and the significantly altered metabolites (P<0.05) between patients and controls were respectively included as nodes of a network. Statistical and topological characteristics of the networks were studied in detail. A few amino acids, glycine, lysine, and cystine, were screened as hub metabolites with higher values of degree (k), and also obtained highest scores of three centrality indices. The short average path lengths and high clustering coefficients of the networks revealed a small-world property, indicating that variances of these amino acids have a major impact on the metabolic change in young hypertensive men. These results suggested that disorders of amino acid metabolism might play an important role in predisposing young men to developing hypertension. The combination of metabolomics and network methods would provide another perspective on expounding the molecular mechanism underlying complex diseases.

Nutraceuticals for blood pressure control

Significant effects on blood pressure (BP) have been reported from large nutritional interventions, particularly the Dietary Approaches to Stop Hypertension (DASH) and the Mediterranean diet. In more recent years, numerous studies have investigated the possible BP-lowering effect of different nutraceuticals; these range from specific foods to minerals, lipids, whole proteins, peptides, amino acids, probiotics, and vitamins. While a very large body of evidence supports the use of potassium, L-arginine, vitamins C and D, cocoa flavonoids, beetroot juice, some probiotics, coenzyme Q10, controlled-release melatonin, aged garlic extract, and coffee, the use of other nutraceuticals, such as green tea, flaxseed, and resveratrol, has not as yet been supported by adequate evidence. In some cases, e.g. proteins/peptides, the responsible component needs also to be fully uncovered. Finally, while for most of the products only short-term studies are available, with no specific end-points, an ongoing very large prospective study on chocolate flavanols will answer the question whether this may reduce cardiovascular risk. Thus, in addition to data on long-term safety, further clinical research is advisable in order to identify, among active nutraceuticals, those with the best cost-effectiveness and risk-benefit ratio for a wide use in the general population with a raised cardiovascular risk consequent to uncomplicated hypertension.

Unraveling the mechanisms of action of lactoferrin-derived antihypertensive peptides: ACE inhibition and beyond

The characterization of lactoferrin-derived antihypertensive peptides shows that they might act on several molecular targets.

Associations of plant and animal protein intake with 5-year changes in blood pressure: the Zutphen Elderly Study

BACKGROUND AND AIM

The aim of the present study was to investigate the association of plant and animal protein intake with 5-year changes in blood pressure (BP) level.

METHODS AND RESULTS

Analyses were based on 702 observations of 272 men participating in the Zutphen Elderly Study. Men did not use antihypertensive medication and were initially free of cardiovascular disease, diabetes mellitus and cancer. Physical and dietary examinations were performed in 1985, 1990, 1995, and 2000. Diet was assessed using the cross-check dietary history method. Men were categorised into tertiles according to their plant and animal protein intake. BP was measured twice at each examination. The associations of plant and animal protein intake with 5-year changes in BP level were investigated by a random intercept model with first-order autoregressive (AR [1]) serial correlation and a nugget effect. Adjustments were made for age, examination year, BMI, socioeconomic status, smoking, physical activity, prescribed diet, alcohol consumption and intake of energy and nutrients. In 1985, men were 70.1 ± 4.6 years old and had a mean BP of 147/84 mmHg. Mean protein intake was 15 en%, of which one-third consisted of plant protein. The higher-intake tertiles of plant protein intake were associated with a mean 5-year change of -2.9 mmHg (95% CI: -5.6, -0.2) systolic and -1.7 mmHg (95% CI: -3.2, -0.2) diastolic, compared with the lowest-intake tertile. No associations were observed for animal protein intake.

CONCLUSION

Intake of plant protein, but not animal protein, was inversely associated with 5-year changes in BP level in elderly men.

Differential effects of proteins and carbohydrates on postprandial blood pressure-related responses

Diet composition may affect blood pressure (BP), but the mechanisms are unclear. The aim of the present study was to compare postprandial BP-related responses to the ingestion of pea protein, milk protein and egg-white protein. In addition, postprandial BP-related responses to the ingestion of maltodextrin were compared with those to the ingestion of sucrose and a protein mix. We hypothesised that lower postprandial total peripheral resistance (TPR) and BP levels would be accompanied by higher plasma concentrations of nitric oxide, insulin, glucagon-like peptide 1 (GLP-1) and glucagon. On separate occasions, six meals were tested in a randomised order in forty-eight overweight or obese adults with untreated elevated BP. Postprandial responses of TPR, BP and plasma concentrations of insulin, glucagon, GLP-1 and nitrite, nitroso compounds (RXNO) and S-nitrosothiols (NO(x)) were measured for 4 h. No differences were observed in TPR responses. Postprandial BP levels were higher after the ingestion of the egg-white-protein meal than after that of meals containing the other two proteins (P≤ 0·01). The ingestion of the pea-protein meal induced the highest NO(x) response (P≤ 0·006). Insulin and glucagon concentrations were lowest after the ingestion of the egg-white-protein meal (P≤ 0·009). Postprandial BP levels were lower after the ingestion of the maltodextrin meal than after that of the protein mix and sucrose meals (P≤ 0·004), while postprandial insulin concentrations were higher after the ingestion of the maltodextrin meal than after that of the sucrose and protein mix meals after 1-2 h (P≤ 0·0001). Postprandial NO(x), GLP-1 and glucagon concentrations were lower after the ingestion of the maltodextrin meal than after that of the protein mix meal (P≤ 0·008). In conclusion, different protein and carbohydrate sources induce different postprandial BP-related responses, which may be important for BP management. Lower postprandial BP levels are not necessarily accompanied by higher NO(x), insulin, glucagon or GLP-1 responses.

Dietary approaches to prevent hypertension

Elevated blood pressure arises from a combination of environmental and genetic factors and the interactions of these factors. A substantial body of evidence from animal studies, epidemiologic studies, meta-analyses, and randomized controlled trials has demonstrated that certain dietary patterns and individual dietary elements play a prominent role in the development of hypertension. Changes in diet can lower blood pressure, prevent the development of hypertension, and reduce the risk of hypertension-related complications. Dietary strategies for the prevention of hypertension include reducing sodium intake, limiting alcohol consumption, increasing potassium intake, and adopting an overall dietary pattern such as the DASH (Dietary Approaches to Stop Hypertension) diet or a Mediterranean diet. In order to reduce the burden of blood pressure-related complications, efforts that focus on environmental and individual behavioral changes that encourage and promote healthier food choices are warranted.

The relationship of dietary sodium, potassium, fruits, and vegetables intake with blood pressure among Korean adults aged 40 and older

BACKGROUND/OBJECTIVES

The inverse relationships of combined fruits and vegetables intake with blood pressure have been reported. However, whether there are such relationships with salty vegetables has rarely been investigated in epidemiologic studies. We evaluated the relation of combined and separate intake of fruits, vegetable intakes, and salty vegetables, as well as sodium and potassium, with blood pressure among the middle-aged and elderly populations.

SUBJECTS/METHODS

The present cross-sectional analysis of a prospective cohort baseline survey was performed with 6,283 subjects (2,443 men and 3,840 women) and free of hypertension, diabetes, cardiovascular diseases, and cancer. Dietary data were collected by trained interviewers using food frequency questionnaire.

RESULTS

The significantly inverse linear trend of diastolic blood pressure (DBP) was found in fruits and non-pickled vegetables (81.2 mmHg in the lowest quintile vs 79.0 mmHg in the highest quintile, P for trend = 0.0040) and fruits only (80.9 mmHg in the lowest quintile vs 79.4 mmHg in the highest quintile, P for trend = 0.0430) among men. In contrast, sodium and sodium to potassium ratio were positively related with blood pressure among men (DBP, 78.8 mmHg in the lowest quintile vs 80.6 mmHg in the highest quintile, P for trend = 0.0079 for sodium; DBP, 79.0 mmHg in the lowest quintile vs 80.7 mmHg in the highest quintile, P for trend = 0.0199 and SBP, 123.8 mmHg in the lowest quintile vs 125.9 mmHg in the highest quintile for sodium/potassium). Kimchies consumption was positively related to DBP for men (78.2 mmHg in the lowest quintile vs 80.9 mmHg in the highest quintile for DBP, P for trend = 0.0003). Among women, these relations were not found.

CONCLUSION

Fruits and/or non-pickled vegetables may be inversely, but sodium, sodium to potassium, and Kimchies may be positively related to blood pressure among men.

Effect of a high-protein diet on maintenance of blood pressure levels achieved after initial weight loss: the DiOGenes randomized study

Randomized trials have shown significant blood pressure (BP) reductions after increased protein compared with carbohydrate intake, but the effect on BP maintenance after initial weight loss is unclear. We examined the effect of a high-protein diet on the maintenance of reduced BP after weight loss in 420 overweight adults from the Diet, Obesity and Genes study. After an 8-week weight-loss period (>8% BW), subjects (42±6 years) were randomized to either a high-protein diet (23-28 en% protein) or a lower-protein control diet (10-15 en% protein) for 26 weeks. BMI after weight loss was 30.3±4.3 kg m(-2), BP was 118/73 mm Hg and 28 subjects (6.5%) used antihypertensive agents. Systolic BP during 26 weeks of weight maintenance dietary intervention increased in both treatment groups, but it was 2.2 mm Hg less (95% CI: -4.6 to 0.2 mm Hg, P=0.08) in the high-protein group than in the lower-protein control group. In 191 (pre)hypertensive subjects (baseline systolic BP⩾120 mm Hg), a larger difference was observed (-4.2 mm Hg (-7.7, -0.7), P=0.02). The effect was attenuated after adjustment for initial BP (-3.4 mm Hg (-6.9, -0.03), P=0.048), and after additional adjustment for weight change (-2.7 mm Hg (-6.1, 0.4), P=0.11). Adjustment for 24-h urinary excretion of sodium and potassium did not change the results. Diastolic BP yielded similar results. These findings suggest that a BP reduction after weight loss is better maintained when the intake of protein is increased at the expense of carbohydrates. This effect is partly mediated by body weight.

Dietary interventions and blood pressure in Latin America - systematic review and meta-analysis

BACKGROUND

High blood pressure is the major risk factor for cardiovascular disease. Low blood pressure control rates in Latin American populations emphasize the need for gathering evidence on effective therapies.

OBJECTIVE

To evaluate the effects of dietary interventions on blood pressure in Latin American populations.

METHODS

Systematic review. Electronic databases (MEDLINE/PubMed, Embase, Cochrane Library, CINAHL, Web of Science, Scopus, SciELO, LILACS and VHL) were searched and manual search for studies published up to April 2013 was performed. Parallel studies about dietary interventions in Latin American adult populations assessing arterial blood pressure (mm Hg) before and after intervention were included.

RESULTS

Of the 405 studies identified, 10 randomized controlled trials were included and divided into 3 subgroups according to the proposed dietary intervention. There was a non-significant reduction in systolic blood pressure in the subgroups of mineral replacement (-4.82; 95% CI: -11.36 to 1.73) and complex pattern diets (-3.17; 95% CI: -7.62 to 1.28). Regarding diastolic blood pressure, except for the hyperproteic diet subgroup, all subgroups showed a significant reduction in blood pressure: -4.66 mmHg (95% CI: -9.21 to -0.12) and -4.55 mmHg (95% CI: -7.04 to -2.06) for mineral replacement and complex pattern diets, respectively.

CONCLUSION

Available evidence on the effects of dietary changes on blood pressure in Latin American populations indicates a homogeneous effect of those interventions, although not significant for systolic blood pressure. Samples were small and the quality of the studies was generally low. Larger studies are required to build robust evidence.

The role of nutrition and nutraceutical supplements in the treatment of hypertension

Vascular biology, endothelial and vascular smooth muscle and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the selected use of single and component nutraceutical supplements, vitamins, antioxidants and minerals in the treatment of hypertension based on scientifically controlled studies which complement optimal nutrition, coupled with other lifestyle modifications.

Protein intake in relation to risk of hypertension and microalbuminuria in patients with type 1 diabetes: the EURODIAB Prospective Complications Study

BACKGROUND

A beneficial association between dietary protein intake (especially from plant sources) with incident hypertension, being strongly correlated to microalbuminuria, has been suggested in healthy populations. Evidence from diabetic populations, in which the prevalence of these diseases is high, is lacking. We examined the associations of total, animal and plant protein intake with incident hypertension (n = 1319) and microalbuminuria (n = 1045) in patients from 16 European countries with type 1 diabetes from the clinic-based EURODIAB Prospective Complications study.

METHODS

Odds ratios (OR) with 95% confidence intervals (CI) for incident hypertension after 7 years of follow-up were calculated in tertiles of protein intake (energy%) with adjustments for age, sex, diabetes duration, HbA1c, BMI, physical activity, smoking, alcohol, total energy, total fat and carbohydrate intake.

RESULTS

After adjustment for potential confounders, total, animal and plant protein intakes were not related to incident hypertension (298 cases). OR's (95% CI) across increasing tertiles of total protein were 1.00 (ref), 0.86 (0.60-1.25) and 0.91 (0.59-1.43). Furthermore, no relation was observed with incident microalbuminuria (135 cases), with ORs (95% CI) across increasing tertiles of total protein being 1.00 (ref), 0.88 (0.53-1.48) and 1.08 (0.57-2.04).

CONCLUSION

Results from our study did not provide evidence that a protein intake commonly consumed by European patients with type 1 diabetes is associated with incident hypertension or microalbuminuria. Prospective studies with more detailed information on dietary intake (including mineral intake) are needed to confirm these findings, and to investigate the impact on vascular and renal complications of a long-term very high protein intake in patients with type 1 diabetes.

Effect of dietary pulses on blood pressure: a systematic review and meta-analysis of controlled feeding trials

BACKGROUND

Current guidelines recommend diet and lifestyle modifications for primary prevention and treatment of hypertension, but do not encourage dietary pulses specifically for lowering blood pressure (BP). To quantify the effect of dietary pulse interventions on BP and provide evidence for their inclusion in dietary guidelines, a systematic review and meta-analysis of controlled feeding trials was conducted.

METHODS

MEDLINE, EMBASE, Cochrane Library, and CINAHL were each searched from inception through 5 May 2013. Human trials ≥3 weeks that reported data for systolic, diastolic, and/or mean arterial BPs were included. Two reviewers independently extracted data and assessed methodological quality and risk of bias of included studies. Effect estimates were pooled using random effects models, and reported as mean differences (MD) with 95% confidence intervals (CIs). Heterogeneity was assessed (χ² test) and quantified (I²).

RESULTS

Eight isocaloric trials (n = 554 participants with and without hypertension) were included in the analysis. Dietary pulses, exchanged isocalorically for other foods, significantly lowered systolic (MD = −2.25 mm Hg (95% CI, −4.22 to −0.28), P = 0.03) and mean arterial BP (MD = −0.75 mm Hg (95% CI, −1.44 to −0.06), P = 0.03), and diastolic BP non-significantly (MD = −0.71 mm Hg (95% CI, −1.74 to 0.31), P = 0.17). Heterogeneity was significant for all outcomes.

CONCLUSIONS

Dietary pulses significantly lowered BP in people with and without hypertension. Higher-quality large-scale trials are needed to support these findings.

CLINICAL TRIAL REGISTRATION

NCT01594567

The effects of soy bean flour enriched bread intake on anthropometric indices and blood pressure in type 2 diabetic women: a crossover randomized controlled clinical trial

Previous studies showed that soy bean has the potential to improve many aspects of diabetes state and provide metabolic benefits that aid in weight management. We aimed to determine the effects of soy bean flour enriched bread on anthropometric indices and blood pressure among type 2 diabetic patients. This randomized, crossover, clinical trial was performed in 30 type 2 diabetic women. There were two trial periods for 6 weeks and a wash-out period for 4 weeks. In the soy bread diet period, 120 g of soy bean flour enriched bread was consumed each day instead of the same amount of their usual bread or other cereal products. After a 4-week wash-out period, participants were crossed over for another 6 weeks. Mean (±SD) age of study participants was 45.7 ± 3.8 years. The results of our study showed no significant effects of soy bean flour enriched bread on anthropometric indices and blood pressure among diabetic patients. Despite the slight reduction in BMI, waist circumference, and percent of body fat, there were no significant differences in changes of these values between two groups. No significant changes in waist to hip ratio and blood pressure were seen.

Evidence of clinically relevant efficacy for dietary supplements and nutraceuticals

Beyond the well-known effects on blood pressure (BP) of the DASH and the Mediterranean diets, a large number of studies have investigated the possible a BP-lowering effect from different dietary supplements and nutraceuticals, mostly antioxidant agents with a high tolerability and safety profile. In particular, a relatively large body of evidence support the use of potassium, L-arginine, vitamin C, cocoa flavonoids, coenzyme Q10, controlled-release melatonin, and aged garlic extract. However there is a need for data about the long-term safety of a large part of these products. Moreover, further clinical research is advisable to identify between the available active nutraceuticals and those with the best cost-effectiveness and risk-benefit ratio for widespread use in a general population with low added cardiovascular risk related to uncomplicated hypertension.

Impact of weight loss and maintenance with ad libitum diets varying in protein and glycemic index content on metabolic syndrome

OBJECTIVES

We investigated the effects of weight loss and maintenance with diets that varied with regard to protein content and glycemic index (GI) on metabolic syndrome (MetSyn) status.

METHODS

Secondary analyses were performed within the Diet, Obesity and Genes (DiOGenes) study (2006-2008), a randomized controlled dietary intervention. Nine hundred and thirty-eight overweight and obese adults from eight European countries entered an 8-wk low-calorie-diet period. Seven hundred and seventy-three adults who lost at least 8% of their body weights were randomized to one of five ad libitum diets for 6 mo: 1) low-protein (LP)/low-GI (LGI); 2) LP/high-GI (HGI); 3) high-protein (HP)/LGI; 4) HP/HGI; and 5) control diet. MetSyn prevalence and a standardized MetSyn score were assessed at baseline, after the low-calorie diet, and after the intervention.

RESULTS

Weight loss among participants while on the low-calorie diet significantly reduced MetSyn prevalence (33.9% versus 15.9%; P < 0.001) and MetSyn score (-1.48 versus -4.45; P < 0.001). During weight maintenance, significant changes in MetSyn score were observed between the groups, with the highest increase detected in the LP/HGI group (P = 0.039, partial η(2) = 0.023). Protein, GI, and their interaction did not have isolated effects on study outcomes.

CONCLUSIONS

Neither protein nor GI affected MetSyn status in this sample of European overweight and obese adults. However, a diet with a combination of an increased protein-to-carbohydrate ratio with low-GI foods had beneficial effects on MetSyn factors.

Associations between dairy protein intake and body weight and risk markers of diabetes and CVD during weight maintenance

Dairy products have previously been reported to be associated with beneficial effects on body weight and metabolic risk markers. Moreover, primary data from the Diet, Obesity and Genes (DiOGenes) study indicate a weight-maintaining effect of a high-protein-low-glycaemic index diet. The objective of the present study was to examine putative associations between consumption of dairy proteins and changes in body weight and metabolic risk markers after weight loss in obese and overweight adults. Results were based on secondary analyses of data obtained from overweight and obese adults who completed the DiOGenes study. The study consisted of an 8-week weight-loss phase and a 6-month weight-maintenance (WM) phase, where the subjects were given five different diets varying in protein content and glycaemic index. In the present study, data obtained from all the subjects were pooled. Dairy protein intake was estimated from 3 d dietary records at two time points (week 4 and week 26) during the WM phase. Body weight and metabolic risk markers were determined at baseline (week -9 to -11) and before and at the end of the WM phase (week 0 and week 26). Overall, no significant associations were found between consumption of dairy proteins and changes in body weight and metabolic risk markers. However, dairy protein intake tended to be negatively associated with body weight gain (P=0·08; β=-0·17), but this was not persistent when controlled for total protein intake, which indicates that dairy protein adds no additional effect to the effect of total protein. Therefore, the present study does not report that dairy proteins are more favourable than other proteins for body weight regulation.

Effects of an isocaloric healthy Nordic diet on ambulatory blood pressure in metabolic syndrome: a randomized SYSDIET sub-study

BACKGROUND/OBJECTIVES

Dietary pattern is central in the prevention of hypertension and blood pressure (BP)-related diseases. A diet based on healthy Nordic foods may have a favourable impact on BP. The objective was to clarify whether a Nordic alternative for a healthy food pattern would have beneficial effects on ambulatory BP in subjects with metabolic syndrome (MetS).

SUBJECTS/METHODS

In total, 37 subjects were randomized to either a healthy Nordic diet or a control diet. A healthy Nordic diet embraced whole grains, rapeseed oil, berries, fruits, vegetables, fish, nuts and low-fat dairy products of Nordic origin. The mean nutrient intake in the Nordic countries formed the control diet, embracing wheat products, dairy fat-based spread and a lower intake of fruits, vegetables and fish. Diets were isoenergetic. Ambulatory BP was monitored and 24-h urine was collected before and after 12 weeks of intervention.

RESULTS

After 12 weeks, ambulatory diastolic BP (-4.4 mm Hg; P=0.001) and mean arterial pressure (-4.2 mm Hg; P=0.006) were lowered by the healthy Nordic diet compared with the control diet, whereas changes in ambulatory systolic BP did not differ significantly between diets (-3.5 mm Hg; P=0.122). Heart rate tended to be lower in those on the healthy Nordic diet (P=0.057). Urinary sodium and potassium excretions were unaffected by diets and consequently not associated with the healthy Nordic diet-induced lowering of BP.

CONCLUSIONS

Consumption of Nordic varieties of health-enhancing foods for 12 weeks decreased diastolic ambulatory BP and mean arterial pressure in subjects with features of MetS during weight-stable condition, suggesting beneficial effects of a healthy Nordic dietary pattern on ambulatory BP.

Nutrition and nutraceutical supplements for the treatment of hypertension: part II

Vascular biology, endothelial and vascular smooth muscle, and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease, and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control, and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation, and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the select use of single and component nutraceutical supplements, vitamins, antioxidants, and minerals in the treatment of hypertension based on scientifically controlled studies, which complement optimal nutrition, coupled with other lifestyle modifications.

Association between dietary protein intake and the risk of hypertension: a cross-sectional study from rural western China

Evidence for an association between dietary proteins and the risk of hypertension in rural Chinese adults, whose diets are protein-poor and unbalanced, is limited. The aim of this study was to investigate the effect of dietary proteins on hypertension among adults of rural western China. A cross-sectional survey was conducted in Hanzhong, China, and 2241 residents were included in the analysis. Logistic regression models were used to examine whether dietary proteins (total, plant and animal protein) were independently correlated with hypertension. The total protein intake was inadequate (51.7 g per day for male and 40.1 g per day for female), accounting for 56-71% of the Chinese recommended nutrient intakes or adequate intakes. Nearly 80% of protein intake derived from plants, especially grains, and the proportion derived from plants was higher in females than in males. The daily animal protein intake was 12.1 g for males and 8.3 g for females. For females, no significant association was found between hypertension and total protein or plant protein intake. However, animal protein intake was significantly and negatively associated with the risk of hypertension after controlling for demographic characteristics, lifestyle factors, body mass index and other dietary nutrients. In addition, the odds ratio for the upper quartile compared with the bottom quartile was 0.64 (95% confidence interval, CI: 0.43-0.95, P for trend <0.05). Furthermore, a significant decrease of 1.082 mm Hg (95%CI: 0.189-1.975) in systolic blood pressure and 0.668 mm Hg (95%CI: 0.105-1.232) in diastolic blood pressure was observed per s.d. increase of animal protein intake in females. For males, we did not observe a significant association between dietary proteins and hypertension or blood pressure. In conclusion, for the western rural Chinese population, especially women, whose dietary protein intake is low and largely derived from plants, the intake of animal protein may be related to a decreased risk of hypertension.

Most important outcomes research papers on hypertension

The following are highlights from the new series, Circulation: Cardiovascular Quality and Outcomes Topic Review. This series will summarize the most important manuscripts, as selected by the Editor, which have published in the Circulation portfolio. The objective of this new series is to provide our readership with a timely, comprehensive selection of important papers that are relevant to the quality and outcomes, as well as general cardiology audience. The studies included in this article represent the most significant research related to hypertension.

Identification of biomarkers for intake of protein from meat, dairy products and grains: a controlled dietary intervention study

In the present controlled, randomised, multiple cross-over dietary intervention study, we aimed to identify potential biomarkers for dietary protein from dairy products, meat and grain, which could be useful to estimate intake of these protein types in epidemiological studies. After 9 d run-in, thirty men and seventeen women (22 (sd4) years) received three high-protein diets (aimed at approximately 18 % of energy (en%)) in random order for 1 week each, with approximately 14 en% originating from either meat, dairy products or grain. We used a two-step approach to identify biomarkers in urine and plasma. With principal component discriminant analysis, we identified amino acids (AA) from the plasma or urinary AA profile that were distinctive between diets. Subsequently, after pooling total study data, we applied mixed models to estimate the predictive value of those AA for intake of protein types. A very good prediction could be made for the intake of meat protein by a regression model that included urinary carnosine, 1-methylhistidine and 3-methylhistidine (98 % of variation in intake explained). Furthermore, for dietary grain protein, a model that included seven AA (plasma lysine, valine, threonine, α-aminobutyric acid, proline, ornithine and arginine) made a good prediction (75 % of variation explained). We could not identify biomarkers for dairy protein intake. In conclusion, specific combinations of urinary and plasma AA may be potentially useful biomarkers for meat and grain protein intake, respectively. These findings need to be cross-validated in other dietary intervention studies.

The role of dietary protein in blood pressure regulation

PURPOSE OF REVIEW

Despite a considerable amount of research, the blood pressure (BP) lowering effect of dietary proteins is still not fully established. This review discusses the most recent findings on BP lowering of dietary proteins and protein sources, the possible mechanisms and the safety of increasing protein intake.

RECENT FINDINGS

Recent short-term, strictly controlled, randomized clinical trials show a BP lowering effect of increased protein intake. Longer-term trials, however, show inconsistent results. Because all recent trials exchanged carbohydrates, and not fats, for proteins, the question remains whether potential beneficial effects of high protein diets are due to increased protein intake or decreased carbohydrate intake. No clear differences between plant protein and animal protein are found in observational studies, and trials comparing plant versus animal protein are lacking. Different protein sources may lower BP via different mechanisms, which might explain divergent findings. Potential harms of high protein diets are not confirmed in recent trials in healthy persons.

SUMMARY

Increasing dietary protein intake or decreasing carbohydrate intake within reasonable limits may be beneficial for BP. The most and least beneficial protein sources still need to be determined.

Dietary amino acids and the risk of hypertension in a Dutch older population: the Rotterdam Study

BACKGROUND

Inverse associations between dietary protein and hypertension have been reported, which may be attributed to specific amino acids.

OBJECTIVE

We examined whether the intake of glutamic acid, arginine, cysteine, lysine, or tyrosine was associated with blood pressure (BP) levels (n = 3086) and incident hypertension (n = 1810) in the Rotterdam Study.

DESIGN

We calculated BP levels in quartiles of amino acid intake as a percentage of total protein intake (% of protein) with adjustment for age, sex, BMI, smoking, alcohol intake, education, and dietary factors. Subsequently, we used Cox proportional models that included the same confounders to evaluate the associations between specific amino acid intake and hypertension incidence.

RESULTS

Glutamic acid contributed most to protein intake (21% of protein), whereas lysine provided 7%, arginine 5%, tyrosine 4%, and cysteine 1.5%. A higher intake of tyrosine (∼0.3% of protein) was significantly related to a 2.4-mm Hg lower systolic BP (P-trend = 0.05) but not to diastolic BP (P = 0.35). The other amino acids were not significantly associated with BP levels in a cross-sectional analysis. During 6 y of follow-up (7292 person-years), 873 cases of hypertension developed. None of the amino acids were significantly associated with incident hypertension (HR: 0.81-1.18; P-trend > 0.2).

CONCLUSION

Our data do not suggest a major role for glutamic acid, arginine, lysine, tyrosine, or cysteine intake (as % of protein intake) in determining population BP or risk of hypertension.

Plants, diet, and health

Chronic disease is a major social challenge of the twenty-first century. In this review, we examine the evidence for discordance between modern diets and those on which humankind evolved as the cause of the increasing incidence of chronic diseases, and the evidence supporting consumption of plant foods as a way to reduce the risk of chronic disease. We also examine the evidence for avoiding certain components of plant-based foods that are enriched in Western diets, and review the mechanisms by which different phytonutrients are thought to reduce the risk of chronic disease. This body of evidence strongly suggests that consuming more fruits and vegetables could contribute both to medical nutrition therapies, as part of a package of treatments for conditions like type 2 diabetes, heart disease, cancer, and obesity, and to the prevention of these diseases. Plant science should be directed toward improving the quality of plant-based foods by building on our improved understanding of the complex relationships between plants, our diet, and our health.

Dietary protein intake and blood pressure: a meta-analysis of randomized controlled trials

The authors conducted a meta-analysis of randomized controlled trials to evaluate the association of dietary protein intake with blood pressure. To identify articles published before April 2011, the authors searched electronic databases, conducted a manual bibliography review, and consulted experts in the field. Forty trials (including 3,277 participants in total) met the eligibility criteria and were included. Using a standardized form, 2 investigators independently abstracted data on study design, participant characteristics, and treatment outcomes. Net change estimates were pooled across trials using random-effects models. Compared with carbohydrate, dietary protein intake was associated with significant changes in mean systolic and diastolic blood pressure of -1.76 mm Hg (95% confidence interval (CI): -2.33, -1.20) and -1.15 mm Hg (95% CI: -1.59, -0.71), respectively (both P 's < 0.001). Both vegetable protein and animal protein were associated with significant blood pressure changes of -2.27 mm Hg (95% CI: -3.36, -1.18) and -2.54 mm Hg (95% CI: -3.55, -1.53), respectively, for systolic blood pressure (both P 's < 0.001) and -1.26 mm Hg (95% CI: -2.26, -0.26) and -0.95 mm Hg (95% CI: -1.72, -0.19), respectively, for diastolic blood pressure (both P 's = 0.014). Blood pressure reduction was not significantly different when vegetable protein was compared directly with animal protein. These findings indicate that partially replacing dietary carbohydrate with protein may be important for the prevention and treatment of hypertension.

Dietary protein, blood pressure and renal function in renal transplant recipients

Hypertension is highly prevalent among renal transplant recipients (RTR) and a risk factor for graft failure and cardiovascular events. Protein intake has been claimed to affect blood pressure (BP) in the general population and may affect renal function. We examined the association of dietary protein with BP and renal function in RTR. We included 625 RTR (age 53 (SD 13) years; 57% male). Protein intake was assessed with a FFQ, differentiating between animal and plant protein. BP was measured according to a strict protocol. Creatinine clearance and albuminuria were measured as renal parameters. Protein intake was 83 (SD 12) g/d, of which 63% derived from animal sources. BP was 136 (SD 17) mmHg systolic (SBP) and 83 (SD 11) mmHg diastolic (DBP). Creatinine clearance was 66 (SD 26) ml/min; albuminuria 41 (10-178) mg/24 h. An inverse, though statistically insignificant, association was found between the total protein intake and both SBP (β = - 2·22 mmHg per SD, P= 0·07) and DBP (β = - 0·48 mmHg per SD, P= 0·5). Protein intake was not associated with creatinine clearance. Although albuminuria was slightly higher in the highest tertile of animal protein intake compared with the lowest tertile (66 v. 33 mg/d, respectively, P= 0·03), linear regression analyses did not reveal significant associations between dietary protein and albuminuria. Protein intake exceeded the current recommendations. Nevertheless, within the range of protein intake in our RTR population, we found no evidence for an association of dietary protein with BP and renal function. Intervention studies focusing on different protein types are warranted to clarify their effect on BP and renal function in RTR.

The role of high-protein diets in body weight management and health

Studies examining the health benefits of high-protein diets typical of most affluent and many developing countries are not consistent. Prospective epidemiological studies relating dietary protein to clinical and metabolic endpoints suggest increased weight gain and increased risk of diabetes amongst those with a high protein intake and an increased risk of cancer with high intakes of red meat, but lower blood pressure and possibly a reduced risk of heart disease with higher protein intakes. The potential for high-protein diets to confer greater benefit than other diets has been examined using ad libitum and energy restricted diets. Of greatest interest have been the comparisons between high-protein and high-carbohydrate diets. Many trials have reported greater weight loss especially in the context of ad libitum diets over the short-to medium-term, sparing of lean body mass, lowering of triglyceride levels, improved HDL: total cholesterol ratio and improved glycaemic control. Limited data regarding insulin sensitivity are less consistent. A major difficulty in interpreting the results of these studies is that carbohydrate quality has not been taken into account. Furthermore, longer term comparisons of weight reducing diets differing in macronutrient composition have reported similar outcomes, suggesting that compliance is a more important consideration. Nevertheless dietary patterns with high-protein intakes are appropriate for weight reduction and weight maintenance and may be useful for those who have high triglyceride levels and other features of the metabolic syndrome.

Dietary protein intake and risk of stroke in women

BACKGROUND

A high protein intake may reduce the risk of stroke but epidemiologic data on protein intake in relation to stroke risk are limited and inconsistent. Our objective was to test the hypothesis that protein intake would be inversely associated with risk of stroke.

METHODS AND RESULTS

We conducted a population-based prospective cohort study consisting of 34,670 Swedish women who were free of cardiovascular disease and cancer in 1997. Diet was assessed with a food-frequency questionnaire. Incident cases of stroke were ascertained from the Swedish Hospital Discharge Registry. We estimated relative risks (RR) with 95% confidence intervals (CI) using Cox proportional hazard regression model. During 10.4 years of follow-up, 1680 stroke events were identified, including 1310 cerebral infarctions, 154 intracerebral hemorrhages, 79 subarachnoid hemorrhages, and 137 unspecified strokes. Intake of total and animal protein, but not vegetable protein, was statistically significantly inversely associated with risk of total stroke and cerebral infarction after adjustment for other risk factors for stroke. The multivariable RRs of total stroke for the highest versus lowest quintile of intake were 0.74 (95% CI: 0.61, 0.91; P for trend = 0.006) for total protein and 0.71 (95% CI: 0.57, 0.88; P for trend = 0.01) for animal protein. The associations were stronger in women with a history of hypertension (RR of total stroke = 0.56; 95% CI: 0.40, 0.78 for highest versus lowest quintile of total protein).

CONCLUSION

These findings suggest that dietary protein intake is inversely associated with risk of stroke in women with hypertension.

Dietary acid load and risk of hypertension: the Rotterdam Study

BACKGROUND

Mild metabolic acidosis, which can be caused by diet, may result in elevated blood pressure (BP).

DESIGN

The analyses included 2241 participants aged ≥55 y who were free of hypertension at baseline (1990-1993) and who had complete dietary and BP data. Dietary data were obtained from a 170-item food-frequency questionnaire. We used 2 measures to characterize dietary acid load: (1) potential renal acid load (PRAL) by using an algorithm including protein, phosphorus, potassium, calcium, and magnesium, and (2) estimated net endogenous acid production (NEAP) based on protein and potassium. HRs for 6-y incidence of hypertension were obtained in tertiles of PRAL and NEAP with adjustment for age, sex, BMI, smoking, education, and intakes of alcohol, fiber, and total energy.

RESULTS

We identified 1113 incident cases of hypertension during 8707 person-years of follow-up. The median dietary acid load ranged from -14.6 to 19.9 mEq/d across categories of PRAL. Hypertension risk was not significantly associated with dietary acid load. The multivariate HRs (95% CIs) in consecutive tertiles of PRAL were 1.00 (reference), 1.01 (0.87, 1.17), and 1.02 (0.88, 1.18) (P trend = 0.83). The median dietary acid loads were 30.4, 36.7, and 43.7 mEq/d, respectively, in consecutive tertiles of NEAP. Corresponding HRs for NEAP were 1.00 (reference), 0.92 (0.80, 1.07), and 0.94 (0.81, 1.10) (P-trend = 0.46).

CONCLUSION

The findings from this prospective cohort study provided no evidence of an association between dietary acid load and risk of hypertension in older adults.

Role of dietary therapies in the prevention and treatment of hypertension

Blood pressure naturally rises with increasing age. The rate of change in blood pressure with age is regulated in part by genetic factors, but can also be altered through sustained dietary modification. Dietary approaches to modify blood pressure remain an important part of cardiovascular health promotion, which is especially important given the aging of the general population coupled with the increasing prevalence of obesity and metabolic disturbances. Specific modification of dietary components such as macronutrients and micronutrients could be helpful to lower blood pressure and alter the slope of blood pressure change whereas nutritional supplements are less likely to have a substantial beneficial effect. Population-wide generalizations regarding diet are impractical as individualized strategies are more likely to be successful in facilitating long-term benefits in improving blood-pressure control. Consequently, more effort needs to be focused on evaluating data from large-scale observational and interventional studies and interpreting their information in a clinically relevant manner, which is likely to be helpful for individual patients. Providing education on the relationship between diet and blood pressure from an early age is most likely to produce tangible benefits.

Methanol may function as a cross-kingdom signal

Recently, we demonstrated that leaf wounding results in the synthesis of pectin methylesterase (PME), which causes the plant to release methanol into the air. Methanol emitted by a wounded plant increases the accumulation of methanol-inducible gene mRNA and enhances antibacterial resistance as well as cell-to-cell communication, which facilitates virus spreading in neighboring plants. We concluded that methanol is a signaling molecule involved in within-plant and plant-to-plant communication. Methanol is considered to be a poison in humans because of the alcohol dehydrogenase (ADH)-mediated conversion of methanol into toxic formaldehyde. However, recent data showed that methanol is a natural compound in normal, healthy humans. These data call into question whether human methanol is a metabolic waste product or whether methanol has specific function in humans.

Here, to reveal human methanol-responsive genes (MRGs), we used suppression subtractive hybridization cDNA libraries of HeLa cells lacking ADH and exposed to methanol. This design allowed us to exclude genes involved in formaldehyde and formic acid detoxification from our analysis. We identified MRGs and revealed a correlation between increases in methanol content in the plasma and changes in human leukocyte MRG mRNA levels after fresh salad consumption by volunteers. Subsequently, we showed that the methanol generated by the pectin/PME complex in the gastrointestinal tract of mice induces the up- and downregulation of brain MRG mRNA. We used an adapted Y-maze to measure the locomotor behavior of the mice while breathing wounded plant vapors in two-choice assays. We showed that mice prefer the odor of methanol to other plant volatiles and that methanol changed MRG mRNA accumulation in the mouse brain.

We hypothesize that the methanol emitted by wounded plants may have a role in plant-animal signaling. The known positive effect of plant food intake on human health suggests a role for physiological methanol in human gene regulation.

Effects of higher- versus lower-protein diets on health outcomes: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Numerous randomised controlled trials (RCTs) published in first tier medical journals have evaluated the health effects of diets high in protein. We conducted a rigorous systematic review of RCTs comparing higher- and lower-protein diets.

METHODS

We searched several electronic databases up to July 2011 for studies focusing on patient-important outcomes (for example, cardiovascular disease) and secondary outcomes such as risk factors for chronic disease (for example, adiposity).

RESULTS

We identified 111 articles reporting on 74 trials. Pooled effect sizes using standardised mean differences (SMDs) were small to moderate and favoured higher-protein diets for weight loss (SMD -0.36, 95% confidence interval (CI) -0.56 to -0.17), body mass index (-0.37, CI -0.56 to 0.19), waist circumference (-0.43, CI -0.69 to -0.16), blood pressure (systolic: -0.21, CI -0.32 to -0.09 and diastolic: -0.18, CI -0.29 to -0.06), high-density lipoproteins (HDL 0.25, CI 0.07 to 0.44), fasting insulin (-0.20, CI -0.39 to -0.01) and triglycerides (-0.51, CI -0.78 to -0.24). Sensitivity analysis of studies with lower risk of bias abolished the effect on HDL and fasting insulin, and reduced the effect on triglycerides. We observed nonsignificant effects on total cholesterol, low-density lipoproteins, C-reactive protein, HbA1c, fasting blood glucose, and surrogates for bone and kidney health. Adverse gastrointestinal events were more common with high-protein diets. Multivariable meta-regression analysis showed no significant dose response with higher protein intake.

CONCLUSIONS

Higher-protein diets probably improve adiposity, blood pressure and triglyceride levels, but these effects are small and need to be weighed against the potential for harms.

Protein supplementation lowers blood pressure in overweight adults: effect of dietary proteins on blood pressure (PROPRES), a randomized trial

BACKGROUND

Dietary protein intake may help to manage blood pressure (BP) and prevent complications associated with elevated BP.

OBJECTIVE

The objective of this study was to determine whether 4 wk of increased protein intake (∼25% compared with ∼15% of energy intake that isoenergetically replaces carbohydrate intake) lowers office and daytime BP compared with increased carbohydrate intake.

DESIGN

A randomized, double-blind, parallel study compared consumption of 3 × 20 g protein/d (20% pea, 20% soy, 30% egg, and 30% milk-protein isolate) with 3 × 20 g maltodextrin/d. Protein or maltodextrin were isoenergetically substituted for a sugar-sweetened drink. Primary outcomes were office and daytime BP. A total of 99 men and women [age range: 20-70 y; BMI (in kg/m²): 25-35] with untreated elevated BP (BP ≥130/85 and <160/100 mm Hg) were randomly assigned. Ninety-four completers (51 subjects in the maltodextrin group, 43 subjects in the protein group) were included in the analyses.

RESULTS

Office systolic blood pressure (SBP) and diastolic blood pressure (DBP) were 4.9 ± 1.7 mm Hg (P = 0.005) and 2.7 ± 1.3 mm Hg (P = 0.05) lower, respectively, in the protein group. Daytime SBP was 4.6 ± 1.7 mm Hg lower in the protein group (P = 0.006), whereas daytime DBP did not differ between groups (P = 0.37). Urinary sodium excretion was higher in the maltodextrin group (P = 0.004).

CONCLUSION

Increased protein intake, at the expense of maltodextrin, lowers BP in overweight adults with upper-range prehypertension and grade 1 hypertension. This trial was registered at www.trialregister.nl as NTR 1362.