Effect of wheat bran on serum lipids: influence of particle size and wheat protein

Exploring the cholesterol-lowering effects of cereal bran cell wall-enriched diets

Cell wall polysaccharides (dietary fiber) in cereal grains contribute to health benefits. The novelty of the current study was an effort to explore the in vivo therapeutic potential of different cereal bran cell walls against hypercholesterolemia. For this purpose, the cell walls were isolated from different cereal brans (wheat, maize, oats, and barley), and the intake of these cereal bran cell walls was evaluated for their anti-lipidemic activity in normal and hypercholesterolemic rats. The serum taken from the rats was tested for cholesterol, lipid, and triglyceride profiles before and after treatment. The outcomes of the current study have shown that the cereal cell wall has a significant hypercholesterolemia effect. The biochemical parameters of the control animals were within the normal clinical ranges, indicating that the experimental diets were safe. Among cereal bran cell walls, barley bran significantly decreased cholesterol (56.35 ± 1.35 mg/dL), low-density lipoprotein (56.35 ± 1.05 mg/dL), triglycerides (105.29 ± 1.95 mg/dL), and increased high-density lipoprotein level (48.35 ± 1.35 mg/dL). These findings provide conclusive evidence that the cereal cell wall is beneficial in the treatment of hypercholesterolemia and may potentially provide protection against other acute, recurring, or chronic illnesses.

Effects of cereal bran consumption on cardiometabolic risk factors: A systematic review and meta-analysis

AIMS

Cardiovascular disease is a prevalent worldwide disease, and cardiometabolic risk factors (CMRFs) include hyperlipidemia, hypertension, diabetes, and adiposity. Healthy diets are the critical factor in controlling these CMRFs risks, especially cereal bran which contains many beneficial substances. However, there are still contradictions in the indicators of improving CMRFs by bran from different grain sources or even the same grain source. Therefore, this study aimed to investigate the effects of cereal bran consumption on CMRFs.

DATA SYNTHESIS

Eligible randomized controlled studies were searched in PubMed, Embase, Scopus, the Cochrane Library and Web of Science until February 2023. The random-effects model was used to calculate overall effect sizes of weighted mean difference (WMD) and 95% confidence interval (CI). Finally, 22 studies were included in the present meta-analysis. Compared to the control, cereal bran consumption had no significant effect on high-density lipoprotein cholesterol, triglycerides, waist circumference, and body mass index, but could reduce systolic blood pressure (WMD: -1.59; 95% CI: -2.45 to -0.72), diastolic blood pressure (WMD: -1.96; 95% CI: -3.89 to -0.04), total cholesterol (WMD: -0.19; 95% CI: -0.34 to -0.04), low-density lipoprotein cholesterol (WMD: -0.21; 95% CI: -0.38 to -0.04), and fasting blood glucose (WMD: -0.13; 95% CI: -0.24 to -0.01). Additionally, oat bran can lower blood lipids in individuals with lipid diseases and blood pressure in obese or hypertensive patients.

CONCLUSIONS

Cereal bran could significantly reduce blood pressure, total cholesterol, low-density lipoprotein cholesterol, and fasting blood glucose in individuals with CMRFs, and oat bran had the most obvious effect.

Are all fibres created equal with respect to lipid lowering? Comparing the effect of viscous dietary fibre to non-viscous fibre from cereal sources: a systematic review and meta-analysis of randomised controlled trials

Although compelling evidence from observational studies supports a positive association between consumption of cereal fibre and CVD risk reduction, randomised controlled trials (RCT) often target viscous fibre type as the prospective contributor to lipid lowering to reduce CVD risk. The objective of our study is to compare the lipids-lowering effects of viscous dietary fibre to non-viscous, cereal-type fibre in clinical studies. RCT that evaluated the effect of viscous dietary fibre compared with non-viscous, cereal fibre on LDL cholesterol and alternative lipid markers, with a duration of ≥ 3 weeks, in adults with or without hypercholesterolaemia were included. Medline, EMBASE, CINAHL and the Cochrane Central Register were searched through October 19, 2021. Data were extracted and assessed by two independent reviewers. The generic inverse variance method with random effects model was utilised to pool the data which were expressed as mean differences (MD) with 95 % CI. Eighty-nine trials met eligibility criteria (n 4755). MD for the effect of viscous dietary fibre compared with non-viscous cereal fibre were LDL cholesterol (MD = -0·26 mmol/l; 95 % CI: -0·30, -0·22 mmol/l; P < 0·01), non-HDL cholesterol (MD = -0·33 mmol/l; 95 % CI: -0·39, -0·28 mmol/l; P < 0·01) and Apo-B (MD = -0·04 g/l; 95 % CI: -0·06, -0·03 g/l; P < 0·01). Viscous dietary fibre reduces LDL cholesterol and alternative lipid markers relative to the fibre from cereal sources, hence may be a preferred type of fibre-based dietary intervention targeting CVD risk reduction.

Health Benefits of Cereal Grain- and Pulse-Derived Proteins

Pulses and whole grains are considered staple foods that provide a significant amount of calories, fibre and protein, making them key food sources in a nutritionally balanced diet. Additionally, pulses and whole grains contain many bioactive compounds such as dietary fibre, resistant starch, phenolic compounds and mono- and polyunsaturated fatty acids that are known to combat chronic disease. Notably, recent research has demonstrated that protein derived from pulse and whole grain sources contains bioactive peptides that also possess disease-fighting properties. Mechanisms of action include inhibition or alteration of enzyme activities, vasodilatation, modulation of lipid metabolism and gut microbiome and oxidative stress reduction. Consumer demand for plant-based proteins has skyrocketed primarily based on the perceived health benefits and lower carbon footprint of consuming foods from plant sources versus animal. Therefore, more research should be invested in discovering the health-promoting effects that pulse and whole grain proteins have to offer.

Non-Celiac Gluten Sensitivity: A Review

Background and objectives: Grain food consumption is a trigger of gluten related disorders: celiac disease, non-celiac gluten sensitivity (NCGS) and wheat allergy. They demonstrate with non-specific symptoms: bloating, abdominal discomfort, diarrhea and flatulence. Aim: The aim of the review is to summarize data about pathogenesis, symptoms and criteria of NCGS, which can be helpful for physicians. Materials and Methods: The PubMed and Google Scholar databases were searched in January 2019 with phrases: 'non-celiac gluten sensitivity', non-celiac gluten sensitivity', non-celiac wheat gluten sensitivity', non-celiac wheat gluten sensitivity', and gluten sensitivity'. More than 1000 results were found. A total of 67 clinical trials published between 1989 and 2019 was scanned. After skimming abstracts, 66 articles were chosen for this review; including 26 clinical trials. Results: In 2015, Salerno Experts' Criteria of NCGS were published. The Salerno first step is assessing the clinical response to gluten free diet (GFD) and second is measuring the effect of reintroducing gluten after a period of treatment with GFD. Several clinical trials were based on the criteria. Conclusions: Symptoms of NCGS are similar to other gluten-related diseases, irritable bowel syndrome and Crohn's disease. With Salerno Experts' Criteria of NCGS, it is possible to diagnose patients properly and give them advice about nutritional treatment.

Metabolic effects in patients with celiac disease, patients with nonceliac gluten sensitivity, and asymptomatic controls, after six months of a gluten-free diet

INTRODUCTION AND OBJECTIVES

It is essential for patients with celiac disease (CD) to be on a gluten-free diet (GFD) but said diet has also been reported to increase the risk for metabolic syndrome. There is no evidence on the metabolic effects of a GFD in patients with nonceliac gluten sensitivity (NCGS) or in asymptomatic subjects. Therefore, the aim of the present study was to evaluate the metabolic effects of a GFD over a 6-month period in patients with CD, patients with NCGS, and in asymptomatic controls (ACs).

MATERIALS AND METHODS

A prospective study was conducted that evaluated metabolic syndrome and its components of obesity, high blood pressure, hepatic steatosis, and hyperglycemia at the baseline and at 6 months.

RESULTS

A total of 66 subjects (22 CD, 22 NCGS, and 22 AC) were included in the study. At the baseline, 10% of the patients with CD presented with obesity, high blood pressure, hepatic steatosis, and metabolic syndrome. After 6 months, obesity and metabolic syndrome increased by 20% (p=0.125). In the patients with NCGS, obesity increased by 5% after the GFD and 20% of those patients presented with de novo hepatic steatosis. The prevalence of obesity decreased by 10% in the controls after the GFD (30 vs 20%, p=0.5) and none of the other components of metabolic syndrome were affected.

CONCLUSIONS

The metabolic benefits and risks of a GFD should be considered when prescribing said diet in the different populations that opt for that type of intervention.

Modifying wheat bran to improve its health benefits

Consumption of wheat bran (WB) has been associated with improved gastrointestinal health and a reduced risk for colorectal cancer, cardiovascular diseases and metabolic disorders. These benefits are likely mediated by a combination of mechanisms, including colonic fermentation of the WB fiber, fecal bulking and the prevention of oxidative damage due to its antioxidant capacities. The relative importance of those mechanisms is not known and may differ for each health effect. WB has been modified by reducing particle size, heat treatment or modifying tissue composition to improve its technological properties and facilitate bread making processes. However, the impact of those modifications on human health has not been fully elucidated. Some modifications reinforce whereas others attenuate the health effects of coarse WB. This review summarizes available WB modifications, the mechanisms by which WB induces health benefits, the impact of WB modifications thereon and the available evidence for these effects from in vitro and in vivo studies.

Gluten intake and risk of type 2 diabetes in three large prospective cohort studies of US men and women

AIMS/HYPOTHESIS

We investigated the association between gluten intake and long-term type 2 diabetes risk among Americans.

METHODS

We followed women from the Nurses' Health Study (NHS, n = 71,602, 1984-2012) and NHS II (n = 88,604, 1991-2013) and men from the Health Professionals Follow-Up Study (HPFS, n = 41,908, 1986-2012). Gluten intake was estimated using a validated food frequency questionnaire every 2-4 years. Incident type 2 diabetes was defined as self-reported physician-diagnosed diabetes confirmed using a supplementary questionnaire.

RESULT

Gluten intake was strongly correlated with intakes of carbohydrate components, especially refined grains, starch and cereal fibre (Spearman correlation coefficients >0.6). During 4.24 million years of follow-up, 15,947 people were confirmed to have type 2 diabetes. After multivariate adjustment, pooled HRs and 95% CIs for type 2 diabetes, from low to high gluten quintiles, were (p_trend < 0.001): 1 (reference); 0.89 (0.85, 0.93); 0.84 (0.80, 0.88); 0.78 (0.74, 0.82) and 0.80 (0.76, 0.84). The association was slightly weakened after further adjusting for cereal fibre, with pooled HRs (95% CIs) of (p_trend < 0.001): 1 (reference); 0.91 (0.87, 0.96); 0.88 (0.83, 0.93); 0.83 (0.78, 0.88) and 0.87 (0.81, 0.93). Dose-response analysis supported a largely linear inverse relationship between gluten intake up to 12 g/day and type 2 diabetes. The association between gluten intake and type 2 diabetes was stronger when intake of added bran was also higher (p_interaction = 0.02).

CONCLUSIONS/INTERPRETATION

Gluten intake is inversely associated with type 2 diabetes risk among largely healthy US men and women. Limiting gluten in the diet is associated with lower intake of cereal fibre and possibly other beneficial nutrients that contribute to good health.

Effect of the gluten-free diet on cardiovascular risk factors in patients with coeliac disease: A systematic review

BACKGROUND AND AIMS

A gluten-free diet (GFD), the mainstay of treatment for celiac disease, is being increasingly adopted by people without this condition. The long-term health effects of this diet, apart from its beneficial effect on enteropathy in celiac disease, are unclear. Concerns exist that the GFD may result in micronutrient deficiencies, increased exposure to toxins such as arsenic, and an increased cardiovascular risk. This systematic review addresses the effect of the GFD on several modifiable cardiovascular risk factors.

METHODS

A systematic search of the literature addressing the GFD and blood pressure, glycaemia, body mass index, waist circumference, and serum lipids in patients before and after adoption of a GFD was conducted using the MEDLINE, EMBASE, PSYCInfo, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases. Two authors performed abstract and full text screening, and quality assessment.

RESULTS

A total of 5372 articles were identified, from which 27 were included. Lack of control groups in all but one study prevented meta-analysis of results. Overall study quality was low and restricted to patients with celiac disease. Consistent findings across studies included an increase in total cholesterol, high density lipoprotein, fasting glycaemia, and body mass index (while remaining within the healthy weight range). Significant changes in low density lipoprotein, triglycerides, and blood pressure were not consistently reported.

CONCLUSIONS

A GFD alters certain cardiovascular risk factors in patients with celiac disease, but the overall effect on cardiovascular risk is unclear. Further studies are warranted.

Whole grain rye intake, reflected by a biomarker, is associated with favorable blood lipid outcomes in subjects with the metabolic syndrome--a randomized study

Background and Aim

Few studies have explored the possible plasma cholesterol lowering effects of rye consumption. The aim of this secondary analysis in the SYSDIET study was to investigate the association between plasma alkylresorcinols (AR), a biomarker for whole grain wheat and rye intake, and blood lipid concentrations in a population with metabolic syndrome. Furthermore, we analyzed the associations between the AR C17∶0/C21∶0 ratio, a suggested marker of the relative intake of whole grain/bran rye, and blood lipid concentrations.

Methods

Participants were 30–65 years of age, with body mass index (BMI) 27–40 kg/m² and had metabolic syndrome. Individuals were recruited through six centers in the Nordic countries and randomized either to a healthy Nordic diet (ND, n = 93), rich in whole grain rye and wheat, as well as berries, fruits and vegetables, rapeseed oil, three fish meals per week and low-fat dairy products, or a control diet (n = 65) for 18/24 weeks. Associations between total plasma AR concentration and C17∶0/C21∶0 homologue ratio and blood lipids were investigated in pooled (ND + control group) regression analyses at 18/24 weeks adjusted for baseline value for the dependent variable, age, BMI and statin use.

Results

When adjusted for confounders, total plasma AR at 18/24 weeks was not significantly associated with blood lipids but the AR ratio C17∶0/C21∶0 was inversely associated with LDL cholesterol concentrations (B (95% CI): −0.41 (−0.80 to −0.02)), log LDL/HDL cholesterol ratio (−0.20 (−0.37 to −0.03)), log non-HDL cholesterol (−0.20 (−0.37 to −0.03)), log apolipoprotein B (−0.12 (−0.24 to 0.00)) and log triglyceride concentrations (−0.35 (−0.59 to −0.12)).

Discussion

Increased proportion of whole grain rye, reflected by a biomarker, in the diet is associated with favorable blood lipid outcomes, a relationship that should be further investigated.

Trial Registration

ClinicalTrials.gov NCT00992641

The benefits of breakfast cereal consumption: a systematic review of the evidence base

There have been no comprehensive reviews of the relation of breakfast cereal consumption to nutrition and health. This systematic review of all articles on breakfast cereals to October 2013 in the Scopus and Medline databases identified 232 articles with outcomes related to nutrient intake, weight, diabetes, cardiovascular disease, hypertension, digestive health, dental and mental health, and cognition. Sufficient evidence was available to develop 21 summary evidence statements, ranked from A (can be trusted to guide practice) to D (weak and must be applied with caution). Breakfast cereal consumption is associated with diets higher in vitamins and minerals and lower in fat (grade B) but is not associated with increased intakes of total energy or sodium (grade C) or risk of dental caries (grade B). Most studies on the nutritional impact are cross-sectional, with very few intervention studies, so breakfast cereal consumption may be a marker of an overall healthy lifestyle. Oat-, barley-, or psyllium-based cereals can help lower cholesterol concentrations (grade A), and high-fiber, wheat-based cereals can improve bowel function (grade A). Regular breakfast cereal consumption is associated with a lower body mass index and less risk of being overweight or obese (grade B). Presweetened breakfast cereals do not increase the risk of overweight and obesity in children (grade C). Whole-grain or high-fiber breakfast cereals are associated with a lower risk of diabetes (grade B) and cardiovascular disease (grade C). There is emerging evidence of associations with feelings of greater well-being and a lower risk of hypertension (grade D), but more research is required.

The effects of a diet rich in inulin or wheat fibre on markers of cardiovascular disease in overweight male subjects

BACKGROUND

Previous studies suggest that the beneficial health effects of a diet rich in whole grains could be a result of the individual fibres found in the grain. The present study aimed to investigate the influence of a diet high in either wheat fibre (as an example of an insoluble fibre) or inulin (a nondigestible carbohydrate) on markers of cardiovascular disease.

METHODS

Ten male participants classified as at higher risk of cardiovascular disease [mean (SD) body mass index 30.2 (3) kg m(-2) , mean (SD) waist circumference 106.4 (7) cm, mean (SD) age 39.8 (9) years] were recruited to a randomised, controlled, cross-over study comparing the consumption of bespoke bread rolls containing either inulin, wheat germ or refined grain (control) (15 g day(-1) ) for 4 weeks with a 4-week washout period between each regime. At the end of each regime, participants underwent an oral glucose tolerance test (OGTT), measures of pulse wave velocity (PWV), 24-h ambulatory blood pressure (AMBP), plasma lipid status and markers of glucose control.

RESULTS

There was no difference in measures of glucose control, lipid status, 24-h AMBP or PWV after the intervention periods and no changes compared to baseline. There was no significant difference between OGTT glucose and insulin time profiles; however, there was a significant difference in area under the curves between the wheat fibre and control interventions when comparing change from baseline (control +10.2%, inulin +4.3%, wheat fibre -2.5%; P = 0.03).

CONCLUSIONS

Only limited differences between the interventions were identified, perhaps as a consequence of the amount of fibre used and intervention length. The wheat germ intervention resulted in a significant reduction in glucose area under the curve, suggesting that this fibre may aid glucose control.

Health benefits of cereal fibre: a review of clinical trials

Cereal fibre and whole-grain intakes have been consistently associated in the epidemiological literature with reduced mortality and risk of chronic disease including obesity, CVD and type 2 diabetes. The present review focuses on intervention trials with three primary aims: (1) understanding the mechanisms through which fibre consumption improves health (for example, examination of intermediate endpoints reflecting improved lipid, glucose and energy metabolism); (2) close evaluation of qualitative factors which modify fibre's effectiveness including physiochemical properties (for example, solubility, fermentability and viscosity), fibre extract molecular weight, fibre particle size and botanical structure of the fibre source grain; and (3) identification of areas in which additional research is needed. The first two aims typify the goals of nutrition research, in that improved understanding of the specific factors which determine fibre's health benefits has critical implications for dietary recommendations as well as improving understanding of physiological mechanisms. The third aim acknowledges the substantial gap between recommended and actual fibre intakes in many developed countries including the USA and the UK. In recognition of this deficit in total fibre intake, food manufacturing processes increasingly utilise fibre extracts and concentrates as food additives. However, whether fibre extracts provide similar health benefits to the fibre supplied in the constituents of whole grain is largely unexplored. The relative benefits of fibre extracts compared with whole-grain fibre sources therefore represent a critical area in which additional research is needed.

The effect of whole grain wheat sourdough bread consumption on serum lipids in healthy normoglycemic/normoinsulinemic and hyperglycemic/hyperinsulinemic adults depends on presence of the APOE E3/E3 genotype: a randomized controlled trial

Background

Epidemiological studies associate consumption of whole grain foods, including breads, with reduced cardiovascular disease (CVD) risk; however, few studies have compared wheat whole grains with wheat refined grains.

Methods

This study investigated effects of 6-week consumption of whole grain wheat sourdough bread in comparison to white bread on fasting serum lipids in normoglycemic/normoinsulinemic (NGI; n = 14) and hyperglycemic/hyperinsulinemic (HGI; n = 14) adults. The influence of single-nucleotide polymorphisms, 3 within the APOE gene (E2, E3, E4) and 2 within the hepatic lipase gene promoter (LIPC -514C>T, LIPC -250G>A) were considered.

Results

At baseline, HGI participants had significantly higher body weight, waist circumference, body fat, and fasted glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), glucagon, triacylglycerols (TAG) and TAG:HDL-cholesterol, compared to NGI participants; however, none of these in addition to none of the other serum lipids, differed between bread treatments, within either participant group. For participants with the APOE E3/E3 genotype, LDL-cholesterol (P = 0.02) increased in the NGI group (n = 7), and TAG (P = 0.03) and TAG:HDL-cholesterol (P = 0.04) increased in the HGI group (n = 10), following consumption of whole grain wheat sourdough compared to white bread.

Conclusions

In summary, 6-week consumption of whole grain wheat sourdough bread did not significantly modulate serum lipids in NGI or HGI adults; however, it significantly increased LDL-cholesterol, TAG and TAG:HDL-cholesterol in participants with the APOE E3/E3 genotype. These data add to limited literature comparing wheat whole grains to wheat refined grains on CVD risk and highlight the need to consider genetic variation in relation to lipoprotein lipid content and CVD risk.

Whole grains, bran, and germ in relation to homocysteine and markers of glycemic control, lipids, and inflammation 1

BACKGROUND

Intake of whole grains is inversely associated with risk of diabetes and ischemic heart disease in observational studies. The lower risk associated with high whole-grain intakes may be mediated through improvements in glycemic control, lipid profiles, or reduced inflammation.

OBJECTIVE

The aim was to examine whether the intake of whole grains, bran, and germ is related to homocysteine, plasma markers of glycemic control (fasting insulin, hemoglobin A1c, C-peptide, and leptin), lipids (total cholesterol, triacylglycerol, HDL cholesterol, and LDL cholesterol), and inflammation (C-reactive protein, fibrinogen, and interleukin 6).

DESIGN

This was a cross-sectional study of the relations of whole grains, bran, and germ intakes with homocysteine and markers of glycemic control, lipids, and inflammation in 938 healthy men and women.

RESULTS

Whole-grain intake was inversely associated with homocysteine and markers of glycemic control. Compared with participants in the bottom quintile of whole-grain intake, participants in the highest quintile had 17%, 14%, 14%, and 11% lower concentrations of homocysteine (P < 0.01), insulin (P = 0.12), C-peptide (P = 0.03), and leptin (P = 0.03), respectively. Inverse associations were also observed with total cholesterol (P = 0.02), HDL cholesterol (P = 0.05), and LDL cholesterol (P = 0.10). Whole-grain intake was not associated with the markers of inflammation. Whole-grain intake was most strongly inversely associated with markers of glycemic control in this population.

CONCLUSION

The results suggest a lower risk of diabetes and heart disease in persons who consume diets high in whole grains.

Fiber and Cardiovascular Disease Risk

Dietary fiber consists of edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine. Fiber can be classified as a dietary source (eg, cereal, fruit, vegetable, or legume) or as a supplement. Based on chemical properties, fiber can be divided to water-soluble (eg, beta-glucans, pectin, and guar) and insoluble (eg, cellulose and lignin) forms. An increasing number of observational findings have reported a lower incidence of coronary heart disease in subjects who report consuming diets high in fiber. Dietary fiber is thought to affect several cardiovascular disease (CVD) risk factors. Soluble fiber decreases serum total and low-density lipoprotein cholesterol concentrations and improves insulin resistance. The effect of fiber on inflammatory markers and coagulation is not yet well established. While soluble, gel-forming fiber has beneficially affected CVD risk factors, food sources of mainly insoluble fibers, primarily contributed by cereal products, have been the most consistently associated with lower incidence rates of CVD. Despite this contradiction, the evidence promotes a food-based approach favoring increased intake of whole-grain cereals, fruit, and vegetables providing a mixture of different types of fibers for CVD prevention.

Plasma carotenoid and vitamins a and e concentrations in older African American women after wheat bran supplementation: effects of age, body mass and smoking history

OBJECTIVE

This study investigated the relationships of plasma vitamins A, E, and carotenoids with age, BMI and former/non-smoking history after adjusting for wheat bran supplementation.

METHODS

All 39 African American women in the church-based, volunteer sample, 40-70 years old, supplemented their daily diets for 5-6 wks. with 1/2 cup of a riboflavin-spiked wheat bran cereal.

RESULTS

Urinary riboflavin concentrations increased from 0.8 +/- 0.1 mg/day at baseline to 7.5 +/- 0.5 mg/day after supplementation, confirming the 99.2 +/- 10.5% self-reported adherence. Plasma nutrient concentrations did not change significantly with supplementation nor was never/former smoking history related to diet. Plasma retinol and serum cholesterol were significantly higher (p < 0.0002) in persons older than 55 years compared to younger adults. Plasma retinol (microg/dL) but not serum cholesterol was associated significantly with menopausal status and hormone replacement therapy (HRT; p = 0.05); progressive increases in retinol concentrations were found in the women after adjusting for pre/post supplementation: lowest in pre-menopause (47.7 +/- 4.8); intermediate concentrations in post-menopause on HRT (54.6 +/- 3.0); highest level in post-menopause without HRT (61.1 +/- 3.0). Similarly, a progressive increase was found in lipid-unadjusted alpha-tocopherol concentrations and menopausal status with or without HRT. Vitamin A and cholesterol intakes were not significantly different by age group. Plasma carotenoids were not significantly different by age or fiber supplementation, but alpha- and beta-carotene and beta-cryptoxanthin were significantly lower with BMI > or = 30. In contrast to carotenoids, both plasma levels of gamma-tocopherol and lipid-adjusted gamma-tocopherol were significantly higher with obesity compared to those with BMI < 30.

CONCLUSION

Plasma alpha- and beta-carotene and beta-cryptoxanthin were negatively associated with obesity, whereas gamma-tocopherol measures were consistently elevated with high BMI. The increase in age-associated plasma retinol in postmenopausal women was likely related to decreased estrogen concentrations in the African American women. Smoking history was not influential in this study.

Intakes of whole grains, bran, and germ and the risk of coronary heart disease in men

BACKGROUND

Previous studies have suggested that a daily intake of 3 servings of whole-grain foods is associated with a reduced risk of coronary heart disease (CHD). However, methods for the assessment of whole-grain intake differ. Furthermore, any additional effects of added bran and germ, which are components of whole grains, have not been reported.

OBJECTIVE

The objective was to evaluate the association of whole-grain, bran, and germ intakes (with the use of new quantitative measures) with the incidence of CHD.

DESIGN

This was a prospective cohort study of 42,850 male health professionals aged 40-75 y at baseline in 1986 who were free from cardiovascular disease, cancer, and diabetes. Daily whole-grain, bran, and germ intakes were derived in grams per day from a detailed semiquantitative dietary questionnaire.

RESULTS

During 14 y of follow-up, we documented 1818 incident cases of CHD. After cardiovascular disease risk factors and the intakes of bran and germ added to foods were controlled for, the hazard ratio of CHD between extreme quintiles of whole-grain intake was 0.82 (95% CI: 0.70, 0.96; P for trend=0.01). The hazard ratio of CHD in men with the highest intake of added bran was 0.70 (95% CI: 0.60, 0.82) compared with men with no intake of added bran (P for trend < or = 0.001). Added germ was not associated with CHD risk.

CONCLUSION

This study supports the reported beneficial association of whole-grain intake with CHD and suggests that the bran component of whole grains could be a key factor in this relation.

The effect of fiber-rich carbohydrates on features of Syndrome X

There has been much debate among nutritionists and scientists regarding the optimal dietary approach for the treatment of the Insulin Resistance Syndrome, also called Syndrome X. This condition, which may affect as many as 47 million individuals in the United States, significantly increases risk of coronary heart disease and stroke. Major health organizations have historically recommended high-carbohydrate, low-fat (HCLF) diets to reduce chronic disease risk. However, there is evidence that a high intake of carbohydrates may adversely affect one or more of the abnormalities associated with this syndrome. Studies in this area have often had limitations. For example, some studies showing adverse effects of an HCLF diet have not taken into account the dietary fiber content of the diet. This article describes abnormalities often associated with Syndrome X, reviews the beneficial effects of fiber-rich carbohydrates, discusses the effect of fiber-rich carbohydrates on features of this syndrome, and concludes with applications of these findings for those involved in treating individuals with features of this disorder. This review indicates that an HCLF dietary pattern such as that used in the DASH trial, with a level of dietary fiber consistent with the recommendations of the American Dietetic Association (eg, 20-35g/day), containing from 3 to 10 g soluble fiber/day, may be beneficial for treating those with Syndrome X.

High-fiber oat cereal compared with wheat cereal consumption favorably alters LDL-cholesterol subclass and particle numbers in middle-aged and older men

BACKGROUND

No studies have examined whether increased consumption of oat cereal, rich in soluble fiber, favorably alters lipoprotein particle size and number.

OBJECTIVE

We examined the effects of large servings of either oat or wheat cereal on plasma lipids, lipoprotein subclasses, lipoprotein particle diameters, and LDL particle number.

DESIGN

Thirty-six overweight men aged 50-75 y were randomly assigned to consume daily for 12 wk either oat or wheat cereal providing 14 g dietary fiber/d. Before and after the intervention, plasma lipid and lipoprotein subclasses were measured with proton nuclear magnetic resonance spectroscopy, and whole-body insulin sensitivity was estimated with the frequently sampled intravenous-glucose-tolerance test.

RESULTS

Time-by-treatment interactions (P < 0.05) for LDL cholesterol (oat: -2.5%; wheat: 8.0%), small LDL cholesterol (oat: -17.3%; wheat: 60.4%), LDL particle number (oat: -5.0%; wheat: 14.2%), and LDL:HDL cholesterol (oat: -6.3%; wheat: 14.2%) were observed. Time-by-treatment interactions were nearly significant for total cholesterol (oat: -2.5%; wheat: 6.3%; P = 0.08), triacylglycerol (oat: -6.6%; wheat: 22.0%; P = 0.07), and VLDL triacylglycerol (oat: -7.6%; wheat: 2.7%; P = 0.08). No significant time-by-treatment interactions were observed for HDL cholesterol, HDL-cholesterol subclasses, or LDL, HDL, and VLDL particle diameters. Insulin sensitivity did not change significantly with either intervention.

CONCLUSIONS

The oat compared with the wheat cereal produced lower concentrations of small, dense LDL cholesterol and LDL particle number without producing adverse changes in blood triacylglycerol or HDL-cholesterol concentrations. These beneficial alterations may contribute to the cardioprotective effect of oat fiber.

Whole wheat and triticale flours with differing viscosities stimulate cecal fermentations and lower plasma and hepatic lipids in rats

Whole flours from oat, rye or barley effectively modify digestive fermentation and lipid metabolism, whereas the effectiveness of whole wheat flour has not been established. To address this question, cecal digestion, short-chain fatty acid (SCFA) metabolism and cholesterol metabolism were investigated in four groups of rats fed the following semipurified diets differing in their carbohydrate source: a control diet (purified wheat starch) and three whole cereal flour diets [Valoris wheat (Wv), Soissons wheat (Ws), or Carnac triticale (Tc)]. Wv is particularly viscous and rich in arabinoxylans, and Tc is richer in hemicellulose than wheat. Compared with controls, rats fed the whole-flour diets had enlarged ceca and a moderate acidification of the bulk pH ( approximately 6.4). In these rats, the cecal SCFA pool size was enhanced (P < 0.05), and the SCFA molar ratio reflected propionic/butyric acid-rich fermentations, especially in those fed TC: The portal SCFA concentrations reflected the rise of the acetic and propionic acid pools in the cecum, whereas portal butyric acid remained relatively low, probably reflecting extensive metabolism by the cecal wall. The fecal excretion of total steroids (bile acids + sterols) was markedly enhanced by all of the whole-flour diets, with Wv (+78%) > Tc (+64%) > Ws (+47%). In parallel, there was a significant plasma cholesterol-lowering effect for rats fed Wv (-27%) and Tc (-32%) and a plasma triglyceride-lowering effect (approximately -40%) in all rats fed whole-flour diets (P < 0.05). This effect was observed mainly for triglyceride-rich lipoprotein-cholesterol, whereas HDL cholesterol was unaffected. These results indicate that whole wheat flours can strikingly affect cecal SCFA, especially butyrate, and are effective plasma cholesterol-lowering agents.

Dietary fiber prevents carbohydrate-induced hypertriglyceridemia

Plant foods rich in carbohydrate and dietary fiber have many health benefits. One concern often expressed about higher carbohydrate, lower fat diets is that they may increase fasting serum triglycerides. Recently the importance of hypertriglyceridemia as an independent risk factor for coronary heart disease has been reaffirmed. For 40 years, clinicians have noted "carbohydrate-induced hypertriglyceridemia" when persons were fed high-carbohydrate, low-fiber diets. The role of fiber in protecting from carbohydrate-induced hypertriglyceridemia has not been discussed by many reviewers. Systematic review of the literature documents that high fiber intakes clearly protect from carbohydrate-induced hypertriglyceridemia. These are reviewed. Thus, recent and earlier research indicates that use of a higher carbohydrate, higher fiber diet compared with a lower carbohydrate, higher fat diet is associated with a small reduction in fasting serum triglyceride values.

Effect of soy protein foods on low-density lipoprotein oxidation and ex vivo sex hormone receptor activity--a controlled crossover trial

Plant-derived estrogen analogs (phytoestrogens) may confer significant health advantages including cholesterol reduction, antioxidant activity, and possibly a reduced cancer risk. However, the concern has also been raised that phytoestrogens may be endocrine disrupters and major health hazards. We therefore assessed the effects of soy foods as a rich source of isoflavonoid phytoestrogens on LDL oxidation and sex hormone receptor activity. Thirty-one hyperlipidemic subjects underwent two 1-month low-fat metabolic diets in a randomized crossover study. The major differences between the test and control diets were an increase in soy protein foods (33 g/d soy protein) providing 86 mg isoflavones/2,000 kcal/d and a doubling of the soluble fiber intake. Fasting blood samples were obtained at the start and at weeks 2 and 4, with 24-hour urine collections at the end of each phase. Soy foods increased urinary isoflavone excretion on the test diet versus the control (3.8+/-0.7 v 0.0+/-0.0 mg/d, P < .001). The test diet decreased both oxidized LDL measured as conjugated dienes in the LDL fraction (56+/-3 v 63+/-3 micromol/L, P < .001) and the ratio of conjugated dienes to LDL cholesterol (15.0+/-1.0 v 15.7+/-0.9, P = .032), even in subjects already using vitamin E supplements (400 to 800 mg/d). No significant difference was detected in ex vivo sex hormone activity between urine samples from the test and control periods. In conclusion, consumption of high-isoflavone foods was associated with reduced levels of circulating oxidized LDL even in subjects taking vitamin E, with no evidence of increased urinary estrogenic activity. Soy consumption may reduce cardiovascular disease risk without increasing the risk for hormone-dependent cancers.

Dietary fibre, lente carbohydrates and the insulin-resistant diseases

Several epidemiological studies link consumption of fibre-rich foods to a reduced risk of type 2 diabetes and CHD. The 'fibre hypothesis' suggested that this was a direct effect of fibre. However, fibre-rich foods contain different types of fibre as well as other potentially beneficial compounds, and many foods naturally high in fibre have low glycaemic and insulinaemic indices, possibly due to food form. The question therefore emerges as to the effect of isolated fibre per se on insulin sensitivity, lipids and other risk factors associated with the metabolic syndrome. Many beneficial effects are seen with pharmacological doses of isolated viscous soluble fibre, including improved insulin sensitivity, decreased LDL-cholesterol levels and decreased clotting factors. Similar effects are seen with low glycaemic-index foods. In contrast, insoluble non-viscous cereal fibre is not seen to act directly on risk factors when taken in refined foods such as in milled flour. Since cereal fibre, the major type of fibre in western diets, does not directly act on the risk factors for the metabolic syndrome, the question remains as to possible mechanisms. Until now, fibre and the nature and processing of the starch and particle size have been seen as the main determinants of the metabolic response to starchy foods. However, fibre-rich foods also have an increased protein-to-carbohydrate ratio. Hence we suggest that the protective effect of fibre may also be due to increased vegetable protein content, which may act directly to reduce clotting factors and oxidized LDL-cholesterol levels.

Viscous and nonviscous fibres, nonabsorbable and low glycaemic index carbohydrates, blood lipids and coronary heart disease

Viscous fibres such as guar, glucomannans, pectins, oat betaglucan and psyllium continue to be seen as hypocholesterolaemic. Nevertheless, in large cohort studies, ironically it is the insoluble cereal fibre that has been demonstrated to relate negatively to cardiovascular disease and diabetes, despite an absence of effect on fasting lipids or postprandial glycaemia. In general, resistant or nonabsorbable starch is lipid neutral, whereas some nonabsorbable sugars or oligosaccharides may raise serum cholesterol, possibly through providing more acetate after colonic fermentation by colonic microflora. On the other hand, fructo-oligosaccharides appear to reduce serum triglycerides for reasons that are not entirely clear. Of possibly greater recent interest have been the carbohydrates that are not so much resistant to absorption, but rather are slowly absorbed. They possess some of the features of dietary fibre in providing a substrate for colonic bacterial fermentation. In the small intestine, however, they form lente or sustained release carbohydrate. In the form of low glycaemic index foods, lente carbohydrate consumption has been shown to relate to improved blood lipid profiles in hyperlipidaemic individuals and improved glycaemic control in diabetes. In larger cohort studies, low glycaemic index foods or low glycaemic load diets have been associated with higher HDL-cholesterol levels and reduced incidence of diabetes and cardiovascular disease.