Effect of dietary cis and trans fatty acids on serum lipoprotein[a] levels in humans

Effects of saturated fatty acid consumption on lipoprotein (a): a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

An inverse relationship between saturated fatty acid (SFA) intake and Lp(a) concentration has been observed; however, there has been no quantification of this effect.

OBJECTIVES

The objective was to determine whether SFA consumption alters Lp(a) concentrations among adults without atherosclerotic cardiovascular disease (ASCVD).

METHODS

A systematic review and meta-analysis of randomized controlled trials contrasting a lower SFA diet(s) with a higher SFA diet(s) among adults without ASCVD was conducted. PubMed, Cochrane Central Register of Clinical Trials, clinicaltrials.gov, and Web of Science databases and registers were searched through October 2023. The standardized mean difference (SMD) in Lp(a) between diets lower and higher in SFA [percentage of energy (%E)] was determined using random-effects meta-analysis. Analyses were also conducted to examine the effect of replacing SFA with carbohydrates (CHO), monounsaturated (MUFAs), polyunsaturated (PUFAs), or trans fatty acids (TFAs).

RESULTS

In total, 6255 publications were identified in the systematic search. Twenty-six publications reporting 27 randomized controlled trials, including 1325 participants and 49 diet comparisons, were included. The mean difference in SFA between lower and higher SFA diets was 7.6%E (3.7%-17.8%E). After lower SFA diets, Lp(a) concentration was higher (SMD: 0.14; 95% confidence interval [CI]: 0.03, 0.24) than after higher SFA diets. Subgroup analyses showed higher Lp(a) following diets where SFA was replaced by CHO (trials = 8; n = 539; SMD: 0.21; 95% CI: 0.02, 0.40) or TFAs (trials = 8; n = 300; SMD: 0.32; 95% CI: 0.17, 0.48). No differences in Lp(a) were observed when MUFA (trials = 16; n = 641; SMD: 0.04; 95% CI: -0.08, 0.16) or PUFA (trials = 8; n = 415; SMD: 0.09; 95% CI: -0.04, 0.22) replaced SFA.

CONCLUSIONS

Lower SFA diets modestly increase Lp(a) compared to higher SFA diets among individuals without ASCVD. This effect appeared to be driven by replacement of SFA with CHO or TFA. Research investigating the atherogenicity of diet-induced Lp(a) changes is needed to inform dietary management of lipid/lipoprotein disorders. This trial was registered with PROSPERO as CRD42020154169.

Dietary n-3 alpha-linolenic and n-6 linoleic acids modestly lower serum lipoprotein(a) concentration but differentially influence other atherogenic lipoprotein traits: A randomized trial

BACKGROUND AND AIMS

Lipoprotein(a) [Lp(a)] is a causal, genetically determined cardiovascular risk factor. Limited evidence suggests that dietary unsaturated fat may increase serum Lp(a) concentration by 10-15 %. Linoleic acid may increase Lp(a) concentration through its endogenous conversion to arachidonic acid, a process regulated by the fatty acid desaturase (FADS) gene cluster. We aimed to compare the Lp(a) and other lipoprotein trait-modulating effects of dietary alpha-linolenic (ALA) and linoleic acids (LA). Additionally, we examined whether FADS1 rs174550 genotype modifies Lp(a) responses.

METHODS

A genotype-based randomized trial was performed in 118 men homozygous for FADS1 rs174550 SNP (TT or CC). After a 4-week run-in period, the participants were randomized to 8-week intervention diets enriched with either Camelina sativa oil (ALA diet) or sunflower oil (LA diet) 30-50 mL/day based on their BMI. Serum lipid profile was measured at baseline and at the end of the intervention.

RESULTS

ALA diet lowered serum Lp(a) concentration by 7.3 % (p = 0.003) and LA diet by 9.5 % (p < 0.001) (p = 0.089 for between-diet difference). Both diets led to greater absolute decreases in individuals with higher baseline Lp(a) concentration (p < 0.001). Concentrations of LDL cholesterol (LDL-C), non-HDL-C, remnant-C, and apolipoprotein B were lowered more by the ALA diet (p < 0.01). Lipid or lipoprotein responses were not modified by the FADS1 rs174550 genotype.

CONCLUSIONS

A considerable increase in either dietary ALA or LA from vegetable oils has a similar Lp(a)-lowering effect, whereas ALA may lower other major atherogenic lipids and lipoproteins to a greater extent than LA. Genetic differences in endogenous PUFA conversion may not influence serum Lp(a) concentration.

All we need to know about lipoprotein(a)

Lipoprotein(a) [Lp(a)], a genetically determined macromolecular complex, is independently and causally associated with atherosclerotic cardiovascular disease (ASCVD) and calcific aortic stenosis via proposed proinflammatory, prothrombotic, and proatherogenic mechanisms. While Lp(a) measurement standardization issues are being resolved, several guidelines now support testing Lp(a) at least once in each adult's lifetime for ASCVD risk prediction which can foster implementation of more aggressive primary or secondary prevention therapies. Currently, there are several emerging targeted Lp(a) lowering therapies in active clinical investigation for safety and cardiovascular benefit among both primary and secondary prevention populations. First degree relatives of patients with high Lp(a) should be encouraged to undergo cascade screening. Primary prevention patients with high Lp(a) should consider obtaining a coronary calcium score for further risk estimation and to guide further ASCVD risk factor management including consideration of low dose aspirin therapy. Secondary prevention patients with high Lp(a) levels should consider adding PCSK9 inhibition to statin therapy.

Non-genetic influences on lipoprotein(a) concentrations

An elevated level of lipoprotein(a) [Lp(a)] is a genetically regulated, independent, causal risk factor for cardiovascular disease. However, the extensive variability in Lp(a) levels between individuals and population groups cannot be fully explained by genetic factors, emphasizing a potential role for non-genetic factors. In this review, we provide an overview of current evidence on non-genetic factors influencing Lp(a) levels with a particular focus on diet, physical activity, hormones and certain pathological conditions. Findings from randomized controlled clinical trials show that diets lower in saturated fats modestly influence Lp(a) levels and often in the opposing direction to LDL cholesterol. Results from studies on physical activity/exercise have been inconsistent, ranging from no to minimal or moderate change in Lp(a) levels, potentially modulated by age and the type, intensity, and duration of exercise modality. Hormone replacement therapy (HRT) in postmenopausal women lowers Lp(a) levels with oral being more effective than transdermal estradiol; the type of HRT, dose of estrogen and addition of progestogen do not modify the Lp(a)-lowering effect of HRT. Kidney diseases result in marked elevations in Lp(a) levels, albeit dependent on disease stages, dialysis modalities and apolipoprotein(a) phenotypes. In contrast, Lp(a) levels are reduced in liver diseases in parallel with the disease progression, although population studies have yielded conflicting results on the associations between Lp(a) levels and nonalcoholic fatty liver disease. Overall, current evidence supports a role for diet, hormones and related conditions, and liver and kidney diseases in modifying Lp(a) levels.

The Demise of Artificial Trans Fat: A History of a Public Health Achievement

Policy Points This article describes a strategic combination of research, advocacy, corporate campaigns, communications, grassroots mobilization, legislation, regulatory actions, and litigation against companies and government to secure a national policy to remove artificial trans fat from the US food system. Sharing lessons we learned can help inform policymakers, academics, policy practitioners, and students across disciplines. Some of our lessons are that system change means that all consumers benefit without the need for individual behavior change; research can both identify opportunities to improve health and support policy adoption; policy efforts can serve as public education campaigns; policy campaigns can drive marketplace changes; and engaging forward-thinking companies can diffuse opposition to passing a policy.

CONTEXT

For many decades, partially hydrogenated vegetable oil (PHO), the primary source of artificial trans fat in the American diet, was used widely in processed and restaurant foods. In the early 1990s, studies linked the consumption of artificial trans fat with heart disease. This article details how research and advocacy led to eliminating artificial trans fat from the US food supply.

METHODS

We synthesized published studies of the health impact of trans fat, the legislative history of state and local trans fat bills, the Food and Drug Administration's (FDA) regulatory docket on trans fat labeling and its declaration that PHOs are no longer Generally Recognized as Safe (GRAS), and our own files, which included strategy documents, notes from meetings with the FDA staff, correspondence between advocates and the FDA, fact sheets, press releases, news clips, and other materials.

FINDINGS

This history of trans fat provides insights into policy strategy and advocacy best practices that resulted in the removal of trans fat from food in the United States, preventing an estimated 50,000 premature deaths a year. The lessons we learned are that system change benefits all consumers without the need for individual behavior change; research can both identify opportunities to improve health through policy and support policy adoption; policy campaigns can serve as public education campaigns; policy can drive changes to products and the marketplace; and engaging forward-thinking companies can help diffuse opposition to passing a policy. Securing this policy required the persistence of scientists and health advocates in first discovering the risks and then using the science to secure policies to mitigate the identified harm.

CONCLUSIONS

An understanding of the tactics used to help attain the targeted policies and how challenges were addressed (such as through communications, leveraging an expanding research base and expert reports, showing that a national policy was feasible through voluntary corporate changes and state and local policy, and litigation against companies and government agencies) may provide a model for scientists, students, advocates, and policymakers. We hope this account will inform efforts to address other public health challenges, such as the current threats of excessive exposure to sodium and added sugars, which persist in the US food system.

The Effects of Linoleic Acid Consumption on Lipid Risk Markers for Cardiovascular Disease in Healthy Individuals: A Review of Human Intervention Trials

Cardiovascular disease (CVD) is the leading cause of death worldwide. Risk factors for developing this disease include high serum concentrations of total cholesterol, triglycerides, low-density lipoproteins, very-low density lipoproteins, and low concentrations of high-density lipoproteins. One proposed dietary strategy for decreasing risk factors involves replacing a portion of dietary saturated fatty acids with mono- and polyunsaturated fatty acids (PUFAs). The essential omega-6 PUFA, linoleic acid (LA), is suggested to decrease the risk for CVD by affecting these lipid risk markers. Reviewing human intervention trials will provide further evidence of the effects of LA consumption on risk factors for CVD. PubMed was used to search for peer-reviewed articles. The purpose of this review was: (1) To summarize human intervention trials that studied the effects of LA consumption on lipid risk markers for CVD in healthy individuals, (2) to provide mechanistic details, and (3) to provide recommendations regarding the consumption of LA to decrease the lipid risk markers for CVD. The results from this review provided evidence that LA consumption decreases CVD lipid risk markers in healthy individuals.

Diet and Lp(a): Does Dietary Change Modify Residual Cardiovascular Risk Conferred by Lp(a)?

Lipoprotein(a) [Lp(a)] is an independent, causal, genetically determined risk factor for cardiovascular disease (CVD). We provide an overview of current knowledge on Lp(a) and CVD risk, and the effect of pharmacological agents on Lp(a). Since evidence is accumulating that diet modulates Lp(a), the focus of this paper is on the effect of dietary intervention on Lp(a). We identified seven trials with 15 comparisons of the effect of saturated fat (SFA) replacement on Lp(a). While replacement of SFA with carbohydrate, monounsaturated fat (MUFA), or polyunsaturated fat (PUFA) consistently lowered low-density lipoprotein cholesterol (LDL-C), heterogeneity in the Lp(a) response was observed. In two trials, Lp(a) increased with carbohydrate replacement; one trial showed no effect and another showed Lp(a) lowering. MUFA replacement increased Lp(a) in three trials; three trials showed no effect and one showed lowering. PUFA or PUFA + MUFA inconsistently affected Lp(a) in four trials. Seven trials of diets with differing macronutrient compositions showed similar divergence in the effect on LDL-C and Lp(a). The identified clinical trials show diet modestly affects Lp(a) and often in the opposing direction to LDL-C. Further research is needed to understand how diet affects Lp(a) and its properties, and the lack of concordance between diet-induced LDL-C and Lp(a) changes.

A Critical Review of the Cholesterolaemic Effects of Palm Oil

This paper reviews recent reports of the cholesterolaemic effects of palm oil. The evidence indicates that the substitution of palm oil or its lipid fractions for the usual fats in the diet does not result in an elevation of total serum cholesterol in lean, normocholesterolaemic individuals with a cholesterol intake of less than 300 mg per day. When threshold dietary levels of linoleic acid (18:2) are met, they tend to counter the cholesterol-raising effects of the 12- and 16-carbon saturated fatty acids. In view of this, the use of a cholesterol saturated-fat index to measure the hypercholesterolaemic and atherogenic potential of foods can be misleading, particularly when applied to palm oil. Nutritionists and health professionals need to keep abreast of recent knowledge on the cholesterolaemic impact of dietary fats and fatty acids.

Limiting trans Fats in Foods: Use of Partially Hydrogenated Vegetable Oils in Prepacked Foods in Slovenia

Consumption of industrially produced trans-fatty acids (TFAs) is a well-established health risk factor that correlates with the increased risk of developing cardiovascular disease. The recommended TFA intake is as low as possible, within the context of a nutritionally adequate diet. Different countries have introduced different measures to minimize the exposure of their population to TFAs. Previous data have shown that TFA content has significantly decreased in Western European countries, while this was not the case in many Central-Eastern European countries, including Slovenia. In the absence of regulatory requirements, a number of awareness campaigns were launched in Slovenia since 2015, with the common goal of lowering the use of partially hydrogenated oils (PHO), which are considered a major source of TFAs. To determine if this goal had been reached, we performed an assessment of the exposure of the population to prepacked foods containing PHOs in years 2015 and 2017. Altogether, data on the composition of 22,629 prepacked foods was collected from food labels, using a specifically developed smartphone application. Furthermore, the food categories with the most frequent use of PHOs were identified. The proportion of PHO-containing products was determined for each specific food category, and adjusted with the market share data. The results showed that in 2015, vegetable cream substitutes, soups, and biscuits were the categories with the highest penetration of declared PHO content. In 2017, the proportion of products with PHO decreased considerably. In vegetable cream substitutes the percentage of PHO containing items dropped from 30 down to 4%, in soups it decreased from 21 to 5%, in biscuits from 17 to 8%, and in crisps and snacks from 10 to 4%. However, PHO content remained notable among cakes, muffins, pastries, and biscuits. We can conclude that the voluntary guidelines and regular public communication of the risks related to the TFA consumption has had a considerable effect on the food supply, but did not result in sufficient removal of PHOs from foods.

Ultra-processed foods in human health: a critical appraisal

The NOVA classification of foods proposes 4 categories: unprocessed or minimally processed foods, processed culinary ingredients, processed foods, and ultra-processed foods and drinks (UPFDs). It is argued that the latter relies heavily on modifications to foods, resulting in enhanced amounts of salt, added sugar, and fat as well as the use of additives in an attempt to make this food category highly palatable. It further argues that controlling food processing, rather than examining nutrients, should be foremost in shaping nutrition policy. This commentary challenges many of the basic arguments of using the NOVA food classification system to examine the link between food and health. We believe that there is no evidence to uphold the view that UPFDs give rise to hyperpalatable foods associated with a quasi-addictive effect and that the prevailing European Union and US data fail to uphold the assertion that UPFDs, which dominate energy intake, give rise to dietary patterns that are low in micronutrients. With regard to the use of the NOVA food classification in the development of food-based dietary guidelines, we show that the very broad definition of UPFDs makes this impossible. Finally, the available evidence does not support the view that the globalization of food is the driver of increased intakes of UPFDs in low- to middle-income countries but rather that this is driven by small indigenous companies. On balance, therefore, there seems to be little advantage from the use of the NOVA classification compared with the current epidemiologic approach, which relies on the linkage of nutrient intakes to chronic disease with subsequent identification of foods that merit consideration in public health nutrition strategies.

Dietary Fat and Risk of Cardiovascular Disease: Recent Controversies and Advances

Health effects of dietary fats have been extensively studied for decades. However, controversies exist on the effects of various types of fatty acids, especially saturated fatty acid (SFA), on cardiovascular disease (CVD). Current evidence supports that different types of dietary fatty acids have divergent effects on CVD risk, and the effects also depend strongly on the comparison or replacement macronutrient. A significant reduction in CVD risk can be achieved if SFAs are replaced by unsaturated fats, especially polyunsaturated fatty acids. Intake of industrially produced trans fat is consistently associated with higher CVD risk. Both n-6 and n-3 polyunsaturated fatty acids are associated with lower CVD risk, although the effects of fish oil supplementation remains inconsistent. The 2015-2020 Dietary Guidelines for Americans place greater emphasis on types of dietary fat than total amount of dietary fat and recommend replacing SFAs with unsaturated fats, especially polyunsaturated fatty acids for CVD prevention.

Red Meat and Health

Despite its nutritional benefits, there is an increasing body of evidence to suggest that regular consumption of red meat may negatively impact health and disease risk, including the risk of most common chronic diseases. This chapter reviews the current evidence linking red and processed meat intakes with chronic disease, obesity and mortality risks and discusses possible mechanisms to explain these associations. Research on the health benefits of diets low in red meat, including vegetarian, vegan, Mediterranean and other plant-based diets, is also reviewed.

Trans fatty acids and cholesterol levels: An evidence map of the available science

High intakes of industrial trans fatty acids (iTFA) increase circulating low density lipoprotein cholesterol (LDL-C) levels, which has implicated iTFA in coronary heart disease (CHD) risk. Published data on iTFA and LDL-C, however, represent higher intake levels than the U.S. population currently consume. This study used state-of-the-art evidence mapping approaches to characterize the full body of literature on LDL-C and iTFA at low intake levels. A total of 32 independent clinical trials that included at least one intervention or control group with iTFA at ≤3%en were found. Findings indicated that a wide range of oils and interventions were used, limiting the ability to determine an isolated effect of iTFA intake. Few data points were found for iTFA at <3%en, with the majority of low-level exposures actually representing control group interventions containing non-partially hydrogenated (PHO) oils. Further, it appears that few dose-response data points are available to assess the relationship of low levels of iTFA, particularly from PHO exposure, and LDL-C. Therefore, limited evidence is available to determine the effect of iTFA at current consumption levels on CHD risk.

Trans fatty acids: are its cardiovascular risks fully appreciated?

OBJECTIVE

The goal of this article was to review the causal link between trans fatty acids (TFA) produced from partially hydrogenated vegetable oil (PHVO) and cardiovascular disease (CVD) risk and its likely mechanisms. The potential risk of TFA from ruminant dairy and meats, which are currently the major sources of dietary TFA, is also discussed.

METHODS

Evidence was derived from observational studies of large cohorts followed up prospectively; from randomized controlled trials of clinical interventions; and from specific case-control studies that investigated biomarkers in tissues. Searches included PubMed and Medline from 1990 to 2013.

RESULTS

Despite TFA from PHVO being associated more strongly with CVD risk than even saturated fats, it may prove difficult to totally eliminate PHVO from all foods. This raises the issue of the lower limit of TFA consumption below which CVD risk is not increased. Limits of <1% of total energy have been suggested. The major mechanism underlying the increased CVD risk from TFA is an increase in LDL-C and Lp(a) lipoproteins and a decrease in HDL-C; increased inflammation and adverse effects on vascular function have also been shown. Both PHVO and ruminant TFA comprise a range of isomers, some specific to each source but including a substantial commonality that supports findings of similar adverse effects at equivalent intakes of TFA. However, the amount of TFA in ruminant fat is relatively small; this limits the CVD risk from eating ruminant products, an inference supported by analysis of prospective cohort studies.

CONCLUSIONS

Two key challenges to the health industry arise from this evidence. They must first determine whether a small intake of TFA from PHVO is safe and what constitutes a safe amount. They must also determine whether TFA from ruminant fat in currently consumed amounts represent limited cardiovascular risk that is balanced by the nutritional benefits of dairy products.

Interactions of Molecules with cis and trans Double Bonds: A Theoretical Study of cis- and trans-2-Butene

Noncovalent interactions of cis- and trans-2-butene, as the smallest model systems of molecules with cis and trans double bonds, were studied to find potential differences in interactions of these molecules. The study was performed using quantum chemical methods including very accurate CCSD(T)/CBS method. We studied parallel and displaced parallel interactions in 2-butene dimers, in butane dimers, and between 2-butene and saturated butane. The results show the trend that interactions of 2-butene with butane are the strongest, followed by interactions in butane dimers, whereas the interaction in 2-butene dimers are the weakest. The strongest calculated interaction energy is between trans-2-butene and butane, with a CCSD(T)/CBS energy of -2.80 kcal mol(-1) . Interactions in cis-2-butene dimers are stronger than interactions in trans-2-butene dimers. Interestingly, some of the interactions involving 2-butene are as strong as interactions in a benzene dimer. These insights into interactions of cis- and trans-2-butene can improve understanding of the properties and processes that involve molecules with cis and trans double bonds, such as fatty acids and polymers.

The relation of saturated fatty acids with low-grade inflammation and cardiovascular disease

The mantra that dietary (saturated) fat must be minimized to reduce cardiovascular disease (CVD) risk has dominated nutritional guidelines for decades. Parallel to decreasing intakes of fat and saturated fatty acids (SFA), there have been increases in carbohydrate and sugar intakes, overweight, obesity and type 2 diabetes mellitus. The "lipid hypothesis" coined the concept that fat, especially SFA, raises blood low-density lipoprotein-cholesterol and thereby CVD risk. In view of current controversies regarding their adequate intakes and effects, this review aims to summarize research regarding this heterogenic group of fatty acids and the mechanisms relating them to (chronic) systemic low-grade inflammation, insulin resistance, metabolic syndrome and notably CVD. The intimate relationship between inflammation and metabolism, including glucose, fat and cholesterol metabolism, revealed that the dyslipidemia in Western societies, notably increased triglycerides, "small dense" low-density lipoprotein and "dysfunctional" high-density lipoprotein, is influenced by many unfavorable lifestyle factors. Dietary SFA is only one of these, not necessarily the most important, in healthy, insulin-sensitive people. The environment provides us not only with many other proinflammatory stimuli than SFA but also with many antiinflammatory counterparts. Resolution of the conflict between our self-designed environment and ancient genome may rather rely on returning to the proinflammatory/antiinflammatory balance of the Paleolithic era in consonance with the 21st century culture. Accordingly, dietary guidelines might reconsider recommendations for SFA replacement and investigate diet in a broader context, together with nondietary lifestyle factors. This should be a clear priority, opposed to the reductionist approach of studying the effects of single nutrients, such as SFA.

Red Meat and Health

Despite its nutritional benefits, there is an increasing body of evidence to suggest that regular consumption of red meat may negatively impact health and disease risk, including the risk of most common chronic diseases. This chapter reviews the current evidence linking red and processed meat intakes with chronic disease, obesity and mortality risks and discusses possible mechanisms to explain these associations. Research on the health benefits of diets low in red meat, including vegetarian, vegan, Mediterranean and other plant-based diets, is also reviewed.

Lipoprotein (a): impact by ethnicity and environmental and medical conditions

Levels of lipoprotein (a) [Lp(a)], a complex between an LDL-like lipid moiety containing one copy of apoB, and apo(a), a plasminogen-derived carbohydrate-rich hydrophilic protein, are primarily genetically regulated. Although stable intra-individually, Lp(a) levels have a skewed distribution inter-individually and are strongly impacted by a size polymorphism of the LPA gene, resulting in a variable number of kringle IV (KIV) units, a key motif of apo(a). The variation in KIV units is a strong predictor of plasma Lp(a) levels resulting in stable plasma levels across the lifespan. Studies have demonstrated pronounced differences across ethnicities with regard to Lp(a) levels and some of this difference, but not all of it, can be explained by genetic variations across ethnic groups. Increasing evidence suggests that age, sex, and hormonal impact may have a modest modulatory influence on Lp(a) levels. Among clinical conditions, Lp(a) levels are reported to be affected by kidney and liver diseases.

Saturated Fats Versus Polyunsaturated Fats Versus Carbohydrates for Cardiovascular Disease Prevention and Treatment

The effects of saturated fatty acids (SFAs) on cardiovascular disease (CVD) risk are modulated by the nutrients that replace them and their food matrices. Replacement of SFAs with polyunsaturated fatty acids has been associated with reduced CVD risk, although there is heterogeneity in both fatty acid categories. In contrast, replacement of SFAs with carbohydrates, particularly sugar, has been associated with no improvement or even a worsening of CVD risk, at least in part through effects on atherogenic dyslipidemia, a cluster of traits including small, dense low-density lipoprotein particles. The effects of dietary SFAs on insulin sensitivity, inflammation, vascular function, and thrombosis are less clear. There is growing evidence that SFAs in the context of dairy foods, particularly fermented dairy products, have neutral or inverse associations with CVD. Overall dietary patterns emphasizing vegetables, fish, nuts, and whole versus processed grains form the basis of heart-healthy eating and should supersede a focus on macronutrient composition.

Aligning food-processing policies to promote healthier fat consumption in India

India is undergoing a shift in consumption from traditional foods to processed foods high in sugar, salt and fat. Partially hydrogenated vegetable oils (PHVOs) high in trans-fat are often used in processed foods in India given their low cost and extended shelf life. The World Health Organization has called for the elimination of PHVOs from the global food supply and recommends their replacement with polyunsaturated fat to maximize health benefits. This study examined barriers to replacing industrially produced trans-fat in the Indian food supply and systematically identified potential policy solutions to assist the government in encouraging its removal and replacement with healthier polyunsaturated fat. A combination of food supply chain analysis and semi-structured interviews with key stakeholders was conducted. The main barriers faced by the food-processing sector in terms of reducing use of trans-fat and replacing it with healthier oils in India were the low availability and high cost of oils high in polyunsaturated fats leading to a reliance on palm oil (high in saturated fat) and the low use of those healthier oils in product reformulation. Improved integration between farmers and processors, investment in technology and pricing strategies to incentivize use of healthier oils for product reformulation were identified as policy options. Food processors have trouble accessing sufficient affordable healthy oils for product reformulation, but existing incentives aimed at supporting food processing could be tweaked to ensure a greater supply of healthy oils with the potential to improve population health.

Trans fatty acids in diets act as a precipitating factor for gut inflammation?

Fatty acids in our daily diet are broadly classified into cis and trans fatty acids (TFAs). TFAs are formed during the manufacturing process of hydrogenated vegetable oils such as margarine. Modern diets such as deep-fried products, frozen foods, and packaged snacks commonly include large quantities of margarine containing TFAs. Although an increased report in the effects of the diet containing TFAs on a risk factor of metabolic syndrome, diabetes mellitus, and coronary heart disease has been observed in the recent years, influence on intestinal inflammation remains unknown. This review describes pro-inflammatory effects of TFAs in our diary diet on various systemic disorders and also discusses a possible role of TFAs on gut inflammation.

Differential effects of adulterated versus unadulterated forms of linoleic acid on cardiovascular health

According to the classic "diet-heart" hypothesis, high dietary intake of saturated fats and cholesterol combined with low intake of polyunsaturated fats can increase levels of serum cholesterol and lead to the development of atherogenic plaques and ultimately cardiovascular diseases. Recently, the beneficial health effects of omega-6 polyunsaturated fatty acids, particularly linoleic acid (LA), on cardiovascular health have been called into question with some scientists suggesting that consumption of LA should be reduced in Western countries. The focus of this critical review is on the controversy surrounding the effects of dietary intake of LA on cardiovascular health. Specifically, we critically examined the effects of both unadulterated and adulterated forms of LA on cardiovascular health outcomes based on findings from epidemiological studies and randomized controlled trials. Additionally, we address common concerns surrounding dietary intake of LA regarding its relationship with arachidonic acid, the ratio of omega-6 to omega-3 fatty acids, and its relationship with inflammation. Our critical review indicates that unadulterated forms of LA are cardioprotective and should be consumed as part of a healthy diet. In contrast, abundant evidence now indicates that adulterated forms of LA, predominantly hydrogenated vegetable oils, are atherogenic and should not be considered part of a healthy diet. The ability to adulterate the natural omega-6 fatty acid, LA, has contributed to mixed findings regarding the effects of this fatty acid on cardiovascular health. Thus, it is critical that the source of LA be taken into account when drawing conclusions about the physiological effects of this fatty acid. The findings of the present review are in line with current dietary recommendations of the American Heart Association.

Supplementation with 1% energy trans fatty acids had little effect on serum cholesterol levels in healthy young Japanese women

The World Health Organization (WHO) has recommended that trans fatty acid (TFA) intake should be less than 1% of total energy intake, but few data are available as to the influence of energy TFA intake of as low as 1% on blood cholesterol levels. A randomized, double-blind, parallel trial was conducted to assess the effects of 1% TFA dietary supplementation on serum cholesterol levels in healthy young women. Sixty-five volunteers consumed cookies containing 1% (TFA) or 0.04% (control) energy of TFA for 4 weeks and blood was harvested after overnight fasting. There were no significant differences in serum LDL- or HDL-cholesterol levels between the two groups. The hemoglobin A1c level was not influenced by dietary TFA. These results suggest that energy of TFAs at less than 1% has little effect on serum cholesterol or hemoglobin A1c levels in healthy young women. This confirms the correctness of the WHO recommendation.

Dietary advice for reducing cardiovascular risk

BACKGROUND

Changes in population diet are likely to reduce cardiovascular disease and cancer, but the effect of dietary advice is uncertain. This review is an update of a previous review published in 2007.

OBJECTIVES

To assess the effects of providing dietary advice to achieve sustained dietary changes or improved cardiovascular risk profile among healthy adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, the Database of Abstracts of Reviews of Effects (DARE) and the HTA database on The Cochrane Library (Issue 4, 2010). We searched MEDLINE (Ovid) (1950 to week 2 October 2010) and EMBASE (Ovid) (1980 to Week 42 2010). Additional searches were done on CAB Health (1972 to December 1999), CVRCT registry (2000), CCT (2000) and SIGLE (1980 to 2000). Dissertation abstracts and reference lists of articles were checked and researchers were contacted.

SELECTION CRITERIA

Randomised studies with no more than 20% loss to follow-up, lasting at least three months and involving healthy adults comparing dietary advice with no advice or minimal advice. Trials involving children, trials to reduce weight or those involving supplementation were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Forty-four trials with 52 intervention arms (comparisons) comparing dietary advice with no advice were included in the review; 18,175 participants or clusters were randomised. Twenty-nine of the 44 included trials were conducted in the USA. Dietary advice reduced total serum cholesterol by 0.15 mmol/L (95% CI 0.06 to 0.23) and LDL cholesterol by 0.16 mmol/L (95% CI 0.08 to 0.24) after 3 to 24 months. Mean HDL cholesterol levels and triglyceride levels were unchanged. Dietary advice reduced blood pressure by 2.61 mm Hg systolic (95% CI 1.31 to 3.91) and 1.45 mm Hg diastolic (95% CI 0.68 to 2.22) and 24-hour urinary sodium excretion by 40.9 mmol (95% CI 25.3 to 56.5) after 3 to 36 months but there was heterogeneity between trials for the latter outcome. Three trials reported plasma antioxidants, where small increases were seen in lutein and β-cryptoxanthin, but there was heterogeneity in the trial effects. Self-reported dietary intake may be subject to reporting bias, and there was significant heterogeneity in all the following analyses. Compared to no advice, dietary advice increased fruit and vegetable intake by 1.18 servings/day (95% CI 0.65 to 1.71). Dietary fibre intake increased with advice by 6.5 g/day (95% CI 2.2 to 10.82), while total dietary fat as a percentage of total energy intake fell by 4.48% (95% CI 2.47 to 6.48) with dietary advice, and saturated fat intake fell by 2.39% (95% CI 1.4 to 3.37).Two trials analysed incident cardiovascular disease (CVD) events (TOHP I/II). Follow-up was 77% complete at 10 to 15 years after the end of the intervention period and estimates of event rates lacked precision but suggested that sodium restriction advice probably led to a reduction in cardiovascular events (combined fatal plus non-fatal events) plus revascularisation (TOHP I hazards ratio (HR) 0.59, 95% CI 0.33 to 1.08; TOHP II HR 0.81, 95% CI 0.59 to 1.12).

AUTHORS' CONCLUSIONS

Dietary advice appears to be effective in bringing about modest beneficial changes in diet and cardiovascular risk factors over approximately 12 months, but longer-term effects are not known.

Current evidence on healthy eating

Large nutritional epidemiology studies, with long-term follow-up to assess major clinical end points, coupled with advances in basic science and clinical trials, have led to important improvements in our understanding of nutrition in primary prevention of chronic disease. Although much work remains, sufficient evidence has accrued to provide solid advice on healthy eating. Good data now support the benefits of diets that are rich in plant sources of fats and protein, fish, nuts, whole grains, and fruits and vegetables; that avoid partially hydrogenated fats; and that limit red meat and refined carbohydrates. The simplistic advice to reduce all fat, or all carbohydrates, has not stood the test of science; strong evidence supports the need to consider fat and carbohydrate quality and different protein sources. This article briefly summarizes major findings from recent years bearing on these issues.

Effect of artificial rearing on lamb welfare and meat quality

Twenty male Comisana lambs were equally divided into two groups. Ten subjects were artificially reared, 10 others were ewe reared and used as control. Unseparated control animals displayed increased cellular immune response to a percutaneous injection of phytohemagglutinin (P<0.001). During the open field test, ewe-reared lambs showed a higher number of flight attempts (P<0.01). Carcass yield were higher for artificially reared animals (P<0.05). Conversely, legs of ewe-reared animals had significantly more fat (P<0.05) and a higher content of saturated fatty acids (P<0.001). Polyunsaturated fatty acid content was higher in artificially reared lamb meat (P<0.01), although the ratio n-6/n-3 was well above the recommended values. The triangle test showed a significant difference in sensory analysis between the two products (P<0.05). Finally, for both rearing systems legs without subcutaneous fat showed a higher percentage of polyunsaturated fatty acids and a corresponding lower content of saturated fatty acids (P<0.001).

Trans fatty acid intake and serum cholesterol levels in young Japanese women

There are very limited data concerning the influence of low-level trans fatty acid (TFA) intake on blood lipid levels. In this study, correlation of total and diene TFA intake with serum cholesterol levels was studied in young Japanese women. The mean intakes of total and diene TFAs were 0.36% and 0.05% of energy, respectively. There was a significant correlation between total fat intake and TFA intake. TFA intake was significantly correlated with erythrocyte TFA content. Total TFA intake was not correlated with total, LDL- or HDL-cholesterol levels. No correlatuon was found between diene TFA intake and cholesterol level. Total and diene TFA intake were not correlated with hemoglobin A1c or C-reactive protein levels. These results suggest that the average TFA intake of young Japanese women does not adversely affect serum cholesterol levels.

Dietary fats and coronary heart disease

The relation of dietary fat to risk of coronary heart disease (CHD) has been studied extensively using many approaches, including controlled feeding studies with surrogate end-points such as plasma lipids, limited randomized trials and large cohort studies. All lines of evidence indicate that specific dietary fatty acids play important roles in the cause and the prevention of CHD, but total fat as a percent of energy is unimportant. Trans fatty acids from partially hydrogenated vegetable oils have clear adverse effects and should be eliminated. Modest reductions in CHD rates by further decreases in saturated fat are possible if saturated fat is replaced by a combination of poly- and mono-unsaturated fat, and the benefits of polyunsaturated fat appear strongest. However, little or no benefit is likely if saturated fat is replaced by carbohydrate, but this will in part depend on the form of carbohydrate. Because both N-6 and N-3 polyunsaturated fatty acids are essential and reduce risk of heart disease, the ratio of N-6 to N-3 is not useful and can be misleading. In practice, reducing red meat and dairy products in a food supply and increasing intakes of nuts, fish, soy products and nonhydrogenated vegetable oils will improve the mix of fatty acids and have a markedly beneficial effect on rates of CHD.

We Spent a Million Bucks and Then We Had To Do Something

Many scholars assume that industry meddles in scientific research in order to defend their products. But this article shows that industry meddling in science can have a variety of consequences. American food manufacturers long denied that trans fats were associated with disease. Academic scientists, government scientists, and activists in fact endorsed trans fats as a healthier alternative to saturated fats. But in 1990, a high-profile study showed that trans fats increased risk factors for heart disease more than saturated fats did. Industry funded a U.S. Department of Agriculture study that they hoped would exonerate trans fats. But the industry-funded U.S. Department of Agriculture study also indicated that trans fats increased risk factors for heart disease more than saturated fats. Industry quickly began developing trans fat alternatives. This confirms that corporations get involved in science in order to defend their products. But involvement in science can be the very means by which corporations persuade themselves to change their products.

Consumer perceptions of trans fats in 2009 show awareness of negative effects but limited concern regarding use in snack foods

The purpose of this study was to determine consumers' perceptions of industrially produced trans fats. A cross-sectional study was conducted in Regina at 3 different grocery store chains located in 3 different regions. A 21-item survey was administered in English by 3 research assistants at the grocery stores over a 5-day period. Of 498 potential respondents who were approached, 211 completed the survey, for a 42% response rate. The majority of respondents were female and over 61 years of age. When respondents were asked if they looked for information on food packages while grocery shopping, none of the respondents indicated that they looked for trans fat on the food label. Ninety-six percent of respondents identified that trans fat is found in processed foods, whereas 42% of respondents incorrectly identified trans fat as being found in nonhydrogenated margarines. More female respondents self-reported that they had made dietary changes to decrease trans fat intake as compared with male respondents (p < 0.05). Those participants who made dietary changes to decrease trans fat intake had higher mean knowledge scores than did those who did not make changes (p < 0.043). Sixty-three percent of respondents indicated that they would not make dietary changes to their snack food selections even if their selections contained trans fat. Consumers know a little about trans fats and consider them to be a concern. However, consumers are reluctant to make dietary changes to limit these fats in their snack food selections.

Enigmatic role of lipoprotein(a) in cardiovascular disease

Lipoprotein (a), [Lp(a)] has many properties in common with low-density lipoprotein, (LDL) but contains a unique protein apolipoprotein(a), linked to apolipoprotein B-100 by a single disulfide bond. There is a substantial size heterogeneity of apo(a), and generally smaller apo(a) sizes tend to correspond to higher plasma Lp(a) levels, but this relation is far from linear, underscoring the importance to assess allele-specific apo(a) levels. The presence of apo(a), a highly charged, carbohydrate-rich, hydrophilic protein may obscure key features of the LDL moiety and offer opportunities for binding to vessel wall elements. Recently, interest in Lp(a) has increased because studies over the past decade have confirmed and more robustly demonstrated a risk factor role of Lp(a) for cardiovascular disease. In particular, levels of Lp(a) carried in particles with smaller size apo(a) isoforms are associated with coronary artery disease (CAD). Other studies suggest that proinflammatory conditions may modulate risk factor properties of Lp(a). Further, Lp(a) may act as a preferential acceptor for proinflammatory oxidized phospholipids transferred from tissues or from other lipoproteins. However, at present only a limited number of agents (e.g., nicotinic acid and estrogen) has proven efficacy in lowering Lp(a) levels. Although Lp(a) has not been definitely established as a cardiovascular risk factor and no guidelines presently recommend intervention, Lp(a)-lowering therapy might offer benefits in subgroups of patients with high Lp(a) levels.

A high-fat/high-cholesterol diet inhibits growth of fetal hippocampal transplants via increased inflammation

A diet containing high levels of saturated fat and cholesterol is detrimental to many aspects of health and is known to lead to obesity, metabolic syndrome, heart disease, diabetes, and cancer. However, the effects of a diet rich in saturated fat and cholesterol on the brain are not currently well understood. In order to determine direct effects of a high saturated fat and cholesterol diet upon fetal hippocampal tissue, we transplanted hippocampal grafts from embryonic day 18 rats to the anterior eye chamber of 16-month-old host animals that were fed either a normal rat chow diet or a 10% hydrogenated coconut oil + 2% cholesterol diet (HFHC diet) for 8 weeks. One eye per rat received topical application of an IL-1 receptor antagonist (IL-1Ra, Kineret®) and the other served as a saline control. Results revealed that the HFHC diet led to a marked reduction in hippocampal transplant growth, and detrimental effects of the diet were alleviated by the IL-1 receptor antagonist IL-1Ra. Graft morphology demonstrated that the HFHC diet reduced organotypical development of the hippocampal neuronal cell layers, which was also alleviated by IL-1Ra. Finally, grafts were evaluated with markers for glucose transporter expression, astrocytes, and activated microglia. Our results demonstrate significant effects of the HFHC diet on hippocampal morphology, including elevated microglial activation and reduced neuronal development. IL-1Ra largely blocked the detrimental effects of this diet, suggesting a potential use for this agent in neurological disorders involving neuroinflammation.

n-6 Fatty acids and cardiovascular health: a review of the evidence for dietary intake recommendations

n-6 PUFA are well known for their critical role in many physiological functions and seem to reduce risks of CHD. However, some argue that excessive consumption of n-6 PUFA may lead to adverse effects on health and therefore recommend reducing dietary n-6 PUFA intake or fixing an upper limit. In this context, the present work aimed to review evidence on the link between n-6 PUFA and risks of CVD. Epidemiological studies show that n-6 PUFA dietary intake significantly lowers blood LDL-cholesterol levels. In addition, n-6 PUFA intake does not increase several CVD risk factors such as blood pressure, inflammatory markers, haemostatic parameters and obesity. Data from prospective cohort and interventional studies converge towards a specific protective role of dietary n-6 PUFA intake, in particular linoleic acid, against CVD. n-6 PUFA benefits are even increased when SFA intake is also reduced. In regards to studies examined in this narrative review, recommendation for n-6 PUFA intake above 5 %, and ideally about 10 %, of total energy appears justified.

Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: a systematic review

BACKGROUND

High stearic acid (STA) soybean oil is a trans-free, oxidatively stable, non-LDL-cholesterol-raising oil that can be used to replace trans fatty acids (TFAs) in solid fat applications.

OBJECTIVE

The objective was to assess the cardiovascular health effects of dietary STA compared with those of trans, other saturated, and unsaturated fatty acids.

DESIGN

We reviewed epidemiologic and clinical studies that evaluated the relation between STA and cardiovascular disease (CVD) risk factors, including plasma lipids and lipoproteins, hemostatic variables, and inflammatory markers.

RESULTS

In comparison with other saturated fatty acids, STA lowered LDL cholesterol, was neutral with respect to HDL cholesterol, and directionally lowered the ratio of total to HDL cholesterol. STA tended to raise LDL cholesterol, lower HDL cholesterol, and increase the ratio of total to HDL cholesterol in comparison with unsaturated fatty acids. In 2 of 4 studies, high-STA diets increased lipoprotein(a) in comparison with diets high in saturated fatty acids. Three studies showed increased plasma fibrinogen when dietary STA exceeded 9% of energy (the current 90th percentile of intake is 3.5%). Replacing industrial TFAs with STA might increase STA intake from 3.0% (current) to approximately 4% of energy and from 4% to 5% of energy at the 90th percentile. One-to-one substitution of STA for TFAs showed a decrease or no effect on LDL cholesterol, an increase or no effect on HDL cholesterol, and a decrease in the ratio of total to HDL cholesterol.

CONCLUSIONS

TFA intake should be reduced as much as possible because of its adverse effects on lipids and lipoproteins. The replacement of TFA with STA compared with other saturated fatty acids in foods that require solid fats beneficially affects LDL cholesterol, the primary target for CVD risk reduction; unsaturated fats are preferred for liquid fat applications. Research is needed to evaluate the effects of STA on emerging CVD risk markers such as fibrinogen and to understand the responses in different populations.