Effect of α-linolenic acid on vascular function and metabolic risk markers during the fasting and postprandial phase: A randomized placebo-controlled trial in untreated (pre-)hypertensive individuals

Current Insights into the Effects of Dietary α-Linolenic Acid Focusing on Alterations of Polyunsaturated Fatty Acid Profiles in Metabolic Syndrome

The plant-derived α-linolenic acid (ALA) is an essential n-3 acid highly susceptible to oxidation, present in oils of flaxseeds, walnuts, canola, perilla, soy, and chia. After ingestion, it can be incorporated in to body lipid pools (particularly triglycerides and phospholipid membranes), and then endogenously metabolized through desaturation, elongation, and peroxisome oxidation to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), with a very limited efficiency (particularly for DHA), beta-oxidized as an energy source, or directly metabolized to C18-oxilipins. At this moment, data in the literature about the effects of ALA supplementation on metabolic syndrome (MetS) in humans are inconsistent, indicating no effects or some positive effects on all MetS components (abdominal obesity, dyslipidemia, impaired insulin sensitivity and glucoregulation, blood pressure, and liver steatosis). The major effects of ALA on MetS seem to be through its conversion to more potent EPA and DHA, the impact on the n-3/n-6 ratio, and the consecutive effects on the formation of oxylipins and endocannabinoids, inflammation, insulin sensitivity, and insulin secretion, as well as adipocyte and hepatocytes function. It is important to distinguish the direct effects of ALA from the effects of EPA and DHA metabolites. This review summarizes the most recent findings on this topic and discusses the possible mechanisms.

Association between dietary intake of omega-3 polyunsaturated fatty acids and all-cause and cardiovascular mortality among hypertensive adults: Results from NHANES 1999-2018

BACKGROUND

Hypertensive adults are at a higher risk of cardiovascular morbidity and mortality. Dietary omega-3 polyunsaturated fatty acids (N3-PUFA) intake has been associated with cardiovascular benefits. However, few studies have specifically investigated whether dietary intake of N3-PUFA is associated with lower risk of all-cause and cardiovascular mortality among hypertensive adults in the U.S.

METHODS

This prospective cohort study included 26,914 hypertensive individuals 18 years or older who participated in 10 NHANES cycles from 1999 to 2018. Dietary levels of N3-PUFA were obtained from the 24-hour dietary recalls. The dietary data were linked to mortality records from the National Death Index through December 31, 2019. The associations between dietary N3-PUFA levels and mortality were evaluated by constructing the Multivariable Cox Proportional Hazards models.

RESULTS

We observed an increasing trend of dietary N3-PUFA intake levels over the years, mainly driven by alpha-linolenic acid (ALA). Lower all-cause mortality risk was observed among hypertensive adults with higher consumption of total N3-PUFA [adjusted hazards ratio, 95% confidence interval: 0.91 (0.86, 0.97)], plant-based ALA [0.88 (0.83, 0.93)], fish oil-based eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) [0.91 (0.83, 0.99)], EPA [0.93 (0.88, 0.98)], docosapentaenoic acid (DPA) [0.73 (0.58, 0.91)], or DHA [0.95 (0.90, 0.99)]. Hypertensive adults were at lower risk of cardiovascular mortality if their diet contained higher levels of total N3-PUFA [0.68 (0.53, 0.88)], ALA [0.89 (0.80, 0.99)], EPA [0.87 (0.79, 0.97)] or DPA [0.86 (0.78, 0.95)]. Weighted quantile sum analysis showed that ALA, EPA, and DPA were the main contributors of the N3-PUFA benefits against mortality among hypertensive adults.

CONCLUSIONS

Dietary intake of N3-PUFA, particularly ALA, EPA, and DPA, was associated with lower risk of all-cause and cardiovascular mortality among U.S. hypertensive adults. These findings suggest that increasing dietary intake of N3-PUFA may serve as a potential strategy to lower hypertension-associated mortality risk.

Effect of Alpha-Linolenic Acid Supplementation on Cardiovascular Disease Risk Profile in Individuals with Obesity or Overweight: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Overweight and obesity are highly prevalent worldwide and are associated with cardiovascular disease (CVD) risk factors, including systematic inflammation, dyslipidemia, and hypertension. Alpha-linolenic acid (ALA) is a plant-based essential polyunsaturated fatty acid associated with reduced CVD risks. This systematic review and meta-analysis aimed to investigate the effects of supplementation with ALA compared with the placebo on CVD risk factors in people with obesity or overweight (International Prospective Register of Systematic Reviews Registration No. CRD42023429563). This review included studies with adults using oral supplementation or food or combined interventions containing vegetable sources of ALA. All studies were randomly assigned trials with parallel or crossover designs. The Cochrane Collaboration tool was used for assessing the risk of bias (Version 1). PubMed, Web of Science, Embase, and Cochrane library databases were searched from inception to April 2023. Nineteen eligible randomized controlled trials, including 1183 participants, were included in the meta-analysis. Compared with placebo, dietary ALA supplementation significantly reduced C-reactive protein concentration (standardized mean difference [SMD] = -0.38 mg/L; 95% confidence interval [CI]: -0.72, -0.04), tumor necrosis factor-α concentration (SMD = -0.45 pg/mL; 95% CI: -0.73, -0.17), triglyceride in serum (SMD = -4.41 mg/dL; 95% CI: -5.99, -2.82), and systolic blood pressure (SMD = -0.37 mm Hg; 95% CI: -0.66, -0.08); but led to a significant increase in low-density lipoprotein cholesterol concentrations (SMD = 1.32 mg/dL; 95% CI: 0.05, 2.59). ALA supplementation had no significant effect on interleukin-6, diastolic blood pressure, total cholesterol, or high-density lipoprotein cholesterol (all P ≥ 0.05). Subgroup analysis revealed that ALA supplementation at a dose of ≥3 g/d from flaxseed and flaxseed oil had a more prominent effect on improving CVD risk profiles, particularly where the intervention duration was ≥12 wk and where the baseline CVD profile was poor.

Flaxseed Oil (Linum usitatissimum) Prevents Cognitive and Motor Damage in Rats with Hyperammonemia

Hyperammonemia is characterized by the excessive accumulation of ammonia in the body as a result of the loss of liver detoxification, leading to the development of hepatic encephalopathy (HE). These metabolic alterations carry cognitive and motor deficits and cause neuronal damage, with no effective treatment at present. In this study, we aimed to evaluate the effect of two subacute oral administrations of flaxseed oil (0.26 and 0.52 mL/kg) on short- and long-term memory, visuospatial memory, locomotor activity, motor coordination, and the neuronal morphology of the prefrontal cortex (PFC) via tests on Wistar rats with hyperammonemia. The goal was to identify its role in the regulation of cerebral edema, without liver damage causing cerebral failure. In contrast with an ammonium-rich diet, flaxseed oil and normal foods did not cause cognitive impairment or motor alterations, as evidenced in the short-term and visuospatial memory tests. Furthermore, the flaxseed oil treatment maintained a regular neuronal morphology of the prefrontal cortex, which represents a neuroprotective effect. We conclude that the oral administration of flaxseed oil prevents cognitive and motor impairments as well as neuronal alterations in rats with hyperammonemia, which supports the potential use of this oil to ameliorate the changes that occur in hepatic encephalopathy.

Effects of olive oil and flaxseed consumption in a healthy diet on endothelial function, plasma lipids and inflammatory factors of patients with coronary heart disease: a randomized clinical trial

OBJECTIVES

A healthy lifestyle, including a healthy diet has been associated with an improvement in cardiovascular risk factors. The aim of the present study was to assess the effect of olive oil and flaxseed consumption as part of a healthy diet on endothelial function, plasma inflammatory factors, and lipid profile in patients with coronary heart disease (CHD).

METHOD

This randomized nonblinded trial was performed on CHD patients. In the control group, participants received general heart-healthy dietary recommendations while in the intervention group, in addition to these recommendations, the participants consumed 25 ml of olive oil and 30 g of flaxseeds daily for 3 months. At baseline and after 3 months, changes in brachial flow-mediated dilation (FMD), plasma asymmetric dimethyl arginine, interleukin-6 (IL-6), IL-10, high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and lipids and lipoproteins were measured.

RESULTS

A total of 50 patients finished the trial ( n  = 24 in the intervention and n  = 26 in the control groups). Compared to the control group, consumption of flaxseed and olive oil significantly improved brachial artery FMD%, and reduced plasma IL-6, TNF-α, MCP-1, total cholesterol, and tended to reduce hs-CRP, and non-HDL-cholesterol but the concentration of other study indices were not different between the two groups.

CONCLUSION

Inclusion of olive oil and flaxseed in the diet of CHD patients may contribute to secondary prevention by improving endothelial function and plasma inflammatory factors.

Unsaturated Fatty Acids and Their Immunomodulatory Properties

Oils are an essential part of the human diet and are primarily derived from plant (or sometimes fish) sources. Several of them exhibit anti-inflammatory properties. Specific diets, such as Mediterranean diet, that are high in ω-3 polyunsaturated fatty acids (PUFAs) and ω-9 monounsaturated fatty acids (MUFAs) have even been shown to exert an overall positive impact on human health. One of the most widely used supplements in the developed world is fish oil, which contains high amounts of PUFAs docosahexaenoic and eicosapentaenoic acid. This review is focused on the natural sources of various polyunsaturated and monounsaturated fatty acids in the human diet, and their role as precursor molecules in immune signaling pathways. Consideration is also given to their role in CNS immunity. Recent findings from clinical trials utilizing various fatty acids or diets high in specific fatty acids are reviewed, along with the mechanisms through which fatty acids exert their anti-inflammatory properties. An overall understanding of diversity of polyunsaturated fatty acids and their role in several molecular signaling pathways is useful in formulating diets that reduce inflammation and increase longevity.

Promising Sources of Plant-Derived Polyunsaturated Fatty Acids: A Narrative Review

(1) Background: Polyunsaturated fatty acids (PUFAs) are known for their ability to protect against numerous metabolic disorders. The consumption of oily fish is the main source of PUFAs in human nutrition and is commonly used for supplement production. However, seafood is an overexploited source that cannot be guaranteed to cover the global demands. Furthermore, it is not consumed by everyone for ecological, economic, ethical, geographical and taste reasons. The growing demand for natural dietary sources of PUFAs suggests that current nutritional sources are insufficient to meet global needs, and less and less will be. Therefore, it is crucial to find sustainable sources that are acceptable to all, meeting the world population's needs. (2) Scope: This review aims to evaluate the recent evidence about alternative plant sources of essential fatty acids, focusing on long-chain omega-3 (n-3) PUFAs. (3) Method: A structured search was performed on the PubMed search engine to select available human data from interventional studies using omega-3 fatty acids of non-animal origin. (4) Results: Several promising sources have emerged from the literature, such as algae, microorganisms, plants rich in stearidonic acid and GM plants. However, the costs, acceptance and adequate formulation deserve further investigation.

Fatty Acid Profiles and Nutritional Evaluation of Fresh Sweet-Waxy Corn from Three Regions of China

Fresh corn is a kind of herbaceous plant with rich nutritive value and a reasonable composition of fatty acids; however, there is little research on methods for the systemic nutritional evaluation of fatty acids in fresh corn. The aim of the present study was to conduct a comparative analysis of the fatty acid profiles of Chinese Huangnuo 9 sweet-waxy corn from the provinces of Inner Mongolia, Jilin, and Heilongjiang by gas chromatography; to establish a nutritional evaluation system according to the impacts of nutrients from fatty acids on human health; and finally, to evaluate, compare and rank fresh sweet-waxy corn grown in different regions. Tocopherols were detected by liquid chromatography in order to demonstrate the anti-oxidation activity of fresh corn’s fatty acids. The fatty acid contents and compositions of the 12 samples from the three regions are significantly different from each other. The nutrient value of the fatty acids in fresh corn was analyzed by factor analysis and a linear structural relation model, followed by the fitting and appraising of the model. The studied fresh sweet-waxy corn 1-4 from Inner Mongolia had the highest γ-tocopherol content and the closest saturated fatty acid:monounsaturated fatty acid:polyunsaturated fatty acid rate to the recommended value. The fatty acid profiles of sweet-waxy corns 2-1, 2-2, and 2-3 were the most diverse, and the comprehensive evaluation result of fresh corn 2-4 was the best; its total fatty acid content was the highest. Fresh corn 3-1 in Heilongjiang had the highest unsaturated fatty acids and lower values in its atherosclerosis index and thrombosis index, which suggested the strongest anti-atherosclerosis and anti-thrombotic ability. This work will give a reference to guide dietary choices and provide data support for dietary recommendations for residents.

Dietary alfalfa powder supplementation improves growth and development, body health, and meat quality of Tibetan sheep

The application of alfalfa powder (AP) in Tibetan sheep to explore its healthy effects and meat quality improvement potential has not been reported. Our study found that AP improved the growth performance, serum metabolism, and antioxidation of Tibetan sheep. The edible quality, sensory quality, and nutritional quality of longissimus dorsi (LD) were analyzed. We observed lower drip loss and hue angle of meat after AP supplementation. AP also increased the cooked meat percentage, pH_24h, a*_24h, chroma_24h, and the contents of protein and fat. The targeted metabolomics profiling revealed that the contents of essential amino acids and flavor amino acids in mutton increased by AP treatments. AP also promoted the deposition of MUFA and PUFA. Therefore, as a promising botanical supplement, AP has a positive effect on the growth, development, and body health of Tibetan sheep, and is also conductive to providing healthy and nutritious high-quality livestock products.

Effects of Dietary α-Linolenic Acid Treatment and the Efficiency of Its Conversion to Eicosapentaenoic and Docosahexaenoic Acids in Obesity and Related Diseases

The essential fatty acid alpha-linolenic acid (ALA) is present in high amounts in oils such as flaxseed, soy, hemp, rapeseed, chia, and perilla, while stearidonic acid is abundant in echium oil. ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by desaturases and elongases in humans. The conversion of ALA to EPA and DHA is limited, and these long-chain n−3 polyunsaturated fatty acids (PUFAs) are mainly provided from dietary sources (fish and seafood). This review provides an overview of studies that explored the effects of dietary supplementation with ALA in obesity and related diseases. The obesity-associated changes of desaturase and elongase activities are summarized, as they could influence the metabolic conversion of ALA. Generally, supplementation with ALA or ALA-rich oils leads to an increase in EPA levels and has no effect on DHA or omega-3 index. According to the literature data, stearidonic acid could enhance conversion of ALA to long-chain n−3 PUFA in obesity. Recent studies confirm that EPA and DHA intake should be considered as a primary dietary treatment strategy for improving the omega-3 index in obesity and related diseases.

A single, high-fat meal adversely affects postprandial endothelial function: a systematic review and meta-analysis

BACKGROUND

Endothelial dysfunction is a predictive risk factor for the development of atherosclerosis and is assessed by flow-mediated dilation (FMD). Although it is known that NO-dependent endothelial dysfunction occurs after consuming a high-fat meal, the magnitude of the effect and the factors that affect the response are unquantified.

OBJECTIVES

We conducted a systematic review and meta-analysis exploring the quantitative effects of a single high-fat meal on endothelial function and determined the factors that modify the FMD response.

METHODS

Six databases were systematically searched for original research published up to January 2022. Eligible studies measured fasting and postprandial FMD following consumption of a high-fat meal. Meta-regression was used to analyze the effect of moderator variables.

RESULTS

There were 131 studies included, of which 90 were suitable for quantitative meta-analysis. A high-fat meal challenge transiently caused endothelial dysfunction, decreasing postprandial FMD at 2 hours [-1.02 percentage points (pp); 95% CI: -1.34 to -0.70 pp; P < 0.01; I2 = 93.3%], 3 hours [-1.04 pp; 95% CI: -1.48 to -0.59 pp; P < 0.001; I2 = 84.5%], and 4 hours [-1.19 pp; 95% CI: -1.53 to -0.84 pp; P < 0.01; I2 = 94.6%]. Younger, healthy-weight participants exhibited a greater postprandial reduction in the FMD percentage change than older, heavier, at-risk groups after a high-fat meal ( P < 0.05). The percentage of fat in the meals was inversely associated with the magnitude of postprandial changes in FMD at 3 hours (P < 0.01).

CONCLUSIONS

A single, high-fat meal adversely impacts endothelial function, with the magnitude of the impact on postprandial FMD moderated by the fasting FMD, participant age, BMI, and fat content of the meal. Recommendations are made to standardize the design of future postprandial FMD studies and optimize interpretation of results, as high-fat meals are commonly used in clinical studies as a challenge to assess endothelial function and therapeutics. This trial was registered at PROSPERO as CRD42020187244.

The effect of camelina oil on vascular function in essential hypertensive patients with metabolic syndrome: a randomized, placebo-controlled, double-blind study

BACKGROUND

The effects of a dietary supplementation with the vegetable ω-3 α-linolenic acid (ALA) on cardiovascular homeostasis are unclear. In this context, it would be interesting to assess the effects of camelina oil.

OBJECTIVE

This study aimed to assess the cardiovascular and metabolic effects of camelina oil in hypertensive patients with metabolic syndrome.

METHODS

In a double-blind, placebo-controlled randomized study, treated essential hypertensive patients with metabolic syndrome received, during 6 mo, either cyclodextrin-complexed camelina oil containing ≈ 1.5 g ALA/d (n = 40) or an isocaloric placebo (n = 41), consisting of the same quantity of cyclodextrins and wheat starch. Anthropometric data, plasma lipids, glycemia, insulinemia, creatininemia, TBARs, high-sensitivity C-reactive protein, and n-3, n-6, and n-9 fatty acids in erythrocyte membranes were measured. Peripheral and central blood pressures, arterial stiffness, carotid intima-media thickness, and brachial artery endothelium-dependent flow-mediated dilatation (FMD) and endothelium-independent dilatation were assessed.

RESULTS

Compared with placebo, camelina oil increased ALA (mean ± SD: 0 ± 0.04 compared with 0.08 ± 0.06%, P <0.001), its elongation product EPA (0 ± 0.5 compared with 0.16 ± 0.65%, P <0.05), and the n-9 gondoic acid (GA; 0 ± 0.04 compared with 0.08 ± 0.04%, P <0.001). No between-group difference was observed for cardiovascular parameters. However, changes in FMD were associated with the magnitude of changes in EPA (r = 0.26, P = 0.03). Compared with placebo, camelina oil increased fasting glycemia (-0.2 ± 0.6 compared with 0.3 ± 0.5 mmol/L, P <0.001) and HOMA-IR index (-0.8 ± 2.5 compared with 0.5 ± 0.9, P <0.01), without affecting plasma lipids, or inflammatory and oxidative stress markers. Changes in HOMA-IR index were correlated with the magnitude of changes in GA (r = 0.32, P <0.01). Nutritional intake remained similar between groups.

CONCLUSION

ALA supplementation with camelina oil did not improve vascular function but adversely affected glucose metabolism in hypertensive patients with metabolic syndrome. Whether this adverse effect on insulin sensitivity is related to GA enrichment, remains to be elucidated.

Impact of α-Linolenic Acid, the Vegetable ω-3 Fatty Acid, on Cardiovascular Disease and Cognition

Given the evidence of the health benefits of plant-based diets and long-chain n-3 (ω-3) fatty acids, there is keen interest in better understanding the role of α-linolenic acid (ALA), a plant-derived n-3 fatty acid, on cardiometabolic diseases and cognition. There is increasing evidence for ALA largely based on its major food sources (i.e., walnuts and flaxseed); however, this lags behind our understanding of long-chain n-3 fatty acids. Meta-analyses of observational studies have shown that increasing dietary ALA is associated with a 10% lower risk of total cardiovascular disease and a 20% reduced risk of fatal coronary heart disease. Three randomized controlled trials (RCTs) [AlphaOmega trial, Prevención con Dieta Mediterránea (PREDIMED) trial, and Lyon Diet Heart Study] all showed benefits of diets high in ALA on cardiovascular-related outcomes, but the AlphaOmega trial, designed to specifically evaluate ALA effects, only showed a trend for benefit. RCTs have shown that dietary ALA reduced total cholesterol, LDL cholesterol, triglycerides, and blood pressure, and epidemiologic studies and some trials also have shown an anti-inflammatory effect of ALA, which collectively account for, in part, the cardiovascular benefits of ALA. A meta-analysis reported a trend toward diabetes risk reduction with both dietary and biomarker ALA. For metabolic syndrome and obesity, the evidence for ALA benefits is inconclusive. The role of ALA in cognition is in the early stages but shows promising evidence of counteracting cognitive impairment. Much has been learned about the health benefits of ALA and with additional research we will be better positioned to make strong evidence-based dietary recommendations for the reduction of many chronic diseases.

α-Linolenic Acid and Risk of Heart Failure: A Meta-Analysis

Background: The α-linolenic acid is a plant origin n-3 fatty acid that may reduce the risk of cardiovascular disease. However, the effect of α-linolenic acid (ALA) on the risk of heart failure (HF) remains unclear. In this meta-analysis, we aimed to determine the role of ALA in the risk of incident HF.

Methods: Electronic databases were searched for studies up to August 10, 2021. Studies were included for meta-analysis if the adjusted risk of HF in different dietary intake or circulating levels of ALA was reported. We used the random-effects model to calculate the estimated hazard ratios (HRs) and 95% CI for higher ALA.

Results: A total of 6 studies (7 cohorts) comprising 135,270 participants were included for meta-analysis. After a median follow-up duration of 10 years, 5,905 cases of HF were recorded. No significant heterogeneity was observed among all the included studies. Random-effects model analyses showed that there was no significant association between ALA and the risk of incident HF, either assessed as quintiles (highest quintile vs. lowest quintile: HR = 0.95, 95% CI = 0.86–1.06) or per 1 SD increment (HR = 0.99, 95% CI = 0.95–1.01). Furthermore, we did not observe any association between ALA and the risk of HF in subgroup analyses performed according to age, sex, follow-up duration, and measuring method of ALA.

Conclusions: We found no association between ALA and the risk of incident HF, suggesting that ALA might not be effective in the prevention of HF.

Effect of dietary chia supplementation on glucose metabolism and adipose tissue function markers in non-alcoholic fatty liver disease subjects

Introduction

Background: adipose tissue dysfunction is a key factor for diabetes and non-alcoholic fatty liver disease (NAFLD) development. Chia (Salvia hispanica) is an abundant source of omega-3 fatty acids, antioxidants, and fiber which could improve adipose tissue functionality. Aim: to analyze the effect of an isocaloric chia-supplemented diet on glucose metabolism, adipose tissue inflammation, and endothelial function markers in patients with NAFLD and early stages of diabetes. Methods: in 32 patients with previous NAFLD diagnosis, without known diabetes, the effect of a diet supplemented with ground chia (25 g/day/8 weeks) was evaluated. Visceral (VAF) and liver fat, plasma lipids, fatty acids, and cytokine profiles, oral glucose tolerance test (OGTT), insulinogenic index (IGI30), insulin disposition index (DIO), and endothelial progenitor cells (EPC) were analyzed. Before and after eight weeks of diet supplementation. Results: chia supplementation promoted increases in plasma alpha-linolenic acid (75 %) and fiber consumption (55 %), and a higher number of EPC (+126 %). Basal OGTT showed that nine patients had normal OGTT, 17 pre-diabetes, and six newly diagnosed diabetes. In patients with diabetes, chia favored a healthier adipose tissue (VAF -7 %, NAFLD -100 %, adiponectin +47 %, resistin -30 %, IL-6 -44 %, IL-1β -22 %) and upturn glucose metabolism through the improvement of beta-cell function (IGI30 +50 %, DIO +66 %). Conclusions: dietary supplementation with 25 g/day of ground chia may promote a healthier adipose tissue and improve pancreatic β-cell and endothelial function. Among patients with early metabolic abnormalities, phytochemical properties of chia may retard diabetes progression and advanced stages of liver damage.

Effect of n-3 polyunsaturated fatty acids on ischemic heart disease and cardiometabolic risk factors: a two-sample Mendelian randomization study

BACKGROUND

The cardioprotective ability of n-3 polyunsaturated fatty acids (PUFAs) is controversial. Most studies suggest a specific role for PUFAs in cardioprotection from ischemic heart disease (IHD). However, few studies have used genetic biomarkers of n-3 PUFAs to examine their potential relationships with IHD. This study aimed to use Mendelian randomization to evaluate whether genetically-predicted n-3 PUFAs affect IHD and cardiometabolic risk factors (CRFs).

METHODS

Genetic variants strongly (p < 5 × 10^-8) and independently (r² > 0.1) associated with n-3 PUFAs were derived from the CHARGE Consortium (including 8,866 subjects of European ancestry) and were used as instrumental variables (IVs) for evaluating the effect of n-3 PUFAs, including α-linolenic acid (ALA), docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). Data on the associations between the IVs and IHD, myocardial infarction, and CRFs (including diabetes, lipids, blood pressure, body mass index, and waist-to-hip ratio (WHR)) were obtained from the UK Biobank SOFT CAD GWAS with the CARDIoGRAMplusC4D 1000 Genomes-based GWAS (113,937 IHD cases and 339,115 controls), the Myocardial Infarction Genetics and CARDIoGRAM Exome consortia (42,335 MI cases and 78,240 controls), the DIAbetes Genetics Replication And Meta-analysis consortium (26,676 diabetes mellitus cases and 132,532 controls), the Global Lipids Genetics Consortium (n = 196,475), the International Consortium for Blood Pressure (n = 69,395), and the meta-analysis of GWAS for body fat distribution in the UK Biobank and Genetic Investigation of Anthropometric Traits (n = 694,649).

RESULTS

Genetically-predicted higher ALA was associated with lower risk of IHD, type 2 diabetes (T2D), and lower serum lipids. The effect size per 0.05-unit increase (about 1 standard deviation) in plasma ALA level) was - 1.173 (95% confidence interval - 2.214 to - 0.133) for IHD. DPA and EPA had no association with IHD but were associated with a higher risk of T2D, higher levels of lipids or WHR. DHA had no association with IHD or CRFs.

CONCLUSIONS

Our study suggests a benefit of ALA for IHD and its main risk factors. DHA, DPA, and EPA had no association with IHD but were partly associated with increasing cardiometabolic risk factors.

The review of alpha-linolenic acid: Sources, metabolism, and pharmacology

α-linolenic acid (ALA, 18:3n-3) is a carboxylic acid composed of 18 carbon atoms and three cis double bonds, and is an essential fatty acid indispensable to the human body. This study aims to systematically review related studies on the dietary sources, metabolism, and pharmacological effects of ALA. Information on ALA was collected from the internet database PubMed, Elsevier, ResearchGate, Web of Science, Wiley Online Library, and Europe PMC using a combination of keywords including "pharmacology," "metabolism," "sources." The following findings are mainly contained. (a) ALA can only be ingested from food and then converted into eicosapentaenoic acid and docosahexaenoic acid in the body. (b) This conversion process is relatively limited and affected by many factors such as dose, gender, and disease. (c) Pharmacological research shows that ALA has the anti-metabolic syndrome, anticancer, antiinflammatory, anti-oxidant, anti-obesity, neuroprotection, and regulation of the intestinal flora properties. (d) There are the most studies that prove ALA has anti-metabolic syndrome effects, including experimental studies and clinical trials. (e) The therapeutic effect of ALA will be affected by the dosage. In short, ALA is expected to treat many diseases, but further high quality studies are needed to firmly establish the clinical efficacy of ALA.

Longer-term soy nut consumption improves cerebral blood flow and psychomotor speed: results of a randomized, controlled crossover trial in older men and women

BACKGROUND

Effects of soy foods on cerebral blood flow (CBF)-a marker of cerebrovascular function-may contribute to the beneficial effects of plant-based diets on cognitive performance.

OBJECTIVES

We aimed to investigate longer-term effects of soy nut consumption on CBF in older adults. Changes in 3 different domains of cognitive performance were also studied.

METHODS

Twenty-three healthy participants (age: 60-70 y; BMI: 20-30 kg/m2) participated in a randomized, controlled, single-blinded crossover trial with an intervention (67 g/d of soy nuts providing ∼25.5 g protein and 174 mg isoflavones) and control period (no nuts) of 16 wk, separated by an 8-wk washout period. Adults followed the Dutch food-based dietary guidelines. At the end of each period, CBF was assessed with arterial spin labeling MRI. Psychomotor speed, executive function, and memory were assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS

No serious adverse events were reported, and soy nut intake was well tolerated. Body weights remained stable during the study. Serum isoflavone concentrations increased (daidzein mean difference ± SD: 128 ± 113 ng/mL, P < 0.001; genistein: 454 ± 256 ng/mL, P < 0.001), indicating excellent compliance. Regional CBF increased in 4 brain clusters located in the left occipital and temporal lobes (mean ± SD increase: 11.1 ± 12.4 mL · 100 g-1 · min-1, volume: 11,296 mm3, P < 0.001), bilateral occipital lobe (12.1 ± 15.0 mL · 100 g-1 · min-1, volume: 2632 mm3, P = 0.002), right occipital and parietal lobes (12.7 ± 14.3 mL · 100 g-1 · min-1, volume: 2280 mm3, P = 0.005), and left frontal lobe (12.4 ± 14.5 mL · 100 g-1 · min-1, volume: 2120 mm3, P = 0.009) which is part of the ventral network. These 4 regions are involved in psychomotor speed performance, which improved as the movement time reduced by (mean ± SD) 20 ± 37 ms (P = 0.005). Executive function and memory did not change.

CONCLUSIONS

Longer-term soy nut consumption may improve cerebrovascular function of older adults, because regional CBF increased. Effects may underlie observed improvements in psychomotor speed.This trial was registered at clinicaltrials.gov as NCT03627637.

Beneficial effects of dietary supplementation with olive oil, oleic acid, or hydroxytyrosol in metabolic syndrome: Systematic review and meta-analysis

BACKGROUND AND AIMS

Olive oil and components might have a beneficial effect on Metabolic Syndrome (MetS). The aim of this review and meta-analysis was to assess whether those effects are related to hydroxytyrosol or oleic acid contents, or the combination of them as olive oil, and how powerful is this effect.

METHODS

A systematic literature search was performed in MEDLINE via Pubmed, Web of Science (WOS) core collection, and Virtual Health Library (VHL) via LILACS and IBECS (Spain). MeSH terms used were "obesity", "body weight", "body mass index", "adipose tissue", "lipid metabolism", "LDL", "HDL", "VLDL", "insulin resistance", "glucose", "insulin", "hypertension", "arterial pressure", "olive oil", "oleic acid", and other (non-MeSH) terms: "total antioxidant capacity", "total antioxidant status", "hydroxytyrosol" (PROSPERO ID: CRD42021247614). Results of the included studies were meta-analyzed with the RevMan 5.3 program, assuming a random effects model.

RESULTS

76 articles (67 different trials) were identified. Hydroxytyrosol had no effect on MetS [combined standardized mean differences (SMD) = 0.01 (CI 95%: [-0.23, 0.25], I² = 83%; p = 0.920)]. Oleic acid had no significant beneficial effect on MetS [SMD = 0.03 (CI 95%: [-0.01, 0.07], I² = 0%); p = 0.150], but it improved lipid profile [SMD = 0.06 (CI 95%: [-0.00, 0.12], I² = 0%); p = 0. 050]. Olive oil had no effect on MetS [SMD = -0.01 (CI 95%: [-0.05, 0.03]), I² = 55%; p = 0.550)]. The supplementation with hydroxytyrosol, oleic acid or olive oil showed a beneficial effect on antioxidant capacity related to components of MetS [SMD = 0.31 (CI 95%: [-0.34, 0.95], I² = 81%)]; p = 0.35).

CONCLUSION

Most articles compared olive oil and oleic acid with other strategies specially designed for MetS management. Our findings suggest that olive oil or oleic acid consumption are as good as the other strategies to manage MetS.

Beyond Fish Oil Supplementation: The Effects of Alternative Plant Sources of Omega-3 Polyunsaturated Fatty Acids upon Lipid Indexes and Cardiometabolic Biomarkers-An Overview

Cardiovascular diseases remain a global challenge, and lipid-associated biomarkers can predict cardiovascular events. Extensive research on cardiovascular benefits of omega-3 polyunsaturated fatty acids (n3-PUFAs) is geared towards fish oil supplementation and fish-rich diets. Nevertheless, vegetarianism and veganism are becoming more popular across all segments of society, due to reasons as varied as personal, ethical and religious values, individual preferences and environment-related principles, amongst others. Due to the essentiality of PUFAs, plant sources of n3-PUFAs warrant further consideration. In this review, we have critically appraised the efficacy of plant-derived n3-PUFAs from foodstuffs and supplements upon lipid profile and selected cardiometabolic markers. Walnuts and flaxseed are the most common plant sources of n3-PUFAs, mainly alpha-linolenic acid (ALA), and feature the strongest scientific rationale for applicability into clinical practice. Furthermore, walnuts and flaxseed are sources of fibre, potassium, magnesium, and non-essential substances, including polyphenols and sterols, which in conjunction are known to ameliorate cardiovascular metabolism. ALA levels in rapeseed and soybean oils are only slight when compared to flaxseed oil. Spirulina and Chlorella, biomasses of cyanobacteria and green algae, are important sources of n3-PUFAs; however, their benefits upon cardiometabolic markers are plausibly driven by their antioxidant potential combined with their n3-PUFA content. In humans, ALA is not sufficiently bioconverted into eicosapentaenoic and docosahexaenoic acids. However, evidence suggests that plant sources of ALA are associated with favourable cardiometabolic status. ALA supplementation, or increased consumption of ALA-rich foodstuffs, combined with reduced omega-6 (n6) PUFAs intake, could improve the n3/n6 ratio and improve cardiometabolic and lipid profile.

Effects of tree nut and groundnut consumption compared with those of l-arginine supplementation on fasting and postprandial flow-mediated vasodilation: Meta-analysis of human randomized controlled trials

INTRODUCTION

l-arginine supplementation may improve vascular endothelial function. As tree nuts and groundnuts are a source of the amino acid l-arginine, we performed a meta-analysis of human randomized controlled trials (RCTs) to compare effects of tree nut and groundnut consumption with those of l-arginine supplementation on fasting and postprandial endothelial function as assessed by flow-mediated vasodilation of the brachial artery (FMD).

METHODS

Summary estimates of weighted mean differences (WMDs) in FMD and 95% confidence intervals (CIs) were calculated using random-effect meta-analyses.

RESULTS

A total of thirteen RCTs focusing on tree nut and groundnut consumption and nineteen RCTs investigating effects of l-arginine supplementation were included. Longer-term consumption of tree nuts and groundnuts increased fasting FMD by 1.09 %-point (PP) (95% CI: 0.49, 1.69, P < 0.001; I²: 76.7%, P < 0.001), while l-arginine supplementation (daily range: 3-21 g) increased fasting FMD by 0.53 PP (95% CI: 0.12, 0.93; P = 0.012; I²: 91.6%, P < 0.001). Effects between treatments were not statistically different (P = 0.31). Tree nut and groundnut consumption did not affect postprandial FMD responses (1.25 PP, 95% CI: -0.31, 2.81, P = 0.12; I²: 91.4%, P < 0.001), whereas l-arginine supplementation (range: 3-15 g) improved FMD during the postprandial phase by 2.02 PP (95% CI: 0.92, 3.13, P < 0.001; I²: 99.1%, P < 0.001). However, treatment effects did not differ significantly (P = 0.60). Overall, these results derive from high-quality evidence.

CONCLUSION

Longer-term consumption of tree nuts and groundnuts, as well as l-arginine supplementation did improve fasting endothelial function, as assessed by FMD. However, the positive effects of tree nuts and groundnuts could not be fully explained by the amount of l-arginine in these nuts. Only l-arginine supplementation did improve postprandial FMD, but effects were not different from those of tree nuts and groundnuts. Future studies should focus on the identifications of the bioactive nutrients in tree nuts and groundnuts and mechanistic pathways behind differences in postprandial and longer-term fasting changes in FMD.