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Association Between Omega-3 Fatty Acid Intake and Dyslipidemia: A Continuous Dose-Response Meta-Analysis of Randomized Controlled Trials.
Wang, T, Zhang, X, Zhou, N, Shen, Y, Li, B, Chen, BE, Li, X
Journal of the American Heart Association. 2023;12(11):e029512
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Dyslipidaemia is considered to be a risk factor for cardiovascular disease (CVD) and the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are thought to confer benefits for both dyslipidaemia and CVD, although results from clinical trials and meta-analyses (studies pooling data from smaller studies to increase statistical power) are mixed. The aim of this meta-analysis, using a particular statistical method, was to evaluate whether dose-response relationships may be non-linear. This meta-analysis included 90 randomised controlled trials with 72,598 participants overall. Lipids evaluated were triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and non-HDL cholesterol. A near linear relationship was seen between intake of combined EPA and DHA and a decrease in TG and non-HDL, both overall and for the subgroups of patients with and without hyperlipidaemia and overweight. For LDL and HDL, J-shaped relationships were seen, with an increase followed by a decrease with increasing EPA + DHA intake, both overall and in the subgroups with and without hyperlipidaemia. The authors also pooled data from studies which used the red blood cell omega index (a measure of omega-3 status) and found that with increasing omega-3 status, TG and non-HDL declined whilst HDL increased in a near linear fashion, whilst there was still a J-shaped curve for LDL. The authors consider that a medium dose of EPA + DHA may be needed for the management of dyslipidaemia, and a high dose for people at high risk of developing CVD.
Abstract
Background Previous results provide supportive but not conclusive evidence for the use of omega-3 fatty acids to reduce blood lipids and prevent events of atherosclerotic cardiovascular disease, but the strength and shape of dose-response relationships remain elusive. Methods and Results This study included 90 randomized controlled trials, reported an overall sample size of 72 598 participants, and examined the association between omega-3 fatty acid (docosahexaenoic acid, eicosapentaenoic acid, or both) intake and blood lipid changes. Random-effects 1-stage cubic spline regression models were used to study the mean dose-response association between daily omega-3 fatty acid intake and changes in blood lipids. Nonlinear associations were found in general and in most subgroups, depicted as J-shaped dose-response curves for low-/high-density lipoprotein cholesterol. However, we found evidence of an approximately linear dose-response relationship for triglyceride and non-high-density lipoprotein cholesterol among the general population and more evidently in populations with hyperlipidemia and overweight/obesity who were given medium to high doses (>2 g/d). Conclusions This dose-response meta-analysis demonstrates that combined intake of omega-3 fatty acids near linearly lowers triglyceride and non-high-density lipoprotein cholesterol. Triglyceride-lowering effects might provide supportive evidence for omega-3 fatty acid intake to prevent cardiovascular events.
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Vitamin B12 Status Upon Short-Term Intervention with a Vegan Diet-A Randomized Controlled Trial in Healthy Participants.
Lederer, AK, Hannibal, L, Hettich, M, Behringer, S, Spiekerkoetter, U, Steinborn, C, Gründemann, C, Zimmermann-Klemd, AM, Müller, A, Simmet, T, et al
Nutrients. 2019;11(11)
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Veganism is growing in western societies and with it comes an increased risk of vitamin B12 deficiency which is principally found in animal products. Vitamin B12 is essential for multiple biological functions including DNA synthesis, digestive function and detoxification processes. It can take 2-5 years to exhaust natural stores of B12 within the body so deficiency risk is considered safe. This 2017 randomised control trial compared vitamin B12 status in 53 healthy omnivore subjects with 26 participants following an unsupplemented vegan diet for 4 weeks and the remaining 27 participants a meat-rich diet. The aim of the study was to answer two questions; (a) Do vitamin B12 markers respond to short-term dietary intervention with a meat-rich or a plant-based diet? and (b) Do meat-rich and vegan diets have an impact on plasma markers of inflammation and cardiovascular disease? Blood and urine samples were taken before and after the 4-week dietary protocol to also measure vitamin D status, Folate and Homocysteine levels as a marker for inflammation. The serum vitamin B12 levels (indicative of dietary B12) dropped significantly from 362.9 +/- 110.9 ng/mL to 296.1 +/- 94.1 ng/mL in the Vegan Diet group (p < 0.001) and remained stable in the Meat Diet group. Other markers measuring cellular B12 metabolism did not significantly vary. The short-term nature of the trial demonstrated rapid decrease in holo-TC, the bioactive form of vitamin B12 in plasma. The other blood and urinary markers demonstrated benefits to plant-based eating including reduced cholesterol intake and adequate profiles of nutrient and micronutrient status.
Abstract
Vegans are at an increased risk for certain micronutrient deficiencies, foremost of vitamin B12. Little is known about the short-term effects of dietary change to plant-based nutrition on vitamin B12 metabolism. Systemic biomarkers of vitamin B12 status, namely, serum vitamin B12 and holotranscobalamin, may respond quickly to a reduced intake of vitamin B12. To test this hypothesis, 53 healthy omnivore subjects were randomized to a controlled unsupplemented vegan diet (VD, n = 26) or meat-rich diet (MD, n = 27) for 4 weeks. Vitamin B12 status was examined by measurement of serum vitamin B12, holotranscobalamin (holo-TC), methylmalonic acid (MMA) and total plasma homocysteine (tHcy). Holo-TC decreased significantly in the VD compared to the MD group after four weeks of intervention, whereas metabolites MMA and tHcy were unaffected. Body weight remained stable in both groups. VD intervention led to a significant reduction of cholesterol intake, and adequate profiles of nutrient and micronutrient status. Lower intake of vitamin B12 was observed in VD, which was mirrored by a lower concentration of serum vitamin B12 and reduced holo-TC after 4 weeks. Plasma holo-TC may be a fast-responding biomarker to monitor adequate supply of vitamin B12 in plant-based individuals.
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Garlic: a review of potential therapeutic effects.
Bayan, L, Koulivand, PH, Gorji, A
Avicenna journal of phytomedicine. 2014;4(1):1-14
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Garlic has been used throughout history, across many different cultures, for its therapeutic effects in supporting cardiovascular diseases, blood glucose dysregulation, and for anti-tumour and anti-microbial properties. Garlic (Allium sativum L.) use is thought to date as far back as the sixth century BC and has subsequently popped up in ancient Greek, Egyptian, Indian and Chinese medicines. This 2013 review looked at evidence to support the therapeutic effects of garlic, and its principal bioactive compound allicin. The authors reviewed clinical studies from the 1960’s through to 2012 and garlic was shown to reduce systolic blood pressure, prevent atherosclerosis, reduce serum cholesterol, LDL and triglycerides in doses ranging from 200 - 960 mg daily. The allylsulfide derivatives in garlic are attributed to its anti-cancer properties with studies showing garlic has a variety of anti-tumour effects, including tumour cell growth inhibition and chemopreventive effects. Garlic has also been shown to have therapeutic effect at reducing fasting blood glucose levels in diabetic patients. Garlic’s antimicrobial uses date back to Louis Pasteur when it was shown to be effective against multiple bacterial strains including Salmonella, Escherichia coli, Klebsiella, and Helicobacter as it is capable of inhibiting sulfhydryl enzymes. Garlic also displays some anti-fungal and anti-viral properties however there are few studies which explore these mechanisms. Anecdotal evidence suggests it reduces the duration of the common cold and aids respiration. The review offers little evidence of dosing or therapeutic efficacy.
Abstract
Throughout history, many different cultures have recognized the potential use of garlic for prevention and treatment of different diseases. Recent studies support the effects of garlic and its extracts in a wide range of applications. These studies raised the possibility of revival of garlic therapeutic values in different diseases. Different compounds in garlic are thought to reduce the risk for cardiovascular diseases, have anti-tumor and anti-microbial effects, and show benefit on high blood glucose concentration. However, the exact mechanism of all ingredients and their long-term effects are not fully understood. Further studies are needed to elucidate the pathophysiological mechanisms of action of garlic as well as its efficacy and safety in treatment of various diseases.