Effects of Supplementation with the Fat-Soluble Vitamins E and D on Fasting Flow-Mediated Vasodilation in Adults: A Meta-Analysis of Randomized Controlled Trials

Abstract

The effects of fat-soluble vitamin supplementation on cardiovascular disease (CVD) risk are not clear. Therefore, we performed a meta-analysis to quantify effects of fat-soluble vitamin supplements on fasting flow-mediated vasodilation (FMD) of the brachial artery, a validated marker to assess CVD risk. Randomized placebo-controlled trials (RCTs) were identified by a systematic search till July 2014. Seven RCTs studying the effects of vitamin E supplements (range: 300 to 1800 IU per day) and nine RCTs examining the effects of vitamin D supplements, that involved, respectively, 303 and 658 adults, were included. No studies with carotenoid or vitamin K supplements were found. Vitamin E supplementation increased FMD vs. control by 2.42% (95% CI: 0.46% to 4.37%; p = 0.015). No effects of vitamin D supplementation were found (0.15%; 95% CI: −0.21% to 0.51%; p = 0.41). These effects did not depend on subject characteristics, treatment characteristics or technical aspects of the FMD measurement. However, no dose-response relationship was evident for vitamin E, statistical significance depended on one study, while the levels of supplement were far above recommended intakes. The current meta-analysis, therefore, does not provide unambiguous evidence to support the use of fat-soluble vitamin supplements to improve fasting FMD in adults.

Nutraceutical Approach to Non-Alcoholic Fatty Liver Disease (NAFLD): The Available Clinical Evidence

“…A recent meta-analysis of 16 controlled clinical trials has shown that the long-term administration of low-dose Vitamin E and alone (not in association with other antioxidant vitamins) is able to reduce the risk of myocardial infarction (RR 0.82; 95%CI, 0.70–0.96; p = 0.01) [ 34 ]. Furthermore, another meta-analysis involving 303 subjects enrolled in seven studies showed that vitamin E supplementation is associated with a 2.5% increase in flow-mediated vasodilatation [ 35 ]. This result is important since it has been estimated that a 1% improvement in flow-mediated vasodilatation would be associated with a 12% reduction in cardiovascular risk [ 36 ].…”

Acute Dietary Nitrate Supplementation Improves Flow Mediated Dilatation of the Superficial Femoral Artery in Healthy Older Males

“…A decrease in reactive oxygen species may have facilitated an increase in FMD, the magnitude of which might reflect eNOS-derived NO [32], rather than NO produced via the NO 3 − –NO 2 − –NO pathway. This theory is supported by evidence of improved FMD following antioxidant treatments, such as vitamin E [78,79] and vitamin B3 (niacin) [80]. Dietary NO 3 − from vegetables such as beetroot may reduce oxidative stress more than individual vitamins or minerals because it may simultaneously restore redox imbalance and enhance NO generation [72].…”

Systemowa równowaga antyoksyacyjna u pacjentów bez klinicznej manifestacji miażdżycy

“…Various attempts were made by the researchers to explain these contradictory outcomes as the effect of known and unknown drug-drug interactions or unexpected adverse drug reactions [30], because antioxidant vitamins in those RCTs were added to each patient's usual dietary regimen. One important factor in explaining the contrary findings of the effect of vitamin E on the course of vascular and neoplasmatic diseases might also be the different vitamin E doses given in respective investigations, which ranged from 300 to 1800 IU per day [42], and the absence of gamma-tocopherol in traditional preparations [43]. This member of tocopherol family exerts stronger cardioprotective, antioxidant and anti-inflammatory effects than alpha-tocopherol [43].…”