Resveratrol is a naturally occurring compound known as a polyphenol which is found in plants. In terms of food sources, it is predominantly found in grapes, wine, grape juice, peanuts, cocoa, and berries of Vaccinium species, including blueberries, bilberries, and cranberries. There is no established Recommended Daily Amount (RDA) for Resveratrol.
Polyphenols are thought to exert a number of health benefits which enhance health and prolong lifespan. It is known to protect against cardiovascular diseases and cancers as well as to promote antiaging effects and reduce insulin sensitivity, glucose tolerance and lipid profiles. It has also been shown to exert beneficial effects in disorders of the nervous system.
Research suggests that resveratrol modulates mechanisms of debilitating neurological disorders, such as strokes, ischemia, Huntington’s disease and Alzheimer’s disease (AD). In AD the cause is thought to be as a result of progressive accumulation and deposition of central nervous system (CNS) amyloid (an abnormal protein) via ageing (1). In animal studies, calorie restriction has been shown to prevent ageing diseases including AD (2). A randomized, double-blind, placebo-controlled trial of resveratrol for individuals with mild-to-moderate AD showed that resveratrol is detectable in cerebrospinal fluid, is safe and well tolerated. It was also shown to preserve blood-brain barrier integrity and modulate the CNS immune response in the same AD patients (3). A further retrospective study involving Alzheimer’s disease subjects showed supplementation with up to 1g daily over a period of 52 weeks modulated neuro-inflammation and induced adaptive immunity in Alzheimer’s disease (4). In a mouse study, resveratrol was found to protect the degeneration of brain cells, suggesting that resveratrol may possess therapeutic value to neuronal degeneration (5).
Cardiovascular Health- Resveratrol has been found to exert a number of protective effects on the cardiovascular system. In vitro studies resveratrol was shown to reduce both platelet activation and aggregation (clumping of platelets) (6), (7), (8). Oral doses of resveratrol have also been shown in animal studies to decrease the risk of thrombosis (blood clots in the veins) and atherosclerosis (build- up of plaques in the arteries) (9), (10). Other protective effects of resveratrol according to in vitro studies include the reduction of cardiac hypertrophy (thickening of the heart muscle) and the lowering of blood pressure, as well as limiting the size of dead tissue as a result of lack of blood supply in rats post-heart-attack (11).
Polycystic Ovary Syndrome– The effects of resveratrol have also been observed in Poly Cystic Ovary Syndrome where it was shown to exert hormonal and metabolic effects. In a randomized, double-blind, placebo-controlled trial involving 34 subjects resveratrol was shown to significantly reduce ovarian and adrenal hormones as a result of improved insulin sensitivity and a decline of insulin levels (12).
Cognitive Function– Resveratrol has also been shown to enhance both blood vessel function and cognition in post-menopausal women. Eighty post-menopausal women aged 45-85 years were randomised to take trans-resveratrol or placebo for 14 weeks. At the end of the trial, significant improvements were observed in the performance of cognitive tasks relating to verbal memory and overall cognitive performance in those taking resveratrol compared to the placebo group, suggesting that regular consumption of resveratrol may reduce the heightened risk of cognitive decline in postmenopausal women (13).
Breast cancer- Furthermore, resveratrol supplementation has been shown to have favourable effects on oestrogen metabolism and sex steroid hormone binding globulin (SHBG) in obese and postmenopausal women. Since oestrogen metabolism and SHBG are risk factors in breast cancer and both have been shown to be modulated by resveratrol, this early research suggests resveratrol may play a role in the prevention of the disease (14).
Reducing the risk of heart disease and stroke- Resveratrol inhibits the formation of blood clots and cholesterol which may help to prevent heart disease and strokes, making it a potentially useful supplement for those with high cholesterol and those with high blood pressure due to its blood pressure lowering effects.
Cognitive function- Resveratrol has been shown to help improve overall cognition, especially in postmenopausal women. A supplement may, therefore, provide benefit for women looking for cognitive support during or following menopause.
In terms of safety, resveratrol has not been shown to cause any adverse effects or toxicity in humans. In a study on rats, daily oral administration of trans-resveratrol at doses up to 700 mg/kg of body weight for 90 days resulted in no apparent adverse effects. No adverse effects have been observed in animal studies at doses of 200mg/kg and 600mg/kg. Furthermore, a trial evaluating the safety of oral trans-resveratrol in 10 subjects found that a single dose of 5,000 mg resulted in no serious adverse effects. However, mild-to-moderate gastrointestinal side effects including nausea, abdominal pain, flatulence, and diarrhoea, have been reported in participants who consume more than 1,000 mg/day of resveratrol for up to 29 consecutive days. There is no established Tolerable Upper Intake Level for Resveratrol.