Resveratrol is an antioxidant polyphenol that is credited with providing many of the health benefits of black grapes and red wine. Resveratrol is currently the subject of intense research into its anti-aging benefits and protective action against age-related diseases such as cancer. At the end of this post is a list of foods that are naturally high in resveratrol to help boost your intakes naturally.
Resveratrol health benefits
Resveratrol was originally discovered in the flowering white hellebore and has now been identified in over 70 different plants. Plants increase their production of resveratrol in response to stress and injury, to protect them against fungal infection and ultraviolet radiation – it’s one of the reasons why grapes don’t burn under intense sunshine, for example.
Resveratrol is classed as a stilbene polyphenol. For a long time, it was the most powerful known activator of the SIRT1 gene, which regulates cell metabolism and the rate at which fat is burned in liver, fat and muscle cells. It is also associated with longevity.
Resveratrol has extended the lifespan of many organisms, from yeast and round worms to fruit flies, honeybees, turquoise killifish and mice by 30% to 70%. Whether or not resveratrol has the same effect in humans is yet to be proven.
Laboratory studies in which human cells were exposed to low levels of resveratrol, similar to those occurring after eating resveratrol rich foods (nanomolar concentrations) or taking supplements (micromolar concentrations), show promise.
Resveratrol has beneficial effects in cell cultures which slow general age-related decline, and to improve metabolic abnormalities associated with diabetes, inflammatory diseases, fatty liver, cataracts, osteoporosis, heart attack, stroke, dementia and cancer.
Resveratrol and heart disease
Resveratrol is one of the compounds thought to account for the so-called French Paradox. At a time when dietary saturated fats were believed to contribute to heart disease, researchers were astounded to find that France, with its high intake of fatty foods, had lower rates of fatal heart attacks than those in the US and the UK.
Red wine consumption was identified as the possible protective factor and data from 17 countries, in which both wine and dietary fat consumption were known, seemed to confirm the link. As the majority (72%) of French wine production was red or rose rather than white, the idea that something in red wine was protective soon caught on with both the alcohol and the polyphenols (especially resveratrol) thought to provide the greatest level of protection.
In studies involving people at risk of heart disease, taking resveratrol supplements was found to significantly lower total cholesterol (by 0.19 mmol/L, systolic blood pressure (by 2.26 mmHg) and fasting glucose levels (by 0.22 mmol/L). The most significant reductions were seen in people taking at least 300 mg resveratrol per day.
Resveratrol and blood pressure
Six studies involving 247 people with high blood pressure found that higher-doses of resveratrol (at least 150 mg per day) significantly reduced systolic blood pressure (the upper reading) by 11.90 mmHg compared with placebo. There were no significant changes in diastolic blood pressure (lower figure) and lower doses of resveratrol did not show a significant effect.
Resveratrol and diabetes
The results from 11 studies involving 388 people found statistically significant positive effects from taking resveratrol supplements, compared with placebo. Improvements occurred in fasting glucose, insulin, glycated hemoglobin (HbA1c) and insulin resistance in those with type 2 diabetes. No significant effects of resveratrol on glycemic measures were seen in nondiabetic people.
No serious side effects occurred, and those that were reported were no different from placebo.
Resveratrol has also been found to improve the elasticity of arteries to reduce arterial stiffness and reduce oxidative stress in people with type 2 diabetes. The researchers suggested that resveratrol may be beneficial in preventing the development of atherosclerosis but larger studies are needed to confirm this.
Resveratrol and memory
Resveratrol has been found to enhance memory in older adults. In a study involving 46 healthy (but overweight) people aged 50 to 75 years, half took resveratrol 200mg per day for 26 weeks, and half took inactive placebo. Memory tasks and brain imaging, carried out before and after, showed significant improvements in those taking the resveratrol supplements. Their word retention over 30 minutes significantly improved, and this was linked with changes in volume, structure and connectivity within the hippocampus of the brain, which is linked with memory and learning.
Other studies involving post-menopausal women show that taking resveratrol improves cerebral blood flow, responsiveness of cerebral blood vessels and cognitive tests showed improve ability to think straight. Even eating grapes, which provide resveratrol, has been found to slow cognitive decline in people with early stages of Alzheimer’s disease.
This is a supplement I definitely plan to start taking!
Resveratrol and weight loss
By switching on genes which stimulate fat burning and increase the amount of energy lost as heat (thermogenesis), resveratrol allows white fat to act like brown fat, and provide a weight loss boost.
Laboratory studies using human fat cells show that resveratrol can suppress the formation of new fat cells, reduce the accumulation of fat in white fat cells and enhance fat burning.
The weight loss potential of resveratrol was compared with that of orlistat (a fat blocking drug) and placebo in a study involving 161 obese people. They were asked to follow an energy-reduced diet that provided 500 fewer calories than their usual diet and were randomised to take either placebo, resveratrol, orlistat, or resveratrol plus orlistat for 6 months.
Of the initial 161 people, only 84 completed the study. A significant weight loss of -6.82 kg occurred in those taking resveratrol plus orlistat compared with -6.02 kg with orlistat alone, -4.68 kg with resveratrol alone and -3.50 kg in the placebo group. Significant decreases in waist circumference, fat mass, triglycerides, Body mass index (BMI) also occurred.
Resveratrol and cancer
Resveratrol has shown beneficial effects against some cancer cells (colon, prostate, breast, skin, liver, brain and lung) in laboratory studies, with negligible toxicity against normal cells. Resveratrol appears to stop the over-proliferation of abnormal cells through several different mechanisms, including SIRT1 activation. It is too early to say whether or not resveratrol supplements protect against cancer however.
Resveratrol and longevity
A fascinating study assessed the resveratrol intakes of almost 800 older people, aged 65 or over, in the Chianti region of Italy which is famed for its rich, red wine. Resveratrol intakes were assessed using a food frequency questionnaire, and the quantity of resveratrol break-down products was measured in their urine.
Over the following 9 years, dietary intakes of alcohol and resveratrol were re-assessed every three years and, over this time-frame, just over a third of participants died. Unexpectedly, no significant differences in survival were seen between those with a low dietary resveratrol intake and those with a high resveratrol intake.
This may seem like bad news, but researchers quickly urged us to keep the faith and not ‘throw out the resveratrol with the bath water’ for a number of reasons:
- Many other factors, apart from just resveratrol, play a role in survival and mortality.
- Those with the highest resveratrol intakes obtained these levels from drinking copious amounts of red wine, excess of which is harmful to health.
- Those with the highest resveratrol intakes drank, on average, thirteen times more alcohol per day than those with the lowest intakes.
- Within wine, resveratrol is found in two forms: cis and trans, which are mirror images of each other, like left-hand and right-hand gloves. Cis-resveratrol is present in red wine but not in grapes as it is formed by yeast during fermentation. Only the trans-resveratrol form is biologically active, so many of the resveratrol metabolites measured in the urine of wine drinkers reflected intakes of this inactive form of resveratrol.
Most important of all, even those assessed as having a ‘high’ dietary intake of resveratrol actually had relatively low intakes, as no supplements were used.
You would have to drink a hundred or more glasses of wine a day to obtain the longevity benefits suggested in cell and animal studies.
While disappointing, these results don’t necessarily mean that resveratrol and other polyphenols won’t help extend average lifespans or protect against the development of age-related diseases.
Only the trans resveratrol form is biologically active, and this is the form found in quality supplements.
Resveratrol is one of the substances that contributes to the health benefits of the Mediterranean diet.
Resveratrol is found in grapes, nuts and berries but the highest concentration is in red wines, whose production involves crushing and macerating the grapes. This allows resveratrol to escape from the dark, pigmented skins into the juice – its solubility in water is greatly enhanced by the presence of alcohol.
Diet should always come first, but it’s neither practical nor healthy to drink more than the recommended intake of red wine.
Resveratrol supplements are available that provide similar daily levels of trans-resveratrol as are obtained from drinking three hundred or more glasses of Chianti per day.
Richest resveratrol wines
Resveratrol per 100 mls
|Red wine made with Californian muscadine grapes
|3 mg resveratrol
|Red wine: Merlot
|1.4 mg resveratrol
|Red wine: Pinot Noir
|1.2 mg resveratrol
|Red wine: Cabernet Sauvignon
|0.10 mg resveratrol
|0.12 mg resveratrol
|0.04 mg resveratrol
Richest resveratrol foods
Resveratrol per 100grams
|3.0 mg resveratrol
|1.92 mg resveratrol
|1.57 mg resveratrol
|0.67 mg resveratrol
|0.35 mg resveratrol
|0.15 mg resveratrol
|0.11 mg resveratrol
|0.08 mg resveratrol
|0.04 mg resveratrol
Resveratrol supplements are generally used in doses of 250 mg to 1g daily. Higher doses have been used in clinical trials.
The most commonly reported side effects from very high doses (1 g twice a day in an Alzheimer’s study) were nausea, diarrhoea, and weight loss.