Beyond the grape: uncorking the health facts about resveratrol

What is Resveratrol?

Resveratrol is a polyphenol - a naturally occurring compound - that is found in the skin and seeds of grapes. Other natural resveratrol sources include blueberries, peanuts, plums, apples, raspberries and products derived from these foods, such as wine. Red grapes usually have between 3-10 times more resveratrol than white grapes.

Dr John Lowe, Restore Care, a Gastroenterologist, based in Utah, USA explains that red wine is famous for having a high concentration of this compound since it's made with red grapes.

Resveratrol is also a phytoalexin - a substance which helps defends against harmful organisms (pathogens) that cause infections and disease. For this reason, resveratrol is thought to have a list of apparent health benefits, which is why some people take it as a supplement.

What are the benefits of resveratrol?

Resveratrol isn't absorbed by our bodies very well, so it's hard to understand or study its health benefits for humans. However, it is thought to have potential in several areas.

Heart health

Resveratrol is a natural antioxidant. Other examples of antioxidants include vitamins A, C and D. They are great for fighting off harmful molecules (free radicals) that increase your chance of developing heart disease.

Cholesterol control

There is limited research which suggests that resveratrol could help in lowering bad cholesterol (LDL) and reducing fat production.

Anti-inflammatory effects

Resveratrol contains properties which lower the production and release of inflammatory substances - however, there is not enough evidence to say that there is enough to have to have anti-inflammatory effects.

Bone health

Resveratrol may be good for bone health.

Anti-ageing properties

All of the natural benefits found in resveratrol are useful against various age-related conditions such as brain disorders, heart disease, and bone loss.

Potential side effects of resveratrol

Resveratrol supplements appear safe, with no obvious side effects reported if taken in small amounts. Long-term studies have not reported significant side effects, with some research suggesting it's safe at doses of up to 5 grams per day. However, these studies involved healthy participants, meaning the effects of resveratrol might differ in people with health conditions.

Lowe warns: "Resveratrol is considered safe for your kidneys if taken in moderation. But in very high amounts it might cause renal problems. People with kidney disease or other kidney problems should talk to a healthcare professional - for example, your pharmacist - before taking resveratrol supplements."

Doses as low as 2.5 grams have also been linked to side effects such as feeling and being sick, vomiting, diarrhoea, and liver problems - especially in people with non-alcoholic fatty liver disease (NAFL).

Dr Elena Salagean, Allergy Consultant, NHS and Holistic Allergy, adds: "The liver contains proteins that break down and process various substances in the body (CYP450 enzymes). Resveratrol inhibits the effects of these proteins, meaning it could intensify the effect of certain medicines by building them up in your body."

Dr Raj Dasgupta, ABIM quadruple board-certified physician says: "Resveratrol might slow blood clotting and increase the chance of bleeding in people with bleeding disorders. It could also act like oestrogen. If you have any condition that might be made worse by exposure to oestrogen, don't use resveratrol."

Which medicines might interact with resveratrol?

According to both Salagean and Dasgupta, resveratrol may react with certain medicines.

These include:

• Blood thinners.

• Statins.

• Calcium channel blockers.

• Anti-fungals.

• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs).

• Beta-blockers.

• Some antidepressants.

• Blood pressure medicines.

Resveratrol may be good for us. However, while research has shown some limited positive findings, all studies have been in small numbers of people for short periods of time. More research is needed to be sure it really works. The amount of resveratrol used in research is also often much higher than what is usually found in resveratrol supplements - which is usually around 500 milligrams.

There's still a lot of work to be done before we know whether resveratrol might be of benefit. However, resveratrol-rich food sources are generally healthy and might provide additional benefits from their resveratrol content.