Resveratrol

What it is

Resveratrol is a plant compound found in grapes, berries and peanuts [1]. Trials have used doses from 10 mg to 1,000 mg a day [2]; one older study used 2 to 3 g a day [3].

How it might work

Proposed mechanisms, not established in humans: resveratrol is thought to act as an antioxidant and anti-inflammatory compound and to support blood vessel function [1]. In a 6-week human study, muscle samples showed more mitochondria, the cell's energy units [3].

What the research says

Blood pressure: a 2022 review of 19 trials in people with type 2 diabetes found that doses of 1,000 mg or more lowered systolic blood pressure by about 8 mmHg [4]. A 2019 review of 17 trials found no overall change, with effects only at doses of 300 mg a day or more and in people with diabetes [5].

Bone density: a 24-month trial in postmenopausal women found a slight rise in bone mineral density after 12 months of 75 mg twice daily [6].

Blood sugar: a Cochrane review of three small trials found no effect on HbA1c or fasting glucose [2]. A 2022 review of 30 studies reported lower HbA1c and insulin resistance [7].

Memory and thinking: a 2018 meta-analysis of four trials found no effect on memory [8]. A 24-month trial in 125 postmenopausal women reported a small improvement in overall thinking scores [9].

Doses used in studies

Doses ranged from 10 mg to 1,000 mg a day in the diabetes reviews [2]. Older adults took 300 mg or 1,000 mg a day for 90 days [10]. One postmenopausal trial used 75 mg twice daily for 24 months [6]. A 2-year biological-age trial used 350 mg twice daily and was stopped early [11].

Safety and interactions

Common side effects in a 52-week Alzheimer's trial were nausea, diarrhoea and weight loss [12]. That trial used up to 2,000 mg a day and reported brain volume loss compared with placebo [12]. A 1,000 mg a day pilot raised two blood markers of vessel stress more than placebo [13]. In a 2-year trial, LDL cholesterol rose on high-dose resveratrol, and that arm was stopped at month 5 [11]. The Cochrane review concluded there was not enough research to judge safety in people with type 2 diabetes [2]. In general adults, one review found small kidney-function changes [14]. The trial abstracts we read did not report interactions with medicines, pregnancy or breastfeeding, or results in people with kidney, liver or bleeding disorders.

Caveats and open questions

Most trials are small and short, from 4 weeks to 2 years [2]. Several had supplier ties [10][11]. Lifespan results come from yeast, worms and mice [3]. Eight ongoing RCTs with about 800 participants were listed in the Cochrane review and may clarify the diabetes results [2].