Dementia and diseases affecting the cerebral vessels are among the main causes of death in older women, alongside cardiovascular diseases. The risk of dying from these diseases is greater for older women than for younger women or men. This is partly due to the decline in oestrogen levels after the menopause. Oestrogen has many important functions in the body, such as memory maintenance and bone health. Because oestrogen decreases after the menopause, there are impairments in these areas. The loss also has a negative effect on microcirculation, causing blood vessels to stiffen more quickly. This reduced adaptability of the arteries to the oxygen demand of the brain is associated with impaired cognitive performance. Based on these processes, resveratrol was investigated in the RESHAW study.
RESHAW study: Resveratrol to support healthy ageing in women: Long-term effects of resveratrol on cognitive performance, cerebrovascular function and cardio-metabolic markers in postmenopausal women
In the RESHAW study, Zaw et al. investigated the long-term effects of Veri-teTM resveratrol (Evolva SA, Switzerland) on the ageing processes in post-menopausal women. The study is a randomized, controlled trial and thus the highest level of scientific evidence.
Studienplan
125 postmenopausal women aged 45-85 years took either 2 x 75mg trans-resveratrol daily (morning and evening) or a placebo for a period of twelve months. Allocation to the respective group was randomized. After this time, the administration was switched for a further twelve months. This means that a woman who received resveratrol in the first year only received a placebo in the second year. However, at no point did the individual study participants know whether they were receiving resveratrol or the placebo. This practice of blinding is common in science and is a sign of the quality of a study. The total observation period was therefore 24 months. To be considered postmenopausal, the last menstrual period had to be at least twelve months ago.
After 12 and 24 months, an examination was carried out to collect data. At the end of the study, the participating women were then compared "with themselves" in order to identify any differences. In concrete terms, this means that a woman's data after 12 months of taking resveratrol was compared with the values after 12 months of taking placebo. This so-called "crossover" design is also scientific practice. The authors examined the following parameters:
- cognitive performance
- cerebral blood flow velocity and reactivity of the brain vessels
- various cardio-metabolic markers
Ergebnisse
The cognitive performance was measured by the authors using various neuropsychological tests. Participating women completed the test battery at the beginning of the study, after the first twelve months and at the end of the study after two years. Overall, women taking resveratrol showed a improvement of 33% in overall cognitive performance. The jump was even greater in individual subtests. For example, the increase in a test relating to working memory was as much as 208% (Forward Spatial Span Test).
The second result criteria were the cerebral blood flow velocity and the responsiveness of the cerebral vessels, which the researchers measured using ultrasound. Here, the resveratrol group showed an 8% improvement in mean blood flow velocity. In addition, a 12% improvement in the reactivity of the cerebral vessels to an excess of CO2 was demonstrated. Overall, the observed increase in neurovascular coupling was 7% with resveratrol versus placebo. This means that more blood is transported to places where there is increased neuronal activity.
Finally, the authors were also interested in various cardio-metabolic markers. More precisely, this includes systolic and diastolic blood pressure, fasting blood glucose, insulin and blood lipids (cholesterol, HDL, LDL). A reduction in fasting insulin of 9% was found here with no change in fasting glucose, which indicates improved insulin sensitivity. There were no significant differences in blood pressure or blood lipids.
Summary
Resveratrol therefore showed a significant improvement in mental performance in all cognitive areas examined by the researchers. The size of the observed effect was comparatively small. In this context, the authors point out that age studies have shown that certain cognitive areas decline by an annual rate (0.02 standard deviations). Due to this fact, the improvement measured in the study is nevertheless clinically significant because resveratrol is able to slow down this process. In addition, there was evidence that resveratrol can sensitize the cells to insulin and could therefore potentially slow down the development of type 2 diabetes mellitus.
The dose of 2 x 75mg resveratrol per day used in the study cannot be ingested in this amount via a balanced diet. The highest concentration was found in grape skins with values of 50 to 400 micrograms (!) per gram of grape skin. For red wine, values between 0.1 and 14 mg/L were found, depending on the grape varieties used. The dose of resveratrol administered in the study is therefore equivalent to three to 27 liters of red wine or approx. 50 kg of grape skins - daily! That's probably not such a good idea.
The authors conclude by emphasizing that 88% of the women who participated in the study stated that they would probably continue with resveratrol supplementation after the study.
