"This study raises the possibility that dietary flavonoid intake is associated with better cognitive evolution," wrote lead author Luc Letenneur in the American Journal of Epidemiology. Cognitive performance declines naturally with age, but the results of the PAQUID (Personnes Agées Quid) study suggests that this could be slowed by increased intake of flavonoids in the diet. Flavonoids have been receiving interest with a mounting body of science, including epidemiological and laboratory-based, continuing to report the cancer-fighting potential of a number of different flavonoids, such as isoflavones, anthocyanidins and flavonols. According to Business Insights, the market potential for flavonoids in the dietetic and nutritional supplement market is in excess of €670m ($862m) for 2007, with annual increases of 12 per cent.
The researchers, from France's Institut National de la Santé Et de la Recherche Médicale (INSERM) and the Université Victor Segalen Bordeaux 2, recruited 1,640 subjects with an average age of 77 and free of dementia at the start of the study and assessed dietary intakes of flavonoids using food frequency questionnaires four times over 10 years. Cognitive function was measured using Mini-Mental State Examination (MMSE), Benton's Visual Retention Test, and the "Isaacs" Set Test. After adjusting the results for potential confounding factors, such as age, sex, and educational level, Letenneur and co-workers report that flavonoid intake was associated with both better cognitive performance at the start of the study and better evolution of mental performance over time. Subjects with the highest flavonoid intakes (between 13.6 and 36.9 milligrams per day) were found to have better cognitive function than those with the lowest intakes. After ten years of follow-up, it was found that, while those with the lowest intakes had lost an average of 2.1 points on the MMSE, subjects with the highest intakes had lost only 1.2 points.
"We showed that higher intake of flavonoids from food may be associated wit a better cognitive evolution over a 10-year period. Whether this reflects a causal association remains to be elucidated," wrote the researchers. "More cohort studies are needed to further investigate the relation between flavonoid intake and cognitive evolution, including other antioxidant molecules," they concluded. The role of flavonoids as antioxidants was recently challenged by a review by scientists from the Linus Pauling Institute at Oregon State University reported that, while the compounds showed excellent antioxidant activity in the lab, they are rapidly metabolised in the body. "This does not preclude the possibility that flavonoids may accumulate in tissues where they might exert local antioxidant effects or that very low concentrations of flavonoids may modulate cell signalling, gene regulation, antiogenesis, and other biological processes by non-antioxidant mechanisms, which may explain the purported health benefits of flavonoids," wrote Silvina Lotito and Balz Frei in the journal Free Radical Biology and Medicine.
Source: American Journal of Epidemiology Volume 165, Number 12, Pages 1364-1371; doi:10.1093/aje/kwm036 "Flavonoid Intake and Cognitive Decline over a 10-Year Period"
Authors: L Letenneur, C Proust-Lima, A Le Gouge, JF Dartigues and P Barberger-Gateau