Polyphenols in berries, grapes and lots more stuff you can buy at the greengrocer’s do indeed extend life expectancy. Researchers at the University of Barcelona in Spain have provided robust evidence – and also discovered why in epidemiological studies so often no effect of polyphenols on life expectancy shows up.
Polyphenols found in fruit and vegetables do wildly interesting things with cells in test tubes and in lab animals. Polyphenols inhibit cancer cells, protect blood vessels, activate the manufacture of connective tissue, protect muscles, prevent the formation of plaques in the brain, stimulate fat burning and help cells carry out repairs on themselves. On paper a diet that is rich in polyphenols should extend life expectancy, but scientists see surprisingly little evidence of this in epidemiological studies.
This is partly due to the general deterioration in the quality of our diet. There are now so few people who actually consume enough fruit and vegetables that epidemiologists are unable to measure the effects of a polyphenol-rich diet.
Another reason is that epidemiologists reconstruct people’s eating habits from questionnaires that they have filled in. The data obtained from these is often unreliable.
The Spanish researchers followed 807 people over the age of 65 for 2 years and measured polyphenol intake in two different ways: in the classical way, using questionnaires, and in a more objective way, by measuring the quantity of polyphenol metabolites in the participants’ urine. The researchers expressed their results in gallic acid equivalents. The structural formula of gallic acid is shown below.
Polyphenols in berries, grapes and lots more stuff you can buy at the greengrocer’s do indeed extend life expectancy. Researchers at the University of Barcelona in Spain have provided robust evidence – and also discovered why in epidemiological studies so often no effect of polyphenols on life expectancy shows up.
The researchers divided the participants into three equal-sized groups depending on their polyphenol intake: tertiles.
The classical method resulted in an inverse effect on mortality rate. The more polyphenols the over 65s said they ate, the greater their mortality risk.
But when the researchers looked at the number of gallic-acid equivalents [GAE] in the participants’ urine they saw a positive effect. And, as the figure above shows, this was pretty strong too.
The figure below shows that the addition of alpha-lipoic acid to the cocktail led to a significant increase in the concentration of phosphocreatine.
The figure below shows another summary of the results. The mortality risk of the participants in the tertile with the highest intake was 30 percent lower than that of the participants with the lowest intake.
“The findings from our study suggest that high total urinary polyphenol concentrations are associated with reduced all-cause mortality in an elderly, free-living population, whereas no significant association was found using total dietary polyphenol intake”, the researchers write. “Further investigations are needed to confirm this protective association in other populations, especially younger people and different countries with higher dietary variability.”
High concentrations of a urinary biomarker of polyphenol intake are associated with decreased mortality in older adults.
Zamora-Ros R, Rabassa M, Cherubini A, Urpí-Sardà M, Bandinelli S, Ferrucci L, Andres-Lacueva C.
Abstract
Polyphenols might have a role in the prevention of several chronic diseases, but evaluating total dietary polyphenol (TDP) intake from self-reported questionnaires is inaccurate and unreliable. A promising alternative is to use total urinary polyphenol (TUP) concentration as a proxy measure of intake. The current study evaluated the relationship between TUPs and TDPs and all-cause mortality during a 12-y period among older adult participants. The study population included 807 men and women aged 65 y and older from the Invecchiare in Chianti study, a population-based cohort study of older adults living in the Chianti region of Tuscany, Italy. TUP concentrations were measured at enrolment (1998-2000) using the Folin-Ciocalteau assay after a solid-phase extraction. TDPs were also estimated at baseline throughout a validated food frequency questionnaire and using our database based on USDA and Phenol-Explorer databases. We modeled associations using Kaplan-Meier survival and Cox proportional hazards models, with adjustment for potential confounders. During the 12-y follow-up, 274 participants (34%) died. At enrollment, TUP excretion adjusted for age and sex tended to be greater in participants who survived [163 ± 62 mg gallic acid equivalents (GAE)/d)] than in those who died (143 ± 63 mg GAE/d) (P = 0.07). However, no significant differences were observed for TDPs. In the multivariable Cox model, participants in the highest tertile of TUP at enrolment had a lower mortality rate than those in the lowest tertile [HR = 0.70 (95% CI: 0.49-0.99); P-trend = 0.045], whereas no significant associations were found between TDP and overall mortality. TUP is an independent risk factor for mortality among community-dwelling older adults, suggesting that high dietary intake of polyphenols may be associated with longevity.
PMID: 23803472 [PubMed – indexed for MEDLINE] PMCID: PMC3743274 [Available on 2014/9/1]
