N° 8 | March 2016

Evidence for a protective effect of polyphenol-rich diet intake on healthy aging from the InCHIANTI study

Diet strategy for slowing effects of aging

The number of people aged 65 years and older is projected to increase from 18% in 2014 to 29% in 2080. The continuing population aging is a challenge for public health policies, since it is desired that this increase in life expectancy does not occur at expenses of lower quality of life. Thus, it is necessary to increase research on the benefits of healthy eating habits in order to identify the best dietary recommendations. These will enable the prevention or delay of symptoms, syndromes and diseases associated with aging, such as frailty, physical and cognitive decline. Amongst existing dietary patterns, diets high in fruits and vegetables have been shown protective effects against cardiovascular and neurodegenerative diseases, cancer and total mortality. Fruits and vegetables are rich, among other potentially beneficial compounds, in phytochemicals, such as polyphenols. Polyphenols constitute a very heterogeneous group, with over 500 different compounds. The number of experimental studies on the protective role of polyphenols in aging has grown exponentially during the last years, even though the epidemiological evidence is still limited. Furthermore, associations observed between polyphenols and health are compromised because the use of self-reported questionnaires, which may be subject to both systematic and random measurement errors. As a result, nutritional biomarkers are being highly used in nutrition research, because they provide a more accurate and objective measure to estimate the dietary polyphenol exposure.

Polyphenols and aging: epidemiological evidence from the InCHIANTI study

Recently, we investigated the associations between dietary polyphenols exposure, using dietary questionnaires and biomarkers, and cognitive and physical decline, frailty and total mortality among the participants aged 65 years or more within the InCHIANTI cohort. The InCHIANTI is a prospective population-based study conducted in two municipalities (Bagno a Ripoli and Greve in Chianti) adjacent to the city of Florence (Italy). It was designed to evaluate risk factors affecting the loss of mobility in the older population. The dietary intake of total polyphenols and resveratrol was estimated using a validated food frequency questionnaire and an ad hoc database of food composition on polyphenols, created from the two only databases available in the literature: USDA and Phenol-Explorer databases. The urinary concentration of total polyphenols and resveratrol metabolites was determined by Folin-Ciocalteu colorimetric and mass spectrometry methods, respectively. We observed that participants in the highest tertile of total urinary polyphenols had a (47, 60, 64 and 30 %) reduction in the risk of global cognitive and physical decline, frailty and total mortality, in comparison with those in the lowest tertile. However, no association with total dietary polyphenols was observed. In these studies, we demonstrate the importance of assessing dietary polyphenol exposure whenever possible, using biomarkers and not only using dietary questionnaires. Additionally, habitual dietary exposure of resveratrol was associated with a lower risk of developing frailty over a three years follow-up combining of both measures (diet and biomarker) as well as individually. The potential underlying mechanism of action of polyphenols may be due to their antioxidant and anti-inflammatory activities. For example, polyphenols reduce neuronal damage and death from oxidative reactions by inhibiting the generation of reactive oxygen species, lipid peroxidation, protein oxidation, metal chelation, neuronal apoptosis, and damage to cellular signaling.

Recommendations and future research plans

The message that we can extract for the general population, so far, could be the recommendation of an intake above 600 mg/d of polyphenols within a healthy dietary pattern, rich in fruits and vegetables. This amount can be achieved by eating 5-6 servings of polyphenol-rich foods per day, such as fruits, vegetables, wine, nuts, chocolate, coffee or tea.

Future clinical and epidemiological studies are warranted to replicate these associations, especially using biomarkers, in other populations. The advances in polyphenols research will be important to make dietary recommendations for developing effective public health policies and for improving the autonomy and quality of life of older people.

Based on: Rabassa M., Cherubini A., Zamora-Ros R., Urpi-Sarda M., Bandinelli S., Ferrucci L., Andres-Lacueva C. Low levels of a urinary biomarker of dietary polyphenol are
associated with substantial cognitive decline over a 3-year period in older adults: The invecchiare in CHIANTI study. J. Am. Geriatr. Soc. 2015;63:938–946. doi:
10.1111/jgs.13379.

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