Can a healthful diet protect seniors from age-related mental decline? Probably not all by itself, but scientists are taking a close look at how antioxidant nutrients abundant in a fruit and vegetable-rich diet might help preserve brain function into old age.
Protective effect of carotenoids
Dutch researchers accessed data previously collected on 203 elderly participants of the Rotterdam Study, an ongoing investigation of the development of chronic diseases in older people. Blood samples collected at baseline gave the researchers serum values for 6 carotenoids with known antioxidant properties-alpha-carotene, beta-carotene, lycopene, lutein, zeaxanthin, and cryptoxanthin. Magnetic resonance imaging (MRI) brain scans documented the presence of white matter lesions (WML). These were categorized as periventricular lesions (measured frontally and laterally, and grouped by size) or subcortical lesions, classified as small <3mm; medium 3-10 mm; large >10 mm.
After controlling for potential confounders-age, gender, smoking history, BMI, diabetes, serum lipid profile, alcohol use, previous MI-researchers found a significant inverse association between total carotenoid intake and the presence of periventricular WML (OR 0.4 per SD; 95% CI=0.2-0.9). There was no association between the degree of subcortical lesions and serum carotenoid levels.
Possible pathways
The authors of the study propose a plausible explanation for their findings. Earlier research done in their lab suggests that atherosclerosis is associated with an increased presence of WML, particularly periventricular lesions. Carotenoids are potent antioxidants, and as such may slow the development of atherosclerosis by inhibiting the oxidation of low-density lipoproteins within the arterial lumen. This explanation is supported by research that has shown an inverse association between serum carotenoid level and asymptomatic carotid atherosclerosis.
In an additional antioxidant role, carotenoids may help preserve the integrity of brain tissue by scavenging free radical oxygen molecules that, left unopposed, will eventually cause cellular damage.
Role of diet
Admittedly, analysis of a single type of nutrient presents only a partial picture-a diet high in carotenoid-rich fruits and vegetables is also high in other nutrients and fiber and tends to be lower in fat. People who eat plenty of produce may also be more likely to exercise regularly and to not smoke. All of these diet and lifestyle factors could, in part, account for the health benefits attributed in this study to carotenoids.
Nevertheless, the results of this study do point to diet as one of the variables that determine how successfully we age. The authors stress that brain lesions develop over a period of years, which underscores the importance of long-term commitment to good nutrition.
The most practical diet advice to patients would be for them to choose lower-fat meals that includes at least 5 servings a day of deep-colored fruits and vegetables. Carotenoids are pigments, and are therefore most plentiful in dark green, dark yellow, orange, and red produce.
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