Fruit, Vegetable Juices May Lower AD Risks

Abstract

Frequent drinking of fruit and vegetable juices is associated with substantially reduced risk of Alzheimer's disease, according to a report by Dr. Qi Dai of Vanderbilt University, Nashville, Tenn., and associates. Results of several studies have suggested that the antioxidants and polyphenols in dietary fruits and vegetables may reduce the risk of Alzheimer's disease (AD) or delay its onset. Dr. Dai and associates hypothesized that intake of fruit and vegetable juices, which are rich sources of both nutrients, also might be protective. They tested their hypothesis using data from 1,836 subjects involved in the Kame Project, a large, population-based prospective study of Japanese Americans living in King County, Wash., who were followed during 1992–2001 as part of a crosscultural study of AD and vascular dementia. The subjects, who were aged 65 years or older at baseline (mean age 72 years), completed food frequency questionnaires and underwent periodic cognitive assessments. Over a mean of 6 years of follow-up, 81 incident cases of AD were diagnosed. The risk of developing AD declined with increasing consumption of fruit and vegetable juices. Subjects who drank juice three times a week or more had a hazard ratio of 0.24, compared with those who drank juice less often than once a week (Am. J. Med. 2006;119:751–9). This apparent protective effect was seen in subjects with all different levels of education, physical activity, and fat intake. The association was not confounded by differences in smoking status or ApoE genotype. As in previous studies, the antioxidant vitamins in dietary fruits and vegetables appeared to be protective, but those in vitamin supplements were not. Although tea was the beverage most often consumed by these subjects, and tea is a rich source of some polyphenols, there was no relation between tea drinking and AD risk in this study. This finding agrees with those of two previous studies of tea drinking and AD. Wine is another potent source of antioxidants, and there was a small but statistically insignificant inverse association between wine or sake drinking and Alzheimer's disease. The lack of statistical significance may be because of the small number of subjects (6%) who drank these beverages at least once per week, the researchers noted. The protective effect of fruit and vegetable juices is being attributed to their antioxidant properties, but it is also possible that other characteristics such as anti-inflammatory properties are at work. Moreover, in addition to possessing antioxidant vitamins and polyphenols, juices may contain other components such as folate and minerals, which contribute to the protective effect, the researchers added. Data were not collected on the specific types of fruit and vegetable juices these subjects consumed, so “we … cannot say at present which [ones] might confer protection or for what duration of time they need to be consumed before delay of AD onset may be realized,” Dr. Dai and associates said. The researchers said that further investigation is needed to confirm the effect of vegetable and fruit juices.