To investigate the protective association between seasonality of consumption of fresh fruit or salad vegetables and cancer and cardiovascular disease (CVD) development.
Face-to-face interviews, including a food frequency questionnaire, were conducted on 1489 men and 1900 women, aged 35–75 years, who were respondents in the British Health and Lifestyle Survey 1984/85 (HALS1). CVD and cancer morbidity and mortality were determined from the 1991/92 British Health and Lifestyle Survey (HALS2) and by NHS Register ‘flagging’.
Risk was assessed by odds ratio (OR) for trend per frequency category. In men, frequent winter salad vegetable consumption was more closely protective than that in summer for cancer (winter OR = 0.79 [0.62–0.99], P = 0.045, summer OR = 0.83 [0.69–1.01], NS) and CVD (winter OR = 0.85 [0.72–1.00], P = 0.049, summer OR = 0.95 [0.82–1.10], NS). Fresh fruit consumption showed no significant protection. In women, frequent salad vegetable consumption at any season was significantly protective of CVD (winter OR = 0.76 [0.65–0.89], P < 0.001, summer OR = 0.76 [0.65–0.89], P < 0.001), although not of cancer. Frequent fresh fruit consumption in women was significantly protective of CVD (winter OR = 0.84 [0.74–0.94], P = 0.004, summer OR = 0.85 [0.74–0.97], P = 0.014) but not quite significant, and only in winter, for cancer (winter OR = 0.87 [0.76–1.00], P = 0.052, summer OR = 0.88 [0.75–1.02], P = 0.097). Maintenance of salad vegetable consumption from summer to winter, to within one frequency category, was associated with further protection for cancer in men (P = 0.050) and CVD in women (P = 0.024).
Diets high in fresh fruit and salad vegetables appear protective against cancer and CVD. It is important to take into account the seasonality of consumption in estimating and establishing significance of risk.
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