Dietary nitrate is mainly obtained from vegetables, especially green leafy vegetables and beetroot. As a result of early research, dietary nitrate is currently viewed as a contaminant linked to increased risks of stomach cancer and methaemoglobinaemia. Consequently, nitrate levels are restricted in certain vegetables and in water supplies to ensure exposure levels remain below an acceptable daily intake of 3·7 mg/kg per d. The average nitrate intake in the UK is approximately 70 mg/d, although some population groups, such as vegetarians, may consume three times that amount. However, recent studies in the last decade suggest that dietary nitrate can significantly reduce systolic blood pressure via the nitrate–nitrite–NO pathway. A small, downward shift in systolic blood pressure across the population could significantly reduce the incidence of hypertension and mortality from CVD such as stroke. Interestingly, vegetarians tend to have lower levels of blood pressure than omnivores and epidemiological studies suggest that vegetarians have lower risks of CVD. Recent evidence is mainly focused on the acute effects of dietary nitrate supplementation and there is a lack of data looking at the chronic effects of high nitrate consumption in humans. Nevertheless, due to potential health benefits, some authors are recommending that nitrate should be considered as a nutrient necessary for health, rather than as a contaminant which needs to be restricted. This review will discuss the emerging role of dietary nitrate in the control of blood pressure and whether there is sufficient evidence to state that nitrate is a ‘new’ nutrient.

Vegetable and fruit intake has been associated with a reduced risk of cancer and CVD, but its relationship to the risk of type 2 diabetes remains unclear. We prospectively examined the association between vegetable and fruit intake and the incidence of type 2 diabetes. Subjects were 21 269 men and 27 168 women aged 45–75 years who participated in the second survey of the Japan Public Health Center-based Prospective Study and had no history of type 2 diabetes or other serious diseases. Intake of vegetables and fruit was estimated using a validated 147-item FFQ. The OR of self-reported, physician-diagnosed type 2 diabetes over 5 years was estimated using multiple logistic regression. A total of 896 newly diagnosed cases of type 2 diabetes were self-reported. Intake of vegetables and fruit combined or fruit only was not associated with a lower risk of type 2 diabetes. However, there was an approximately 20 %, albeit not statistically significant, risk reduction associated with vegetables (men only), green leafy vegetables (men and women) and cruciferous vegetables (men only). Such risk reduction was somewhat greater among obese or smoking men than non-obese or non-smoking men. In conclusion, although a small beneficial effect of vegetables, especially green leafy and cruciferous vegetables, cannot be excluded, vegetable and fruit intake may not be appreciably associated with the risk of type 2 diabetes for Japanese adults.