Fruit, Veg Intake Has Dose-Response Link With CV, All-Cause Deaths

Shelley Wood

July 30, 2014

LONDON, UK — A new meta-analysis has taken a stab at identifying the number of fruits and vegetables a person needs to eat per day to reduce the risk of an early death and concludes that five daily "portions" is about right[1].

Moreover, say the researchers, led by senior author Dr Frank Hu (Harvard School of Public Health, Boston, MA), there is a clear dose-response relationship that continues up to five servings a day, "after which there was no further reduction in risk," they write.

The inverse association between increased fruit and vegetable consumption and mortality was particularly noticeable for cardiovascular mortality; higher consumption was not significantly linked with reduced risk of cancer mortality, they add.

Hu, with first author Dr Xia Wing (Shandong University, Jinan, China) and colleagues conducted a multilanguage literature search, looking back as far as 1950, ultimately including any prospective cohort studies that included levels of fruit and vegetable consumption, as well as all-cause, cardiovascular, or cancer mortality.

For seven studies that looked at all-cause mortality, daily consumption of one serving of fruit or vegetables (compared with consumption of none) was associated with an 8% reduction in deaths, a number that reduced further with two and three daily servings, respectively (hazard ratio 0.85 and 0.79). Five or more servings was associated with a risk reduction of 26%, but this did not decrease further with additional fruit and vegetable consumption.

Cancer and Heart Disease Deaths

Wing et al conducted similar analyses for studies that included cardiovascular mortality (four studies) and cancer mortality (two studies).

For the CVD-mortality analysis, each additional portion of fruit or vegetables was associated with an approximate 4% reduction in risk of CVD death up to five servings. Considered separately,each additional portion of fruit was associated with a 5% average reduction in CV disease mortality, whereas additional vegetable consumption was associated with a 4% reduction.

For the cancer-mortality analysis, fruit and vegetable consumption was not statistically significantly associated with a reduction in cancer deaths. Wing and colleagues point out that other studies of cancer and fruit/vegetable consumption have also been inconsistent, and this might be partly explained by the variable effects of different types of foods on different types of cancer.

All of the pitfalls of the component studies are present in the meta-analysis, the authors warn, including the fact that fruit and vegetable intake is typically self-reported. Not all studies adjusted for other types of foods consumed, including saturated fats, processed meats, etc. The definition of "portions" may also have been different across studies, the authors caution.

Overall, however, the study "provides further evidence that higher consumption of fruit and vegetables is associated with a lower risk of mortality from all causes, particularly from cardiovascular diseases," they conclude.

The authors disclosed having no conflicts of interest.

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