Whole grains

The 2023 review compared intakes per extra 30 grams of whole grains a day [1]. The relative risk (the risk in one group relative to another) for all-cause mortality was 0.94, with a 95% confidence interval (the range the true value probably lies in) of 0.92 to 0.97 [1]. The same analysis found a relative risk of 0.94 for coronary heart disease and 0.92 for cardiovascular disease [1]. The association with all-cause mortality was non-linear, meaning the risk did not fall by the same amount with each added serving [1].

An earlier 2016 meta-analysis found a relative risk of 0.83 for all-cause mortality and 0.85 for cancer mortality per 90 grams a day [2]. A 2017 review of food groups found a relative risk of 0.92 for each daily serving [3]. Whole grains are a main source of cereal fiber, described under dietary fiber.

The evidence is observational (it tracks people's existing diets rather than assigning them), so it shows an association rather than proof of cause. People who eat more whole grains also tend to have healthier diets overall, and statistical adjustment reduces but cannot remove this confounding (distortion by other factors linked to both diet and death). Intake is usually measured with food questionnaires, which are imprecise. The 2023 review graded the evidence for all-cause mortality and cardiovascular disease as high quality and for stroke and coronary heart disease as moderate [1]. The place of grains in whole diets is described under dietary patterns, and the contrast with refined grains in its own article.