Letter by Tikhonoff et al regarding article, "dietary fiber intake and risk of first stroke: a systematic review and meta-analysis".

In a recent systematic review and meta-analysis published in Stroke, Threapleton et al1 reported a significant inverse association between risk of stroke and total dietary fiber intake in primary prevention setting from the United States, Northern Europe, Australia, and Japan. These findings support recommendations to increase dietary fiber intake. As a North–South gradient in fruit and vegetable consumption exists, studies performed in the Mediterranean diet area should also be taken into account. Indeed, the consumption of vegetables is higher in Southern, Central, and Eastern Europe (≈250 g/d) than in Northern Europe (140 g/d).2 Threapleton et al1 also claimed for future studies focusing on differences in dietary fiber intake. Nutritional data recorded at a population level, recently published by our group in Clinical Nutrition, may be complementary in such topic. In 1647 subjects representative of Italian general population, we have recently reported an inverse association between the incidence of stroke and the dietary fiber intake in a 12-year follow-up.3 This association was present both for soluble and for insoluble fiber, and independent of age, sex, and classic atherogenetic risk factors. This is consistent with a recent metaanalysis by Chen et al4 on dietary fiber intake and risk of stroke, suggesting no significant difference between sexes. Our analysis also allowed us to identify 2 clear cut-off values, 1 for soluble (>25 g/d) and 1 for insoluble dietary fiber (>47 g/d), over which the risk of stroke was significantly lower. The highest incidence of stroke was detected in subjects intaking ≤25 g/d soluble and ≤47 g/d insoluble fiber, whereas higher daily intake of soluble or insoluble fiber, also separately, significantly reduced both the incidence and the multivariate risk of stroke in the follow-up. These cut-off values could, therefore, be considered as the minimal recommendable daily intake of soluble and insoluble fiber, respectively, to prevent stroke at a population level. Actually, they are higher than those commonly and arbitrarily proposed as adequate by scientific societies. Unfortunately, the majority of people from small-income countries consumes <5 portions of vegetables and fruit daily recommended by the World Health Organization, with a trend toward decline also because of increase in the consumer price index.