LAUSR

The article Guo et al. (1) is a systematic review that was published in Frontiers in Nutrition on 8th October 2021 in the Research Topic “Functional Foods and Bioactive Food Ingredients in Prevention and Alleviation of Metabolic Syndrome.” The introduction to the review explained the importance of dietary vegetables and fruits for maintaining and enhancing human health, and that intake of these foods is negatively associated with the incidence of the metabolic syndrome (2). Considering that vegetables and fruits are the primary dietary sources of vitamin C, and the review found a significant negative association between vitamin C intake or plasma concentration with incidence of metabolic syndrome, the results of the review clearly confirmed this association. Vegetables and fruits contain a wide range of constituents with potential impact on human health. However, the discussion focused exclusively on the potential role of vitamin C itself, with no mention of any of the other potentially beneficial constituents of vegetables and fruits, such as nitrate (3), phytochemicals (4), and folate (5). There is no mention of the possibility that the vitamin C intake/plasma concentration might be simply a marker of intake of vegetables and fruits, in which case vitamin C itself may have only a minor role in the association or, maybe, none at all. On 5th November 2021, this article was featured by https://www.nutraingredients.com/, a newsletter for the functional food and nutritional supplements industry, possibly due to perceived relevance to marketing of commercial vitamin C supplements.