Critique of Public Health Guidance for Vitamin D and Sun Exposure in the Context of Cancer and COVID-19.

Official public health pronouncements about sun exposure and vitamin D can be summarized as follows: First, there is no such thing as a safe tan. Therefore, avoid exposing the skin to sunshine. Second, in the absence of sunshine, a daily intake of 800 IU/day (20 mcg/d) vitamin D or less is sufficient for the health needs of almost all members of the population. However, exposure of the skin to sunlight induces multiple mechanisms that lower blood pressure, while also initiating production of vitamin D, which is needed to produce a hormone that regulates multiple systems including the cellular biology that affects cancer mortality. Disease-prevention relationships point to a beneficial threshold for serum 25-hydroxyvitamin D [25(OH)D; the index of vitamin D nutrition] that is at least 75 nmol/l (30 ng/ml). To ensure the threshold for all adults, an average per-day minimum total input of vitamin D3 from sunshine/UVB exposure, and/or from food (natural food like fish or fortified food like milk), and/or vitamin supplementation of at least 4,000 IU/d (100 mcg/d) is required. Strong, although not Level-1, evidence indicates that the maintenance of that threshold will lower mortality overall, lower mortality from cancer, and lower the risk of certain other diseases such as respiratory infection and COVID-19.

An Appraisal to Address Health Consequences of Vitamin D Deficiency With Food Fortification and Supplements: Time to Act!

A symposium entitled "Vitamin D in Prevention and Therapy" was held on May 4-5, 2022, in Homburg, Germany to discuss important new advances in the field, including identification of new vitamin D signaling pathways, of new biologic effects of vitamin D-compounds (e.g., on the microbiome), and convincing proof of the relevance of vitamin D deficiency for the risk and outcome of many chronic diseases, including cancer, cardio-vascular, auto-immune, metabolic, and infectious diseases. Concerning the COVID-19-pandemic, an inverse association between 25(OH)D serum concentrations and SARS-CoV-2-infections, morbidity, and mortality was shown. In relation to cancer, several meta-analyses recently demonstrated an association of vitamin D-supplementation with significantly decreased mortality rates, which presumably would reduce health care costs. Considering the impressive body of evidence and the high safety of oral supplementation and food fortification with vitamin D, it was concluded that there is now an urgent need to act. In many countries worldwide, health care authorities need to increase efforts to address vitamin D deficiency, e.g., via food fortification and/or supplementation with vitamin D, and/or promoting moderate UV-exposure. It was estimated that in many countries, vitamin D intakes of the order of appr. 1,000 IE (25 µg)/day would be needed to bring and/or keep the vast majority of people over a serum 25(OH)D threshold of 20 ng/ml (50 nmol/l), which would be difficult to obtain alone from food fortification. New developments in personalized medicine may represent helpful tools to identify populations at risk for vitamin D deficiency and their responsiveness to vitamin D treatment.