Vitamin D Supplementation: Safety, Gaps, and Alternative Strategies

What is it about?

This paper discusses the safety of vitamin D applications, presenting an experiment on squirrel monkeys that showed long-term oral vitamin D intake in non-toxic amounts can cause atherosclerosis in large arteries. The author argues that the transport mechanisms for vitamin D from food and endogenous synthesis in skin are different and suggests alternative strategies for addressing vitamin D deficiency, rather than food fortification and supplementation. The author proposes UV-exposure and transdermal administration as preferred routes for obtaining optimal vitamin D status. However, the cited study is not a nutritional study, as the doses given to monkeys were 10-fold higher than established Upper Tolerable Levels, and the author's concerns about oral intake are not consistent with average intake levels in humans.

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Why is it important?

This research is important because it raises awareness of the potential risks and adverse effects of long-term oral vitamin D supplementation at high doses, which may cause atherosclerosis in large arteries. The study highlights the need for alternative strategies to address widespread vitamin D deficiency in humans. Key Takeaways: 1. The author argues that the transport mechanism for vitamin D from food and endogenous synthesis in the skin is different and proposes alternative strategies for addressing vitamin D deficiency. 2. The cited squirrel monkey trial is not a nutritional study, as it involved a high dose of vitamin D (1000 µg/d), exceeding established safety levels, and is not comparable to the typical average oral intake of vitamin D. 3. Several randomized controlled clinical trials using amounts of vitamin D in the range of 2000-4000 IU/d (50 to 100 µg/d) for several years have been published, showing that side effects and adverse events were rare and not different from the placebo groups. 4. Blood 25(OH)D levels are the appropriate measure of vitamin D status, and the author suggests that 50-80 nmol/l represents a 'good' vitamin D status, which is usually achieved by the recommended daily allowance of 15-20 µg/d. 5. Food fortification, oral supplementation with vitamin D, and moderate UV exposure are safe ways to improve vitamin D status, and experts recommend addressing vitamin D deficiency worldwide through these strategies.