Vitamin D

Overview: 

Vitamin D, a fat-soluble vitamin often considered a hormone, is essential for overall health and well-being. Surprisingly, more than 50% of people in the U.S. are deficient in vitamin D, partly because it's hard to get enough from food alone. With modern lifestyles involving less time outdoors and more time sitting inside, many people miss out on the natural boost of vitamin D from sunlight. Those with darker skin tones also face a challenge, as their bodies produce less vitamin D from sun exposure. This makes vitamin D supplementation important—not only to support bone health by maintaining healthy calcium levels but also to enhance recovery after exercise, ensuring your body performs at its best [2].

Simple: 

For people who get plenty of sunlight, vitamin D supplements aren’t usually necessary, but they may help those who spend little time outdoors or do a lot of exercise. Studies show that vitamin D supplements don’t provide big health benefits for most people, except for raising vitamin D levels in the blood. Some research suggests that high doses of vitamin D can even be harmful, like causing bone loss or more frequent falls. However, for people with low vitamin D, supplements may help with muscle recovery and reduce inflammation after exercise, especially if taken at doses of 2000 IU/day or more for at least a week. While the benefits for muscle soreness and strength are mixed, vitamin D could also reduce oxidative stress. More studies are needed to figure out the best dose and long-term effects, but for now, it seems most useful for people who are deficient.

Complex:

For individuals with fair complexions who get ample sunlight exposure, vitamin D supplementation is generally unnecessary. However, for those who spend little time outdoors and engage in weight-bearing exercise, the antioxidative benefits of vitamin D supplementation may be more relevant. Many studies suggest that vitamin D supplementation alone has limited effects on daily life and health markers, aside from raising serum vitamin D levels. For instance, one study found that "vitamin D supplementation had no effect on most physical function, body composition, or metabolic health parameters when taken alone or during exercise in overweight or obese older adults with vitamin D deficiency" [3,4]. While these findings highlight the need for more research on healthy, active individuals, they also suggest that supplementation may be less crucial for certain populations.

Further reviews add to this understanding, indicating that vitamin D supplementation in vitamin D-replete adults (those with adequate levels) does not significantly impact major diseases like cancer, cardiovascular disease, or type 2 diabetes. There is no solid rationale to recommend supplementation for this group. While severe vitamin D deficiency can lead to issues like rickets and vitamin D combined with calcium may benefit older adults, high doses of vitamin D (>4,000 IU daily) could increase risks such as bone density loss and falls [1]. Ongoing studies may better define who benefits from vitamin D, but for now, supplementation should be limited to those with deficiencies.

In another systematic review focused on exercise-induced muscle damage (EIMD), vitamin D supplementation, particularly at doses of 2000 IU/day or higher for more than a week, was found to reduce muscle damage and inflammation post-exercise. Although findings on muscle soreness and functional recovery are mixed, many studies report reduced muscle soreness with supplementation. Research on oxidative stress also shows positive results, suggesting that vitamin D may have antioxidant effects, though more studies are needed to confirm this. The review noted several limitations, including variations in study protocols, participant fitness levels, and dosages, underscoring the need for further research. Nonetheless, vitamin D supplementation appears to be a promising strategy for athletes and individuals prone to EIMD, but definitive dosage guidelines remain unclear [5].

Works Cited:

1. Bouillon R, Manousaki D, Rosen C, Trajanoska K, Rivadeneira F, Richards JB. The health effects of vitamin D supplementation: evidence from human studies. Nat Rev Endocrinol. 2022 Feb;18(2):96-110. doi: 10.1038/s41574-021-00593-z. Epub 2021 Nov 23. PMID: 34815552; PMCID: PMC8609267.
2. Libon F, Cavalier E, Nikkels AF. Skin color is relevant to vitamin D synthesis. Dermatology. 2013;227(3):250-4. doi: 10.1159/000354750. Epub 2013 Oct 17. PMID: 24134867.
3. Mesinovic J, Rodriguez AJ, Cervo MM, Gandham A, Xu CLH, Glavas C, de Courten B, Zengin A, Ebeling PR, Scott D. Vitamin D supplementation and exercise for improving physical function, body composition and metabolic health in overweight or obese older adults with vitamin D deficiency: a pilot randomized, double-blind, placebo-controlled trial. Eur J Nutr. 2023 Mar;62(2):951-964. doi: 10.1007/s00394-022-03038-z. Epub 2022 Nov 4. PMID: 36333495; PMCID: PMC9638202.
4. Fischer C, Jakob F, Kohl M, Kast S, Von Stengel S, Kerschan-Schindl K, Lange U, Thomasius F, Peters S, Uder M, Kemmler W. Additive Effects of Exercise and Vitamin D Supplementation (with and without Calcium) on Bone Mineral Density in Older Adults: A Systematic Review and Meta-Analysis. J Osteoporos. 2023 Aug 8;2023:5570030. doi: 10.1155/2023/5570030. PMID: 37588008; PMCID: PMC10427236.
5. Rojano-Ortega D, Berral-de la Rosa FJ. Effects of vitamin D supplementation on muscle function and recovery after exercise-induced muscle damage: a systematic review. J Hum Nutr Diet. 2023; 36: 1068–1078. https://doi.org/10.1111/jhn.13084