Vitamin D, as you know, is the sunshine vitamin. It gets this designation because sunlight is the best source of “D,” the vitamin that supports bone and immune health. In fact, exposure to sunlight accounts for 80% of the vitamin D that people accumulate in their bodies. How does sunlight drive the production of vitamin D? When you expose your skin to the sun’s rays, the energy from the sun converts compounds on your skin to vitamin D precursors. Then, your liver and kidneys transform these precursors to forms of vitamin D your body can use.
When everything works properly, your body gets enough vitamin D to sustain health and well-being. However, many people don’t get enough exposure to the sun in the winter months to maintain a healthy vitamin D level. In addition, some individuals are at higher risk of vitamin D deficiency because of factors like age, health conditions, and obesity. That’s why vitamin D deficiency is relatively common.
Is vitamin D important for other reasons? Beyond its implications for health, a recent study suggests that vitamin D supports muscle health in older adults. That’s important! Both men and women lose muscle and bone mass with age and over time this loss can have devastating consequences. Without adequate muscle mass and strength, you can’t generate the force you need to do the activities you enjoy. As you continue to lose muscle mass, the risk of falls rises too. Since you lose bone too, you could end up with a disabling fracture.
Losing muscle also has implications for metabolic health. Research shows that having more muscle cells improves glucose clearance from the blood and this improves insulin sensitivity. So, muscle is important for fitness, functionality, and for health! Now, let’s dig deeper and see if vitamin D can impact other aspects of physical function.
The Role of Vitamin D in Muscle Health
Can a low vitamin D level interfere with muscle performance? Researchers from Trinity College in Dublin found a link between low vitamin and muscle weakness in adults over the age of 60. When they looked at the muscle function of over 4,000 adults and compared it to their vitamin D level, they discovered those who were deficient in vitamin D were more likely to have impaired muscle function. In fact, adults low in vitamin D had double the risk of having muscle weakness. Their muscles also performed less well.
How low can you go and still have a normal vitamin D level? In this study, the cut-off for deficiency was below 30 nmol/L. As health care professionals point out a significant number of people, even in areas that get direct sunlight, have a vitamin D level that falls below this threshold. Plus, many people have one or more risk factors for vitamin D deficiency.
Risk factors for vitamin D deficiency include:
- Age over 60
- Being overweight or obese
- Having darkly pigmented skin
- Living in a Northern latitude with less direct sunlight
- Wearing sunscreen all year round
- Spending lots of time indoors
- Having health conditions that reduce vitamin D absorption
If this study holds up to scrutiny, it expands the list of what we can do to preserve muscle strength and mass as we age. It becomes important to maintain an adequate vitamin D level. We also need enough protein and regular resistance training. We already know that resistance training and protein are vital for keeping our muscles strong and functional as we age. Some studies also suggest that adults over the age of 60 need more protein for healthy muscles than younger adults. That’s because older adults have muscle cells that are more resistant to the anabolic effects of strength training.
Can Vitamin D Improve Sports Performance Too?
If you need adequate vitamin D for muscle strength and performance, it’s not a stretch to think that boosting vitamin D might improve sports performance too. In fact, being deficient could worsen performance in certain sports. Does science support this?
In one small study, researchers tested 13 individuals on an ergometer. They asked each participant to cycle for 20 minutes. Beforehand, they gave the subjects a vitamin D supplement or a placebo for 2 weeks, Prior to getting the supplement, they tested their performance on the ergometer to get a baseline. The results? The individuals who took the vitamin D supplement covered a 30% greater distance during the 20-minute ergometer session relative to those who took the placebo.
The Bottom Line
Now there’s another reason to keep tabs on your vitamin D level and make sure you’re getting enough of it! Remember, vitamin D levels often drop as we get older. Don’t guess! Ask your physician to check a vitamin D level to see where you stand. Based on research, most people need supplemental vitamin D, but you won’t know how much to take unless you know your level.
What about dietary sources of vitamin D? It’s hard to get enough vitamin D from diet alone. Natural sources of vitamin D include eggs, fatty fish, and food fortified with vitamin D, including some yogurt, cereals, and milk. one of the few plant-based sources of vitamin D is mushrooms exposed to sunlight. The high-energy rays of the sun ramp up vitamin D synthesis in the mushroom. However, most people don’t eat enough of these foods to sustain a healthy vitamin D level. So, keep your eye on your level and get outdoors as much as you can. Sunscreens reduce or block your skin’s ability to make vitamin D precursors, so you won’t get the benefits if you’re wearing sunscreen.
Keep in mind that your body can accumulate too much vitamin D if you take high doses in supplement form. So, don’t assume that more is better. It’s not yet clear what the optimal level of vitamin D is. It’s possible that the benefits to muscle health apply only to people deficient in vitamin D. If you’re not low, taking more vitamin D won’t help your muscle performance. But one thing is clear–we all need strength training to keep our muscles strong and healthy!
References:
- J Steroid Biochem Mol Biol. 2014 Oct; 144PA: 138–145.Published online 2013 Nov 12. doi: 10.1016/j.jsbmb.2013.11.003.
- Pediatr Health. 2010;4(1):89-97.
- Clinical Interventions in Aging, 2019; Volume 14: 1751 DOI: 10.2147/CIA.S222143.
- 2013 Apr 1; 2(2): 92–98.Published online 2013 Apr 1. doi: 10.4161/adip.22500.
- Med Sci Sports Exerc. 2013 Jan;45(1):157-62. doi: 10.1249/MSS.0b013e31826c9a78.
- MedLine Plus. “Vitamin D”
- Endocr Connect. 2019 Feb; 8(2): R27–R43. Published online 2019 Jan 16. doi: 10.1530/EC-18-0432.
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