If there’s one vitamin that’s been in the spotlight the past few years, it’s vitamin D. More a hormone than a vitamin, D is best known for its role in bone health. With osteoporosis being so common, maintaining an adequate vitamin D level is important for preventing bone fractures. Yet there’s growing evidence that vitamin D plays other roles in the human body. For example, having an adequate vitamin D level may lower the risk of health problems by normalizing immune function.
We now know the immune system plays a role in a variety of health problems, including autoimmune diseases, heart disease, and cancer. So, vitamin D is a multi-dimensional compound with a variety of functions.
Vitamin D Deficiency and Muscle Strength
Since one of the signs of vitamin D deficiency is muscle weakness and fatigue, scientists have also questioned whether vitamin D might improve sports performance or enhance muscle strength. What athlete or weight training enthusiast doesn’t want to maximize strength and muscle performance?
Vitamin D is also important for adequate muscle strength and function. Research in older people shows a link between low vitamin D levels, muscle weakness, and a decrease in muscle function. Correcting a low vitamin D level with supplements improves muscle strength and balance, although it’s not clear whether vitamin D supplements in the elderly prevent falls. Some studies show they do while others do not.
So, vitamin D supplementation in older people who are deficient improves muscle strength and function – but what about young, healthy people? Vitamin D may be beneficial even in young, healthy people with a normal vitamin D level. In a meta-analysis of seven studies carried out by researchers in Great Britain, scientists found supplementing with 4,000 International units of vitamin D daily improved both upper and lower muscle strength in young, healthy adults. Of course, you’re likely to reap the most benefits if you’re deficient in vitamin D.
Another interesting study looked at the impact of vitamin D on muscle strength and growth in response to resistance training. In this double-blind study, healthy, untrained men, ages 20-30 and 60-75, took part in a resistance training program. One group received a vitamin D supplement (1920 IU) and 800 milligrams of calcium daily while the other received only calcium over the course of the study. Each did a series of lower body resistance training exercises, using a resistance of between 65 and 70% of their one-rep max. They trained a total of three times weekly. Over the course of the 12-week study, the weight was increased for purposes of progressive overload.
The results? Both groups made gains in muscle strength and size and there were no differences between the vitamin D supplemented group and the control group in either young or older participants. What is worth noting is the older group DID show improvements in muscle QUALITY relative to the non-supplemented group, most notably their type 2A muscle fiber percentage increased more than the control group who didn’t take vitamin D. That’s important because type 2A fibers are fast-twitch fibers that are activated during strength and power moves. These are the fibers we lose more of as we age.
Also, of note is the older participants who took vitamin D had reduced expression of myostatin, a compound that sets a limit on muscle protein synthesis. So, less myostatin would be favorable for building lean body mass.
Although this study didn’t reveal differences in muscle strength in those supplemented with vitamin D, it did show some improvements in muscle quality in the older age group, particularly with regards to fast-twitch muscle fibers. What interesting is this was a group that already had a normal vitamin D level and vitamin D supplementation still had some effect on muscle quality. All in all, you would expect vitamin D supplementation to have the most impact on muscle strength for people who have low or marginally low levels of vitamin D.
Are You Getting Enough Vitamin D?
What’s your vitamin D status? The best source of vitamin D is exposure to direct sunlight. Depending upon where you live and the time of year, you may or may not be absorbing enough light rays for your body to make vitamin D. Plus if you have darker skin, you need more than someone with lighter skin. Sunscreen also reduces your ability to get vitamin D from the sun.
Diet is typically not a good source of vitamin D, although salmon and fortified foods like milk contain respectable amounts. The best way to ensure you’re not deficient is to ask your doctor to check a vitamin D level, a simple blood test. If you’re low, you may need a vitamin D supplement.
Other risk factors for vitamin D deficiency include:
. Living in a part of the country that gets little direct exposure to sunlight.
. Darkly, pigmented skin (as mentioned above)
. Being over the age of 65
. Being a breastfeeding mom
. Taking anti-seizure medications
. Having a health problem that reduces vitamin D absorption from the intestinal tract
If one of the above risk factors applies to you, talk to your doctor about potentially taking a vitamin D supplement.
The Bottom Line
If you have a low or marginally low level of vitamin D, boosting your level through diet, sun exposure, or supplements could enhance muscle strength and quality. It’s less clear whether taking ADDITIONAL vitamin D when your level is normal offers any added benefits.
It’s possible, based on the study above, that you might experience some improvements in muscle quality if you’re over the age of 60 and take a vitamin D supplement, assuming you are resistance training too. Keep in mind that maintaining an adequate vitamin D level is important for more than just muscle strength but also for the health of your bones and immune system. Make sure you’re exposing your skin to sunlight for 15 minutes several times a week if you’re not taking a supplement.
References:
BMC Musculoskeletal Disorders 2015,16 (Suppl 1):S16.
BioMed Research International Volume 2015 (2015), Article ID 953241, 11 pages.
Jour12+ e in Sport. September 2015Volume 18, Issue 5, Pages 575-580
Fitness RX. February 2016. “Vitamin D Increases Upper and Lower Body Muscle Strength”
Nutr Metab. 2015;12(32)
Related Articles By Cathe:
Can Vitamin D Improve Exercise Performance?
Can Vitamin D Improve Your Body Composition?
This Vitamin May Help You Retain Muscle Mass after Menopause
6 Surprising Reasons You Gain Weight in the Winter
Calcium and Vitamin D: Too Much of a Good Thing?
5 Factors That Negatively Affect Your Vitamin D Level
3 Ways Muscles Age and How You Can Prevent It
