The sunshine vitamin – most of us don’t get enough of it. Not only is vitamin D vital for health, there’s growing evidence that a deficiency increases the risk for a variety of health problems ranging from osteoporosis to autoimmune diseases.
Although we call vitamin D a vitamin, it really isn’t in the classical sense. Instead, the active form of vitamin D acts more like a hormonal signal that turns on and off hundreds of genes that regulate bodily functions – even your muscles. Now a new study shows supplementing with vitamin D may have another benefit – it may improve exercise performance.
Vitamin D and Exercise
In a new study published in the journal Consultant, researchers gave 13 healthy individuals a daily vitamin D supplement or a placebo for a 14-day period. Before, during, and after the 14-day study, researchers tested the participants’ endurance by asking them to cycle on an ergometer for 20 minutes.
The results? The participants who took vitamin D supplements were able to cover a 30% greater distance in 20 minutes compared to what they could do before starting vitamin D supplementation. The participants experienced other benefits as well. For example, they perceived exercise to be less strenuous. Who wouldn’t want that?
In addition, the participants taking vitamin D supplements had lower blood pressure readings AND lower levels of the stress hormone cortisol, released in response to physical or mental stress. According to research, vitamin D blocks the activity of an enzyme necessary to produce cortisol, So, getting enough vitamin D may be a natural way to keep cortisol and the stress response in check.
Why is it important to keep your cortisol level under control? High levels of cortisol are linked with poor blood sugar control and immune function. Plus, elevations in cortisol can lead to a rise in blood pressure and changes in body composition due to the breakdown of muscle and redistribution of fat stores to areas you don’t want, such as around your waist and tummy. This is a common problem in people with metabolic syndrome and insulin resistance.
As the lead researcher in the study, Dr Emad Al-Dujaili points out:
“Vitamin D deficiency is a silent syndrome linked to insulin resistance, diabetes, rheumatoid arthritis, and a higher risk for certain cancers”
Stress, Cortisol, and Vitamin D
If you train too often or for long stretches at a time, especially endurance exercise, your cortisol levels can shoot up in response to training. You can bet marathon runners fight a battle with cortisol during their training and on the day of the big race! Vitamin D may have the added benefit of keeping your cortisol level under better control when you train. This could lead to better exercise performance and, possibly, better recovery after a workout. At the same time, a lower cortisol level bodes well for heart health.
Interestingly, muscles have receptors that bind vitamin D and people with low vitamin D levels often experience muscle weakness and fatigue. Based on some studies, vitamin D may even help muscle recovery, so you bounce back more quickly after a tough workout. Other research suggests vitamin D can enhance muscle strength and balance.
Excessive training can also suppress the function of your immune system and increase the risk for colds and viruses. By modulating immune function, vitamin D may help you avoid picking up the latest virus going around.
Regardless of whether you train hard or hardly train, getting enough vitamin D is essential for health. Although older adults, people with darker skin color, and individuals who live in areas with little direct sunlight are at greatest risk for vitamin D deficiency, the problem impacts people of all ages, even young, healthy athletes.
Sources of Vitamin D
The most reliable source of vitamin D is exposure to sunlight. When light hits your skin, it converts a compound found naturally on the surface of your skin to a vitamin D precursor. Your liver and kidneys then convert this precursor to active vitamin D. Despite the ready availability of sunlight in many locations, most of us don’t have time to “soak up the sun” and probably shouldn’t due to the risk of skin cancer. Unfortunately, when you slather on sunscreen, you greatly reduce the amount of vitamin D your body is able to make.
To make matters worse, the number of foods that contain vitamin D are limited. One of the best natural sources is salmon. Some products, like orange juice, cereals, and dairy products, are fortified with vitamin D. Most people have a problem getting enough dietary vitamin D, and if you eat a vegetarian or vegan diet, it’s almost impossible. Are you at risk? To be safe, ask your doctor to check your vitamin D level with a simple blood test. Based on the results, you’ll find out whether you need to supplement with vitamin D and how much is appropriate.
According to current guidelines, adults age 70 or under should get 600 I.U. of vitamin D and you need 800 I.U. daily if you’re over the age of 70.
Drawbacks to the Study
This study isn’t the final word on exercise performance and vitamin D. Keep in mind, this study was very small in size, but when you combine the results with other research showing vitamin D’s impact on muscle function, it bears watching.
The Bottom Line
Now there’s another reason to make sure you’re not deficient in the sunshine vitamin. When it comes to vitamin D, know your numbers. With the easy availability of vitamin D testing, it’s not hard to know where you stand and whether you need a supplement. Don’t assume because you’re young and healthy that you can’t be vitamin D deficient – find out.
Consultant. ‘Study: Vitamin D Improves Exercise Performance, Reduces CVD Risk” 11-02-15.
Eurekalert.org. “Vitamin D pill a day may improve exercise performance and lower risk of heart disease” November 1, 2015.
Precision Nutrition. “Research Review: Can vitamin D make you a better athlete?”
Asian J of Sports Med. 2(4):211-219.
Med Sci Sports Exerc. 2013 Jan;45(1):157-62. doi: 10.1249/MSS.0b013e31826c9a78.