Dr. Dwayne Jackson

The Vital Science Blog

Starting Living Your Best

Body Shop: Vitamin D for Strength!

Vital Science Vitamin D

Vitamin D for Strength!


Dwayne N. Jackson, PhD


Vitamin D increases the absorption of calcium and other minerals in the body, keeping the bones strong and cells happy. But, did you know that vitamin D also helps reduce body fat, increase muscle strength, and promote muscular development? One way vitamin D promotes such an array of fitness benefits is by binding to receptors on muscle cells that enhance muscle contraction and promote increased protein synthesis.



When the skin is exposed to UV radiation (or sunlight) the body can produce its own supply of vitamin D, by converting 7-dehydrocholesterol in the skin— Because of this, vitamin D is more accurately described as a hormone, than a true vitamin. Since the endogenous production of vitamin D depends greatly on sun exposure, and more people are protecting themselves from harmful UV radiation, then it should be of no surprise that vitamin D deficiency is common worldwide, especially in those athletes who train/perform indoors.


A recent systematic review, published in the Journal of Strength Conditioning Research, investigated the effects of vitamin D supplementation on muscle strength in athletes. The authors analyzed 5 randomized controlled trials, which were assessed as ‘excellent quality’, and 1 controlled trial, which was assessed as ‘good quality’. Overall, it was found that supplementing with vitamin D2 did not improve muscular strength; however, vitamin D3 supplementation promoted up to an 18.75% improvement in strength—pretty impressive!


How do you know if you are Vitamin D deficient?


The are many symptoms of vitamin D deficiency; but, to be accurate you should have your blood tested for 25-hydroxy-vitamin D or 25[OH]D, the blood metabolite of vitamin D. This test can be done by your physician or there are also several home “finger prick” tests available online.  Current research suggests that athletes should strive to achieve blood 25[OH]D levels >75 nmol/L.


What form of vitamin D is best?


Research over the past decade clearly shows that vitamin D3 has much higher bioavailability than its sister, vitamin D2. In fact, research suggests that vitamin D3 is at least 300% more functionally effective than vitamin D2.


ACTION POINT: Vitamin D is fat-soluble, so you can choose to take your daily amount in one shot or split it up among the day’s meals. We suggest taking a total (including what is in your multivitamin) of 2000 to 4000 IU of vitamin D3 daily. Research shows that doses in this range boost serum 25 [OH]D to > 75 nmol/L in about 8 weeks.



Chiang CM, Ismaeel A, Griffis RB, Weems S. Effects of Vitamin D Supplementation on Muscle Strength in Athletes: A Systematic Review. J Strength Cond Res. 2017 Feb;31(2):566-574.



Lube up your workouts with fish oil!


Over the years, evidence supporting the health benefits of fish oil supplementation has been astounding.  The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found in cold water fish have been shown to reduce inflammation, increase cardiovascular health, increase the efficiency of the heart during exercise, maintain healthy blood lipid profiles, and, increase fat metabolism and lean mass gain.


Recent work published in the Journal of the International Society of Sports Nutrition gives us yet another reason to be supplementing with fish oil—as it has been shown to increase workout performance, especially if you include heavy eccentric contractions in your training. In this randomized, double-blind, placebo-controlled, and parallel-design study, subjects took daily fish oil (containing 600 mg of EPA and 260 mg of DHA) or a placebo for 8 weeks before and on the day of exercise testing. They continued to take the supplement or placebo for 5 days after exercise testing.


It was found that that the fish oil supplement inhibited motor nerve deficits normally observed after intense eccentric exercise. Overall, fish oil supplementation for 8 weeks promoted greater strength, improved muscle flexibility, and decreased delayed onset muscle soreness (DOMS) after intense eccentric exercise. The authors speculated that the mechanisms underlying these observations are a result of improved nerve structure and function associated with fish oil supplementation.


ACTION POINT: To reap all the health and exercise benefits of fish oil, take 1 to 3 grams of high EPA and DHA fish oil with breakfast, lunch, and dinner.



Ochi E, Tsuchiya Y, Yanagimoto K. Effect of eicosapentaenoic acids-rich fish oil supplementation on motor nerve function after eccentric contractions. J Int Soc Sports Nutr. 2017 Jul 12;14:23.




Coaching Subscriptions packages

Weight Loss Transformer

Starting at $549.99

Fully Optimized Human (Exclusive access to Dr. Dwayne)

Starting at $1,499.99

Muscle Builder Elite

Starting at $549.99

Coaching The Coach

Starting at $199.99

Gut Health

Starting at $499.99

Optimized Human

Starting at $749.99
Starting Living Your Best

If you’re interested in staying fit, eating healthy, and living a healthier life, then you should join my newsletter! I’ll be sending out regular updates on fitness nutrition and health, so you can stay informed and make the most of your health.

Scroll to Top