Tip: The Vitamin You've Got To Take... Seriously.

Let's start with a question bound to pique every meathead's curiosity: Does vitamin D supplementation affect your strength? And if so, by how much?

Science says yes. A comprehensive research paper noted that daily vitamin D intake significantly increases both upper and lower limb strength (2).

Another review investigating the effects of vitamin D on strength measures in athletes found a positive impact on muscle strength. It should be noted that not all D's are equal. Vitamin D2 had no effect whereas vitamin D3 showed a clear trend for strength gains, which ranged from 1.37 to 18.75% in the studies analyzed (3).

The promise of adding pounds to your bench press and squat max should convince even the most skeptical gym bro of its performance-enhancing powers. But does extra D contribute to sports performance on the field?

In a UK study conducted on professional athletes and healthy non-athletes, subjects supplementing with 5000 IU of D3 per day for eight weeks witnessed a significant improvement in 10-meter sprint time and vertical jump height over subjects taking placebo. Interestingly, the researchers also stated that inadequate vitamin D concentration is downright detrimental to athletic performance (4).

Yet another study done on college football players participating in the NFL Scouting Combine found a link between low D and lower extremity muscle strain or core muscle injury (5).

If that wasn't enough, the positive effects of vitamin D aren't limited to increased strength, improved sports performance, or injury prevention. Vitamin D levels are inversely related with upper respiratory tract infections. If you're low on D, your risk of catching the flu goes way up (6). On a larger scale, this can have a jarring effect not only on the performance of individual athletes but on the entire team as well if the flu works its way through the roster.

As you can guess by now, a daily dose of D protects against acute respiratory tract infection (7). So, do yourself and those around you a favor by stocking up on bottles of vitamin D and make sure your buddies follow suit. That way, if you happen to sneeze right in some poor sap's grill after he tickles your ribs with an illegal jab or two in a wild goal-mouth scramble during practice, he'll be spared the vile phlegm fest otherwise bound to ensue.

If you suspect your vitamin D is low, your first step is to get a blood test. Past your 30's, you should be monitoring your health markers through regular blood work anyway, so this is nothing to scoff at.

Even if your lab results indicate you're within range of "acceptable" D levels, popping a pill or two every day, thus pushing your D numbers from average to optimal, can only help.

Probably more than you'd think. According to the Food and Nutrition Board, 2000 IU is a safe daily "tolerable upper intake level" for vitamin D. However, this may be lower than justified. In fact, daily doses of D3 up to 10,000 IU have been deemed safe in healthy subjects (8).

Nevertheless, you can't go wrong with taking some extra vitamin D. It's cheap, convenient, and most importantly, it works.

1. Galesanu C et al. Vitamin D Deficiency and the Clinical Consequences. Rev Med Chir Soc Med Nat Iasi. Apr-Jun 2015;119(2):310-8. PubMed.
2. Abrams GD et al. Effects of Vitamin D on Skeletal Muscle and Athletic Performance. J Am Acad Orthop Surg. 2018 Apr 15;26(8):278-285. PubMed.
3. Chiang CM et al. Effects of Vitamin D Supplementation on Muscle Strength in Athletes: A Systematic Review. J Strength Cond Res. 2017 Feb;31(2):566-574.
4. Close GL et al. Assessment of vitamin D concentration in non-supplemented professional athletes and healthy adults during the winter months in the UK: Implications for skeletal muscle function. J Sports Sci. 2013;31(4):344-53. PubMed.
5. Hospital for Special Surgery. More than half of college football athletes have inadequate levels of vitamin D: Vitamin D deficiency linked to muscle injuries. ScienceDaily. 17 March 2017.
6. Ginde AA et al. Association Between Serum 25-Hydroxyvitamin D Level and Upper Respiratory Tract Infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009 Feb 23;169(4):384-90. PubMed.
7. Martineau AR et al. Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data. BMJ 2017; 356:i6583. PubMed.
8. Hathcock JN et al. Risk assessment for vitamin D. Am J Clin Nutr. 2007 Jan;85(1):6-18. PubMed.