Vitamin D, BCAA, and Arginine
Dwayne N. Jackson, PhD
Recent research has been focused on vitamin D supplementation for athletes. Although the body can make this stuff when the skin is exposed to sunlight (by converting cholesterol to vitamin D), this mechanism of vitamin D “intake” depends greatly on the season and your sunbathing habits. Beyond sun exposure, vitamin D is found in fortified dairy products, fatty fish (salmon, mackerel), and cod liver oil. Classically, vitamin D is intimately involved in calcium handling, bone metabolism, and neuromuscular function—however the latest research shows it does much more.
The recent interest in vitamin D supplementation for athletes has spawned from data showing that skeletal muscle has vitamin D receptors that are involved in muscle strength production and muscle growth through skeletal muscle regeneration. To add to this, it has been suggested that most athletes are vitamin D deficient, especially in the winter months largely as a consequence of inadequate sun exposure, combined with low variety diets.
Signs of deficiency? Many who are vitamin D deficient complain of tiredness, overall weakness, and muscle aches. Since these signs are universal for many problems, your best bet is to take a blood test for 25-hydroxyvitamin D (25[OH]D), which can be done through your family physician or by purchasing an online test kit.
If you are an athlete and tend to avoid sun exposure, then you are likely vitamin D deficient. Supplementation varies, but the daily upper limit of vitamin D intake in adults is generally reported as 2000 iu, however studies in athletes have shown that up to 10,000 iu per day is safe, well tolerated, and beneficial.
You have likely heard of protein spiking that is used by unscrupulous supplement companies to artificially elevate protein levels in protein powders. Well, recent evidence suggests that modest spiking of protein powder with the branched-chain amino acid (BCAA) leucine can maximize protein synthesis after endurance exercise.
In a recent study published in Medicine and Science in Sports and Exercise, researchers sought to determine if a low dose of leucine mixed with a postworkout whey protein/carbohydrate blend would boost protein synthesis after a bout of interval training. In a nutshell, they found that taking 5g of leucine with 23g of whey protein isolate in a postworkout shake maximized protein synthesis.
This is not surprising, since leucine is the primary BCAA involved in turning on anabolism, but it does show that you easily can get more from your protein shakes. It cannot be overstated that we do not recommend using products that add amino acids simply to boost protein scores. As such, we recommend buying blended or pure protein powders (i.e., with no added amino acids), then simply add 5g of free-form leucine to your postworkout shake to maximize anabolism.
It’s been a while since we have seen any research on arginine, but a recent placebo-controlled study published in Biology of Sport highlights new ergogenic benefits for this amino acid. In the study elite level male strength athletes (wrestlers) were given an incremental cycling test that went to max effort and were given either arginine (1.5g /10g body mass) or placebo pre-workout. They found that when the athletes were given arginine, their time to exhaustion increased by 74 seconds compared to placebo— a remarkable difference considering it was during exhaustive exercise.
These data provide one more reason why arginine should be taken prior to heavy training. We recommend taking 3-10g of arginine three times per day with one (large) dose being 30-40 prior to training.