With the help of my wife and mother-in-law, both of whom are Russian, and with the help of Marc Sorenson (whose book Solar Power for Optimal Health is a must-read) I was able to look at translations of the old Russian and German literature. Combining that old literature with the abundant, modern, English-language literature on vitamin D and neuromuscular performance, the conclusion was inescapable: the readers who wrote me were right!
If you are vitamin D deficient, the medical literature indicates that the right amount of vitamin D will make you faster, stronger, improve your balance and timing, etc. How much it will improve your athletic ability depends on how deficient you are to begin with. How good an athlete you will be depends on your innate ability, training, and dedication.
However, peak athletic performance also depends upon the neuromuscular cells in your body and brain having unfettered access to the steroid hormone, activated vitamin D. How much activated vitamin D is available to your brain, muscle, and nerves depends on the amount of 25-hydroxyvitamin D in your blood. In turn, how much 25-hydroxyvitamin D is in your blood depends on how much vitamin D you put in your mouth or how often you expose your skin to UVB light.
One might ask why I would write about such a frivolous topic like peak athletic performance when cancer patients all across this land are dying vitamin D deficient. The reason is that, like many vitamin D advocates, I have been disappointed with the medical profession's and the public's lack of enthusiasm over vitamin D. Maybe people like my young basketball player will take an interest in vitamin D if they know of its potential benefit to their athletic performance? Let's see... Hey jocks! Want to improve your game? Take vitamin D. Listen up—I'm talking speed, balance, choice reaction time, muscle mass, muscle strength, squats, reps—important stuff! Want to learn more? Here's the first-ever Sports Edition Vitamin D Quiz:
German and Russian Olympic athletes have used UVB radiation to strengthen their performance.
1 False True
True. I found tantalizing evidence that the Russians, and especially the Germans, possessed the knowledge that vitamin D increases physical performance, using it to their advantage during the '60s and '70s when those two nations took turns placing first and second in the Olympics every year. For example, in 1938, Russian researchers reported that a course of ultraviolet irradiation improved speed in the 100-meter dash in college students compared to matched controls, both groups undergoing daily training. Average 100-meter dash times decreased from 13.51 seconds to 13.28 seconds in the non-irradiated training students, but from 13.63 seconds to 12.62 seconds in the irradiated students undergoing training. Here we see training improved times but training and irradiation improved times much more. Obviously, irradiation or vitamin D would not render the same magnitude of improvements in world-class sprinters, but they might be happy with a few milliseconds. Gorkin Z, Gorkin MJ, Teslenko NE. The effect of ultraviolet irradiation upon training for 100m sprint. The Journal of Physiology of the USSR [Fiziol, z. (RSSR)] 1938;25: 695–701. In Russian.
If you would like to know what German scientific-thinking was, read this summation of the early German literature:
"It is a well-known fact that physical performance can be increased through ultraviolet irradiation. In 1927, a heated argument arose after the decision by the German Swimmers' Association to use the sunlamp as an artificial aid, constituting an athletic unfairness, doping, so to speak. In 1926, Rancken had already reported the improving effect of sunlamp irradiation on muscle work with the hand-dynamograph. Heib observed an improvement in swimming times after repeated irradiations. In thorough experiments, Backmund showed that a substantial increase in muscle activity happens after radiation of larger portions of the body with an artificial sunlamp; that this performance increase is not caused through local (meaning direct or indirect) effects on the musculature, but through a general effect. This general effect, triggered by ultraviolet irradiation, is caused by a systemic effect on the nervous system." Parade GW, Otto H. Die beeinflussung der leistungsfahigkeit durch Hohensonnenbestrahlung. Zeitschrift fur Klinische Medizin (Z Klin Med),1940;137:17–21. In German.
In 1945, two Americans measured the cardiovascular fitness and muscular endurance of eleven male Illinois subjects undergoing training in an indoor physical education class, comparing them to 10 matched controls. Both groups underwent similar physical training. Treatment consisted of ultraviolet irradiation, given in the nude, up to two minutes per session, three times per week, for ten weeks in the late fall and winter. After ten weeks, the treatment group had a 19% standard score gain in cardiovascular fitness compare to a 2% improvement in the control students. To regular readers of this newsletter, it should come as no surprise that the un-irradiated control group reported twice as many viral respiratory infections as the treatment group. Allen R, Cureton T. Effects of Ultraviolet Radiation on Physical Fitness.Arch Phys Med 1945;10:641–44.
In 1952, the German sports medicine researcher, Spellerberg, reported on the effects of wholesale irradiation of athletes studying and training at the Sports College of Cologne—including many elite athletes—with a "central sun lamp." The College routinely irradiated athletes in their bathing suits, on both sides of their bodies, for up to ten minutes, twice a week, for 6 weeks, resulting in a "convincing effect" on athletic performance and a "50% reduction" in chronic sports injuries. Results were particularly impressive for swimmers, soccer, handball, hockey, and tennis players, as well as for boxers and most track and field athletes. He reported that irradiation leading to burns, further irradiation of athletes having achieved peak performance, and irradiation within 24 hours of competition, all impaired athletic performance. Their results were so convincing, the "Sports College of Cologne officially notified the National German and International Olympic committee." Spellerberg AE. Increase of athletic effectiveness by systematic ultraviolet irradiation. Strahlentherapie. 1952;88(3–4):567–70. In German.
In 1952, Ronge exposed 120 German schoolchildren to UV lights installed in classrooms and compared them to 120 un-irradiated control children. Over a two-year period—excluding summer vacations—he tested both groups with a series of six cardiovascular fitness tests using a bike ergometer. Un-irradiated children showed a distinct seasonality in fitness, with the highest values right after summer break and the lowest values in the spring. Treated children showed no seasonal differences in physical performance. Differences in work performance between the irradiated and un-irradiated children were most conspicuous in the spring with 56% difference between the two groups. In a final experiment, he gave 30 children in the control classrooms 6.25 mg (250,000 IU) of vitamin D as a single dose in February and found their performance had "increased considerably," one month later but did not report the actual numbers. He concluded that vitamin D, either as a supplement or induced via UV irradiation, improved physical performance. Ronge HE. Increase of physical effectiveness by systematic ultraviolet irradiation. Strahlentherapie 1952;88:563–6. In German.
In 1954, another researcher, at the Max-Planck Institute for Industrial Physiology in Dortmund, Germany, administered three different wavelengths of UV light over 8 weeks to university students. He found that ultraviolet light in the vitamin D-producing UVB range was consistently effective in reducing resting pulse, lowering the basal metabolic rate, and increasing athletic performance. UVA had no effect. Interestingly, artificial UVC irradiation (normally completely filterd out by the atmosphere and therefore not naturally present on earth) also gave some positive results. Lehmann G. Significance of certain wave lengths for increased efficacy of ultraviolet irradiation. Strahlentherapie. 1954 Nov;95(3):447–53. In German.
In 1956, Hettinger and Seidel irradiated seven subjects in two different experiments: athletic performance on bike ergometers and forearm muscle strength. They found that UV radiation induced a significant improvement in both muscle strength and athletic performance. Hettinger T, Seidl E. Ultraviolet irradiation and trainability of musculature. Int Z Angew Physiol. 1956;16(3):177–83. In German.
Another German researcher, at the Institute for Medical Physics and Biophysics at the University of Gottiingen, studied reaction times (the time needed to recognize a light and switch it off) during October and November in a series of controlled experiments on sixteen children and an unspecified number of adults. He first controlled for practice effects (getting better by practicing) and then administered nine full-body, UV radiation treatments over three weeks to the two treatment groups, using placebo radiation in the two control groups. UV radiation improved choice reaction time by 25% in the children and 20% in the adults while reaction time worsened in the controls. The improvements in the irradiated groups peaked at the end of the three weeks of UV treatments, reverting to baseline levels three weeks later. In the two control groups, he found distinctly improved reaction times in the sunnier months. Sigmund R. Effect of ultraviolet rays on reaction time in man. Strahlentherapie. 1956;101(4):623–9. In German.
The next study threw me because it was very well conducted, meticulously designed, and completely negative. In 1963, Berven reported on the effects of ultraviolet irradiation and vitamin D supplementation in a group of thirty Stockholm schoolchildren, aged 10–11, comparing them to appropriate controls. He found no seasonality of fitness in the control group and no effect on bike ergometer performance from either irradiation or from two different vitamin D supplementation protocols (1500 IU of cholecalciferol daily for two months or a single dose of 400,000 IU of ergocalciferol). Berven H. The physical working capacity of healthy children. Seasonal variations and effect of ultraviolet irradiation and vitamin D supply. Acta Paediatr Suppl. 1963;:suppl 148:1–22.
However, two things were not right and got me thinking. One, Berven found no seasonality of physical fitness and was the only author who found no such seasonal variations in athletic performance. Second, he found no effect from irradiation—again, the only author to do so. Then I realized he was working with Swedish children in the late 1950s. Supplementation of children with high doses of vitamin D, often as cod liver oil, was routine in Scandinavia in the past, particularly in children. For example, in neighboring Finland, the official recommended daily dose of vitamin D for children, including infants, was 4,000 IU/day until 1964, when authorities reduced it to 2,000 IU/day—yes, you read that correctly—4,000 IU per day for infants (which is too much by the way). Hypponen E, et al. Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study. Lancet. 2001 Nov 3;358(9292):1500–3.
Hypponen reports that, in 1975, Finnish authorities reduced the recommended dose to 1,000 IU/day. In 1992 they reduced it even further, to 400 IU/day. I emailed Professor Elina Hypponen who confirmed that the Swedish recommendations were similar to the Finnish ones. Therefore, it seems highly unlikely that many of Berven's Swedish children, studied in 1958 and 1959 and all from "families with a good standard of living," were vitamin D deficient. Therefore, this study showed that vitamin D will not improve athletic ability in vitamin D replete people. That's very important because it indicates that more is not necessarily better, it's only better if you are not taking enough.
In the 1960s, three American researchers conducted experiments with university students. Rosentswieg studied the effects of a single six-minute dose of UV light on each side of the trunk in twenty-three college women. In various tests he recorded changes of muscle strength at 1 and 5 hours. He found a trend towards significance after five hours in the white students, but not in those who were black. Then, in 1968, Cheatum found that a six-minute administration of UV light on each side of the trunk increased the speed of fifteen college women in the 30-yard dash and in '69, Rosentswieg found it improved bicycle-ergometer performance in college women. However, unlike the Germans and Russians, I could find no evidence that any of these American findings interested any American professionals involved in the care or training of athletes. Rosentsweig J. The effect of a single suberythemic biodose of ultraviolet radiation upon the strength of college women. J Assoc Phys Ment Rehabil. 1967 Jul–Aug;21(4):131–3. Cheatum BA. Effects of a single biodose of ultraviolet radiation upon the speed of college women. Res Q. 1968 Oct;39(3):482–5. Rosentswieg J. The effect of a single suberythemic biodose of ultraviolet radiation upon the endurance of college women. J Sports Med Phys Fitness. 1969 Jun;9(2):104–6.
Athletic performance peaks in the winter and is lowest in the summer.
2 False True
False. The studies below show that tests of physical performance peak in the summer (when vitamin D levels peak), start to decline in early autumn as vitamin D levels decline, and reach their lowest point in late winter (when vitamin D levels bottom out). However, it is reasonable to assume that any associations between athletic performance and summer season may be due to "reverse causation." That is, improved athletic performance in the summer might be secondary to increased outdoor physical and recreational activity in the warmer weather with an indoor sedentary lifestyle during the colder months. Maybe people have better athletic ability in the summer simply because they exercise more? If that is true—and using the same logic—athletic performance should not begin to decline until late autumn, because at most temperate latitudes early fall weather is ideal for outdoor physical activities.
However, some of the studies below did control for seasonal variations in time spent exercising. Besides a consistent positive association of summer season with improved athletic performance, they found an unexplained, abrupt reduction in athletic performance beginning in the early fall, when vitamin D levels decline.
For example, in 1956, German researchers found a distinct seasonal variation in the trainability of musculature when studying wrist flexor strength in twenty-one German subjects undergoing daily training. They found highly significant seasonal differences with peak performance in late summer and an unexplained sharp decline beginning in October followed by nadirs (low points) in the winter. Hettinger T, Muller EA. Seasonal course of trainability of musculature. Int Z Angew Physiol. 1956;16(2):90–4.
A study of Polish pilots and crew found physical fitness and tolerance to hypoxia were highest in the late summer with an unexplained sharp decline starting in September. The authors hypothesized that seasonal variations in an unidentified hormone best explained their results. Kwarecki K, Golec L, Klossowski M, Zuzewicz K. Circannual rhythms of physical fitness and tolerance of hypoxic hypoxia. Acta Physiol Pol. 1981 Nov–Dec;32(6):629–36.
Cumulative work ability among 1,835 mainly sedentary Norwegian men during bicycle exercise tests also showed an August peak, a sharp decline in autumn, and a wintertime nadir. There were no seasonal changes in body weights, as would be expected if it was more caloric-demanding recreational activity during the sunnier months that explained their results. Erikssen J, Rodahl K. Seasonal variation in work performance and heart rate response to exercise. A study of 1,835 middle-aged men. Eur J Appl Physiol Occup Physiol. 1979 Oct;42(2):133–40.
Koch and Raschka controlled for seasonal variations in the time spent exercising by instituting a controlled year-long training regimen beginning in December. The training regimen consisted of at least 20 push-ups/day and two or three long distance races each week for the entire year. They found that both the number of push-ups and muscle strength peaked in late summer followed by a rapid decline in the fall, and a nadir in the winter despite continued training. They concluded that seasonal variations in an unidentified hormone best explained their results. Koch H, Raschka C. Circannual period of physical performance analysed by means of standard cosinor analysis: a case report. Rom J Physiol. 2000 Jan–Dec;37(1–4):51–8.
Vitamin D stimulates growth of muscle fibers that are critical to athletic ability.
3 False True
True. Both animal and human studies have found that vitamin D increases muscle mass in subjects who are vitamin D deficient. Birge and Haddad found that vitamin D caused new protein synthesis in rat muscle. Birge SJ, Haddad JG. 25-hydroxycholecalciferol stimulation of muscle metabolism. J Clin Invest. 1975 Nov;56(5):1100–7.
As for humans, in 1981 Young performed muscle biopsies on twelve severely vitamin D deficient patients, both before and after vitamin D treatment. What he found was that type-2 (fast-twitch) muscle fibers, small before treatment, became significantly enlarged after. Sorensen performed the same study on eleven older patients with osteoporosis and had the same results—an increase in muscle fibers despite lack of physical training. Young A, Edwards R, Jones D, Brenton D. Quadriceps muscle strength and fibre size during treatment of osteomalacia. In: Stokes IAF (ed) Mechanical factors and the skeleton. 1981. pp 137–145. Sorensen OH, Lund B, Saltin B, Lund B, Andersen RB, Hjorth L, Melsen F, Mosekilde L. Myopathy in bone loss of ageing: improvement by treatment with 1 α-hydroxycholecalciferol and calcium. Clin Sci (Lond). 1979 Feb;56(2):157–61.
Sato reported that two years of vitamin D treatment at 1,000 IU per day significantly increased muscle strength, doubled mean diameter, and tripled fast-twitch muscle fiber percentage in the functional limbs of 48 severely vitamin D deficient, elderly stroke patients. The placebo control group suffered declines, both in muscle strength and in fast-twitch muscle fiber size and percentage. Sato Y, Iwamoto J, Kanoko T, Satoh K. Low‑Dose Vitamin D Prevents Muscular Atrophy and Reduces Falls and Hip Fractures in Women after Stroke: A Randomized Controlled Trial. Cerebrovasc Dis. 2005 Jul 27;20(3):187–192 [Epub ahead of print]
These studies reveal that vitamin D stimulates growth (in size and number) of muscle fibers critical to athletic ability in those who are vitamin D deficient.
Neuromuscular performance improves with higher vitamin D blood levels.
4 False True
True. I found thirteen positive studies of associations between vitamin D levels and various parameters of neuromuscular performance. However, they were all in older people. Of course, old people can be athletes too. Furthermore, age differences in physiology and pharmacology are quantitative, not qualitative. That is, what is true in old people will be true in young people, although the magnitude might be different. Higher vitamin D levels are associated with a wide variety of athletic performance but appear to have the strongest associations with balance, timing, and timed tests of physical performance.
The three largest studies had more than7,000 elderly subjects. All found evidence of a vitamin D threshold between 30–50 ng/mL, above which further improvements in athletic performance were not seen. Wicherts and her colleagues found a linear correlation between vitamin D and neuromuscular performance: scores were 78% better for those with vitamin D levels greater than 30 ng/mL as compared to those with levels less than10 ng/mL. Bischoff-Ferrari HA, Dietrich T, Orav EJ, Hu FB, Zhang Y, Karlson EW, Dawson-Hughes B. Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged > or =60 y. Am J Clin Nutr. 2004 Sep;80(3):752–8. Gerdhem P, Ringsberg KA, Obrant KJ, Akesson K. Association between 25-hydroxy vitamin D levels, physical activity, muscle strength and fractures in the prospective population-based OPRA Study of Elderly Women. Osteoporos Int. 2005 Nov;16(11):1425–31. Wicherts IS, et al. Vitamin D status predicts physical performance and its decline in older persons.J Clin Endocrinol Metab. 2007 Jun;92(6):2058–65.
Professor Heike Bischoff-Ferrari, now in Switzerland, did the largest study. She and her colleagues found a strong positive correlation as well as a suggestion of a U-shaped curve with athletic performance on one test. The curve peaked at vitamin D levels of 50 ng/mL before deteriorating with higher levels. The possibility that vitamin D levels around 50 ng/mL may be optimal for athletic performance is intriguing, because such levels are common in humans living in a "natural" state of sun exposure, such as lifeguards or tropical farmers. Bischoff HA, Stahelin HB, Urscheler N, Ehrsam R, Vonthein R, Perrig-Chiello P, Tyndall A, Theiler R. Muscle strength in the elderly: its relation to vitamin D metabolites. Arch Phys Med Rehabil. 1999 Jan;80(1):54–8.
Also interesting, all three studies that looked for an association between mental abilities and vitamin D levels found one. A fourth study, unrelated to athletic function, also found an association. The obvious explanation for these findings is that cognitively impaired patients do not go outdoors as often as higher functioning patients and thus have lower vitamin D levels. However, Dhesi found the association after excluding all but mildly-demented patients, making such an explanation more difficult. Flicker and, more recently, Przybelski and Binkley found the association after controlling for outdoor activities, raising the possibility that the association of vitamin D levels with cognitive abilities is causal. Both the vitamin D receptor and the enzyme necessary to activate vitamin D are present in a wide variety of human brain tissue. If vitamin D deficiency impairs cognitive abilities, it is likely that such deficiencies will also impair the brain's ability to process the complex circuits needed for peak athletic performance. Dhesi JK, Bearne LM, Moniz C, Hurley MV, Jackson SH, Swift CG, Allain TJ. Neuromuscular and psychomotor function in elderly subjects who fall and the relationship with vitamin D status. J Bone Miner Res. 2002 May;17(5):891–7. Kenny AM, Biskup B, Robbins B, Marcella G, Burleson JA. Effects of vitamin D supplementation on strength, physical function, and health perception in older, community-dwelling men. J Am Geriatr Soc. 2003 Dec;51(12):1762–7. Flicker L, Mead K, MacInnis RJ, Nowson C, Scherer S, Stein MS, Thomas J, Hopper JL, Wark JD. Serum vitamin D and falls in older women in residential care in Australia. J Am Geriatr Soc. 2003 Nov;51(11):1533–8. Przybelski RJ, Binkley NC. Is vitamin D important for preserving cognition? A positive correlation of serum 25-hydroxyvitamin D concentration with cognitive function. Arch Biochem Biophys. 2007 Jan 8; [Epub ahead of print].
There can be no doubt that higher vitamin D levels are associated with improved athletic performance in the elderly. From what we know of physiology and pharmacology, the same associations should hold true in young people, including young athletes.
Vitamin D has been found to improve both balance and reaction time.
5 False True
True. Eleven studies found vitamin D improved physical performance in terms of balance and reaction time. Again, almost all the studies were performed with older persons and none of them used world-class athletes. However, there is no medical reason why vitamin D would improve the physical performance of older people who are vitamin D-deficient but not that of younger people. Although, one study did use younger subjects (55 severely vitamin D deficient women) and showed dramatic physical performance effects. Sorensen OH, Lund B, Saltin B, Lund B, Andersen RB, Hjorth L, Melsen F, Mosekilde L. Myopathy in bone loss of ageing: improvement by treatment with 1 α-hydroxycholecalciferol and calcium. Clin Sci (Lond). 1979 Feb;56(2):157–61. Gloth FM 3rd, Smith CE, Hollis BW, Tobin JD. Functional improvement with vitamin D replenishment in a cohort of frail, vitamin D deficient older people. J Am Geriatr Soc. 1995 Nov;43(11):1269–71. Glerup H, Mikkelsen K, Poulsen L, Hass E, Overbeck S, Andersen H, Charles P, Eriksen EF. Hypovitaminosis D myopathy without biochemical signs of osteomalacic bone involvement. Calcif Tissue Int. 2000 Jun;66(6):419–24. Prabhala A, Garg R, Dandona P. Severe myopathy associated with vitamin D deficiency in western New York. Arch Intern Med. 2000 Apr 24;160(8):1199–203. Verhaar HJ, Samson MM, Jansen PA, de Vreede PL, Manten JW, Duursma SA. Muscle strength, functional mobility and vitamin D in older women. Aging (Milano). 2000 Dec;12(6):455–60. Pfeifer M, Begerow B, Minne HW, Abrams C, Nachtigall D, Hansen C. Effects of a short‑term vitamin D and calcium supplementation on body sway and secondary hyperparathyroidism in elderly women. J Bone Miner Res. 2000 Jun;15(6):1113–8. Bischoff HA, Stahelin HB, Dick W, Akos R, Knecht M, Salis C, Nebiker M, Theiler R, Pfeifer M, Begerow B, Lew RA, Conzelmann M. Effects of vitamin D and calcium supplementation on falls: a randomized controlled trial. J Bone Miner Res. 2003 Feb;18(2):343–51. Dhesi JK, Jackson SH, Bearne LM, Moniz C, Hurley MV, Swift CG, Allain TJ. Vitamin D supplementation improves neuromuscular function in older people who fall. Age Ageing. 2004 Nov;33(6):589–95. Sato Y, Iwamoto J, Kanoko T, Satoh K. Low-Dose Vitamin D Prevents Muscular Atrophy and Reduces Falls and Hip Fractures in Women after Stroke: A Randomized Controlled Trial. Cerebrovasc Dis. 2005 Jul 27;20(3):187–192 [Epub ahead of print]
Five converging—but totally separate—lines of scientific evidence leave little doubt that vitamin D improves athletic performance. There is actually a sixth line of evidence that i left out due to its complexity: the two studies I found on muscle strength and vitamin D receptor polymorphisms (genetic variations), both were positive. Anyway, the scientific evidence that UVB radiation, either from the sun or a sunbed, will improve athletic performance is overwhelming and the mechanism is almost certainly vitamin D production. Peak athletic performance will probably occur with 25OHD levels of about 50 ng/mL, a level that can be obtained through the use of supplements as well.
All that is missing is a big time professional or college team identifying, and then treating, their elite athletes who are vitamin D deficient. Can you imagine what such performance-enhancing effects would do for basketball players, the majority of which are black and practice and play indoors all winter? Or gymnasts? Weight lifters? Can you imagine what it might do for those chronic neuromuscular injuries which are so common in sports medicine?
A word of caution, though. The above studies suggest that taking too much vitamin D (more than 5,000 IU/day) may actually worsen athletic performance. So take the right amount, not all you can swallow. Take enough to keep your 25-hydroxyvitamin D levels around 50 ng/mL, year-round. Easier yet, regularly use the sun in the summer and a sunbed (once a week should be about right) in the winter—with care not to burn.
When you think about it, none of this should surprise anyone. Every bodybuilder knows that steroid hormones can improve athletic performance and they certainly increase muscle mass. Barry Bonds knows they increase timing and power. Activated vitamin D is as potent a steroid hormone as exists in the human body. However, unlike other steroids, levels of activated vitamin D in muscle and nerve tissue are primarily regulated by sun exposure. That's right, the rate-limiting step for the autocrine function of activated vitamin D is under your control and depends on how much daily vitamin D you receive. It's ironic that many athletes now avoid the sun. Organized baseball is even promoting sun avoidance and sunblocks. The ancient Greeks knew better; they had their elite athletes train on the beach and in the nude.
So the level of vitamin D (50 ng/mL) associated with peak athletic performance is the very same level that recent studies show also helps to prevent cancer, diabetes, hypertension, influenza, multiple sclerosis, major depression, cognitive decline, etc. But who cares about all that disease stuff old people get! We're talking about important stuff here: speed, balance, reaction time, muscle mass and strength, squats, reps. As for my young basketball player, guess who's now taking 5,000 IU vitamin D a day? That's right! And his 25-hydroxyvitamin D level is now 54 ng/mL. Has this improved his game? Well...he said to me he feels his timing is better, can jump a little higher, run faster and...oh yeah! and that the ball feels "sweeter"—whatever that means. -John Jacob Cannell, MD
My note: this was written in 2007. He now generally says to start with 5,000 IU D3 (125 mcg) then go up or down from there. He also advises parents to give children 1000 IU (25 mcg) per 25 lbs (11kg) body weight - this is the same as 400 IU/10 mcg per 10lbs/4.5kg. In my experience, this is the same dosing required by most high latitude and sun avoidant adults to reach higher optimal 25(OH)D levels.