An Interview with John J. Cannell, M.D

The interests of young adults are more in tune with athletic performance than with preventing the diseases of aging. John J. Cannell, M.D., is reaching out to the young adult audience to help them be healthier for life, by teaching them how to become faster, quicker and stronger as athletes. However, we all can learn how to be healthier from his teachings. Dr. Cannell is a physician, scientist, researcher, teacher and perhaps most importantly, a health activist. He has actively worked to help coal miners avoid black lung, help smokers avoid lung cancer, to reduce the incidence of influenza and address the modern epidemics of childhood (i.e., autism, asthma and autoimmune disorders such as type-1 diabetes mellitus).

In his new book, Dr. Cannell discusses the research that began with Eastern European athletic trainers and is now being confirmed by Western researchers. Few researchers suspected that this vitamin controlled muscle tone, muscle strength, balance, reaction time and physical endurance. It also protects the immune system against the effects of overtraining and improves general health. Most athletes believe they get enough of this vitamin, but blood tests show that the majority of them (as well as non-athletes) are well below the levels needed to produce optimal performance. Even baseball players playing in the mid-day sun in Florida can be very vitamin D deficient, thanks to the liberal use of sunscreens. The good news is that athletes can improve their performance by optimizing their blood levels of this vitamin. Studies show that optimization of vitamin D makes athletes perform faster, quicker and stronger. As discussed in this interview with Dr. Cannell, this optimization of performance can be the difference between champions and also-rans.

Studies have also shown that optimizing vitamin D levels will help non-athletes go about the tasks of daily living better. Everyone needs balance and strength for daily activities including standing on one leg to put on underwear, getting out of the bathtub or springing up out of the rocking chair.

Dr. Cannell graduated with a degree in zoology from the University of Maryland, where he was a member of Phi Beta Kappa. He received his M.D. from the medical school at the University of North Carolina. After a year-long surgery internship at the University of Utah and four years of practicing itinerant emergency medicine, he began as a general practitioner in the coalfields of Appalachia.

Later, Dr. Cannell left general practice and went back to school to study psychiatry. He moved to Atascadero, CA, in the late 1990s and began working as a psychiatrist at Atascadero State Hospital, the largest hospital in America for the criminally insane. There, his long-held interest in clinical nutrition was re-awakened. The further he studied nutrition, the more and more vitamin D3 (cholecalciferol) caught his attention.

As Dr. Cannell began to study the effects of vitamin D, he immediately realized that the recommendations of the IOM’s Food and Nutrition Board (FNB) were placing many Americans at risk. He found that vitamin D insufficiency was common in older adults, even using conservative cutoff points for vitamin D blood levels. Dr. Cannell was left wondering whom he should believe: Nature or the FNB? In 2003, he recruited professional colleagues, scientists and friends for a board of directors and took the steps necessary to incorporate The Vitamin D Council as a tax-exempt, nonprofit, 501(c)(e) corporation.

In September 2006, Dr. Cannell’s seminal article, “Epidemic Influenza and Vitamin D” was published in the journal, Epidemiology and Infection. The article presented a revolutionary new theory on vitamin D’s link to influenza and was co-written with some of the world’s top vitamin D experts.

After a number of other publications, including one on the role of vitamin D deficiency in the autism epidemic, in 2009, he published “Athletic Performance and Vitamin D,” in Medicine & Science in Sports & Exercise, the flagship journal of the American College of Sports Medicine.

His new book, The Athlete's Edge: Faster, Quicker, Stronger With Vitamin D (2011) (, is based on this paper.

Passwater: Dr. Cannell, what a clever way to educate millions of young adults on improving their general health. You used athletic competition to reach a large audience.

Cannell: Yes, I hope that all athletes will read this and know that their noon basketball game is one kind of athletic performance, but their grandmother’s ability to dress herself is the same kind of athletic performance. In The Athlete's Edge: Faster, Quicker, Stronger With Vitamin D, I actually discussed neuromuscular performance, something we all use and need, to educate people about vitamin D.

Passwater: The concept that vitamin D improves athletic performance was new to modern science until you wrote a newsletter about it in March 2007 ( Let’s get right to the point. Do you present evidence that ideal blood levels of vitamin D improve timing, balance, muscle strength, quickness, speed and endurance in your book? Is vitamin D status significantly associated with muscle power and force?

Cannell: Yes, and the effect is not minor. A study in Manchester, England measured the jumping power, jumping height and jumping velocity of teenage girls along with their blood levels of 25-hydroxy vitamin D. The researchers found that that the higher the vitamin D levels, the higher, the stronger and the faster the jumps of these teenagers, and all of the associations were statistically highly significant. The researchers concluded, “Vitamin D status is significantly associated with muscle power and force.”

At least 18 studies in the scientific literature, some of them very large, specifically tried to determine whether physical performance is associated with vitamin D levels.

Passwater: How can this be so? How can vitamin D do all of this?

Cannell: We evolved outside where these physical assets were essential for survival in a cruel and unpredictable world. Given that it is a steroid hormone, it would surprise me if vitamin D were not involved in athletic performance. It can do all of this because, as a steroid hormone, it has as many mechanisms of action as genes it regulates; the number of vitamin D genes is now above 2,500. 

Passwater: You are in essence saying that research shows low vitamin D levels ensure deficient athletes never achieve their peak athletic performance. I’ll bet that most every athlete who takes a multivitamin or who spends time outdoors (begging the sunscreen problem) feels that he or she is not vitamin D deficient. What do studies show about this reality? What do blood tests indicate?

Cannell: Not only are all indoor athletes deficient, but many outdoor athletes are lacking vitamin D as well because they either exercise when the sun is low in the sky or they slather on the sunblock. If you want to see what outdoor athletes can do, look at the 1968 Mexico City Olympics, where the most world records were set.

Passwater: Yes, the sun intensity is greater at higher altitudes and lower latitudes and produces more vitamin D. Many of the athletes reported early to Mexico City to acclimate to the altitude and received a bonus of extra vitamin D.

What piqued your interest in vitamin D and athletic performance?

Cannell: Remember when the Germans and Russians won every Olympics in the 1960s and 1970s and then upset us in basketball in the 1980s? Well, it turns out that the most convincing evidence that vitamin D improves athletic performance was published in old German and Russian medical literature.

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. When I combined that old literature with the abundant, modern, English-language literature on vitamin D and neuromuscular performance, the conclusion was inescapable.

Passwater: In hindsight, we can look back and see the biochemistry involved. We have discussed in earlier columns that more than 10% of our genes (2,500 out of 22,000) must be told by vitamin D what to do. Is vitamin D involved in instructing our genes to make more muscle?

Cannell: Yes, but little is known about vitamin D and muscle growth in the absence of exercise and training.

Passwater: Let’s get back to some of the studies. I know of no gold-standard, placebo-controlled, double-blind studies on vitamin D and athletic performance with elite athletes. However, as you mentioned, there are various studies with non-elite athletes of various ages.

Cannell:  Studies have been done on populations of healthy persons and persons receiving medical treatment and they have been done on populations of older and younger persons. Seven of eight studies with medical patients found that patients with the highest vitamin D levels had stronger grip or quadriceps strength, better balance or better reaction times.

All seven large cross-sectional, community-based studies of healthy persons showed positive associations between physical performance and vitamin D levels. As one example, a French study of 845 older men found skeletal muscle mass was higher in those with levels above 30 ng/ml than in those with levels of less than 10 ng/ml.

Another example is a Swiss study of more than 300 older persons that confirmed a direct association between vitamin D levels and leg power. As I discuss in my book, a Dutch study of 1,200 individuals found that athletic performance was 78% better in those having vitamin D levels above 30 ng/ml compared to those having levels lower than 10 ng/ml.

Passwater: I found the graphs you provided in your book to be quite striking in the manner in which athletic performance dramatically and steeply improved with vitamin D levels until they plateaued at about 50 ng/ml.

Cannell: Yes. Athletic performance tends to optimize at a blood level of about 50 ng/ml. In a study of 4,100 American adults, Professor Heike Bischoff-Ferrari found a very strong statistical association (p value less than 0.001) between vitamin D levels and athletic performance that indicated the optimal level was about 50 (1).

Passwater: Can vitamin D reduce sports injuries?

Cannell: The Germans thought so and routinely irradiated their athletes with ultraviolet light to prevent injuries, especially repetitive stress injuries. 

Passwater: Inflammation, be it from overuse or overtraining or the tearing of a muscle, is a serious problem for many athletes. Can vitamin D help reduce inflammation?

Cannell: Again, yes, vitamin D is anti-inflammatory, it makes the immune system smarter, not stronger, and gets rid of useless inflammation, retaining only useful inflammation.

Passwater: How about stress fractures?

Cannell: Yes, studies show it definitely reduces the incidence of stress fractures.

Passwater: Many athletes have impaired performance because of nagging back pains. Does vitamin D help prevent this too?

Cannell: Probably; in many cases, I suspect it reduces or even stops the back pain.

Passwater: Why are they inadequately nourished with vitamin D if they want to achieve their peak performance?

Cannell: The same reason as everyone else; the sun scare propagated by the dermatologists.

Passwater: We have discussed some of the points here that you make in your book about vitamin D and performance. There are many more in your book. Is there any evidence that vitamin D improves brain function in athletes, which would also improve athletic performance?

Cannell: Yes, studies suggest exactly that. It appears that vitamin D improves athletic performance not only by improving the function of nerves and muscles, but also by enhancing how quickly the brain can process information. Low levels of vitamin D may impair the central nervous system’s ability to control athletic performance. By that, I mean that vitamin D deficiency may negatively affect the brain’s ability to rapidly sense an athlete’s position, sense which way the athlete needs to move, and reduces the brain’s ability to rapidly transmit the proper signals to the muscles.

Passwater: The book is just what is needed for everyone — a practical, down-to-earth, plain language, common sense approach that has well thought out reasoning and explanations. Non-athlete readers who want to learn about vitamin D or help someone else understand, can forget that the book is aimed at athletes -- which is an important, but secondary aspect – read this book and refer it to your friends. Where is the book available?

Cannell: It is only available on the web at

Passwater: Dr. Cannell, thanks once again for informing our readers about how important adequate levels of vitamin D are for everyone’s health— even athletes who train outdoors and take supplements. Readers can find much more information about vitamin D on the Vitamin D Council Web site at WF

Dr. Richard Passwater is the author of more than 45 books and 500 articles on nutrition. Dr. Passwater has been WholeFoods Magazine’s science editor and author of this column since 1984. More information is available on his Web site,


1. H.A. Bischoff-Ferrari, et al., “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. 80 (3), 752–758 (2004).

Published in WholeFoods Magazine, February 2012