A recent Wall Street Journal article titled Elite Athletes Try a New Training Tactic: More Vitamin D garnered a lot of attention on one of the randonneuring chat lists I frequent.
The article discussed how some college and pro sports teams “think the nutrient may help players avoid injury, among other benefits.” While it’s an interesting topic, to be sure, a causal reading of the article would lead one to conclude that vitamin D alone prevents all kinds of injuries – especially bone fractures.
The facts are that vitamin D + calcium + weight-bearing exercise strengthens bones and helps prevent bone injuries.
Our Bones Require Constant Rebuilding
The WSJ piece makes the case that low vitamin D may result in more injuries, but it doesn’t explain why until well into the story:
“Vitamin D helps the body absorb calcium to keep bones dense.”
Our bones are constantly wearing out, and we need to keep rebuilding them. That takes calcium, and that’s the main reason why vitamin D is important.
But you can consume massive amounts of vitamin D and calcium and still have weak bones if all you do is ride your bike.
Bones are like muscles. They get stronger if you overload them and weaker if they aren’t subjected to overload. Olympic cyclists were tested at the Olympic Training Center in Colorado Springs. At full sprint on the bike, the load on their leg bones was less than the load on their bones just walking!
Cyclists Need Much More Than Just Vitamin D
Bone health in later life also depends on how strong your bones were developed in your formative years. Gymnasts have the strongest bones because of the flying dismounts.
I have all of my clients over age 50 walk (at least) 90 minutes a week. The weight-bearing strength training exercises are also beneficial: step-ups with a load, squats, split squats, lunges, etc. If your knees tolerate running, that’s great for bone health. I just finished a 3-hour XC ski when I wrote this. That’s another weight-bearing exercise. Social dancing is also good, as are sports like racquetball, basketball, soccer, etc.
Vitamin D is also important for other reasons. According to the Mayo Clinic:
“Low vitamin D status has been associated with an increased risk of type 1 diabetes mellitus, cardiovascular disease, certain cancers, cognitive decline, depression, pregnancy complications, autoimmunity, allergy, and even frailty.”
Get Enough, But Not Too Much, Vitamin D
I average two hours a day outdoors even in the winter. But in the winter, the sun angle is low in the Northern Hemisphere so it’s not stimulating much vitamin D production. Since D may help with seasonal depression, I take 4,000 IU in the winter, the dose considered safe by the Mayo Clinic. This is more than the recommended daily allowance of 600 IU for people age 1-70 and 800 IU for people over 70.
But you can effectively overdose on Vitamin D, too. Some vitamins (B, C, for example) are water soluble and if you take too much the result is yellow urine. Other vitamins,including D, are fat-soluble, and if you take too much it builds up in your fatty tissues rather than being excreted. According to the Mayo Clinic:
“The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), which can cause poor appetite, nausea and vomiting. Weakness, frequent urination and kidney problems also may occur. Treatment includes the stopping of excessive vitamin D intake.”
A personal anecdote: Finishing a snowy, winter century a few years ago I crashed on railroad tracks and broke my pelvis. Since I knew the risk of weaker bones in older folks, I asked the doctor, “Do I have weak bones?” She replied, “No, just bad luck!”