Vitamin D has long been known to prevent rickets (malformation and weakness of bones) and osteoporosis, but its benefits go far beyond bone health.
We now know that vitamin D supplementation during pregnancy and infancy may reduce the risk of a child developing type 1 (juvenile) diabetes by 80 to 90 percent!
The vitamin D and diabetes connection
Finland now has the highest incidence of type 1 diabetes in the world. But why? Before the 1960s, Finland was near the world averages for diabetes.
As Dr. Whitaker reported, in 1964, Finnish health authorities lowered the vitamin D recommendation for infants from 4,500 IU to 2,000 IU per day. Cases of type 1 diabetes began to rise. When it was reduced to 1,000 IU a decade later, the incidence climbed even faster. But it gets worse.
In 1992 the suggested intake was cut back to 400 IU. The rate of type 1 diabetes ballooned, and has continued to go up ever since.
Type 1 diabetes is now epidemic in Finland, affecting about 65 out of 100,000 children, four times what it was 50 years ago. But childhood diabetes in sun-drenched countries is so rare that it’s considered an oddity.
Cuba, for instance, has only 2 cases per 100,000 kids. Cuba may not have the world's best healthcare or even adequate vitamin D recommendations, but it does have sunshine—and lots of it, all year long. And as Dr. Whitaker points out, there’s no question that sunshine slashes the rate of type 1 diabetes!
How vitamin D prevents diabetes
Frank Garland, PhD, of the University of California explains that the cells in various tissues and organ systems work together. Strong, healthy interfaces among similar cells allow them to function as a unit, share resources, and maintain tight barriers that screen out microbes, immune cells, and the like. Proteins called cadherins play a key role in holding cells together, and their proper function is dependent on ample amounts of vitamin D.
When D levels are low, these intercellular junctions become weak and leaky. In the case of type 1 diabetes, breaks in the barriers allow immune cells to slip through and attack insulin-producing cells, or islet cells, in the pancreas. This interaction creates antigens that spur the immune system to attack more vigorously, and a full-fledged autoimmune reaction ensues. Sufficient levels of vitamin D simply tighten up the junctions and stop leakage and islet cell destruction, thus preventing diabetes.
Forty-to-sixty percent of the U.S. population is vitamin D deficient, and most of the world’s population—including 85 percent of Americans—are always deficient in vitamin D during the winter, every single year.
Getting enough D to prevent diabetes and other disease
Misconceptions about getting adequate vitamin D from food abound. As Dr. Whitaker points out, you’d need to eat two or three daily servings of salmon or sardines, drink five glasses of fortified milk, or take a spoonful of cod liver oil just to get the meager RDA of vitamin D, which isn’t nearly enough. In fact, it’s almost impossible to get optimal levels from food alone.
There are only two ways to get adequate vitamin D: sunshine and supplements. The majority of your body’s vitamin D is produced through a chemical reaction in your skin, and just 15–20 minutes of sunlight helps activate that process.
But we've become so sun-phobic, even in summer deficiencies are prevalent. Dr. Whitaker's recommended daily doses of vitamin D are as follows:
- for infants, 1,000–1,800 IU;
- for children ages 1 to 12, 2,000 IU;
- for adults, 2,000–4,000 IU—or more, if needed, to bring blood levels into the optimal range (between 40 and 70 ng/mL)






