Vitamin D deficiency is a global epidemic affecting 40% of Americans. It is associated with increased risk of cancer, cardiovascular disease, autoimmune disease, and all-cause mortality.
The Vitamin D Deficiency Epidemic
Vitamin D deficiency (blood level <20 ng/mL) affects approximately 40% of Americans and up to 80% of people in northern latitudes during winter. Insufficiency (20-30 ng/mL) affects an additional 40%.
The primary cause is reduced sun exposure — the result of indoor lifestyles, sunscreen use, and the shift away from outdoor work. Dietary sources of vitamin D are limited and insufficient to maintain adequate levels.
The Evidence for Vitamin D
Cancer: Multiple observational studies find that low vitamin D levels are associated with increased risk of colorectal cancer, breast cancer, prostate cancer, and all-cause cancer mortality. A meta-analysis found that vitamin D supplementation reduces cancer mortality by 16%.
Cardiovascular disease: Low vitamin D levels are associated with increased cardiovascular risk. Vitamin D improves endothelial function, reduces blood pressure, and reduces inflammatory markers.
Autoimmune disease: Vitamin D is essential for immune regulation. Low vitamin D levels are associated with increased risk of multiple sclerosis, rheumatoid arthritis, type-1 diabetes, and inflammatory bowel disease.
All-cause mortality: A meta-analysis of 73 randomized controlled trials found that vitamin D supplementation reduces all-cause mortality by 6%.
Vitamin D deficiency affects 40% of Americans. A meta-analysis found that vitamin D supplementation reduces all-cause mortality by 6% and cancer mortality by 16%.
Optimal Vitamin D Levels
The conventional "normal" range for vitamin D (30-100 ng/mL) is based on bone health. For non-skeletal health benefits, many researchers believe the optimal range is 40-60 ng/mL.
Most people need 2,000-4,000 IU/day of vitamin D3 to maintain levels in the optimal range. Blood testing is recommended to determine the appropriate dose.
Vitamin K2: The Essential Cofactor
Vitamin D increases calcium absorption. Without adequate vitamin K2, this calcium may be deposited in arteries rather than bones. Vitamin K2 (particularly MK-7) directs calcium to bones and away from arteries.
People supplementing with vitamin D should also take vitamin K2 (100-200 mcg/day of MK-7) to prevent arterial calcification.
Sun Exposure
Sun exposure is the most natural and effective way to maintain vitamin D levels. 15-20 minutes of midday sun exposure to arms and legs (without sunscreen) produces 10,000-20,000 IU of vitamin D3 in light-skinned individuals. This is far more than dietary supplementation can provide.
