Feature Summary

Vitamin D is a hormone now widely recognized to be important to many body systems and a large number of physiological processes and it may also be one of the most common nutrient deficiencies in the world.¹ Many recent studies have linked lower levels to an increased risk of cardiovascular disease including hypertension, peripheral vascular disease, coronary artery disease and heart failure, as well as several types of cancer, autoimmune disease and type 2 diabetes.^2,3,4 Vitamin D is needed for intestinal calcium absorption, skeletal bone integrity as well as skeletal muscle strength and function and has been associated with overall physical fitness.^5,6,7 Vitamin D is critical for healthy immune function and may reduce the risk of infection, especially respiratory tract infections.^8,9 Given that essentially every tissue in the body has a receptor for vitamin D, it is hard to overestimate its importance.¹⁰ Many practitioners recommend supplementation to achieve blood levels of 25-OH-vitamin D between 50-80 nmol/L, which often requires doses of 1000-2000 IU per day, and more for those with common genetic variants affecting vitamin D metabolism.