Vitamin D’s best known role is aiding the intestinal absorption of calcium, necessary for bone health including bone growth and remodeling. Would it surprise you to learn that vitamin D has many other roles in the human body? Many of the body’s tissues contain vitamin D receptors, including the heart and prostate, blood vessels, muscles and the endocrine glands. Vitamin D is involved in cell growth modulation, neuromuscular and immune function and the reduction of inflammation. It might also surprise you to learn that the active form of vitamin D functions as a hormone. Currently, there are at least 200 genes that are known to respond to vitamin D. Vitamin D breaks the rules for all other vitamins in that it is produced by the human body.
Sunlight exposure, specifically ultraviolet B energy, converts the precursor to vitamin D3 in combination with naturally present cholesterol produced by the skin. Vitamin D3 is then processed by the liver and the kidneys into an active usable form. Approximately 10 minutes per day of direct mid-day sunlight exposure is all that is needed to produce vitamin D. However, The National Institutes of Health (NIH) recommends using three sources to ensure sufficient blood levels of vitamin D. These include adequate sunlight exposure, fortified foods and supplementation.
Some of the roles of vitamin D are believed to include:
Immune function: Low levels of vitamin D are believed to compromise immune function. T-lymphocyte cells, the killer cells of the immune system, require vitamin D for activation. When T cells detect a foreign pathogen, they activate a signaling device known as a vitamin D receptor. Without sufficient vitamin D, mobilization of T cells does not occur. T cells that activate successfully become either killer cells that attack and destroy pathogenic cells, or they become helper cells, which enable the body to recognize and remember the pathogen, effectively building immunity against a future encounter.
Bone health: Vitamin D facilitates calcium absorption by influencing calcium-binding proteins, allowing calcium from foods to be better absorbed. Due to the increased absorption of calcium, parathyroid hormones (PTH) levels are better regulated. When adequate levels of calcium are not maintained, increased levels of PTH lead to leaching of calcium out of the bone matrix, resulting in decreased bone strength. Vitamin D works to increase bone strength by mediating the incorporation of calcium into the bone matrix, strengthening bone fibers.
Cancer prevention: Vitamin D helps to regulate cell proliferation by promoting cellular differentiation. It plays a role in the decreased proliferation of cells and their maturation. Cells that reproduce quickly are at a greater risk of developing mutations. Studies suggest that vitamin D helps prevent unrestrained cell multiplication by reducing cell division, restricting blood tumor supply, increasing the death rate of cancer cells and limiting their spread.
Cardiovascular health: Osteoporosis is linked to an increased risk of coronary artery disease. Low blood levels of vitamin D are linked to increased coronary artery calcification, and increased risk of stroke and congestive heart failure.
Autoimmune disease: Low levels of vitamin D have been linked to multiple sclerosis, lupus, rheumatoid arthritis and ulcerative colitis. Vitamin D is also known as an immunomodulator. It helps to regulate the function of lymphocytes, cytokines and macrophage activity. Its role in immune function may aid in the prevention of autoimmune diseases when adequate serum levels are maintained.
Diabetes: Vitamin D plays a role in the secretion of insulin where increased levels of insulin are required. Deficiencies of vitamin D are found to a large degree in people with poorly managed type 2 diabetes and correlates with the presence of cardiovascular disease in diabetics.
Lifestyle factors and the environment have contributed to vitamin D deficiencies in up to 75% of the U.S. population. Increasingly, those deficits are being blamed for many health concerns including osteoporosis, heart disease, cancer and diabetes. Factors that influence vitamin D uptake include aging, skin pigmentation, sunlight exposure, location, obesity, diet, metabolic abnormalities, liver dysfunction, kidney disease and exclusively breast fed infants. Populations at high risk for deficiency include the elderly, adolescents, darker skinned people, obese people and those with limited sun exposure.
Highly bioavailable formulas for vitamin D supplementation include:
Vitamin D3 1000 IU by Pure Encapsulations provides 1,000 IU of vitamin D3 in support of bone health, calcium absorption, immune cell activity and healthy cell metabolism.
D3 1000 by Metagenics supplies 1,000 IU of bioactive vitamin D3 as cholecalciferol to aid in bone strength maintenance and in support of cardiovascular and immune health.
Vitamin D Liquid (D168) by Thorne Research provides 1,000 IU of vitamin D3 in liquid form for easy dosing.
Vitamin D 1,000 IU (83007) by Douglas Laboratories provides 1,000 IU of vitamin D3 for osteo and general health support.