The Deal with Vitamin D

Vitamin D, also known as calciferol, is a fat-soluble vitamin (stored in the liver and fatty tissue). We obtain Vitamin D from food, or from skin exposure to UVB sunlight; and, it is processed by the liver and kidneys to its active form (1,25-hydroxycholecalciferol).

Dietary sources for Vitamin D include fish (catfish, salmon, mackerel, sardines, tuna, eel), eggs, fortified milk, and cod liver oil with lesser amounts in beef liver, cheese, and egg yolks. Mushrooms are the only vegan source of Vitamin D. At least ten minutes of UVB sun exposure per day is needed for adequate skin production. Deficiency may occur when dietary intake is insufficient, with malabsorption (the intestinal tract is bypassed or diseased), kidney disease (prevents conversion to the active form), chronic steroid use, or when exposure to sunlight is limited. The NIH has not established recommended daily intake due to lack of sufficient data; however, it is generally recommended that adults get at least 400 IU daily.

The main function of Vitamin D is to regulate our blood levels of calcium and phosphorous. It helps to “mineralize” (add calcium crystals for strength) bone, so deficiency may lead to bone softening or thinning. Supplementation will prevent/treat osteomalacia in adults and rickets in children. Vitamin D may help to prevent high blood pressure, limit heart disease, enhance immune function, and may even protect against some forms of cancer, particularly pancreatic and colon. It is important to note that appropriate calcium and magnesium levels are necessary for Vitamin D therapy, and should be supplemented if needed.

Vitamin toxicity (also known as hypervitaminosis, vitamin poisoning) refers to symptoms or side effects from inappropriately high levels in the blood. Vitamins that may cause toxicity are those that are fat-soluble (Vitamins A, D, E, and K). Toxicity is extremely rare, especially with doses less than 10,000 IU daily, and cannot occur from sun exposure. The earliest signs of Vitamin D toxicity are usually from elevated calcium levels and include loss of appetite, nausea, vomiting, weakness, confusion, or even kidney stones. If you are taking any of the fat-soluble vitamins on a regular basis, please be sure to have a clinician monitor your blood levels routinely!