Q: The RDV for vitamin D is 400 IU. Why are your soft gels 1000 IU? Isn't this too much vitamin D?
A: No. Vitamin D intoxication is extremely rare and even doses of 10,000 IU of Vitamin D3 per day for up to 5 months have not been shown to cause toxicity. 1 A recent review in the New England Journal of Medicine suggested recommended intakes for vitamin D are inadequate and need to be increased to at least 800 IU of Vitamin D3 per day. 2 In addition, scientists from the National Institutes of Health recently called for raising the tolerable upper limit intake of vitamin D that is currently set at 2,000 IU per day.
Q: My multiple vitamin formula contains vitamin D2. Is that the same as vitamin D3?
A: No. The two forms of vitamin D used for nutritional supplementation are the secosterols ergocalciferol (vitamin D2) and cholecalciferol (Vitamin D3). Vitamin D2 is derived from fungal and plant sources. Most of our Vitamin D3 is produced in our bodies by the action of sunlight on 7-dehydrocholesterol in the skin. Vitamin D3 is superior to vitamin D2, as it has been shown to raise blood levels 70% better than D2.3
Q: What foods are natural sources of vitamin D?
A: Very few foods are natural sources of vitamin D. Foods that do contain vitamin D include fatty fish, fish liver oils (cod liver oil) and eggs from hens that have been fed vitamin D. Almost all the vitamin D intake from foods comes from fortified milk and other foods, such as breakfast cereals, that have been fortified with vitamin D.
Q: I spend a lot of time outdoors. Don't I get enough vitamin D from sun exposure?
A: Not likely. As people age, they often lose the ability to make Vitamin D3. In fact, Americans age 50 and older are believed to be at increased risk of developing vitamin D deficiency. Furthermore, season, geographic latitude, time of day, cloud cover, smog, and sunscreen can greatly affect UV ray exposure and consequently alter vitamin D synthesis.4
Q: My mother has stage 4 chronic kidney disease. Her doctor wants her to take Vitamin D3. Is this safe?
A: Yes. Many people with stage 4 chronic kidney disease are unable to make enough Vitamin D. They often must supplement with Vitamin D3 in order to maintain appropriate calcium metabolism and to decrease parathyroid hormone levels and the risk of renal bone disease.5-7
1. J Steroid Biochem Mol Biol 2004;89:575-579.
2. Holick MF. Vitamin D deficiency. N Engl J Med. 2007 Jul 19;357(3):266-81.
3. Am J Clin Nutr. 1998 Oct;68(4):854-8.
4. Curr Opin Endocrinol Diabetes 2002;9:87-98.
5. Am J Kidney Dis. 2003 Oct;42(4 Suppl 3):S1-201.
6. Am J Kidney Dis 2001;38:Suppl5:S3-S19.
7. Semin Dial. 2005 Jul-Aug;18(4):266-75.