Q: The RDV for vitamin D is 400 IU. Why are your soft gels 5000 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. The general trend is to recommend higher RDV for Vitamin D3. 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. Scientists from the National Institutes of Health called for raising the tolerable upper limit intake of vitamin D that is currently set at 2,000 IU per day. Finally a new study published by the University of Chicago suggests at least 5.000-10.000 IU as a RDV in order to support our immune system to fight against virus infections like COVID-19 and to reduce the intensity of inflammation involved. We therefore believe 5.000 IU Vitamin D3 per day is a safe and effective, and thus recommendable dose. Please confirm with your physician.
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 secosteroid 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.
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. Otherwise why would so many people in Florida, California or the Mediterranean Countries suffer from Vitamin D deficiency? 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. 
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
Q: Is it correct that people of color suffer more frequently from Vitamin D deficiency?
A. This has been seen in many studies carried out during the last 20 years in the US.
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6. Am J Kidney Dis 2001;38:Suppl5:S3-S19.
7. Semin Dial. 2005 Jul-Aug;18(4):266-75.