To D Or Not to D

Our press is rife with the preventive power of Vitamin D against the flu, breast cancer, osteoporosis, multiple sclerosis, depression & arthritis. Yet there is controversy still about how much is enough. My response? Show me the data. 

What's Your Level? When we are figuring out if you have enough, we measure in your blood 25-hydroxyvitamin D [25(OH)D]. I happen to agree with the National Osteoporosis Foundation (NOF) and believe you should have a level of:

• 75 nmol/L or higher
• 30 ng/mL or higher 

How much should I take? Our government set the RDA goal at 400 IU/day, which is ridiculous in my opinion. NOF has a higher goal: 400-800 IU/day for those < 50, and 800-1000 IU/day in those > 50. 10-20 min of sunshine per day gets you 10,000-20,000 IU. From nutritional sources such as mild, egg yolks, and oily fish (salmon, tuna - you know, the ones that contain mercury), you get about 100 IU per serving or less. I generally recommend 1000-2000 IU/day. Ergo, you need a supplement. 

How much is too much? From my review of the data, I believe you can safely take up to 10,000 IU/day especially in the Bay Area of California where we have dense cloud cover much of the year. Toxic symptoms are kidney stones and kidney problems, both thought to be related to high blood calcium levels. NOF suggests that you can only become toxic if you are using a prescription form of Vitamin D, and supplements are relatively safe. 

Which supplement? There are two types: D2 (ergocalciferol) and D3 (cholecalciferol). Old data suggested D3 was superior but recent research suggests they are equally good. 

What about my pumpkins? We have no consensus on the best level in kids, despite recent studies in this week's Pediatrics urging higher levels. Last year, the American Academy of Pediatrics recommended 400 IU/day in all kids beginning within the first few days of life and including breastfed infants. Funny, my pediatrician didn't mention that in our 10-minute appointment each year.