**For my October 20, 2009 Vitamin D Update:Everything You Ever Wanted to Know About Vitamin D from the Expert, Dr. Michael Holick. How Much Do We Need? Why Is It So Hard to Get Enough? What About Breast-Fed Babies? Why Is It So Important for Good Health? click here.
Just about every 2 weeks another study comes out about the benefits of Vitamin D. This week in Circulation Vitamin D deficiency was linked to cardiovascular disorders. Other weeks it's been multiple sclerosis, osteopororis, depression, obesity, type 2 diabetes, colorectal, breast and prostate cancer, & respiratory infections.
In Sept. 2007, an Archives of Internal Medicine meta-analysis of 18 studies, following over 57,000 people for over 5.7 years found a lower risk of death from all causes in those people who supplemented their vitamin D.
An astounding study published in Aug. 2007 in Nutrition Reviews suggests that to prevent colorectal and breast cancers one needs to supplement at levels from 1000-2000 IUs at a minimum, to an ideal of 2000-3500 IUs (the Current Daily Recommended Intake-DRI is 400 IUs for anyone over 50), in order to get one's blood levels of Vitamin D to a recommended level of 55 ng/mL. These researchers say 50% of the colon cancer would be prevented with Vitamin D blood levels over 34, and a 50% reduction of breast cancer with blood levels over 52.
Since the "sunshine vitamin" is only available from the sun (non-existent at this time of year where I live), fortified foods like milk, oily fish like salmon, or supplements, you really have to go out of your way to be sure you're getting enough.
Let me put all these numbers into perspective.
The current US DRI (Daily Recommended Intake) for Vitamin D for the middle-aged is 400 IUs. That's what's in most multivitamins. The average US adult gets only about 230 IUs, and that's mostly from the less potent D2. Check your milk & multivitamin ingredients and you'll probably see D2. In the winter the average American's blood levels of D are 15-18 ng/mL. To get our blood levels up to 55 and achieve significant reductions in cancer risk, the Nutrition Reviews researchers recommend getting a combined daily Vitamin D intake of 2,000-3,500 IUs. Make sure your supplement is D3 cholecalciferol, not D2! These researchers, as well as Dr. Bruce W. Hollis, say there's little evidence of adverse effects under 10,000 IUs a day.
Note: most recommendations are not this high, and will max out at the 1000-1200 IU level. Even the National Osteoporosis Foundation revised their recommendations upward on July 26, 2007 based on the considerable amount of research in recent years. They now recommend 400-800 IUs for under age 50, and 800-1000 IUs for over age 50.
Here's how the Vitamin D supplementation has played out for me:
My doctor measured my vitamin D levels with a serum 25-hydroxyvitamin D test in Feb. 2007, because of my decreasing bone density. Remember, a deficiency in D prevents calcium from being absorbed into our bones. I measured a TOO LOW 29, & at the time I was taking just 1-2 tablets of Citrical on most days, which would give me about 200-400 IUs of D3 a day. I also drank 1-2 glasses of milk fortified with D2, but was rarely in the sun. She recommended I supplement to a total of 1000 IUs of D3 a day & get rechecked in 3 months. The goal was to get me over 32, but closer to 50. Three months later I was checked & I had moved up to 33. Higher, than before, but still too low. I'm now supposed to up my D3 to 1200 IUs. Combined with a multivitamin, & any milk I drink, I'm now supplementing to about 1800 IUs a day, not far off from the researcher's recommendations in Nutrition Reviews. I'll find out next month how I'm measuring up. On a side note, every single one of my friends who has taken the Vitamin D serum test has been found to be in the deficient range. Definitely makes me wonder about the cancer, osteoporosis, type-2 diabetes, heart diseases connections.
Take away tip: If you're at risk for osteoporosis, dark-skinned, live in the North, rarely get sun exposure, always wear suncreen while outside, or you're over age 50 it might be a good idea to talk to your doctor about taking the serum 25-hydroxyvitamin D test. Then you'll be able to gauge how much Vitamin D you need.