My email sizzled with questions after recent news headlines featured results of vitamin D supplementation research. What should I do? Would you recommend stopping my supplement? I’m taking 2000 IU daily, is that too much?
CALGARY VITAMIN D STUDY
The Calgary Vitamin D Study published in the August 27, 2019 issue of JAMA reported no bone benefit with high daily vitamin D doses of 4000 IU or 10,000 IU in healthy people. Bone density by DXA of the total hip remained stable after three years of use with no significant differences between dose groups. However using high-resolution CT scanning, the highest 10,000 IU dose had bone loss compared with 400 IU.
The amount of bone loss observed with 10,000 IU daily dose is not enough to increase fracture risk over a three-year period but raises concern of the effect over a longer duration of time.
At the American Society for Bone and Mineral Research (ASBMR) annual meeting in September 2019, Dr. Meryl LeBoff presented a substudy of 771 healthy adults from the VITamin D and OmegA-3 TriaL (VITAL) at Brigham and Women’s Hospital. A vitamin D supplement daily dose of 2000 IU after two years showed no effect on bone density compared with those not taking a supplement. LeBoff said. “Participants may have already reached the vitamin D level needed for bone health.”
I recommend supplementation because you can’t count on the sun or food. Our skin is the biggest reservoir of vitamin D but sunlight is required for activation. Aging skin, use of sunblock, non-summer months, darker skin pigmentation and obesity are common reasons you don’t produce enough of your own vitamin D.
Few foods are rich in vitamin D. Fatty fish like sardines, salmon, and herring have high amounts. Others like mushrooms may claim that they are high in vitamin D but are not. In the US, all milk is fortified with vitamin D. However, one cup of milk only contains 100 IU of vitamin D. Most milk substitutes are fortified as well. Check your labels.
What you are left with—supplements to ensure adequate blood levels.
Most vitamin D supplementation recommended-doses range from 400 to 2000 IU daily.
These study findings along with previous studies suggest that range for healthy adults is appropriate. You may think of supplements as the “Goldilocks Principle.” Too little or too much is bad. But 400 to 2000 IU is just right. If you have osteoporosis, your doctor may want to check your vitamin D blood level to ensure your vitamin D dose is adequate to maintain a normal level.