Vitamin D is promoted as the vitamin for healthy bones and teeth. It is often recommended for preventing fragile bones or osteoporosis and reducing the risk of fractures. Dozens of independent studies have shown that.
However, time and again, a research paper comes out claiming that vitamin D supplementation does not reduce the fracture risk. How is that possible? Let us look at a bit of science to understand why.
Since calcium is vital for muscle contractions and heart functioning, its blood levels are very tightly controlled in a narrow band.
When blood calcium levels fall due to inadequate calcium intake, a certain gland increases production of a hormone called parathyroid hormone or PTH. This hormone stimulates vitamin D production in the body.
Vitamin D’s main role is to increase calcium absorption in the intestines. However, if there is insufficient calcium in the diet itself, the additional vitamin D cannot help.
Simultaneously, the PTH stimulates large calcium stores in the body, such as bones, to release calcium into the blood, weakening them but protecting the heart and muscle functioning. Once the blood calcium levels normalise, PTH levels go down. Read more: Everything you want to know about strong bones.
Now think about it. If you take vitamin D supplement but your dietary calcium is insufficient, how will your bones become stronger by just the vitamin D intake? Since the additional vitamin D is not able to garner calcium from food, PTH keeps pulling out calcium from the bones. Increased vitamin D but weaker bones!
When researchers study changes in fracture risk with vitamin D supplementation, they must ensure, or control, adequate calcium intake, too. Unfortunately, many studies don’t take this basic precaution, which is why we see conflicting results.
Keep in mind that 39% of the adults in the developed world eat less than recommended amounts of calcium a day. This number is much higher in developing countries such as India. When at least 39% of individuals in your clinical trials don’t have enough calcium through diet, what exactly are you testing with vitamin D?
My advice is you take 2000 IU of supplemental vitamin D on a daily basis along with 500 to 750 mg of supplemental calcium. Divide calcium in doses of 250 mg or smaller. Read more: Vitamin D: A complete guide.
First published on: 7th August 2022
Image credit: Clement Eastwood on Pexels