In the early 1960s when my first baby tooth fell out I made a big decision: rather than leave it under my pillow for the tooth fairy, I helped my mother put my tooth in an envelope to send it away. Before long a small package arrived in the mail addressed to me. Inside was a button with the picture of a gap-toothed child, and the words, “I gave my tooth to science”.
What did “science” do with my tooth? It turns out I was part of the Montreal Baby Tooth Survey that was tracking the concentration of radioactive strontium-90 in the population. At that time, as the nuclear arms race heated up there was widespread concern about the dangers of radiation that was being absorbed in bones. And the most available supply of bone that could be used for testing was discarded baby teeth. Correlating these with the date and place of birth, researchers could determine how much radiation was affecting people in the year those teeth were formed.
Now I have a new interest in strontium. Rather than hoping to minimize it, I’m deliberately adding it to my bones. One important distinction: this time it’s not the radioactive isotope, but a naturally-occurring salt called strontium citrate. This strontium is an abundant mineral that is chemically similar to calcium, and absorbed by bones in comparable amounts. Once inside, it increases the activity of the bone-building cells (osteoblasts) while slowing down the clean-up cells (osteoclasts).
Strontium-rich foods include beets, brazil nuts, and cabbage, and a typical daily intake is estimated at 1 – 5 mg. A wide variety of studies have shown that intakes quite a bit higher than this – between 340 and 680 mg per day – build significant bone density, while reducing fractures. The effect is so pronounced that the pharmaceutical companies have grasped the possibilities and found a way to combine naturally-occurring strontium that can’t be patented with a synthetic compound that can to make a drug called Protelos, made of strontium ranelate. So far this drug is only marketed in Europe, so Canadians like me can enjoy the benefits of the cheaper, safer over-the-counter form.
Because strontium competes with calcium for absorption, it must be taken hours after calcium-rich foods. If I don’t snack in the evening I can take it at bedtime; otherwise I’m trying to take it in the night when I get up to the washroom.
There is some controversy over strontium as a bone-builder because the necessary dosage so far exceeds the amount of strontium a person would normally consume. Still, despite long-term safety studies, the only issues that have come up so far have been with the expensive synthetic prescription version, which leads to increased incidence of blood clots and drug hypersensitivity syndrome.
One important warning if you choose to take strontium citrate for your bones: make sure you always ingest more calcium than strontium.