Milk and osteoporosis: too much of a good thing?

You may think this title is wrong, or cheap publicity. It isn't. Sadly, this is a sensitive subject, and many specialists don't accept it.

We all know that bones are made mainly of calcium, and that milk and dairy products are a main source of the calcium bones need to grow. So what is the problem?

Bones are hard and strong enough to carry and protect all the other organs, mainly thanks to the calcium salts hardened in them. What we forget is that bone is living tissue, not just a solid block. Inside it, two groups of cells maintain it: cells that break bone down and cells that build it, rebuilding what the first group removed. If you think this demolition and rebuilding is pointless bureaucracy, try replacing your leg bones with the hardest steel. The constant pressure of walking and jumping, from childhood to old age, wears down any supporting frame, even the best steel: the damage starts as hairline cracks and grows until the bone breaks. This is where the two kinds of cells come in.

The breaking-down cells work on the stressed parts of the bone that have started to crumble and dissolve them. Then the building cells rebuild the bone. This gives the body flexible movement, relatively light bones and the ability to repair itself.

The building cells need calcium and phosphorus as raw materials, helped by vitamin D and some hormones.

To be more precise, what matters for these cells is less the amounts than the ratio of calcium to phosphorus, and that is where the problem lies. Cow's milk has a lot of calcium and relatively little phosphorus, so drinking large amounts raises calcium without raising phosphorus. As the saying goes, too much of anything turns into its opposite.

The fix is simple. I don't advise drinking less milk, but getting more phosphorus. I also advise more vitamin D to help fix calcium in the bones, especially for women after the menopause, because their lower hormone levels slow down the building cells without slowing the breaking-down cells.

The best source of phosphorus is fish, so my advice is "fish and yoghurt"! Of course, there's no need to eat them in the same meal…