Two milk questions

[owenransen]

1) Harvard Medical School has an article on it's site that milk is not a great source of calcium compared with, for example, the same volume of broccoli. Whereas many many other sites say milk is neccessary for healthy bones. I'd believe Harvard, but I'm no expert, so is there any other research about dairy products and calcium?


2) I've heard it said that our bodies learned to process milk only about 6000 years ago, and that it was a part of evolution. But I thought evolution worked in longer timescales. Am I wrong in thinking that our predecessors and other modern mammals get their calcium from sources other than milk?

- Confused in Italy!

[shadron]

I can address the second question.

Milk is a great source of what a growing infant needs: water, minerals including calcium, fat and sugar, protein in basic forms, even vitamins and immune antibodies. Of course infants can handle it; The female mammary glands express it for the exact purpose of supplying an infant with this nearly universal, sufficient diet.

By "processing milk" you no doubt mean the production of lactase which can break down the milk sugar into simpler sugars efficiently. All children naturally have this mechanism in their digestion, but it is "shut off" during puberty for most people, and presumably that is because in Africa there was no need to have it active, and is therefore a needless metabolic expense to an adult. For the several millions of years when all of our ancestors lived in Africa, food was relatively plentiful, and basic nourishment was not very much of a problem. Evolution created a neatly conformal milk handling response.

However, when people started moving out to more temperate climates (as in Asia), the food got scarcer, and nourishment harder to come by. At the same time they started domesticating animals, and the animal milk that more-or-less suddenly became available to them was not a nutritional source that could be ignored. They learned to make cheese and such (which removes the lactose) and adults could benefit, but the body became open to appreciating a mutation which shutdown the puberty-age shutdown of lactase production (sorry about the double negative). It is estimated about 30% of adults have that mutation at this point in time; it has probably been in the works for 50,000 years or so, mainly in those temperate climate populations.

Adults that have the mutation can drink whole milk without problems. Those that do not have the lactose sugars broken down by bacterial fermentation, with accompanying gas production. The resulting gastric distress is lactose intolerance. There are other metabolic problems with milk unassociated with lactose intolerance, mostly various allergies to specific proteins in it.

[Monketey Ghost]

We're pretty sure our daughter is lactose intolerant and that it's giving her the runs. The evidence is, excuse me, piling up.

We have bought lactose-free milk for her, which has twice the calcium as regular milk.

Personally, I have osteopenia. I asked my doc if I could get the needed calcium by just drinking a lot more milk. He laughed and said, "Oh, no, you need supplements with vitamin D, and you need to eat them a lot."

[shadron]

We're pretty sure our daughter is lactose intolerant and that it's giving her the runs. The evidence is, excuse me, piling up.

We have bought lactose-free milk for her, which has twice the calcium as regular milk.

Personally, I have osteopenia. I asked my doc if I could get the needed calcium by just drinking a lot more milk. He laughed and said, "Oh, no, you need supplements with vitamin D, and you need to eat them a lot."

Your daughter might have a genetic condition to not produce the lactase needed to handle the lactose. (This is not a diagnosis, just a "fer instance".) That is fairly innocuous in our culture, and works out, perhaps, to being more of a joke than a problem, as you point out. However, had this happened to a child in Africa 20,000 years ago (or even, perhaps, 100 years ago), the child would be slow to grow, weak and probably dead within a short time after birth, with no ability to pass that genetic weakness along.

I hope you can get the issue settled for her; it cannot be fun for anyone in the family. Best of luck.

[dakotajudo]

1) Harvard Medical School has an article on it's site that milk is not a great source of calcium compared with, for example, the same volume of broccoli. Whereas many many other sites say milk is neccessary for healthy bones. I'd believe Harvard, but I'm no expert, so is there any other research about dairy products and calcium?

Milk isn't strictly necessary (see http://www.ajcn.org/cgi/content/full/72/3/681 ) but for most people it's probably the most reliable source of calcium; we also should consider that healthy bones require a good bit of protein, of which milk is a better source than broccoli.

It is true that broccoli and other plant sources have higher concentrations of calcium than does milk, but the issue to consider is that in many cases plant calcium is not a biologically available as milk calcium. Plants contain acids and sugars (calcium is a major structural component of the plant cell wall) that chelate (bind) calcium and limit its absorption.