"My thinking got started along a certain path in 1960 when they were analyzing the amount of strontium-90 from atomic bomb fallout and collecting babies teeth from all around the world to measure their exposure to radioactive isotope. Strontium-90 happens to be concentrated in the bone, and the bone marrow is turning over rapidly and so the exposure to fall out would show up as mutated blood cells. and radiation exposure to the bone marrow is a known promoter of leukemia - and so they were looking at the connection between child hood disease and strontium-90. Strontium 90 is similar to calcium, in that it dissociates in milk, and so the government was warning their parents not to feed their children so much milk because of the radioactive strontium that the bomb test were putting into it. i looked at how the strontium 90 got into the milk. it turned out that it falls under the ground in the rain - and the plants that needed the water and soil to grow - absorbed both calcium and strontium 90, and so the concentration in the soil is relatively very high after bomb test in the ratio of strontium 90 to calcium. And when the cow eats the grass, the cow purifies and selects for the calcium over the strontium. If you look at the ratio in grass and cow milk/meat, milk has the least strontium 90 in proportion to other nutritional factors, especially calcium. so every organism is a purifiying system - getting whats good and excluding as much as possible what is bad - even to the matter of being able to select between the isotopes of potassium for example. radioactive potassium goes down every time it passes through an organism in the food chain. and so the safest thing is to get the purest food possible from an animal such as a cow producing milk which is multiply filtered. When they talk about the chemical purity, that's only really a reality in the mind of a chemist - its maybe better from something from a crude or factory - but in relation to a biological nutrients - it is just wildly out of the ball park in terms of contamination. any natural food is extremely purified, whereas any supplement made chemically is going to be dirty just in principle".