In the '50s, people in England were worried about their children's health, so English milk was enriched with 1,600 units of Vitamin D to the quart. At the same time, Americans were enriching milk with Vitamin D too, but only 400 units.
But vitamin metabolism can be complicated. After a couple of years, it was found that super-enriched milk was actually bad for children. The 1,600-unit milk could cause a Vitamin D overdose.
It wasn't a lethal overdose, though such a possibility exists: A number of Arctic explorers have been killed by eating polar bear liver, the most concentrated source of Vitamin D known. But the 1,600-unit milk could cause vomiting, anorexia and severe mental retardation. On top of that, some of the children developed a peculiar "elfin" look to the face.
Meanwhile, flax seed is supposed to be good for you, but it interferes with your ability to get thiamine and pyridoxine (Vitamin B6) from your food. In the same way, kidney beans are "antagonistic" to Vitamin E.
None of this means you shouldn't eat any of those things, just that you shouldn't overdo it. You want to find a happy medium between not getting the benefits of beans and flax, on one hand, and not getting enough vitamins, on the other; between Vitamin D deficiency and vomiting, anorexia and an elfin look.
But come to think of it, a mild Vitamin D overdose sounds pretty much like a fashion model's dream. Might some models be abusing Vitamin D milk a la steroid abuse among athletes? Or to be blunt about it: Got milk, darling?