Vitamin K

A newly published study in the American Journal of Clinical Nutrition points to Vitamin K2 as associated with lower rates of cancer incidence and mortality. The main sources of Vitamin K2 are animal products, including meat and cheese. There is a vegan source of the vitamin, "natto", a Japanese fermented bean dish, but most people outside of Japan probably don't eat or have access to it. Vitamin K2 also has been associated with good bone health and there is some evidence to suggest it may help prevent Alzheimer's.

Of course, this is all associative data, which means it doesn't show conclusively whether or not Vitamin K2 has a direct causative role in preventing these diseases. Another thing to keep in mind is that this particular study was done in Europe. Meat and dairy farming practices are a bit different there than in the States, so the Vitamin K2 sources those people are getting might be more beneficial. Still, it does warrant a re-evaluation of the common "animal products are bad" mantra.

As a final note, Vitamin K (like vitamins A, D, and E) is fat-soluble, which means your body won't absorb it properly if you're not consuming fats. This means getting it in a multivitamin taken without eating some fat with it might render it useless. If you are getting it from cheese or meat, however, it will be better absorbed.