I've been saying for ages that diet has an effect on hair loss...even with healthy diets, people who are genetically prone to hair loss will lose their hair, but I imagine that this would occur later in life and at a slower pace.
Western diets these days have replaced pastured meat, organ meats, real dairy, and properly prepared grains; with soy substitutes, pasteurized skimmed dariy, grain-fed muscle meat, vegetable oils, and refined flour. Calorie intake is on the rise and exercise and sunlight exposure has dropped. Defiencies in Vitamin A, Vitamin D, fatty acids, and minerals are occuring much more often, contributing to early puberty, obesity, myopia, acne, the need for dental braces, and, of course, early onset hair loss.
Some would say that some people are just genetically inclined to lose their hair at 13 (like me). But personally I think there's a big difference between someone who loses their hair at 21 and someone who loses it at 50.