It's said that 'you are what you eat' and your hair is no exception. The connection between diet and hair loss goes back a long way, but it's only recently that the scientific world has begun to shed light on the exact mechanisms at work. As a rule of thumb, if you eat a balanced diet, your hair should be getting everything that it needs to be healthy. However there are several dietary elements that, if absent, can cause hair loss.
Thankfully the average first world diet means that hair loss through protein deficiency is something of a rarity. However, people on faddish weight loss programs (particularly low-protein and crash diets) should be aware of the risks. Many protein rich foods, such as eggs and liver, are also good sources of another essential nutrient - biotin. Biotin belongs to the vitamin B complex, and while deficiencies are uncommon they are not unheard of in the vegetarian and vegan communities. Anyone using long term antibiotics should also consider taking biotin supplements.
Omega 3 fatty acids are known to play an important part in maintaining a healthy scalp (and skin) as well as being more immediately associated with hair growth. Fish eaters are unlikely to have any problems, especially if they have penchant for mackerel or salmon, while other sources include walnuts and flax seed. Zinc and magnesium are the two primary minerals necessary for a healthy head of hair.
The good news is that any hair lost as a result of dietary causes usually grows back once the nutritional shortfall is addressed. Dietary supplements for hair loss prevention are big business, but this doesn't mean that they need to break the bank. Remember that hair loss specialists often have a vested interest in selling you as many products as possible (it's called profit), and that you may be better off buying multi-vitamins and multi-nutrients form your local health care store.