You usually lose about 100 hairs per day naturally, but if you find yourself losing a lot more, nutrition could be to blame. While hormones, such as low thyroid or high levels of testosterone, may be the cause, too little protein or iron can also affect hair's health. Protein is made up of amino acid building blocks, some of which your body can produce and others that you must get from your diet. If your doctor determines you're low in iron, your hair loss may also be compounded by a less-than-optimal intake of the amino acid L-lysine.

About L-Lysine

L-lysine is one of eight essential amino acids, those that your body cannot produce on its own. It's found in complete proteins, including red meat, poultry, pork, eggs, cheese, certain fish -- particularly cod and sardines -- and soybeans. Nuts, legumes and brewer's yeast are vegetarian sources of the amino acid. If you're following a very-low-calorie diet without a lot of protein or a vegan diet that doesn't contain adequate nuts and beans, you could be deficient in this amino acid.

Effects on Hair Loss

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Hair loss is a known symptom of iron deficiency. A paper published in a 2002 issue of "Clinical and Experimental Dermatology" noted that increased hair loss corresponds with iron deficiency and suboptimal intakes of L-lysine 4. When subjects are given iron supplements and lysine supplements, hair shedding decreased. It may take several months, though, to notice changes in your hair after you start taking these supplements.

Overall Low Protein

L-lysine is one major amino acid that could explain hair loss, but an overall protein deficiency may as well. Because proteins are made up of amino acids, including L-lysine, the hair loss could result from low L-lysine levels or from a deficiency in any one of the other essential amino acids. The Institute of Medicine recommends you get 10 percent to 35 percent of your daily calories from protein or a minimum of 0.36 grams of protein per pound of body weight each day. If you weigh 140 pounds, you should aim for about 50 grams per day. Those with eating disorders, on crash diets or with certain conditions that prevent nutrient absorption are prone to not getting enough protein, and potentially losing hair as a result.

Too Much of a Good Thing

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Getting too much of particular supplements can also cause excessive hair loss. Excessive vitamin A supplementation, for example, is one potential cause. Consult with your doctor to ensure you have a true deficiency before adding supplemental amino acids or vitamins and minerals to your diet.