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Leucine is one of the eight essential amino acids, which means you must get sufficient amounts of this nutrient from food because your body cannot produce it. Much of the leucine in the human body is in the skeletal muscle tissue, where it is one of the most concentrated amino acids. The main functions of leucine are to assist in the building of protein and lean muscle mass. Foods high in leucine can help maintain muscle as you lose body fat during weight loss, and the amino acid may also help prevent age-related muscle loss and enhance function of the immune system.
Sources of Leucine
The main food sources of leucine include dairy products, such as milk and cheese, and especially cottage cheese, which is especially high in the nutrient. Bodybuilders and athletes who want to build lean muscle mass often turn to protein powder supplements that contain a rich source of leucine called whey protein, which is a derivative of dairy. Soy protein, also available in a protein powder supplement, is another source of leucine, although it contains less of the amino acid than the dairy source.
Many popular foods, although not necessarily always healthful ones, contain high levels of leucine, which means it can be relatively easy to meet the suggested daily amount. For example:
- Four ounces of meat provides from about 500 mg to more than 2,100 mg of leucine
- Four ounces of poultry contains about 875 mg to more than 2,100 mg
- A 3.5 ounce serving of salmon provides more than 1,600 mg of leucine, while other seafood can contain from 500 mg to 2,500 mg per 4 ounce serving
- One half cup of peanuts has about 2,250 mg of leucine, and ½ cup of almonds provides more than 650 mg. Sesame seeds are an excellent source, and sunflower and pumpkin seeds are also good food choices for leucine.
- In the dairy department, ½ cup of cottage cheese has at least 1,400 mg of leucine, while 1 cup of yogurt contains about 1,274 mg
Although leucine possesses some characteristics important for general healthy functioning, it also may have a negative impact on prostate health, as one recent study has shown.
Leucine and Prostate Cancer
Another characteristic of the amino acid leucine is the relationship between leucine and prostate cancer tumor cells. This fact led researchers at the Centenary Institute in Sydney, Australia, to propose that a potential treatment for prostate cancer may be to deprive prostate cancer tumor cells of leucine.
According to Dr. Jeff Holst, who headed the work with leucine, and his team, prostate cancer cells have an excessive number of pumps that allow them to take in great amounts of leucine to feed themselves. In turn, the cancerous cells outgrow normal, healthy prostate cells.
Thus far the scientists have reduced the uptake of leucine by prostate cancer cells in a laboratory by interfering with the function of the pumps, and also by using a drug that competes with leucine. Some of their experiments resulted in a reduction in tumor growth by as much as 50%.
While the findings of this study open doors for new potential treatments for prostate cancer, they also are important because they offer support regarding the connection between dairy, calcium milk and prostate cancer, and thus leucine and prostate cancer. Numerous previous studies have indicated that red meat, dairy, poultry, and eggs may increase the risk of prostate cancer.
Leucine Supplements
The recommended daily intake of leucine is 25 mg to 65 mg for every 2.2 pounds of body weight; thus a 175-lb man needs 2,000 to 5,200 mg daily. Given the high levels of leucine in many common foods, most men should have no problem meeting this range. In fact, given the possible connection between leucine and prostate cancer, taking supplements that contain leucine is not recommended, and foods high in leucine that are also associated with prostate cancer, such as red and processed meats and dairy foods, should be avoided or significantly limited.
See also
Leucine May Cause Prostate Cancer
Reference
Wang Q et al. Androgen receptor and nutrient signaling pathways coordinate the demand for increased amino acid transport during prostate cancer progression. Cancer Research 2011; doi: 10.1158/0008-5472.CAN-11-1821
