Branched-Chain Amino Acids

In addition to protein deficiency, liver cirrhosis is characterized by low blood levels of (BCAAs) in relation to other amino acids. This imbalance may contribute to the development of PSE. BCAA supplementation could be a way to correct this problem, as well as to provide a source of needed protein, but its effectiveness is unclear. BCAAs (isoleucine, leucine, and valine) represent a good protein source for people with cirrhosis because they are less likely to induce PSE. A controlled study of protein-intolerant people with cirrhosis showed that BCAA supplementation corrected abnormal protein metabolism about as well as an equivalent amount of dietary protein without inducing PSE as frequently. In a small double-blind trial, people with liver cirrhosis taking 5 grams per day of BCAAs had significant improvement in their ability to process protein.

However, treatment trials using BCAAs alone or in solutions containing other amino acids in people with cirrhosis and PSE have reported conflicting results. It may be that certain people with liver cirrhosis can benefit from supplementation with BCAAs while others cannot, for reasons that are unclear. In a double-blind trial, people with liver cirrhosis and PSE received 0.24 grams per 2.2 pounds body weight (approximately 16–17 grams per day) of BCAAs for 15 days, after which most experienced significant improvement in brain function, mental status, and protein metabolism. Those who continued taking BCAAs for three months also had mild improvement in liver function tests.

Therapeutic effects of oral BCAAs have also been shown in children with liver failure and in adults with cirrhosis of the liver without PSE. Overall, it appears that BCAA supplementation does not always help in cirrhosis, but some people with and without PSE may benefit. A qualified doctor must closely supervise such BCAA supplementation.

In a double-blind trial, regular use of (BCAAs) (i.e., valine, isoleucine, and leucine) by adolescents and young adults with PKU improved performance on some tests of mental functioning.Participants received either placebo, or 150 mg per 2.2 pounds of body weight each of valine and isoleucine, and 200 mg per 2.2 pounds of body of leucine, taken with meals and at bedtime. Participants received one mixture or the other for four three-month periods, for a total of six months' supplementation of each regimen over the course of a year.

Some research has shown that supplemental (BCAA) (typically 10 to 20 grams per day) do not result in meaningful changes in body composition, nor do they improve exercise performance or enhance the effects of physical training. However, BCAA supplementation may be useful in special situations, such as preventing muscle loss at high altitudes and prolonging endurance performance in the heat. One controlled study gave triathletes 6 grams per day of BCAA for one month before a competition, then 3 grams per day from the day of competition until a week following. Compared with a placebo, BCAA restored depleted glutamine stores and immune factors that occur in elite athletes, and led to a reported one-third fewer symptoms of infection during the period of supplementation. Studies by one group of researchers suggest that BCAA supplementation may also improve exercise-induced declines in some aspects of mental functioning.

Some research has shown that supplemental (BCAA) (typically 10 to 20 grams per day) do not result in meaningful changes in body composition, nor do they improve exercise performance or enhance the effects of physical training. However, BCAA supplementation may be useful in special situations, such as preventing muscle loss at high altitudes and prolonging endurance performance in the heat. One controlled study gave triathletes 6 grams per day of BCAA for one month before a competition, then 3 grams per day from the day of competition until a week following. Compared with a placebo, BCAA restored depleted glutamine stores and immune factors that occur in elite athletes, and led to a reported one-third fewer symptoms of infection during the period of supplementation. Studies by one group of researchers suggest that BCAA supplementation may also improve exercise-induced declines in some aspects of mental functioning.

Preliminary research has linked TD to the inability of the body to metabolize the amino acid phenylalanine. Supplementing with (BCAA), including valine, isoleucine, and leucine, could reduce excess phenylalanine in people with this disorder. In one trial, researchers examined the effects of BCAA supplementation in people with TD (from 150 mg per 2.2 pounds body weight, up to 209 mg per 2.2 pounds body weight) after breakfast and one hour before lunch and dinner for two weeks. The BCAA mixture included equal parts valine and isoleucine plus 33% more leucine than either of the other two amino acids. Of nine people treated, six experienced at least a 58% reduction in symptoms, and all nine had a least a 38% decrease.