DEFINITION

HMB (short for beta-hydroxy methyl-butyrate) is a breakdown product of the amino acid leucine. HMB may play a role in helping regulate muscle growth.

DESCRIPTION

HMB occurs naturally in the body as a breakdown product of leucine. Leucine is an amino acid that is found in high amounts in skeletal muscle. HMB levels are increased in the muscle following training due to increased breakdown of leucine.

The goal of people trying to increase their muscle mass (such as bodybuilders and strength athletes) is to decrease muscle breakdown and increase muscle synthesis. It is thought that by taking additional HMB, muscle levels of HMB will be increased. Preliminary studies have shown that increased amounts of HMB in the muscle may signal the body to slow down the destruction of muscle tissue after heavy exercise.

- Some studies have confirmed that HMB may increase muscle strength and mass, although two studies have failed to confirm this effect - One study has found that a combination of HMB and the amino acids glutamine and arginine may help decrease loss of muscle mass in people with AIDS. This combination may be of potential benefit in any chronic disease with associated muscle wasting. - Endurance athletes may also benefit from HMB supplementation, providing they are undertaking a strenuous training schedule. HMB may help limit muscle breakdown, speeding recovery following heavy training sessions. HMB may also decrease the effects of the stress hormone cortisol which helps contribute to the breakdown of muscle tissue for energy. Cortisol levels are often raised in endurance athletes who have overtraining syndrome, where not enough time is available for damaged muscle to repair itself

PHARMACIST'S ADVICE

1) A range of protein supplements are available for athletes and bodybuilders. Your Pharmacist can help you choose a product appropriate for your needs. 2) Some studies suggest particular amino acids may improve sports performance. Individual amino acids are available as dietary supplements. 3) Other supplements commonly used by weight trainers include multi-vitamins and minerals, antioxidants, creatine monohydrate and vanadyl sulfate. Ask your Pharmacist for more advice. 4) See the Sports Diet (Strength), Bulking Up Eating Plan, Bulking Up Meal Plan and Sports - Supplements topics for more information.

SOURCES

HMB is metabolised from the amino acid leucine. Small amounts are also present in many foods of animal and plant origin. HMB is also available as a dietary supplement.

NOTES

- The safety of HMB in pregnant and lactating women, young children or those with kidney or liver disease is yet to be established. Ask your health care professional for advice.