HMB is available from many outlets as a dietary supplement for humans, particularly bodybuilders and other athletes who are trying to increase lean body mass and muscle strength.

HMB or beta hydroxy beta methylbutyrate is a by product of leucine metabolism. Leucine is one of the essential amino acids and is found in a variety of foodstuffs, but potatoes have a high percentage of leucine for the amount of protein they supply for example! Small amounts of HMB can be found in certain foods such as catfish and alfalfa.
Typical research doses use a total of 1.5-3.0g HMB per day (taken in small multiple doses). Normal HMB production in the body is 0.2-0.4g depending on leucine dietary intake (based on 70kg man).

The general theory is that HMB reduces or prevents protein breakdown, with the majority of research carried out on animals. If it seems beneficial in animals, why not in humans? Human data however is thin on the ground, although 3 preliminary studies from Iowa State University have shown some results that are positive towards HMB. 1 study looked at untrained subjects, and the other 2 showed that the end results for those taking HMB and those not on HMB were not scientifically significantly different or only some aspects of strength performance were improved. More well-controlled research, from additional research institutes, is needed to provide data on which to base any advice.

What about safety?

In human studies, no reported adverse side effects have been reported in 4.0g HMB a day for several weeks (one study was 50 days). However:

1. HMB is a patented product, so anyone using it should check that it carries the patent number by metabolic technologies (MTI) because fake HMB can be marketed and who knows what can be added!
2. HMB is often used in combination with other supplements e.g. creatine, pyruvate etc, the effects of which may be zero, beneficial or harmful.
3. HMB is often used in sports where IOC ruling does not apply i.e. "other substances may be inadvertently added" so that the punter gets results and presumes its the HMB rather than anything else that may be omitted from the label. Remember we are talking about food supplements and not medicine and so labelling and other laws are different.
4. What research has been done on females?
5. My understanding is that HMB was initially looked at 30 years ago as a possible treatment for muscle wasting diseases: if you could prevent skeletal muscle wasting away, then you offered hope to sufferers. What the researchers found was that although skeletal muscle breakdown was reduced, HMB was not specific enough to the muscle under investigation and it prevented other muscle from being (naturally) broken down - an effect which is desirable in other muscles. The research was halted and other avenues of treatment pursued....