HMB (beta-hydroxy beta-methylbutyrate) (C5H10O3)

HMB is synthesised by the body from the BCAA, leucine; an indispensible amino acid that must be obtained from the diet. Several studies have shown that HMB supplementation can lead to increased strength and muscle mass, especially in the elderly and those new to training. The muscle mass of previously untrained athletes normally increases by 0.5kg to about 1.0kg over a period of three to six weeks’ training, but the effects after this are unclear.

As for trained athletes, the benefits are generally trivial or non-existent, though one recent study did show a notable improvement in lower-body strength. HMB may also be useful for the recovery of damaged muscle cells, so its continued usage by trained and untrained athletes alike may be better for this reason, rather than expecting continual improvement in muscle mass and strength. The effect of HMB on body composition is thought to be negligible.


In many trials the dosage has been taken in one go; often, but not always, near – or even during – training.

Sports supplement guide for beginners

HMB: suggested dosage is between 1.5g and 3.0g a day

However, some prefer to take two or three equal servings during the day, especially if their training continues intermittently or for long periods. Nevertheless, if possible, with HMB’s suggested benefits regarding muscle cell damage it might be better to take two equal servings either side of your training.

Many body builders take a specific dosage, 38mg per kg of BM, but this may take the dosage into largely unknown territory. For instance, according to this dosage a 120-kg athlete should take about 4.6g (38mg × 120, then divide by 1000) of HMB a day, but most research has not tested doses exceeding 3g a day, so it is advisable that you do not exceed it either. In any case, as body builders are ‘trained’ athletes, the muscle-building and strength benefits will be negligible, so any dosage for this purpose may well be a waste of time and money.

No matter, the reason it is thought safe to take high amounts of HMB is because it is water-soluble, so excessive amounts will probably be excreted in the urine, and furthermore, it is believed to have no side-effects. That apart, although some researchers suggest that 3g a day may have better results – in terms of strength and muscle mass – than 1.5g a day, it seems that a jump to 6g a day has no additional benefits. It may turn out that a specific dose will be better in some or all respects, but such a dose is yet to be confirmed.

HMB is found in several foods, including avocado, citrus fruit, alfalfa and catfish, but in very small amounts.

You can find more information about sport nutrition here!

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