Hydroxymethylbutyrate (HMB): Benefits, Downsides, and More

HMB is a substance that your body produces naturally.

It has a few different names, depending on the version of the molecule. It is also known as beta-hydroxy beta-methylbutyric acid, beta-hydroxy beta-methylbutyrate, and hydroxymethylbutyrate.

It’s made when your body breaks down leucine, a branched-chain amino acid (BCAA) that’s essential for protein synthesis and muscle repair (1).

However, your body only produces HMB in small amounts. So, many people take it as a dietary supplement to increase HMB levels in their body (2).

Studies have linked taking HMB supplements to certain benefits, such as increased exercise performance, reduced muscle breakdown, and increased muscle growth in untrained and older adults (3, 4, 5).

HMB is widely available from supplement stores, health food stores, and online. It comes in various forms, such as capsule, tablet, and powder.

Summary

The body naturally produces HMB in small amounts when it metabolizes the amino acid leucine. People take supplements to raise HMB levels in the body. This may aid muscle growth and performance.

Studies have found that taking HMB may be associated with numerous benefits, especially in the area of body composition. These include increased muscle growth and reduced muscle breakdown.

While quite a few studies have examined the impact of HMB, additional research is needed to fully understand its effects in various populations.

Here are some of the promising benefits of taking HMB.

May aid muscle growth in certain people

Companies commonly market HMB as a supplement that aids muscle growth. However, research on HMB in this area shows mixed results and is inconclusive.

Older studies, from the early 2000s and before, have found that it may help in certain populations.

These studies looked at the effects of HMB in untrained individuals and older people. Those who combined taking HMB with doing resistance training experienced more muscle growth than those who did resistance training alone (6, 7, 8, 9).

In addition, a review of 7 studies in 287 older adults looked at the effects of taking 2–3 grams of HMB daily over periods ranging from 8 weeks to 12 months (3).

Participants who took HMB gained an average of 0.78 pounds (0.35 kg) more muscle than those who received a placebo supplement (3).

However, other studies have found that HMB didn’t influence muscle growth.

For example, a review of 10 studies looked at the effects of HMB in 384 adults ages 50 and over (10).

It found that combining HMB supplements with physical exercise had little to no effect on changing body composition, strength, or exercise performance, compared with exercise alone (10).

One analysis of 6 studies in 193 participants found it may not improve these factors for trained and competitive athletes, either.

It found that when athletes took 3–6 grams of HMB daily for a period of 3 days to 12 weeks, they experienced no increases in strength or changes body composition (11).

In short, research on HMB and muscle growth shows mixed results. However, some research shows this supplement may benefit muscle growth for untrained individuals and older people.

May help reduce muscle breakdown

Research suggests HMB may help reduce muscle breakdown.

Test-tube studies suggest that HMB may help prevent muscle breakdown in various ways inside cells, such as by suppressing genes and enzymes that promote the breakdown of muscle proteins (12).

An analysis of 15 studies looked at the effects of taking HMB in 2,137 people. These participants had health conditions that promote muscle loss, such as cancer, HIV, kidney failure, and malnutrition (4).

The analysis found that taking 3–4 grams of HMB daily over a period of 7 days to 6 months was significantly more effective at preventing muscle loss than a placebo (4).

Similarly, other studies in older people have shown that taking HMB can help preserve muscle mass during periods of bed rest (13, 14).

However, scientists need to do more research on HMB and its potential protective effects against muscle breakdown in a wider variety of participants, such as young people and healthy adults, before recommending it for this purpose.

May aid exercise adaptations

Some research has indicated that HMB could improve adaptations to exercise. This refers to a longer-term change rather than an immediate one.

For example, a 12-week study in 16 elite rowers found that taking 3 grams of HMB daily significantly increased aerobic exercise capacity and peak anaerobic power, and helped reduce body fat, compared with a placebo (5).

Anaerobic power refers to the maximum power you can produce during high-intensity exercise.

Similarly, another 12-week study in 42 combat sports athletes found that taking 3 grams of HMB daily significantly increased both aerobic and anaerobic exercise capacity, compared with a placebo (15).

Other studies in athletes and healthy adults have shown that taking 3 grams of HMB daily has similar effects on aerobic and anaerobic capacity (16, 17, 18).

Other potential benefits

Studies have associated HMB with several other benefits. However, there are fewer studies or weaker evidence to support these.

That’s why more research is needed on the potential benefits below before experts can understand them comprehensively and make recommendations.

A review of 9 studies in 254 participants looked at the effects of taking 1–3 grams of HMB daily in addition to a regular weightlifting program.

Participants experienced significantly reduced markers of muscle damage and better recovery (19).

Research from animal studies suggests HMB may help reduce age-related mental decline. However, scientists need to study these effects in humans (20, 21, 22).

Several test-tube and human studies have shown that taking HMB may reduce inflammatory markers, such as TNF-α, IL-8, and INFγ (23, 24).

A 4-week study in 11 people with diabetes who were on dialysis found that taking a supplement containing HMB along with arginine and glutamine significantly improved wound healing (25).

An older review of 9 studies found that taking 3 grams of HMB daily significantly lowered total cholesterol, LDL (bad) cholesterol, and systolic blood pressure compared with taking a placebo.

Systolic blood pressure is the upper number on a blood pressure reading.

However, it’s unclear whether HMB, exercise, or both were responsible for these effects (26, 27).

More, higher quality research is needed to look into this further.

Summary

Studies have linked HMB to various health benefits, such as improved exercise adaptations, reduced muscle loss, better exercise recovery, and more. It may also increase muscle growth in untrained individuals and older people.

Research has looked into how combining HMB with other supplements may affect exercise performance and muscle building.

It may provide benefits if you take it with creatine, vitamin D, or the amino acids arginine and glutamine. However, these combos may be more effective for some people than others. Here’s the evidence.

A review of 6 studies looked at the effects of taking HMB with creatine in 201 athletes and individuals who had already been resistance training.

It found that taking 3 grams of HMB along with varying doses of creatine significantly improved strength and high intensity exercise performance. It also aided muscle growth and reduced body fat (28).

However, other studies show mixed results when participants combined creatine and HMB. Some showed the combo aided athletic performance and raised testosterone, while others found it had no additional benefit compared with taking creatine alone (29, 30, 31).

An individual’s vitamin D status plays a role in muscle strength, especially among older people.

Studies have found that when older people took HMB with vitamin D, it may have helped increase muscle strength — even without an exercise routine (32, 33, 34).

Other studies combined HMB with other amino acids, such as glutamine and arginine. They found that these particular combinations may help prevent muscle loss that occurs with certain conditions, such as AIDS and cancer (35, 36).

Summary

HMB may have beneficial effects on muscles when you take it with other supplements. These include creatine, vitamin D, and the amino acids glutamine and arginine. However, some of this research found mixed results.

HMB appears to be generally safe and well tolerated, with little to no known side effects (37, 38).

In rare cases, people may experience stomach pain, constipation, or itching while taking HMB (10).

HMB is widely available. You can purchase it from health stores, at supplement stores, and online. It comes in several forms, including capsule, tablet, and powder form.

Although there’s no standardized dosage for HMB, most studies have used a dosage of 3 grams per day.

As with any dietary supplement, it’s important to speak with a healthcare professional before taking HMB, especially if you are on medications or have preexisting health conditions.

Summary

HMB appears to be generally safe in standard doses of 3 grams daily. As with any dietary supplement, speak with a healthcare professional before taking HMB.

HMB is a substance your body produces naturally when it breaks down the amino acid leucine.

It may offer benefits when some people take it as a supplement.

Some evidence suggests it may help reduce muscle loss and aid exercise adaptations. Plus, it may increase muscle growth in untrained individuals and older people.

Other potential benefits include aiding exercise recovery and reducing inflammation and age-related mental decline.

It may offer additional benefits when you combine it with creatine, vitamin D, and other amino acids, such as glutamine and arginine. Taking these combos may aid muscle growth and performance, increase muscle strength, and help prevent muscle loss, respectively.

It is important to note that more research is needed on many of these potential benefits.

HMB appears to be safe in standard doses of 3 grams daily. As with any dietary supplement, speak with a healthcare professional before taking HMB.