β-Hydroxy β-Methylbutyrate (HMB) is a dietary supplement that helps increase muscle strength and exercise performance. It also may help prevent muscle loss and protect the heart. Read below to learn if this supplement is worth the hype.

What Is HMB?

HMB, also known as β-Hydroxy β-Methylbutyrate (or β-Hydroxy β-Methylbutyric acid), is a popular bodybuilding supplement. Since the 1990s, athletes and bodybuilders have used HMB to build muscle and improve recovery from exercise [1].

It is also naturally produced in our body. HMB is created when the body breaks down leucine, an essential amino acid that also plays an important role in muscle growth [1].

Only a small amount of leucine is metabolized into HMB in our body. Some foods also contain limited amounts of HMB, including grapefruit, asparagus, and catfish [2, 3].

Research is discovering that HMB may have several health benefits. Besides improving muscle growth, HMB might also help prevent muscle loss caused by illness as well as protect the heart [1, 4].

Snapshot

PROS

  • Improves exercise performance
  • Improves muscle growth
  • Prevents muscle loss due to aging and disease
  • May help protect the heart
  • No reported side effects or safety concerns

CONS

  • Research results are mixed
  • Not effective without exercise
  • Less effective in trained athletes

HMB Benefits

1) Improves Strength and Exercise Performance

Many clinical trials have examined HMB’s effect on exercise performance and muscle growth.

What do these studies reveal?

A recent review searched through hundreds of HMB-related studies and identified 18 clinical trials that focused on exercise and muscle growth. These studies reveal several benefits, including [1]:

  • Increase in muscle mass
  • Increase in strength
  • Reduction of muscle damage
  • Increase in anaerobic and aerobic performance
  • Increase of lean body mass

The International Society of Sports Nutrition (ISSN) has also performed a critical analysis of the scientific literature. The ISSN concluded that HMB [5]:

  • Enhances muscle recovery after exercise in trained and untrained individuals
  • Works when taken close to a workout
  • Is most effective when taken for 2 weeks before heavy exercise
  • Increases lean body mass and functionality in the elderly

But hang on a minute, a few things must be mentioned.

Research suggests that healthy people who do not exercise may see no benefit. Non-exercising individuals saw no changes to body composition or exercise performance [1].

Some studies also show that HMB has little effect on athletes who are already strength-trained. However, trained individuals may see some benefit if the exercise intensity is high enough [5].

What does this all mean?

HMB increases muscle mass, strength, and exercise performance in untrained people who start regular exercise [1, 5].

Strength-trained athletes may still see benefits after high volume or intense exercise [1, 5].

But HMB may not be effective without exercise [1, 5].

2) Prevents Muscle Loss

Muscle loss commonly occurs in the elderly and in certain diseases.

Age-related muscle loss (also called sarcopenia) affects up to 10% of elderly people. This loss of muscle can lead to weakness and increased risk of falls [6].

An analysis of 7 trials including 146 older adults found that HMB effectively preserves muscle. There are increases in leg and handgrip strength as well [7].

Researchers also discovered that HMB supplements may prevent muscle loss caused by long periods of bed rest [7].

And there’s more. HMB may help in cachexia, which is muscle and weight loss caused by certain illnesses (like cancer and AIDS) [1].

Based on a review of 13 clinical trials, HMB shows several benefits, including [1]:

  • Increases lean body mass
  • Improves immune status
  • Decreases risk of death
  • Reduces feeling of weakness

There are a few things to note.

Many of these studies used other supplements as well, including proteins and amino acids [1].

HMB was especially effective for cachexia caused by cancer, steroids, and immobility [1].

Also, these results were not universal – some clinical trials found no benefit compared to placebo [1].

3) May Protect the Heart

HMB may have antioxidant and anti-inflammatory properties that can promote heart health.

A review of 9 studies found that HMB supplements lower total cholesterol, LDL, and blood pressure. These effects could potentially decrease the risk of heart attack or stroke [4].

But there are a few problems. A recent comprehensive review of the scientific literature has revealed mixed results.

For example, some studies show that HMB reduces inflammation after exercise. However, almost an equal number of studies say otherwise [8].

HMB’s effect on heart disease risk factors and oxidative stress are also unclear. Researchers suggest that HMB does not protect the heart more than exercise alone [8].

In other words, the heart-protective effects of HMB may be due to an increase in exercise activity rather than the supplement itself [8].

How Does HMB Work?

Research shows that HMB has anti-catabolic, anabolic, and regenerative effects on muscle [5, 1].

But first, let’s talk about our muscles.

Our body is constantly building and breaking down proteins in our muscles. This continual process is how our body maintains its metabolism and energy [5].

When our body is in a state of building it’s referred to as anabolism. On the other hand, when our body breaks down molecules it’s called catabolism [9].

As you may expect, when anabolism is greater than catabolism there is a net gain in muscle protein [5].

Anti-Catabolic Effects

HMB is often called an anti-catabolic, and for good reason.

Many studies show that HMB slows down catabolism and the degradation of muscle [10, 11].

HMB reduces catabolism by blocking proteasomes (proteins that break down other proteins). This makes HMB especially effective in catabolic states, such as fasting, aging, and disease [11, 10, 12].

Anabolic Effects

HMB also may have anabolic effects, to a lesser extent.

Research shows that HMB stimulates muscle protein creation through increases in growth hormone, IGF-1, and the mTOR pathway [13, 14, 15].

Other Effects

To top it off, HMB promotes the growth of satellite cells, which are the precursors to muscle cells. This may in part explain the regenerative effects that HMB has on muscle [15, 5].

The antioxidant and anti-inflammatory effects of HMB may be linked to cytokines. More specifically, HMB alters the effects of TNF-alpha and IFN-gamma [16].

Side Effects and Safety

Multiple clinical trials show that HMB is safe no side effects have been reported [17, 18, 19].

In fact, rats didn’t experience side effects after taking a dose equivalent to a 180 lb man taking about 50 grams of HMB for 3 months [20].

A long-term long study in elderly people also did not find any safety concerns after taking HMB for a year [21].

However, there is one potential issue. HMB’s effects on muscle may decrease the availability of certain amino acids [1].

Specifically, one study found that HMB lowers glutamine, an important amino acid involved with the immune response [22, 1].

Limitations and Caveats

Research on HMB is not clear-cut. While many clinical trials are promising, a good number of studies have found conflicting results.

For example, one review identified 9 separate studies that show HMB has no effect in trained or untrained people [1].

This extends to muscle loss and heart protection as well–studies have found conflicting results for these effects [1, 8].

It’s also important to note that the majority of studies use the calcium form of HMB (as opposed to the free acid form). Studies sometimes combine HMB with other types of supplements as well.

HMB Supplement Forms

HMB-Ca vs HMB-FA

Supplements generally combine HMB with calcium (Ca) to add chemical stability [5].

Usually, when we talk about HMB, we are actually referring to the HMB-Ca form. This is because, for a while, HMB-Ca was the only form of HMB available [5].

However, HMB in its free acid form (HMB-FA) has recently become commercially available. And there are important differences.

HMB-FA works faster than HMB-Ca. A study found that HMB-FA reaches peak blood levels in 30 minutes vs HMB-Ca which takes about 120 minutes [23, 5].

HMB-FA reaches higher levels in the blood. Peak blood levels of HMB-FA are nearly twice the amount seen with HMB-Ca [23, 5].

The half-life of HMB-FA is also slightly longer. HMB-FA half-life is 3 hours while HMB-Ca is 2.5 hours [23, 5].

Here’s the best part. The plasma clearance of HMB-FA is 25% greater than HMB-CA. Plasma clearance indicates how fast the body is using up HMB. This implies that our body uses HMB-FA more quickly and effectively [23, 5].

But there’s a catch. The vast majority of clinical trials focus on HMB-Ca. The safety and effectiveness of HMB-FA is not as clear.

However, initial studies on HMB-FA do show the same promising effects on exercise and muscle [24].

Clear Muscle and BetaTOR

Clear Muscle is a popular supplement marketed as a muscle and strength builder.

The one and only active ingredient in Clear Muscle is a compound called BetaTOR.

What exactly is BetaTOR?

BetaTOR is a brand name for the free acid form of HMB, also known as HMB-FA.

Does it work?

Research does show that HMB-FA works quicker and reaches higher blood levels than HMB-CA [23].

Several clinical trials have also looked specifically at BetaTOR supplements. Researchers found that BetaTOR increases aerobic fitness and growth hormone [25, 26].

The problem is there is far less research on BetaTOR compared to HMB-Ca. It’s unknown if the two forms have the same effectiveness and safety.

Creatine HMB

HMB is available as a combination product with creatine, another popular workout supplement.

One study shows that the combination increases lean body mass and strength. More importantly, this effect is greater than when either supplement is used alone. This suggests the effects are additive and there is a benefit to taking them together [27].

However, two other studies looking at highly trained athletes found no benefit. This means that, at the very least, the combo supplement may not be effective for trained athletes [28, 29].

Other Supplement Forms

A variety of other HMB combination products are commercially available. This includes combos with BCAA, glutamine, L-Carnitine, and HICA.

Little to no research has been done on these combinations so it’s unclear if there’s a benefit to mixing these supplements.

Dosage

HMB supplements are available as a capsule or powder.

3 grams of HMB per day appears to be the optimal dose, based on research [5, 1].

Lower doses of HMB have been shown to be less effective [5, 1].

HMB should be divided into 3 equal servings each day in order to optimize chronic effects [5, 1].

Conveniently, supplements are typically available as 1 gram (1000 mg) capsules, to be taken 3 times a day.

When to Take HMB

HMB-Ca should be taken at least 60 minutes prior to exercise [5].

HMB-FA should be taken 30-60 minutes prior to exercise [5].

Supplements should be taken at least 2 weeks before increasing workout intensity or starting a new training period [5].

HMB Reviews & User Experiences

Online reviews of HMB supplements (including all forms and combinations) are generally positive.

Many users report seeing better muscle growth and recovery time after workouts. Some users report seeing benefits after just one week. Others have also seen great results when stacking with other workout supplements.

Negative reviews primarily consist of people who saw little to no benefit. Some users also report experiencing side effects including nausea, stomach pain, and diarrhea, especially from HMB-FA products.

Buy HMB Supplements

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Take-Away:

HMB has good evidence for increasing muscle mass, strength, and exercise performance – but mainly when it’s combined with exercise.

You are most likely to see these benefits if you’re someone who is out of shape, but even if you’re an Olympic athlete, you may experience benefits if you train hard after supplementing HMB.

There isn’t enough evidence to conclude positive health effects for the heart or other conditions.

Despite mixed scientific evidence, anecdotal reports from users are generally positive.

HMB is generally very safe. 

Those looking for a safe and natural bodybuilding supplement should try HMB, assuming you’re willing to do the heavy lifting!

About the Author

Mathew Eng, PharmD

PharmD

Mathew received his PharmD from the University of Hawaii and undergraduate degree in Biology from the University of Washington.

Mathew is a licensed pharmacist with clinical experience in oncology, infectious disease, and diabetes management. He has a passion for personalized patient care and believes that education is essential to living a healthy life. His goal is to motivate individuals to find ways to manage their chronic conditions.

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