Why is hmb good?

HMB may act as a gateway to help keep your muscles in balance by slowing muscle breakdown. In fact, HMB has been shown to help preserve muscle mass in healthy older adults. Maintaining a well-balanced diet rich in protein and exercising regularly supports the natural balance.

β-hydroxy-β-methylbutyrate (or HMB) is a popular muscle building supplement. HMB is a metabolite derived from the essential amino acid leucine. Some studies have suggested that HMB is an anabolic compound that increases muscle building after resistance exercise training and improves lean body mass. There are also claims that it decreases fat mass alongside the increase in muscle mass. A further claim is that HMB increases muscle strength after resistance exercise training. But how strong is this evidence? Does HMB really have all these effects or is it largely hype?

HMB has been shown to stimulate protein synthesis in cells in vitro. This means that it seems to work in a petri dish. Similarly, some studies have provided evidence for an effect of HMB on protein degradation. The studies in humans on the functional effects (body composition, muscle mass, muscle strength), however, have provided mixed results. Over the last few years several meta-analyses have been performed trying to draw conclusions from all the human studies but even those analyses did not result in convincing conclusions. HMB is available in two different forms as a supplement: HMB that is calcium bound or HMB in a free form (HMB Free acid). There is, however, little evidence that these two forms have different effects.

Most recently a comprehensive meta-analysis was performed by Jakubowski et al (1) and what I like about this paper is that apart from a thorough meta-analysis, this review also includes a more qualitative point of view and asks critical questions about the results of published studies.

When the authors of this new meta-analysis searched the literature, they initially found 1731 papers and this was narrowed down to 303 for more detailed screening. In the end, 11 double blinded clinical trials were included in the analysis. In these 11 studies, both forms of the available HMB were included. The average study duration was just under 8 weeks. Below are the results of the meta-analysis.

After careful analysis of the 11 studies, they reported the effects of HMB on body weight. There was an average weight gain after the training program of 0.78 kg. This was increased to 1.12 kg with HMB. The mean difference between placebo and HMB-groups was 0.34 kg. A modest increase. The initial study by Nissen et al (1) (the patent holder of HMB, which showed the largest increase ever reported was still included in this increase and removing this study from the analysis would mean there would be no difference at all).

Eleven studies also measured changes in lean body mass. Here, the mean difference between supplemented and placebo groups was a few hundred grams. The HMB-supplemented groups gained an average of 1.57 kg and the placebo groups gained 1.17 kg of lean body mass.

The mean fat loss was equivalent in these same studies. There was no significant difference in the amount of fat that was lost.

The analysis of muscle strength with or without HMB revealed no differences. For example, subjects that undertook resistance exercise training with placebo increased their total 1RM (repetition max) strength by 30.6 kg. HMB-supplemented individuals increased their total 1RM strength by 32.0 kg. This difference was not significantly different.

The authors point out that some studies have reported extraordinarily greater lean mass

and strength gains by individuals ingesting HMB (2, 3), or HMB + ATP (4) when undertaking resistance exercise training.

The results of these studies were excluded from the analysis because the results were so far from what is considered a “normal” response. These studies met the inclusion criteria for the meta-analysis but were excluded due to the fact that there were so far removed from the average response. For comparison: the average gain in fat free mass of all other studies was 1.57kg versus 1.17kg with placebo (training without HMB). Increases of more than 7kg are therefore way out of the normal physiological range. In one study 9.3 kg (2) gain of fat free mass was reported after 12 weeks of training and supplementation and in the other (3) 7.4 kg of fat free mass was reported. Such changes are normally only seen in subjects using anabolic steroids.

HMB, as would be expected as a metabolite of leucine, can acutely activate skeletal muscle protein synthesis and the main signaling pathways leading to protein synthesis. But there is little or no reason to believe that HMB would have a superior effect to leucine or to meals containing leucine containing foods (5, 6). In fact, the large changes seen by Nissen et al (7) may have been because HMB was ingested with 37 g of milk protein.

The authors of the review concluded: systematic review and meta-analysis showed that HMB supplementation during resistance exercise training may result in a small increase in body weight but does not result in a significant enhancement of gains in free fat mass or losses of fat mass. Thus, there is no rationale for prescription of HMB as a supplement to improve body composition caused by RET in young subjects. In addition, effects on strength were also not significant.

Beta-hydroxy-beta-methyl butyrate, or HMB for short, is made in our body from the amino acid leucine. Leucine has been known as a powerful nutritional supplement for increasing strength, muscle, and decreasing body fat.1 Leucine has also used for years to prevent muscle fatigue and soreness, which previously made researchers believe that it was also responsible for slowing breakdown of muscle proteins, or proteolysis.1 However, it’s actually HMB, which comes from leucine, that slows this protein breakdown. The combination of benefits that leucine and HMB provide can make a dramatic difference in your workouts and body composition over time.

Beta-hydroxy-beta-methyl butyrate, or HMB, is a chemical produced by the body when breaking down the amino acid, leucine. It is often used to slow down muscle protein breakdown.

In short, HMB works in two ways — increasing protein synthesis while decreasing protein breakdown.1 This combined anti-catabolic (anti-muscle protein breakdown) and anabolic (muscle protein building) impact means you build lean mass more efficiently – so, that’s greater gains in muscle and strength.2

While you build muscle and increase your strength, you’ll have greater power and reduced muscle breakdown after exercise with consistent HMB supplementation. As your lean body mass increases from building muscle, you’ll increase your metabolism and will be able to level up your workouts. Studies have shown varying impacts of HMB supplementation based on an individual’s fitness level and type of exercise, so let’s break them down one at a time.

One study compared strength performance results of sedentary, overweight women before and after six weeks of supplementing with HMB. Although there was weight loss and fat loss over the course of the study in the group who took HMB, the significant impact was the improvement in their strength performance after 6 weeks (without following a weight training routine).3 This study proved that HMB can increase muscle strength without exercise, even in overweight, sedentary individuals.3

Those who are new to intense training like weightlifting seem to benefit the most from HMB. Since a new high-intensity exercise routine increases the likelihood of muscle damage that needs repairing, HMB can have a hugely positive effect. It is in this population that several studies saw increases in lean body mass and strength, but this is likely to also be due to the combination of a new training routine with supplementation.1

Those who are trying to up their strength and work their muscles to hypertrophy (muscle growth) are likely performing intense activities that leads to muscle damage. This type of intense training leads to muscle soreness and longer recovery periods. Experienced athletes following this type of training can use HMB to reduce soreness, damage, and shorten recovery by boosting muscle synthesis and slowing breakdown. HMB enables these types of athletes to train more often and see benefits more quickly.1

A study of a small group of elite male rowers compared the impact of HMB on endurance cardiovascular training. Twelve weeks of HMB supplementation increased the athletes’ VO2 max (aerobic endurance) and decreased their body fat.4 The study also indicated that the HMB supplementation might have a positive impact on peak anaerobic power as well.4

The main benefit of HMB it its ability to create a net positive balance of muscle turnover — that’s more muscle building than breakdown.1 For this reason, taking HMB while also cutting calories for weight loss, can help preserve lean body mass while targeting fat mass. This can be useful for people who are trying to lose weight without losing muscle.

Another promising study focused on the change of HMB levels as we age, showing that there’s a general decline in HMB as we age (correlated with losing muscle).5 The study also discovered that individuals with higher levels of HMB had greater muscle mass and greater strength than those with lower levels.5

Overall, the beneficial effects of HMB seem to be tied with intensity of the training and level of the athlete who is taking it. The groups who seem to have the greatest benefits from taking HMB are trained athletes who perform intense, challenging workouts that would otherwise be more damaging to the muscles.6 While there’s evidence of increase in strength in groups who are brand new to resistance training, it may be less effective for the occasional exerciser or someone who doesn’t perform very challenging workouts.7

HMB has consistently been shown to benefit those who are new to weightlifting and those who are dramatically increasing the intensity of their workouts by preventing muscle damage.1 There’s less effect in highly trained individuals who aren’t performing exercises that challenge their bodies.

HMB is produced by our bodies from the amino acid leucine. When present in high enough concentrations, it works by speeding the recovery of muscle after prolonged or intense exercise.1 Many studies also show varying degrees of reduced muscle soreness and faster recovery when taking HMB consistently.

Because HMB is a product of leucine, to increase your dietary intake you should focus on foods that are high in leucine. High levels of leucine are typically found in high-protein animal-and plant-based foods.8 Examples include:

The greater the amount of leucine in your diet, the more HMB will become available, but only about 5% of leucine is converted to HMB. For this reason, an HMB supplement is the most efficient way to get more in your diet.

HMB supplements can be available as powdered or capsule forms. Sometimes the HMB is combined with calcium (HMB-Ca) and other times it’s considered a “free acid”, or HMB-FA.1 Most products on the market as supplements are the HMB-Ca form, but some research shows that the free acid (FA) form works more quickly, and may become a more popular option in the future.1 Sometimes HMB is sold in combination with creatine due to its similar additive effects.

Several different research studies support the theory that the greatest benefit from supplementing with HMB happens when you consistently supplement with HMB for two weeks before changing or intensifying your training.1

The recommended dosage is 3 grams of HMB-Ca at least one hour before intense exercise, but ideally “loading” with 1g, 3 times a day for two weeks before a change in training routine and intensity.1 The HMB-FA form acts more quickly, so this can be taken in a 1-2g dose between 30 and 60 minutes prior to exercise.1

When taken with carbohydrates or as part of a meal, HMB might take longer to become available for maximum benefit. For this reason, if carbs are taken at the same time, consume your HMB about 2 hours before your training session.1

HMB is an effective supplement for those who want to speed up their recovery from high-intensity exercise — both weight training and endurance cardio. It helps to boost and preserve muscle mass and strength, and can be useful for weight loss.1,5

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.

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.

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.

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).

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).

Suzette Pereira, PhD, an Abbott researcher specializing in muscle health, explains that HMB stands for beta-hydroxy-beta-methylbutyrate, and as scientific as that sounds, its purpose is easier to understand when you realize it’s been part of your diet for a long time.

HMB is naturally produced in small amounts when your body breaks down leucine, an essential amino acid that you can get through eating protein foods including milk and Greek yogurt, soybeans, beef and chicken. It can also naturally be found in very small amounts in foods like avocado, grapefruit, cauliflower and catfish. But it’s difficult to get amounts found to support muscle health just by diet alone and is often found in nutrition supplements.

HMB isn’t new — it’s been studied for more than 25 years in over 90 clinical studies, including more than 20 studies in healthy or hospitalized adults along with other nutrients. But it’s easier to understand how HMB helps when you first look at how muscles function.

Our Muscles at Work

Muscles are always working and supporting our body in terms of mobility, balance, posture and even strength and energy. Through these activities there is a natural process of regeneration occurring.

"Muscle is dynamic," explains Pereira. "Both muscle protein breakdown and muscle protein synthesis, or building, are happening in the body throughout the day. The goal is to ensure that breakdown isn't happening faster than building."

However, breakdown can accelerate with age, illness and immobility.

While younger people are typically able to offset natural breakdown, the balance can shift with age as the body becomes less adept at using protein for muscle synthesis. A review paper published in Age and Ageing reported that age-related muscle loss, known as sarcopenia, affects approximately one in three adults age 50 and older. This decline in muscle health can contribute to fatigue, losses in strength and energy as well as poor mobility.

An Abbott-supported review paper in the Annals of Medicine illustrated how factors like inflammation and bedrest during illness, surgeries and hospital stays can contribute to muscle loss too.

"People can lose a lot of muscle in a short amount of time," says Pereira, noting that this kind of muscle loss is often associated with delayed recovery from illness, slow wound healing and reduced quality of life. "The catch is to get ahead of muscle loss before it accelerates.”

How does HMB work?

So what can you do to maintain muscle health? That’s where HMB might be able to help.

HMB may act as a gateway to help keep your muscles in balance by slowing muscle breakdown. In fact, HMB has been shown to help preserve muscle mass in healthy older adults. Maintaining a well-balanced diet rich in protein and exercising regularly supports the natural balance.

“Levels of HMB in the body are significantly correlated with existing muscle mass. One thing we can do to benefit our muscle health is eat a good diet, including getting more HMB and keeping up with strength building exercise," points out Pereira.

How to Get HMB

Getting more HMB naturally isn’t always easy. In the body, less than five percent of all leucine is converted to HMB1. Even on a good day, protein-packed foods can leave adults coming up short.

Pereira agrees that meeting HMB goals through food alone is very difficult. "You'd have to eat around 6,000 avocados to get enough to get a few grams of HMB" she explains, "and I think you'd turn green before you got there."

It's a joke, but it's also a problem she and the Abbott team have worked hard at driving education around to help doctors and people understand how to supplement with HMB to help preserve muscle mass.

Getting in the practice of incorporating HMB supplements into your diet can support muscle health. Talk to your healthcare provider or a dietitian.

"Our goal is to help people stay healthy," says Pereira. "At the end of the day, we want people to live their best life."