B-Hydroxy-BMethylbutyrate (HMB): Benefits, Side Effects & Dosage
What Is B-Hydroxy-BMethylbutyrate (HMB)? HMB is short for B-hydroxy-B-methylbutyrate and it is a metabolite of leucine, an essential amino acid that is also part of branched chain amino acids (BCAA) (x). The body converts leucine into alpha-Ketoisocaproic acid (KIC), which then metabolizes into either HMB or isovaleryl-CoA. The majority of KIC is converted into isovaleryl-CoA, while just a minor amount metabolizes into HMB.
Leucine is also present in food and ultimately, the body oxidizes about 5 percent of it into HMB. Foods like alfalfa, fish, meat and grapefruit contain trace amounts of HMB (x, x). The body produces about 0.25 to 1.0 g of HMB from approximately 1 g of protein per kg bodyweight.
Dr. Steven L. Nissen is a researcher at the University of Iowa. He was the first person to discover the vital role that HMB plays in protein synthesis. For more than 20 years, studies aimed to discover the effects of B-hydroxy-B-methylbutyrate on muscle metabolism in respect to resistance training. Over the years, it has become an important component in the dietary supplement market. Bodybuilders and athletes use HMB extensively to decrease muscle proteolysis and increase muscle mass, strength and power. Currently, it is an anti-catabolic supplement to help protect the muscles from degradation (x).
Benefits of HMB Reducing Muscle Damage Evidence suggests that HMB supplementation has anti-catabolic effects, helping prevent muscle damage during resistance training periods. HMB blocks proteasomes, which are proteins that degrade other proteins. This is why supplement manufacturers do not just market HMB as a muscle building supplement alone. Manufacturers also market it as an anti-catabolic agent effective in catabolic states such as disease, aging and fasting (x).
In a heart psychology report, researchers at Vanderbilt University suggest that HMB supplementation may inhibit protein degradation caused by high-intensity resistance training (x). The European Journal of Applied Physiology also published a study on HMB. The research shows that although it is not as effective as leucine for muscle building, it appears to be a more effective method to prevent muscle breakdown (x).
Stimulating Muscle Recovery In addition, B-hydroxy-B-methylbutyrate can help shorten recovery time after an intense workout session (x). In a 2013 study, researchers examined the effects of short-term supplementation on protein breakdown and muscle damage in twenty resistance-trained athletes. The results showed that when the athletes took the supplements before a high-volume resistance training, it reduced muscle damage and improved recovery between training days (x).
Preventing Age-Related Muscle Degradation Aging comes with loss of muscle mass and a decline in overall skeletal muscle health. This is a natural process, but sometimes it leads to sarcopenia, a condition that causes degenerative muscle loss. It affects about 10 percent of elderly patients. This condition can limit physical function, cause weak muscles and increase the risk of falling. It can even impact mortality risk (x). While aging is natural and inevitable, HMB may help slow down muscle loss (x, x). The supplements may help increase strength and muscle mass in senior citizens and it may have an even stronger effect alongside physical exercise.
The Geriatrics Department of Padova University carried out an 8-week study on older female adults to determine the effects of HMB supplements. The researchers divided the subjects into an experimental and control group for the randomized controlled trial. The experimental group regularly ingested a 1.5 gram calcium HMB dosage and at the end of the eighth week, they showed increased muscle strength and physical activity (x).
In another study, researchers conducted seven trials on 146 elderly subjects. The results showed that B-hydroxy-B-methylbutyrate helped preserve muscles and increased muscle mass. It also helped increase the patients’ grip strength in the patients’ hands and legs (x). Additionally, the International Society of Sports Nutrition (ISSN) published a critical analysis of scientific literature on HMB-related studies. It concluded that HMB can increase lean body mass in elderly patients (x).
Protecting the Heart Evidence suggests that HMB contains anti-inflammatory and antioxidant properties that may have a positive effect on cardiovascular health (x). In an in-depth review, nine studies revealed that HMB may help reduce total body cholesterol level, LDL cholesterol levels and systolic blood pressure. It may ultimately decrease the risk of stroke and heart attack, two conditions associated with high cholesterol and high blood pressure (x). According to a recent study, patients with chronic obstructive pulmonary disease (COPD) who ingested 3 g daily doses of HMB for seven days showed signs of anticatabolism and anti-inflammation in the body. The study also suggests that the patients showed improved lung function (x).
However, medical researchers still need to conduct further studies in this area because a recent scientific literature review showed mixed results. For instance, some studies revealed that B-hydroxy-B-methylbutyrate only cuts down on inflammation after exercise. These researchers believe that it does not have a clear effect on risk factors for heart disease. They further suggest that its heart-protective effects are not just a result of the supplement itself. It may be a result of an increase in physical activity (x).
Benefiting Chronic Health Conditions Some chronic health conditions can cause a reduction in muscle mass. For example, HIV/AIDS or cancer can cause weight loss and reduce tissue in the body. Paired with exercise physiology, HMB supplements with the amino acids glutamine and arginine may help increase strength and muscle mass in patients with these conditions (x, x).
A recent meta-analysis discovered that supplementing with HMB helped increase muscle mass and strength in patients affected by a number of chronic health conditions including chronic obstructive pulmonary disease, rheumatoid arthritis, cancer cachexia and HIV (x). However, the meta-analysis discovered that it had a small effect on physical function and body composition. From this observation, it is quite possible that these small effects may be more significant in those affected by muscle wasting than those in a healthy athletic group.
Increasing Strength and Muscle Mass The body is able to build muscles from protein and B-hydroxy-B-methylbutyrate can help support this process. Although it may not be as popular as other muscle building supplements, it has the potential to be very effective. Several clinical trials have examined its effects on muscle growth and exercise performance.
A randomized double-blind, placebo-controlled study published in 2014 showed that after 12 weeks of supplementation, participants showed incredible gains in power, strength and muscle mass (x). Also, the supplement produced even greater results compared to testosterone supplements. In 2016, the same lab published another study that concluded that a combination of HMB and ATP increased lean mass, strength and power in trained participants (x).
In 2011, a journal called Nutrition published a study that recorded a significant increase in lean and strength gains with a combination of HMB and creatine (x). Also, in January
2008, the journal Nutrition and Metabolism published a review article that indicated a number of studies found a positive link between HMB and lean body mass. The study concluded that the supplement reduced soreness and increased strength in trained athletes (x).
Reducing Body Fat Because the supplement increases muscle mass and strength, it may increase metabolism with exercise and increase the potential for the body to burn fat. Previous studies associate HMB supplements with large amounts of fat loss in subject groups (x).
According to another study, B-hydroxy-B-methylbutyrate may also reduce body fat during periods of energy restriction. The study focused on eight highly trained female judo athletes and split them into two groups. The experimental group supplemented with 3 g daily for three days, while the control group did not receive any supplements. After the three-day period of energy restriction, the experimental group showed a significant reduction in body fat and body weight percentage, but there were no changes in the control group (x). However, neither group showed changes in performance and muscle mass.
Side Effects of HMB This supplement may be safe for most people in proper dosages. However, medical researchers have not provided sufficient evidence for a definite conclusion. It may not be safe for pregnancy or breastfeeding patients, so it is best to avoid it to be safe (x). HMB may also interfere with other medications (x). Side effects may include gastrointestinal discomfort and an upset stomach.
Dosage Instructions for HMB As a dietary supplement, the recommended dosage for HMB powder is 1,000 mg. Divide this dosage into a maximum of three equal servings throughout the day with food. Patients who are pregnant or breastfeeding should avoid this supplement completely. Always consult with a doctor before starting a supplement regimen.
Bottom Line The body produces B-hydroxy-B-methylbutyrate (HMB) when it breaks down leucine. In its supplemental form, athletes and bodybuilders commonly use HMB to increase the benefits of exercise and strength training. In combination with other high-quality proteins, it can induce muscle protein synthesis to help build and protect muscle mass. It can also help promote heart health and prevent muscle loss that occurs in a number of clinical conditions, including HIV, rheumatoid arthritis and cancer cachexia. Although it may be safe and provide health benefits, consult a doctor before taking this
supplement.