A new muscle drink on the market isn't for bodybuilders or workout fanatics: It's aimed at middle-aged and older adults who are losing muscle naturally because of age. Ensure Muscle Health promises that its 13 grams of protein and special ingredient "HMB" will help such folks shore up muscle and muscle strength into their golden years.
HMB — beta-hydroxy-beta-methylbutyrate — has been getting a lot of attention from researchers lately because of reports that it can help preserve or increase muscle mass. But, as seems to be the case with all supplements, "there's still a lot of conflicting evidence," says Kate Pollock, a sports nutrition specialist in San Diego. "Some studies show it may increase muscle strength and decrease muscle damage, but other studies show no effect."
The compound is a breakdown product of the amino acid leucine, which has long been known to play a role in building muscle.
In the 1990s, a handful of studies began to show that leucine's effects might be because of HMB.
In one study, published in 1996, researchers at Iowa State University had a small group of young men lift weights for an hour and a half, three times a week, for three weeks. Some took no supplements, while others took 1.5 grams or 3 grams of HMB per day.
By measuring metabolites in the men's urine, the researchers showed that the men taking the most HMB had the least muscle damage, and those who took no supplements had the most damage. Muscle strength also increased most in the men who took the 3 grams of HMB daily — by an average of 18.4% compared with 13% for men who took 1.5 grams of HMB and 8% in the men who took none.
But the results of subsequent studies varied.
A few small preliminary studies suggested that HMB supplementation might help preserve and restore muscle in people experiencing muscle loss because of disease or hospital stays that kept them immobilized for long periods of time.
But a 2003 study of 35 college football players at Oklahoma State University who took 3 grams of HMB daily while undergoing a rigorous four-week exercise program showed no effect on muscle strength or muscle mass.
In 2009, researchers in New Zealand looked at 14 published studies on HMB use in healthy young men. They found that HMB appeared to have the greatest effect in men who were not routine weight lifters or resistance trainers. For such men, taking the supplement for an average of five weeks resulted in an average 6.6% increase in body strength when they stuck to an exercise routine. But men who were already experienced weight lifters or resistance trainers showed little to no benefit from the supplement.
Scientists aren't sure why HMB seems to have a more pronounced effect in people who aren't already on a workout regimen; the New Zealand researchers speculated that it may be because muscle protein turnover, or replacement, is decreased in people who do regular weight or resistance training.
The fact that HMB — so far, at least — seems to be most helpful to people who are out of shape, ill or elderly explains why it's now being marketed to people in middle age and beyond, says Mary Ellen Camire, professor of food science and human nutrition at the University of Maine in Orono.
In most people, muscle mass and strength peaks at age 40, says John Rathmacher, a research scientist who studies HMB at Metabolic Technologies Inc., a nutritional products company founded by Iowa State University researchers who conducted early studies on the compound. According to government data, 35% of U.S. adults 60 and older have moderate loss of muscle mass and strength. Some studies have shown that when adults reach their 70s, they may lose 2% to 4% of their muscle strength each year.
Rathmacher adds that HMB's appeal stems from the fact that it provides the benefits of leucine on a concentrated scale. "You'd have to consume 10 times the amount of leucine to get the HMB you need" to have an effect on muscle health, Rathmacher says.
Still, leucine is just one of many amino acids the body needs for strong muscles, Camire notes. She points out that the only proven way to prevent age-related muscle loss and weakening is to consume a diet with adequate calories and a variety of proteins while practicing strength training.
Supplements like HMB may seem like an easy shortcut to preventing muscle loss, she says, but they're not miracle products.