This issue presents part 3 of BI's exclusive hydroxymethylbutyrate (HMB) interview with Jacob Wilson, PhD. Dr. Wilson is Assistant Professor of Exercise Science and Sports Studies at the University of Tampa. He has conducted numerous studies on HMB, including some referenced in The Book of Muscle Synergy, available free on the BI Web site. HMB is one of the most studied sports nutrition ingredients of all time.

Before we begin, let's quickly review mitochondria, as this topic relates to the first question posed to Dr. Wilson below. Mitochondria are tiny structures found inside virtually every cell in your body, including muscle cells. As you may know, it is inside mitochondria that fat (specifically, fatty acids) are burned (or as scientists say, "oxidized") to provide energy. Carnitine, incidentally, plays a critical role in transporting fat into mitochondria. Of course, in order to lose fat, you must burn more of it than your body stores.

Supplements have appeared in the marketplace containing ingredients purported to stimulate mitochondrial biogenesis, the process by which your cells make more mitochondria. An increase in the number of mitochondria inside your cells may provide a number of benefits, including but not limited to higher rates of fat-burning and protein synthesis, delay of aging, and increases in muscle mass and performance.

Q: Dr. Wilson, does HMB affect mitochondria in any way, such as by stimulating mitochondrial biogenesis? What benefits might this provide to humans?

A: We're still trying to answer this question definitively in the lab. Currently all of our theories on HMB's effects on fat metabolism are based on indirect evidence, but I believe they point to an increase in mitochondria: 

1.      HMB's parent molecule, leucine, increases mitochondrial biogenesis.

2.      HMB may increase protein synthesis, and it is likely that this increases the energy demand inside the cell, which may in turn increase mitochondrial biogenesis.

3.      In athletes, HMB delays the accumulating of lactic acid in the blood, which may be indicative of increased oxidative metabolism and thus an increase in mitochondria.

4.      We also know that HMB increases fatty acid oxidation in cell culture.

So far this is the best explanation I have for why HMB may be having these effects. 

Q: Studies such as yours suggest that HMB reduces muscle damage caused by exercise. However, advanced bodybuilders and other experienced athletes suffer little or no muscle damage unless they suddenly change their workout routine or resume training after a layoff, for instance. With the exception of these circumstances, will the damage-reducing effects of HMB be noticeable to experienced users?

A: Good question. Particularly for bodybuilders, HMB has other beneficial effects, including stimulating fat metabolism, as well as perhaps sparing muscle under catabolic conditions. For example, HMB spares muscle under caloric restriction.  Thus, it may be beneficial for bodybuilders to supplement with HMB when they are preparing for competition, regardless of the damage response. In a building phase however, the weights will need to be heavy enough, or the stimulus novel enough to cause damage, in which case HMB can noticeably enhance recovery.

Q: Most of us don't want to get any older. Can HMB delay aging? What dose might be required?

A: In both 3-month and year-long studies, HMB was shown to increase lean body mass, strength and functionality in elderly subjects. Currently, doses are generally set at 3 grams for the elderly. We don't really know what the optimal dose is. I would therefore stick in the range of 3-6 g per day. In rats, we studied the mechanisms by which HMB may be working in the elderly and found that it prevented the loss of muscle fiber dimensions [size] with age. The advantage of our research is that it simulates all of senescence [aging] instead of just 3-12 months.

Q: Is it possible to experience tolerance to HMB? Or can it be taken continually without a deterioration of benefits?

A: I don't think you would experience tolerance while supplementing with HMB any more than you would from taking leucine. 

Q: HMB continues to be studied by scientists. What do you think is the principle motivation behind this?

A: Scientists are interested in understanding the situations under which supplementation with HMB can be useful. Briefly, these are:

1.      Catabolic situations (e.g. dieting, aging, cancer)

2.      Extreme muscle damage, such as occurs when changing your training program

3.      Situations where the individual is trying to lose body fat

4.      When an athlete is injured and trying to prevent muscle loss

In some studies, the effects of HMB supplementation are small. However, this should not discourage experienced bodybuilders from using it. I say this because it is the sum of such small improvements that eventually produces large changes in body composition (e.g. gain of muscle mass, loss of body fat), particularly over years of training.

Summary

According to Dr. Wilson, HMB and its parent molecule, the amino acid leucine, stimulate mitochondrial biogenesis. HMB also increases protein synthesis, which may in turn stimulate mitochondrial biogenesis. Muscle cells with larger number of mitochondria should be able to burn more fat and sustain higher rates of protein synthesis, resulting in more muscle mass and less body fat.

HMB has been shown to reduce muscle damage caused by high-intensity exercise. While advanced bodybuilders and other experienced athletes may suffer from muscle damage only infrequently, HMB supplementation can provide other benefits, including promoting fat loss and preventing muscle loss when following a carbohydrate-restricted diet (e.g. pre-competition).

HMB may also delay aging. In clinical studies, elderly subjects have gained muscle mass, strength and functionality when supplementing with this ingredient in doses ranging from 3 to 6 g. 

Anyone who drinks coffee regularly knows about tolerance. Dr. Wilson thinks that HMB is no more likely to produce tolerance than will supplementing with leucine. Thus, users can take HMB year-round.

Additional Information about HMB

·         Each serving of Muscle Synergy (tablets or the new powder) contains 3 g of HMB.

·         Small amounts of leucine are converted into HMB by the human body. Leucine powerfully stimulates muscle protein synthesis and, according to Dr. Wilson, mitochondrial biogenesis. There are more than 2 g of leucine in each serving of Muscle Provider.