There is some evidence that this innovative nutrient can raise anabolism (the constructive phase of metabolism) and promote recovery in trained athletes. As well, there may be some other beneficial effects for the endurance athlete who chooses to use this novel supplement. HMB stands for beta-hydroxy-beta-methyl butyrate. I think we’ll just stick with its acronym. Like so many other sport nutrition supplements, it was the bodybuilding community that first started using HMB in early 1996. However, endurance have since picked up on this supplement, which potentially may be of more benefit to them than the strength athlete or bodybuilder.
HMB is a metabolite of the branched-chain amino acid leucine. Depending on the diet, the can body produce 0.3 to 1 gram of HMB per day in muscle tissue (9). It is found in both plants and animals and is particularly concentrated in alfalfa, corn silage, grapefruit and catfish. Although HMB is found in higher concentrations in these foods, the amounts are still far too small to get a beneficial amount. You would likely have to eat several pounds of this food to get close to the amount needed for a beneficial effect.
Some have also questioned whether taking large amounts of leucine, a much cheaper supplement than HMB, can raise HMB levels. It was suggested though that you would have to consume 60 grams of leucine a day to get the body to make 3 grams (the least amount for a beneficial effect) of HMB.
Research has indicated that up to 10% of the amino acid leucine can be oxidized (catabolized) to HMB in muscle and that about 20% of HMB produced is lost in the urine (9). The site(s) of further metabolism is currently unknown. It is thought that most of the HMB produced exits muscle to be used elsewhere in the body, leaving very little for muscle use. When additional HMB is introduced, however, either by infusion or through diet, increased uptake by muscle occurs (up to 30%), indicating that muscle tissue can be a major site of HMB metabolism when concentrations are high.
The increased anabolism that has been found in other studies, through the use of HMB, may be from the reversed flow of HMB travelmaybe there is actually enough HMB in the body for other processes, so any surplus can be used by muscle. Or perhaps, because HMB plasma levels are increased through supplementation, the body does not have to break down its own muscle to liberate leucine for the production of HMB for other metabolic processes.
It has been suggested that HMB is effective at building strength, increasing lean body mass and enhancing recovery because it guards against or slows muscle proteolysis (protein breakdown). In one of the better studies on HMB and exercise (6), 41 healthy males were randomly assigned to receive either 0, 1.5 or 3 grams of HMB per day in orange juice. Diets were meat-free for 3 days each week during which blood and urine were collected. The subjects were weight-trained 3 times per week for three weeks. The group who consumed 3 grams per day of HMB showed a 55% increase (over the control) in lean tissue over the 3 week study.
The changes in lean mass were as follows for each group respectively: The control (0 grams of HMB per day) group showed a 0.4 kg increase in lean mass, the 1.5 gram HMB group showed a 0.8 kg increase in lean mass and the 3 gram HMB group showed a 1.2 kg increase on average. There was also a measured strength increase which appeared to be dose dependent. The researchers measured the muscle/protein breakdown biomarkers creatine phosphokinase (CPK), 3-methylhistidine (3-MH), and lactate dehydrogenase (LDH) to determine HMB¹s effect.
They also looked at nitrogen balancea measure of protein use and excretion in the body. The major finding of this work was that HMB supplementation resulted in an enhancement of muscle function in humans undergoing resistance exercise. Improvements in muscle strength (295% greater than subjects who didn’t use HMB) and increases in lean tissue mass (55% more than the group of non-users) were also found. As well, nitrogen retention improved, a 20% decrease in 3-MH excretion occurred, and a 20-60% decrease in the levels of the enzymes CPK and LDH were also found. Finally, the investigators discovered that there was a greater increase in plasma amino acids in the unsupplemented group compared to the HMB supplemented group. This is significant because blood samples were taken after an overnight fast. This means that food had nothing to do with increased plasma amino acids. Instead, it is likely the amino acids came from muscle breakdown. This data suggests HMB somehow supports the body¹s ability to minimize muscle damage associated with muscular work or stress.
Think what this could do for a road cyclist competing in a stage race. HMB could be very useful for protecting the muscles from the damage of racing, allowing the athlete to recover more completely after each race. Imagine the advantage a cyclist would have in the final stages of a tour. For the same reasons, HMB may be very useful for any endurance athlete during their heavy training periods.
Although it is not known exactly how HMB works, one hypothesis is that HMB helps decrease muscle protein turnover. It has been suggested by some magazine writers that this decrease in muscle damage in turn results in a more rapid neural recruitment by the muscle fibers and may act as a catalyst to faster increases in strength (7). Unfortunately, it was not explained what this meant and how they got this idea. It seems to me like a bit of a stab in the air. Nevertheless, HMB seems promising. In the same study it was also found that the unsupplemented group lost strength in the first week of weight training while the HMB supplemented grouped gained some strength.
More pertinent to endurance athletes, a study performed by researchers at Wichita State University in Kansas found that HMB supplementation increased VO2max in well-trained cyclists by an average of 4% (12). Eight cyclists took either 3 grams of HMB, 3 grams of leucine, or 3 grams of a placebo during a two week period. The results showed the above stated improvement in VO2max, with no effect seen in the leucine or placebo groups. Although the results were not statistically significant, the researchers also found that lactate levels increased in the HMB group, indicating that they were able to work harder, produce more lactate, and tolerate it more. That means an endurance athlete with a VO2max of 70 ml/kg/min could potentially raise his/her VO2max to about 73 ml/kg/min in just two weeks!
That could easily be the difference between first and tenth place in a race. Now, before getting too excited about these results, it is important to understand that it was just one study performed on just 8 subjects, and the research was only presented as an abstract. Published research presented as abstracts are often not scrutinized as carefully as a full journal article would be. Nevertheless, the results are promising. So much so that I recommend its use if you are seeking a nutritional way to boost performanceexperiment to see how it works for you.
A study on women was performed to determine if the same results with HMB that have been found in men occurred in women (5).
A group of non-exercising women were given either 3 grams of HMB per day or a placebo for 4 weeks. Another group was given the same thing along with an exercise program to perform. The group of women who didn¹t exercise while using HMB had no statistically significant changes in body composition, while the women who both took HMB and exercised experienced lean tissue gains, fat losses, and strength gains similar to those of men.
One of the most recent studies by Vukovich et al. looked at the effects of HMB consumption on body composition in older men and women between the ages of 69 and 71 (11). Over the 8-week period subjects performed resistance exercises 2 times per week while orally consuming 3 grams of HMB per day. The results were quite dramatic. One repetition maximum leg curl strength after 8 weeks increased on average 42.4% as compared to only 18% for the placebo subjects. Lean body mass increased by an average of 1.5 kg for the HMB group while the placebo group’s average lean body mass declined by about a half kilogram. Lastly, fat mass declined by 4% in the 8 week period for the HMB users, while it actually increased slightly (0.31%) in the placebo trial. Another recent study by Cheng and colleagues supports these fat loss results by showing increases in fat metabolism in cultured heart and skeletal muscle cells after exposure to HMB (1).
Although HMB is currently not an IOC banned substance, it can easily be tested for by blood and urine samples and the use of gas chromatography and mass spectrometry (2). Because of the invasiveness of blood testing, it’s not likely the IOC or any other sport governing body will test for HMB in that manner. However, it has been shown that about half of all HMB, whether it be from dietary sources or produced in the body, is lost in the urine. That means a urine test can probably detect HMB use. This doesn’t necessarily have to be a problem for an athlete wishing to boost recovery with HMB and who has a chance of being tested.
HMB has been found in various animal species to have a relatively short half-life. The half-life was found to be about 1 hour in rats, 2 hours in pigs, and 3 hours in sheep (4). This suggests that the half-life in humans would probably range between 2 and 4 hours and indicate that HMB would perhaps be undetectable as early as 8 hours after cessation of use.
Knowing that HMB has an approximate half-life of 2-4 hours in humans is important when deciding how to consume this nutrient. Let¹s say you take HMB only in the morning. With a short life span the HMB will decline back to normal levels in just a couple of hours and you will not benefit from its use for the rest of the day. Instead, spread out HMB consumption throughout the day for best results. I think 3-6 grams per day should be used. If your budget is tight then just use 3 grams a day. If you really want a kick in the pants, use 6 grams a day. I suggest that you take some HMB as soon as you awake in the morning, after every workout, with each meal, and finally just before bed. And try to consume food with each HMB intake. Using this strategy, you spread the doses of HMB throughout the day, thereby maximizing its potential effects.
Taking it right before bed and immediately upon waking will ensure that your body doesn’t go too long without this nutrient.
As well, because one of HMB¹s positive effects is to protect muscle tissue during the stresses of training, it is likely a good idea to load yourself up with the stuff before every workout, especially the hard ones. In theory, HMB may also be useful for delaying fatigue caused by muscle damage in events like marathons and Ironman races. And as I’ve said earlier, it would probably be beneficial for a road cyclist competing in a stage race.
HMB is becoming more accessible as more and more supplement companies include it in their nutritional lines and health food stores learn of its growing popularity. But finding it is not nearly as easy as finding a vitamin supplement. If your health food store doesn’t carry HMB you can easily mail order it. Just be careful if you do try to mail order a supplement either by phone or through the internet. Mail order companies often seriously gouge you with freight and shipping charges.
I have just learned that GNC will soon have its own HMB products. That may be your best choice. GNC is a big company, they can’t take the chance of cheating with their products, so you are pretty much guaranteed to get quality products from them. And because they deal in such large volumes, they can get better prices from manufacturers which can then be passed onto the customer. Also, some of you may be familiar with GNC’s “First Tuesday of the Month” deals they offer. GNC will also soon have their online store open for anyone in the world to use (www.gnc.com).
The patent for HMB use as a sport supplement is owned by Iowa State University Research Foundation (ISURF) and has been licensed to Metabolic Technologies, Inc. under U.S. patent number 5,348,979. If you come across an HMB supplement that doesn’t have this patent number on its label, don’t buy it. It’s very likely fake. This does not mean that an HMB product that doesn’t have the patent number on the label is certainly counterfeit. The current patents protect the nutritional uses of HMB for promoting nitrogen retention and the explanation of those methods. These “use” patents do not prevent others from manufacturing HMB, it just prevents them from saying their products improve nitrogen retention and muscle growth. However, because HMB is not a simple nutrient to manufacture, in all likelihood any product that doesn¹t have the patent #5,348,979 is fraudulent.
In terms of safety, a number of animal species have been fed large amounts of HMB for varying periods of time (4). In all the animal studies, there were no adverse effects or increases in death rates. When animals were autopsied, there were no pathological changes in their organs or tissues. Instead, the investigators found a lowered LDL (bad cholesterol) response, increased immune function, fewer respiratory illnesses, more lean body mass, and reduced fat mass. Even when pigs were fed 100 times that used by humans, no problems occurred.
In human studies using 2-5 grams of HMB, blood chemistry, liver function, and kidney function all remained normal. All the human studies that looked at cholesterol found an average LDL decrease of 7% (4).
This brings me to one theory of how HMB may work to increase anabolism. It is thought that HMB converts to cholesterol in muscle cells for use in growth and enhanced function. Although cholesterol has been given a bad rap, it is still a crucial substance in the human bodywe would die without it. Since many tissues do not absorb cholesterol from the blood, inadequate production may limit cell and tissue growth, which potentially can be corrected by HMB supplementation. This increase in muscle cholesterol may signal the liver to slow cholesterol production and thereby explain possibly why serum LDL levels decline with HMB use.
Although HMB has been found to be quite safe there is one effect that is somewhat concerning, especially for the endurance athlete. There is some science showing that HMB binds to phosphate (8). This study showed that HMB is as efficient as calcium acetate in binding phosphate in vitro (test tube), and it may be an effective treatment for uremia patients. Uremia is a state of excess urea, creatinine, and other nitrogenous end products of protein and amino acid metabolism, often caused by kidney failure. When the kidneys fail, the filtration rate decreases causing electrolytes like sodium phosphate to accumulate. HMB may help bind to this excess phosphate. Unfortunately, for healthy endurance athletes this is not a good thing. Phosphate is a very important mineral for normal bodily processes and endurance athletes are very dependent on it for optimal performance. In fact, supplementing with sodium phosphate can have potential ergogenic effects.
Some supplement companies have recognized this problem and have added phosphate, usually either as sodium or potassium phosphate, to their preparations. If you do choose to use HMB, carefully check the ingredients on the label to determine whether the product contains additional phosphate. If it doesn’t, use another product that does or use a separate phosphate supplement along with the HMB supplement.
1. Cheng, et al., Beta-hydroxy-beta-methyl butyrate increases fatty acid oxidation by muscle cells. FASEB J. 11:A381, 1997.
2. Nissen1, et al., Analysis of ß-Hydroxy-ß-methyl Butyrate in Plasma by Gas Chromatography and Mass Spectrometry. Anal. Biochem. 188:17-19, 1990.
3. Nissen2, et al., Effect of ß-hydroxy-ß-methyl butyrate (HMB) supplementation on strength and body composition of trained and untrained males undergoing intense resistance training. FASEB J. 11:A150 ,1996.
4. Nissen3 and Abumrad, Nutritional role of the leucine metabolite ß-hydroxy ß-methylbutyrate (HMB). J. Nutri. Biochem. 8:300-311, 1997.
5. Nissen4, et al., Effect of feeding ß-hydroxy-ß-methyl butyrate (HMB) on body composition and strength of women. FASEB J. 11:A150, 1997.
6. Nissen5, et al., Effect of leucine metabolite S-hydroxy-ß-methylbutyrate on muscle metabolism during resistance-exercise training. J. Appl. Physiol. 81:2095-2104, 1996.
7. Phillips, HMB. Muscle Media 2000, 47:46-51, 1996.
8. Sousa, Calcium ß-hydroxy-ß-methylbutyrate. Potential role as a phosphate binder in uremia: In vitro study. Nephron 72:391-394, 1996.
9. Talleyrand, et al., Uptake and output of the leucine metabolite ß-hydroxy-ß-methyl butyrate (HMB) across the leg of pigs. FASEB J. 7:A71, 1993.
10. Van Koevering and Nissen, Oxidation of leucine alpha-ketoisocaproate to ß-hydroxy-ß-methylbutyrate in vivo. Am. J. Physiol. 262:E27-E31, 1992.
11. Vuckovich, et al., The effect of dietary ß-hydroxy-ß-methyl butyrate (HMB) on strength gains and body composition changes in older adults. FASEB J. 11:A376, 1997.
12. Vuckovich and Adams, Effect of ß-hydroxy-ß-methyl butyrate (HMB) on VO2 peak and maximal lactate in endurance trained cyclists. Med. Sci. Sports Exerc. 29:S252, 1997.
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