Hydroxymethylbutyrate also known as HMB or β-Hydroxy β-Methylbutyrate is a popular supplement for advanced trainers looking at furthering their muscle growth. HMB is an extremely safe supplement to use, as you will see later, however people are still worried about any potential side effects. As such, here is a comprehensive guide looking at busting any myths regarding the side effects of HMB supplementation.
What are the Benefits of HMB?
If one had a search through Google, they would find a heap of articles looking at the benefits of HMB, which behind Leucine may be one of the most anabolic and ergogenic ingredients around. After all, HMB is a metabolite of leucine metabolism and will affect similar pathways. In short, supplementing with HMB can help:
- Increase Strength
- Decrease Muscle Damage
- Improve Power Output
- Increase Muscle Protein Synthesis or Muscle Growth
Does HMB have Side Effects?
In short, several studies have shown next to no negative side effects of HMB use. General recommended supplementation of 3g/day for up to 8 weeks has not resulted in negative changes in blood samples1. Similarly a dose of 6g/day over a month also did not show any toxic or negative side effects on the body including blood profiles, liver function and kidney function2. A meta-analyses of HMB supplementation also found that the supplement was safe to take over extended periods of time3, especially in healthy adult males and females. No long term studies however have looked at side effects of HMB supplementation on pregnant women and children, so these populations should treat the supplement with caution. It should be noted though that a recent rodent study found a slight decrease in insulin sensitivity, however this result has never been observed in human studies4.
Calcium HMB Side Effects
The most common form of HMB supplementation is in the compound calcium HMB, in which HMB is bound to a monohydrated calcium salt. Calcium is a mineral with fairly low toxicity and only extremely high levels over a long time can pose any serious concerns. The amount in 3g or even 6g of Calcium HMB would not be enough to cause any serious concern as evidenced by many of the studies looking at the safety of HMB supplementation.
Free Acid HMB Side Effects
The other common form HMB supplements come in is as a free acid like that found in Muscletech’s latest supplement Clear Muscle. Again, no negative side effects have been shown with free acid HMB in doses between 3-6g.
HMB Side Effects Long Term
As mentioned above, HMB supplements have been taken for a year without any negative side effects. In addition, an examination of a range of studies looking at HMB supplementation found surprising benefits of supplementation in longer stints of between 3-8 weeks. These benefits include:
- Decrease in LDL Cholesterol (the unhealthy kind)
- Decrease in Blood Pressure
- Decrease in Cardiovascular Risk
In addition, the year long study on HMB showed that HMB along with arginine and glutamine may help to reduce muscle wasting, making it an ideal supplement for older people, people suffering from muscle wasting diseases and even for those who are going to have an extended break from training, such as during injury.
HMB & Bodybuilding
Overall, HMB is an extremely safe supplement to take and one with an astounding amount of benefits, both for muscle building and general health. While leucine is still considered the most anabolic single ingredient supplement, HMB can offer some further benefits. If you’re an intermediate or advanced trainer looking at promoting bigger gains, HMB might just be the supplement for you.
1. Nissen S, et al. beta-hydroxy-beta-methylbutyrate (HMB) supplementation in humans is safe and may decrease cardiovascular risk factors. J Nutr. (2000)
2. Gallagher PM, et al. Beta-hydroxy-beta-methylbutyrate ingestion, part II: effects on hematology, hepatic and renal function. Med Sci Sports Exerc. (2000)
3. Rathmacher JA, et al. Supplementation with a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine is safe and could improve hematological parameters. JPEN J Parenter Enteral Nutr. (2004)
4. da Justa Pinheiro CH, et al.: Metabolic and functional effects of beta-hydroxy-beta-methylbutyrate (HMB) supplementation in skeletal muscle. Eur J Appl Physiol 2012, 112:2531-2537.