AMES, Iowa — A new study by Iowa State University researchers has found that two dietary supplements — creatine and HMB (b-hydroxy-b-methylbutyrate) — have a positive effect on lean mass and strength gain in humans.
The study by Rick Sharp, professor of health and human performance, and Steve Nissen, professor of animal science, found that both creatine and HMB demonstrated significant increases in net lean mass and strength gains when combined with resistance training.
The study, "Effect of Dietary Supplements on Lean Mass and Strength Gains with Resistance Exercise: A Meta-Analysis," was published in the January 2003 issue of the Journal of Applied Physiology and has been rated as the number one article referenced by online readers.
Sharp and Nissen examined scientific research (conducted between 1967 and 2001) of more than 250 dietary supplements. Six of those met study criteria for review: creatine, HMB, chromium, dehydroepiandrosterone (DHEA), androstenedione and protein. Only creatine and HMB were shown to significantly affect lean mass or strength gain.
The other four supplements studied — chromium, dehydroepiandrosterone (DHEA), androstenedione and protein — do not significantly affect lean gain or strength.
Most of the 250 supplements failed to meet study criteria because there had not been more than two scientifically sound studies published. Sharp and Nissen also required that studies reviewed had a duration of at least three weeks and involved resistance-training two or more times a week during the original study period.
Sharp said this compendium study is important because the use of general and specific dietary supplements is widespread among serious and casual athletes with several hundred specific formulas marketed.
Creatine and HMB showed significant net gain in lean mass and strength each week, according to Iowa State research. The study also showed that there is a possible additive effect between creatine and HMB.
"Creatine and HMB both seem to work differently and independently to positively impact lean mass and muscle strength," said Sharp. "That means they could potentially work together for a maximum benefit, which doesn't happen very often."
The safety of creatine and HMB supplements has been addressed in several papers, Sharp said. Creatine shows no adverse health effects. HMB had no major health effects but did result in a net decrease in total cholesterol, LDL cholesterol and systolic blood pressure.
HMB, a natural body building compound, was discovered through ISU research conducted by Nissen.
Of the other four supplements studied, the results were:
Chromium — caused a small, non-significant increase in net lean mass and strength gain.
Androstenedione and DHEA — both failed to significantly affect lean mass or strength gain with resistance training.
Protein — both lean mass and strength gain were unaffected.
Sharp said the protein result is significant because that supplement is the most widely and popularly sold to the public.
"There is a disconnect between what the evidence is and what the market is showing us," said Sharp. "But the research hasn't borne out any significant benefit of protein-based supplements. The average American already consumes more than enough protein daily to augment lean mass and muscle strength. However, he added, more studies are being conducted on protein supplements that vary the composition of the protein and timing of its use.
Rick Sharp, College of Education, (515) 294-8650
Cathy Curtis, College of Education, (515) 294-8175
Kevin Brown, News Service, (515) 294-8986