Presented as an infographic, the results are based on a review of
data from 49 randomized controlled trials in 17 countries and more
than 1,800 participants.
The upshot: supplementing protein while doing resistance training
can increase strength by about 9% and add about one pound of muscle.
The effect levels off at a certain point, after which extra protein
provides no additional benefit.
"Lots of people take protein supplements with the expectation that
they are going to gain lots of muscle because of the protein
supplement," said senior study author Stuart Phillips of McMaster
University in Ontario, Canada.
"Supplement companies tout huge benefits," Phillips told Reuters
Health by email. "We thought it was time to do some science."
Phillips and colleagues conducted a systematic review and
meta-analysis of research published on the topic of protein
supplementation and resistance training, looking at how much extra
muscle men and women gained, as well as how much stronger they
became.
The studies had to be at least six weeks long, include resistance
training at least twice a week, and one group had to be given a
protein supplement that didn't have other muscle-building
ingredients such as creatine or testosterone-enhancing compounds.
Ten of the studies involved people who were experienced in
resistance training and 14 studies had exclusively female
participants.
The team found that protein supplementation led to an increase in
muscle, but not much. In addition, protein supplements were more
effective in people who were already lifting weights and less
effective in people over age 60.
The analysis didn't find any differences between types of protein
supplements or a distinction between getting protein from food or
from supplements.
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When Phillips' team analyzed the relationship between the amount of
muscle gained and total amount of dietary protein consumed, they
found that gains leveled off at around 1.6 grams of protein per
kilogram of body weight per day, or about 0.7 grams per pound. That
is twice the recommended daily amount in most official nutrition
guidelines, they note.
"Going to the gym is where most of the benefits come from," Phillips
said.
Current studies are investigating the key amino acids in protein
that aid this muscle-building process, particularly leucine, and
especially for adults over age 60 who may have muscle and bone loss
known as sarcopenia.
"It's a big deal to have sufficient enough quantities to stimulate
muscle growth," he added.
Future studies will focus on ways to boost muscle mass and the
effect of protein supplementation in older adults, including through
everyday foods such as milk and meat.
"Older adults experience age-related physiological changes that
affect body weight and body composition," said Li-Qiang Qin of
Soochow University's School of Public Health in Suzhou, China.
Qin, who wasn't involved in the current review, has studied the
effect of milk protein supplementation among older adults taking
part in a resistance training program.
"Milk proteins are excellent sources of all the essential amino
acids and may represent an ideal protein source to promote muscle
anabolism in older adults undergoing resistance training," Qin said.
SOURCE: https://bit.ly/2kTTTBU British Journal of Sports Medicine,
September 6, 2019.
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