40 | NewScientist | 20 April 2019
“muscle fuel” on packaging and, in some
cases, images of bulging biceps. Those selling
protein-fortified food use ambiguous
language, describing their products as
“contributing” to the “maintenance” of
muscle mass. The intended message is clear:
that consuming lots of protein will make you
stronger. But they don’t say so explicitly,
because they aren’t allowed to. In 2010, the
European Food Safety Authority concluded
that there was insufficient evidence to support
claims that whey protein increased strength,
muscle mass or endurance in the general
population. This means the chances that
opting for a high-protein version of your usual
breakfast cereal, for instance, will make you
stronger are somewhere between minutely
small and zero.
The science is less conclusive for people
regularly doing resistance training. Indeed,
research on the effects of high protein intake
on muscle mass and various measures of
athletic performance is conflicting.
A 2016 review by UK researchers concluded
that protein supplementation didn’t augment
the effects of resistance training in people
over 70 years old. But another review,
published in 2017, found that extra protein
did have a positive effect on strength and
muscle mass in adults of all ages who were
asked to do weights-based exercise, although
these gains were minimal in those who
hadn’t previously done such exercise. Pooling
data from 49 previous studies, the review
concluded that extra protein did increase
the maximum weight that people could lift,
typically over the course of six weeks,
that it increases strength or muscle mass.
The promise of strength gains isn’t the only
thing driving the protein craze. The other big
claim is that consuming more protein will
help you lose weight. The idea is that by
keeping you feeling full for longer, protein
stops you from snacking. And it seems people
are buying into that message. A 2016 report
by Mintel found that a quarter of people who
consume high-protein food or drinks in the
UK did so to lose or maintain weight, and
36 per cent said they thought their purchases
would keep them fuller for longer.
Are they misguided? Here again the
science isn’t clear-cut. Research has linked
the consumption of protein to the release of
compounds known as peptides in the gut that
are associated with feeling full. However, a
2011 review of eight randomised controlled
studies looking at this found there was no
conclusive evidence that high-protein diets
were better for weight loss than high-fat or
high-carbohydrate diets. Unfortunately,
comparing high-protein diets with other
weight-loss strategies over the long term
is hard because people can neither be
imprisoned in laboratories, nor relied
on to accurately report what they eat.
This means we often have to measure the
effects of high protein consumption on short-
term hunger, appetite or later food intake.
Again, different approaches have generated
different answers. But there is some evidence
that consuming more protein can make
people feel fuller. A 2016 analysis of previous
studies found that people eating high-protein
meals reported feeling fuller than those
consuming lower-protein meals.
However, Richard Mattes at Purdue
University in Indiana, who led the 2016
analysis, doesn’t believe that feeling fuller in
the short term necessarily translates to long-
term weight loss. That is because how much
we eat depends on cultural factors, such as
portion sizes and snacking behaviour, as well
as how hungry or full we feel. “The protein
effect is also quite small,” he says. “So for it
to play a meaningful role would require a
substantial change of diet, which I believe
is not sustainable for most people.”
Ultimately, the jury is still out on the likes
of the Atkins and Dukan diets and the use of
protein-based supplements as ways to lose
weight. “There have been studies that show
the successful use of high-protein diets for
weight loss, but they have been no more
effective than other diets,” says Gray.
“It’s very individual. High-protein diets can
work for some people, but what’s importantIf you are a vegetarian or
a vegan, you have almost
certainly been asked, “But
how do you get enough
protein?” Is there any truth
in the idea that plant foods
don’t contain enough protein
to sustain us?
The short answer is no.
Proteins are constructed
from a selection of 20 types
of amino acids, often
referred to as the building
blocks of human tissue, of
which eight are known as
essential because our body
can’t make them. The
relative proportions of
essential amino acids in
foods derived from animals is
closer to the profile needed
by humans. However, all
plant-based foods contain
the full complement of
amino acids, and it isn’t
difficult to get the right
blend in a plant-based diet.
As Christopher Gardner
at Stanford University in
California and his colleagues
wrote in a recent paper:
“The difference between
protein quality from a
mostly plant-based dietand protein quality from a
more animal-based diet is
negligible for most people.”
The trick is to mix foods
that might be limited in one
essential amino acid with
foods that are limited in
different ones. That means
consuming grains, for
example, which tend to be
limited in lysine but high in
methionine, with beans,
which have the opposite
profile. That is why baked
beans on wholegrain toast
is always a better bet than
either on their own.THE VEGETARIAN QUESTION
compared with those taking either placebos
or just getting their standard levels of protein.
Then again, of the extra weight they could lift,
just 8.5 per cent was down to the extra protein
and the rest was attributed to exercise. Those
people who did resistance training only, with
no extra protein, added 27 kilograms to the
amount they could lift. Those who did the
same training and ate more protein could
lift an extra 29.49 kilograms.
“If people go to the gym and lift weights
with some kind of plan then their muscles will
grow to a variable degree,” says Stuart Phillips
of McMaster University in Hamilton, Canada,who led the study. “Extra protein adds an
additional layer but it’s a much smaller
contribution than just going to the gym.”
That may be surprising to those people who
believe their muscle gains are down to protein
shakes. But it is a conclusion supported by
nutrition and exercise researchers. “For elite
athletes, [supplemental protein] might give
you an extra 3 to 4 per cent,” says Stuart Gray
at the University of Glasgow, UK. “For most
people, it won’t have a noticeable effect.”
Another myth worth busting here is the
notion that it is best to consume protein
supplements or high-protein foods shortly
before or after workouts. US researchers who
reviewed previous studies on this in 2013
found no evidence to support the hypothesis“ For most people, extra
protein won’t bring any
noticeable strength gains”