You may have seen one or more of the following headlines over the past week:
Muscle-building protein shakes may threaten health (Medical News Today)
News headlines about nutrition, however, are nearly always written simply to get clicks.
Often, they grossly misrepresent the findings of the study they claim to report.
The examples listed above, and countless others like them from the past week, are no different.
Read on to find out what the study in question actually tells us, and why you might think twice before throwing out your protein supplements.
First, let’s cover a little bit of background info to make sure we’re on the same page.
What is protein?
Protein – found in foods like chicken, fish, beef, pork, and eggs – is made up of chains of amino acids that our bodies break down and then reassemble to serve various purposes, including building and maintaining muscle mass.
Our bodies use roughly twenty unique amino acids – some of which we’re able to produce on our own (endogenously), others we must obtain from outside sources (protein in food).
The amino acids we must obtain from outside sources are referred to as the “essential” amino acids.
When a food contains protein comprising all essential amino acids in roughly the ratio that our bodies use them, that protein is referred to as a “complete” protein.
Some folks supplement their diets with protein powders as a convenient means for helping to reach their protein goals.
What are BCAAs?
Branched-chain amino acids (BCAAs) are three specific amino acids – leucine, isoleucine, and valine – named as such due to their structures including a branch off to one side.
BCAAs help with muscle growth and maintenance, as well as reducing fatigue during exercise.
We’ll touch more on this BCAA-tryptophan-serotonin connection elsewhere throughout this post.
Folks often opt for BCAA supplements over other protein powders or whole foods because pills and shakes are more convenient than food and BCAAs alone offer fewer calories than an equivalent amount of BCAAs packaged in more complete proteins.
This makes BCAA supplements a popular choice for those who train while fasting or who find reaching their protein targets through food difficult.
The question of whether BCAA supplementation is “worth it” or not is beyond the scope of this article.
What is tryptophan?
Another amino acid we’ll be discussing is “tryptophan”.
Our bodies use tryptophan to create a neurotransmitter called “serotonin”, which helps regulated mood, digestion, and appetite.
Remember how we mentioned that BCAAs reduce fatigue?
Elevated BCAAs in the blood prevent tryptophan from being taken up by the brain to produce serotonin, which is a neurotransmitter responsible for fatigue.
Now that we’ve covered a few basics, let’s dive into the study.
What did the study actually tell us?
The study in question was titled “Branched-chain amino acids impact health and lifespan indirectly via amino acid balance and appetite control”, published in Nature Metabolism.
During the study, a team of researchers at University of Sidney split 312 mice into four groups, each of which was fed a different diet.
All four diets provided identical macronutrient ratios (18% total protein, 64%, carbohydrate, 18% fat), but each diet offered a different amino acid profile.
The control diet was labeled BCAA100 and contained the standard amount of BCAAs.
The three intervention diets were:
- BCAA200 (twice the standard amount of BCAAs)
- BCAA50 (half the standard amount of BCAAs)
- BCAA20 (one fifth the standard amount of BCAAs)
The mice eating the BCAA200 diet were observed to eat approx. 20% more energy than the other diet groups.
They gained weight, developed fatty liver, and died earlier than the other mice, too.
The scientists noticed that across all four diets, the mice ate consistent levels of three amino acids – methionine, tryptophan, and threonine.
When the researchers supplemented the BCAA200 diet with tryptophan or threonine, the mice eating that diet no longer ate more than the other mice, confirming that these two amino acids played a role in determining how much the mice ate.
The researchers found that the increased BCAA content of the BCAA200 diet was interfering with tryptophan uptake, which in turn prevented serotonin production.
The reduced serotonin production was determined to be driving the mice to overeat, which in turn was driving the weight gain.
The same mechanism mentioned earlier by which BCAAs reduce fatigue – serotonin inhibition – appears to, at least in this study, also drive overeating.
The researchers also concluded that the adverse health effects observed in the BCAA200 mice (fatty liver and early death) were the result of the weight gain, and not a toxic effect of the BCAAs themselves.
So, the study didn’t show protein powders to have some magical fattening, depressing, life shortening effect, as this past week’s headlines suggest.
Rather, it showed that manipulation of amino acid profile influences neurotransmitter production, setting off a chain of events that results in negative health outcomes.
Let’s now explore what these results do and do not mean for you.
After all, what good are studies such as these if not used to direct our efforts?
What can you do?
Recall that the negative health effects experienced by the mice were observed only when BCAA intake was increased above normal levels.
If you’re supplementing with traditional complete protein shakes like whey, casein, or well-balanced plant-based sources, you’ll be getting all the amino acids you need in the ratios that your body will use them.
You won’t see the same effects on tryptophan uptake and serotonin production.
Thus, you likely won’t see an increase in appetite.
If you’re supplementing with BCAAs, then you might want to take this study into consideration.
Chances are that your supplemental BCAA intake isn’t resulting in the 200% above baseline BCAA intake shown in the study.
However, you might not be that far off.
If, for example, you’re eating a baseline of 160 grams of protein a day, and 25% of that protein comprises BCAA, then this equates to a baseline BCAA intake of 40 grams per day.
Doubling this, as was done in the study, would only require four 10 gram servings of supplemental BCAA to bring your BCAA intake from 40 grams per day to 80 grams per day.
This demonstrates that the dosage in the study isn’t unrealistic, especially if you’re taking several doses of BCAA a day, as you might during a fasting protocol like Martin Berkhan’s LeanGains method.
If you’d like to continue taking BCAAs but want peace of mind against any effect BCAAs might have on your appetite, the simplest solution may be to supplement with tryptophan and/or threonine.
Tryptophan supplementation would be most relevant to the effect on serotonin production, and may result in benefits to mood as well.
Another alternative would be to swap out the BCAA supplements for a more complete amino acid source like essential amino acids (EAAs) or traditional protein powder.
EAAs or traditional protein powder would provide a marginally higher caloric load, but if you’re getting the majority of your protein from real food, the difference won’t be that significant relative to your total daily intake.
Finally, you might consider not supplementing with protein powder or BCAA at all, instead getting your protein from minimally processed animal sources.
You’ll not only benefit from a complete amino acid profile (including tryptophan) but also from other nutrients like B vitamins, creatine, carnitine, carnosine, and essential fats.
You’ll get the most bang for your buck in this regard if prioritizing wild fish, game, and ruminants like beef or lamb.
Of course, whole food sources aren’t as convenient as protein powders, and we’ve all got to do what we can within in the context of our needs, preferences, goals, budget, and time constraints.
Whatever approach you choose, pay attention to how you feel.
Change one thing at a time.
Constantly assess your progress.
Never stop asking “how’s this working for me?”
Oh, and if you see a headline telling you that a single ingredient or nutrient will ruin your life, grab the salt shaker.