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Protein, Cortisol, and GABA: Why Moderating Protein Reduces Anxiety (and Lengthens Life)

Protein, composed of amino acids, is the building block molecule.  For this reason, we usually think of it as constructing our bones, our skin, and our muscles.  A lesser-known fact of amino acids, however, is that they are also the building blocks of neurotransmitters.

This means that when certain amino acids break down from proteins during digestion, we can experience mood changes and anxiety.  Other amino acids can help relieve anxiety, depending on what foods are consumed.

Tyrosine uniquely increases dopamine concentrations in the brain, for example.  This can have positive effects for people with dopamine deficiencies, but it can hurt people who are already excitable.  Another example is Leucine.   Leucine increases m-Tor signalling, which is somewhat inflammatory and has been shown in many cases to be associated with aging and poor immune response.

High Protein Diets, Stress and Anxiety in the Short Term

Regardless of the differences in amino acids, higher protein diets correlate with anxiety in both animal and human studies.   Here, in one study, researchers set out to show that a high carbohydrate diet would induce more stress than a high protein diet, yet their finding ended up being the opposite: a high protein meal created a greater cortisol response than a high carbohydrate meal in women.

Here, high protein diets are shown to decrease testosterone and increase cortisol in men.   These studies demonstrate that high protein meals increase stress responses.    Moreover, MDs anecdotally report acute anxiety in patients once they start high protein diets.    Finally, protein can raise norepinephrine and dopamine levels, both of which are usually high in anxious individuals, and both of which stimulate arousal.

Protein and the neurobiology of GABA

So on the surface the literature on protein intake and mental health is present, but its actually pretty sparse.  Certainly, it seems as though cortisol is associated with high protein consumption, especially in the short term.

But the amount of data out there is not all that much compared to how much research has been done on fat and carbohydrates.  For example: nearly everyone agrees that fluctuating blood sugar is bad for mental health; they also know that tryptophan, a result of carbohydrate metabolism, helps induce feelings of calm and well-being.  So these are ways in which carbohydrates have been thoroughly studied.

Furthermore, nearly everyone also agrees that fat is excellent for mental health.  High fat diets, but not higher protein, nor high carbohydrate, decrease anxiety in rats.   So we know a lot about fat, too.

What about protein?  What we might be able to assert about protein comes not, then, from any epidemiological data, but from neurobiology.  What does looking at amino acid chemistry and neurobiology tell us might be going on with protein metabolism?

It all has to do with GABA.  For more on GABA neurons in general, refer to this post.   In sum:  GABA neurons are inhibitory neurons.  They tell the brain to be quiet.  For people who are depressed and fatigued, therefore, GABA might seem like a problematic molecule, but that’s inaccurate.  GABA malfunctioning has been shown to play a role in almost all mood disorders, and in insomnia, and really any kind of imbalance in the brain that might lead to disordered behavior.  GABA is strongly associated with well-being, calmness, proper memory function, proper circadian rhythms, and good sleep.  GABA, because it inhibits the amygdala, also has been shown to inhibit pain and fear.

Low protein diets enhance GABA production.

One particularly powerful animal study showed the complex relationship between protein restriction and GABA.  The researchers were interested in longevity, which is a topic for a whole other slew of posts, but the  high GABA activity that manifests as a result of protein restriction applies equally well to mental health.

Aging rats, when eating a lower protein diet, saw a long-term elevation of GABA activity.   This increased the functioning of the rats’ immune systems as well as prolonged their lives.  A high protein diet had the exact opposite effect.  Another study found the same effect, except that both young and old rats saw the highest GABA activity on a low protein diet.  These studies are conducted over weeks and months and years.  What this means is that over time, a lower protein diet is optimal for GABA activity in the brain.  This helps with aging, with immune function, and presumably with mood disorders.

The fact of increased GABA activity, along with having the lowest cortisol response to a meal, means that a lower protein diet may be optimal for some people’s mental health.    The cortisol response is immediate; the GABA activity, also immediate, but it’s also more important on long time scales.

The best way to move forward with this information is to just be cognizant of mood throughout the day.  Is heart-rate spiking, or the mind racing, after a high protein meal?  On a day with a particularly high protein intake?   Try mitigating this by spreading protein intake out throughout the day, instead of eating it all at once.  Or try keeping the absolute total to a minimum.  Most people recommend .5 g of protein per lean pound of body weight, and I stand by that as well.  It’s important both in the hour-by-hour day-to-day, as well as for long term mental health.

Of course, protein is also essential for mental health.   I mentioned above that amino acids make up and heavily influence neurotransmitters.  This is true.  It is only an imbalance that can do real harm.   For this reason, the best bet is to eat a sufficient amount of protein, and feel the way forward cautiously, respecting the individuality of each person’s needs. Check out my book, Sexy by Nature, for more about the types and amounts of protein that might be right for you.



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Managing director of Paleo for Women and author of Sexy by Nature.


  1. How can you limit protein while maintaining a paleo diet? I suffer from fairly severe anxiety and problems with insomnia (and did before I went paleo as well, though the insomnia got worse after paleo…but there were other simultaneous life changes at that time so it’s hard to say), so the info in this post is interesting to me. I’ve been taking high doses of GABA supplements and have found that it helps, and am on a mild benzo to help with sleep (I know I know…I went to a naturopath first and tried every blood test and cortisol test and natural remedy under the sun before I submitted to drugs…but hey, they just work). Anyway, rambling aside, I honestly have no idea how you could go about eating low protein while maintaining a paleo diet, unless you ate a meal or two of only veggies, but then you’d be hungry all the time (or at least I would be). I was keeping an online food diary for awhile (through myfitnesspal-it has terrible diet guidelines but it’s useful because it calculates the fat/carb/protein/calorie breakdown of every entry so that you can track it), and I don’t think I had a single day when I went under 100 grams of protein. Even when I was experimenting with an extreme fat/calorie restricted version of paleo for a few weeks I was getting close to or over 100gm of protein a day, at only 1200 calories a day (going paleo has not resulted in any weight loss for me which is insanely frustrating, as I’m about 30 pounds overweight. So I’ve been experimenting with different things. My boyfriend went paleo with me and dropped 15 or 20 pounds almost instantly and he only half-asses it most of the time. Neither of us even realized he had all that weight to lose, but now he just looks all svelte and muscley. Men…). I was eating a ton of veggies at that time as well. When I’m not restricting anything, I eat close to my body weight in protein a day. So if, according to the Whole30 plan, you should be restricting fat somewhat, and according to these studies you should be restricting protein, and by going paleo you are naturally restricting carbs because paleo is just lowish in carbs (unless you’re binging on fruit and starches-but many paleo advocates suggest that that’s unhealthy as well), but you’re also not supposed to feel deprived or restricted or hungry, then what exactly do you eat? I believe wholeheartedly in the paleo lifestyle in general, but the specifics of it are so vague and often conflicting. It’s confusing as hell.

    As a side thought, I also don’t see how our ancestors could have had restricted protein intake, and most modern hunter-gatherer societies eat it as the bulk of their diets.

    • How not? Stick to 50 g of protein per day, and definitely for breakfast and lunch, and not dinner. 🙂 Supplement with fat and carbs. Coconut, avocado (at one point in my life I ate four avocadoes per day), butter…sweet potatoes, potatoes, rice. I advocate starch, as you’ll see in my post on carbohydrates. And whole 30… they want you to eat .5 – 1 avocado (that’s 150-300 calories) of fat per meal! I’d say that’s a whole lot of fat, and that actually brings you up to at minimum 900 calories of fat each day. Plus 400 for your protein calories is 1300, and you can fill in the rest with carbohydrates–veggies and starches, both–of your choosing.

      No, modern “traditional” societies do not. Some eat as high as 90 percent carbohydrate (to no ill health effect) and others as high as 90 percent fat. Few binge on protein. See wholehealthsource.blogspot.com for excellent work on traditional cultures.

      Perhaps you are not losing weight because you are overly restrictive, both with calories and with carbs. (A real Whole 30 wouldn’t restrict calories to 1200 calories a day.) Some women find that decreasing calories too much, fasting, or decreasing carbohydrates too much (because low carbohydrate can signal starvation and decrease thyroid function and upregulate fat storage) will stall their weight loss efforts. Not ALL women, mind you, but some. You might want to give a bit higher carbohydrate and higher calorie a chance.

      I would guess, moreover, that a low calorie diet and a low carbohydrate diet (you did say you got worse when you went paleo) would be creating your anxiety more than your protein levels. Low calorie diets are stressful for women, as you can tell I think from paging through my blog, and increasing carbohydrate intake is fairly well hypothesized (and known?) to increase serotonin levels.

    • I think the type of protein is more important than the total amount. If you eat a protein food that is high in the amino acids tryptophan and/or glycine, it will increase GABA production and have a calming effect. This is true of proteins found in poultry, beans, dairy, gelatin and pork skins, for example).

  2. I’m shooting for 60-80 grams of protein in a day (realizing I might be eating too much). Is it possible to explain what this would look like in an average day’s meals? Perhaps even share some of your meals?

    • I roughly correlate grams to pounds.. ie, a pound of protein = 100 g of protein. That’s not totally fair but it’s close enough. So I usually eat a bit more than half a pound of animal each day

  3. I have read similar recommendations for restrictions on protein both on several paleo blogs/sites and through The Perfect Health Diet. Here’s my thing: every time I try to bring protein below 120g (I weigh 155Lbs) my eating hits the fan. I tried doing a strict ketogenic diet and replaced those calories with fats and still had issues. I tried raising carbs with lower protein- same thing I just never feel satisfied if my protein drops below that and when I am really active i.e. swimming, kayaking, weight training, biking, which is most of the time, anything below 140g leaves me unsatisfied and craving more- usually fats or fatty meats more specifically and I feel more anxious as it were. however, if I get my protein in my mind is more peaceful and I have less urges to overeat- it is pretty darn hard to overeat pure paleo protein. As with everything else in nutrition, I take this with a grain of salt especially since I am trying to listen to my body as opposed to enforcing on it what may turn out to be arbitrary rules in the next five years. Now if someone could just tell me why my body wants so much protein!

  4. Pingback: How much protein do we really need to eat? | Mark's Daily Apple Health and Fitness Forum page

  5. Very great post. I simply stumbled upon your blog and wanted to say that I’ve truly enjoyed browsing your blog posts. In any case I will be subscribing on your feed and I’m hoping you write again soon!

  6. Pingback: My Journey from Sugar Burner to Fat Burner - jenn26point2's Primal Journal - Page 124 | Mark's Daily Apple Health and Fitness Forum page 124

  7. I am going through the process of getting diagnosed for Cushing’s Disease which is marked by high cortisol levels and stumbled across this when I was looking up protein and cortisol. I am very intrigued by this, but it seems that your audience is interpreting protein as meat . . . vegetables and legumes of all kinds have tons of protein, and eggs and cheese also count. I know this as I am a vegetarian. I have to watch what I eat to makes sure I get enough protein in my daily diet. For granted, I am not paleo. I love whole grains and dairy along with legumes; I just wanted to point out that you can still add to your protein levels (and thereby, cortisol) adding broccoli to your meals, for example. It’s not as easy to do as by chomping on a piece of meat, but it’s all in there.

    My question is this: did the study make any distinctions between animal protein and other meat-free proteins? Also, this “study” was a bit vague. Can you provide information on the study the researchers conducted? Where and when did this study take place? Has it been repeated?

  8. You can get plenty of long-burning, whole carbs from root vegetables, as well as whole grain seeds (some of which are not actually grains, but high starch vegetables) ex. buckwheat, quinoa, amaranth, etc. you can get plenty of high quality fat calories, as well as some caarbs, from seeds and nuts (the types of fats in these foods are very good for your body). They do have some protein too. Eating lots of green vegetables does actually provide a great source of long burning carbs, and you would be surprised- you probably wouldn’t be as hungry as you fear you might. Eating a huge amount of excess protein- especially as meat- not only increases stress hormones, it also taxes the kidneys, which have the job of filtering all the excess nitrogen back out of it. It’s not good for your kidneys to eat protein as a source of calories. You should only eat as much protein as the amount of protein your body will actually use in protein form. For most people, this is a modest amount.

  9. This seems to contradict the clinical experience of Krispin Sullivan. She states that “many cases of depression, PMS, symptoms of menopause, fatigue and other chronic complaints have disappeared completely with an increase of protein.” [http://www.krispin.com/protein_basics.htm]

    Her formula: Desired body weight, in kilos times 0.8-1.2 grams. “Use the lower figure if you are in perfect health and physically fit. Use a higher number if you are under stress, emotional or physical. The highest number, 1.2 grams per kilo or 0.6 grams per pound, is used pre- and post-surgery, during pregnancy, after illness and for weight training.”

    She also offers another way to calculate protein needs.

  10. Pingback: 3 Ways to Manage Anxiety Without Drugs

  11. Pingback: 3 Ways to Manage Anxiety Without Drugs

  12. Howdy! This article could not be written any better! Looking at this post reminds me of my previous roommate! He constantly kept preaching about this. I’ll send this information to him. Fairly certain he’s going to have a good read. Thanks for sharing! ddbdecbccake

  13. Pingback: 3 conseils pour réduire son anxiété naturellement | MaNaturopathe.com

  14. My sleep is all messed up since giving up Milk, grains/bread, packaged food, potatoes and went paleo due to gut pain, which went away along with my chronic sinus congestion. I can’t stay asleep longer than 3-4 hours. Always wake up at 2:15am or 3:15am. I lost 13 pounds but wasn’t overweight to begin with. I don’t eat much to begin with but eat breakfast and dinner, sometimes skipping lunch. I have always been a meat eater. I just wish I knew how to get my sleep back. Somehow I messed up my adrenals/cortisol/hormones??? I have tried throwing in more carbs but the sinus congestion starts to come back. Any ideas?

  15. Great article as always. This is also likely an even more pertinent issue for people with certain genetic polymorphisms (like CBS 699), which often lead to excess production of Glutamate, which may not always get regulated by the body and converted into GABA – particularly if there is heavy metal toxicity or B6 deficiency.

  16. I’ve been eating high protein dinners for most of my life, I’m suffering from insomnia (tests confirmed high cortisol in the evening), depression and anxiety. I’m going to stop eating so much protein at dinner and more carbs, but a smaller meal overall. I’ve tried all sorts of supplements to reduce cortisol, increase gaba, serotonin etc, all haven’t worked and I continue to have problems sleeping. I get into bed at night and it takes me hours to get off to sleep.

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