One Reason A Carnivore Diet Could Wreck Your Health

Methionine and The Goldilocks Principle of Protein Intake

I’m sometimes asked how much protein consumption is optimal and what types of protein are most easily metabolized by the body. I have some clients who consume very little protein and others who consume large amounts, in some cases bordering on a carnivore diet (i.e., a diet of principally meat).

Just to be transparent, I am a meat eater, and this article is not about meat being a bad thing from a nutrition standpoint.

The truth is that too little or too much protein will potentially cause a host of issues and side effects. In other words, the Goldilocks principle applies to protein consumption—not too much and not too little protein is best.

There are a couple of reasons as to why this is the case, which I will break down here.

How to Calculate Required Grams of Protein

There is a trick I sometimes use to quickly calculate how many grams of protein your body needs daily, minimally. Multiply your body weight by 0.40 (or  40%) and that is the number, approximately, that your body requires in grams per day to function. 

So, if a person weighs 150 lbs, they would require a minimum of 60 grams (150 x 0.40 = 60) of protein daily, as a baseline. Of course, this does not account for those who need higher amounts of protein, such as bodybuilders, personal trainers, and professional athletes, to name a few.

But before I get ahead of myself, let’s circle back to the essentials.

What is Methionine?

Methionine is an essential amino acid. We obtain methionine from protein, which is converted to homocysteine in the body.

Recent research demonstrates that methionine serves to regulate metabolism, the innate immune system, and digestive function. (1) 

Methionine, Homocysteine and Methylation

If we have too much homocysteine, we downregulate our ability to use SAM (S-Adenosyl Methionine), which is a critical cofactor that helps many of our genes function properly. (2)

Without SAM, methylation does not occur, histamine cannot be properly broken down, and we are in danger of developing chronic disease.  

For example, histamine, which is released by mast cells when they degranulate, is responsible for causing the symptoms of an allergic reaction, such as itching and redness. 

This compound cannot be broken down properly, by way of the HNMT gene (pathway), without the presence of cofactor, SAM. (3, 4)

SAM, of course, requires methylfolate or vitamin B9 (L-5-MTHF), as a cofactor, in order to be made. (5, 6)

In kind, we may be low in B9 because we don’t have enough vitamin B2 (riboflavin). (7)

Hence, someone who is eating a carnivore diet may experience the effects of higher histamine; their faces may become more ruddy in complexion, they may report episodes of pruritus on various areas of their bodies, or they may even report that their breathing becomes restricted or asthmatic, as histamine causes smooth muscle contraction in the lungs. (8)

The Role of Methionine in Glutathione Biosynthesis

It is a lesser known fact that methionine intervenes in the biosynthesis of glutathione to prevent  oxidative stress. (9)

Hence, a person who does not consume enough methionine will likely become depleted in glutathione, the body’s main antioxidant. And if the body doesn’t have sufficient antioxidant status, then it won’t be able to stave off the free radicals which cause cellular damage.

Summary

In summary, eating too much protein can block methylation and interfere with the breakdown of histamine.

On the other hand, eating too little protein can deplete your body of its main antioxidant, glutathione.

In conclusion, the Goldilocks Principle applies to protein consumption—not eating too much and not eating too little is generally best; and about 40% of your body weight in grams per day is likely the safest amount. 

But, as always, I recommend that you work with a naturopathic doctor or other integrative medicine practitioner to dial in what is optimal for you.

Resources

1. Martínez Y, Li X, Liu G, Bin P, Yan W, Más D, Valdivié M, Hu CA, Ren W, Yin Y. The role of methionine on metabolism, oxidative stress, and diseases. Amino Acids. 2017 Dec;49(12):2091-2098. doi: 10.1007/s00726-017-2494-2. Epub 2017 Sep 19. PMID: 28929442. https://pubmed.ncbi.nlm.nih.gov/28929442/ 
2. Guo T, Chang L, Xiao Y, Liu Q. S-adenosyl-L-methionine for the treatment of chronic liver disease: a systematic review and meta-analysis. PLoS One. 2015 Mar 16;10(3):e0122124. doi: 10.1371/journal.pone.0122124. PMID: 25774783; PMCID: PMC4361566.
3. Comas-Basté O, Sánchez-Pérez S, Veciana-Nogués MT, Latorre-Moratalla M, Vidal-Carou MDC. Histamine Intolerance: The Current State of the Art. Biomolecules. 2020 Aug 14;10(8):1181. doi: 10.3390/biom10081181. PMID: 32824107; PMCID: PMC7463562.
4. Yoshikawa T, Nakamura T, Yanai K. Histamine N-Methyltransferase in the Brain. Int J Mol Sci. 2019 Feb 10;20(3):737. doi: 10.3390/ijms20030737. PMID: 30744146; PMCID: PMC6386932.
5. Papakostas GI, Cassiello CF, Iovieno N. Folates and S-adenosylmethionine for major depressive disorder. Can J Psychiatry. 2012 Jul;57(7):406-13. doi: 10.1177/070674371205700703. PMID: 22762295.
6. Vidmar M, Grželj J, Mlinarič-Raščan I, Geršak K, Dolenc MS. Medicines associated with folate-homocysteine-methionine pathway disruption. Arch Toxicol. 2019 Feb;93(2):227-251. doi: 10.1007/s00204-018-2364-z. Epub 2018 Nov 29. PMID: 30499019.
7. Kennedy DO. B Vitamins and the Brain: Mechanisms, Dose and Efficacy–A Review. Nutrients. 2016 Jan 27;8(2):68. doi: 10.3390/nu8020068. PMID: 26828517; PMCID: PMC4772032.
8. Maintz L, Novak N. Histamine and histamine intolerance. Am J Clin Nutr. 2007 May;85(5):1185-96. doi: 10.1093/ajcn/85.5.1185. PMID: 17490952.
9. Wang ST, Chen HW, Sheen LY, Lii CK. Methionine and cysteine affect glutathione level, glutathione-related enzyme activities and the expression of glutathione S-transferase isozymes in rat hepatocytes. J Nutr. 1997 Nov;127(11):2135-41. doi: 10.1093/jn/127.11.2135. PMID: 9372907.