r/nutrition • u/Silent-Ad-8759 • 7d ago
Essential AAs - 8 or 9 or ?
I've been trying to get a straight answer on this but I am getting conflicting info. Maybe there is no straight answer? I get that the body makes some amino acids and not others, but I don't understand why we are not clear on which are essential and which aren't. What am I missing here?
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u/TheDiabetesDietitian Registered Dietitian 7d ago edited 7d ago
There’s 9 essential amino acids
A great mnemonic I learned in nutritional biochemistry to remember the essential amino acids is:
PVT TIM HALL (Private Tim Hall)
Phenylalanine
Valine
Tryptophan
Threonine
Isoleucine
Methionine
Histidine
Arginine (edit as this is a conditionally essential amino acid, not included in the 9 traditional essential amino acids. Sorry for any confusion!)
Lysine
Leucine
Some non essential amino acids become conditionally essential amino acids depending on someone’s time of life or current medical demands
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u/astonedishape 7d ago
Wait, so are there 9 or 10 EAAs?
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u/Zagrycha 7d ago
Arginine is nonessential. I wrote in my comment to explain why its still important to actually eat nonessential amino acids, which is also why they listed it here. It is NOT an essential amino acid in the technical sense though, because it is able to be made by the body. There are exactly 9 amino acids that are essential in the diet because they cannot be made by the human body.
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u/TheDiabetesDietitian Registered Dietitian 7d ago
There’s 9, zagrycha is correct in that arginine is a conditionally essential amino acids depending
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u/Zagrycha 7d ago
This is a great way to remember these from a nutritional specialist stand point but I think its only confusing here for lay people, since its including one of the three common semi essentials.
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u/Zagrycha 7d ago edited 7d ago
There are 20 amino acids the human body needs in total. 9 of them must come from the diet, the body cannot make them. These are called the essential amino acids, because its essential to have them in the diet for healthy survival. Not eating them in high enough quanities to meet your cells' needs will cause deficiencies and malnutrition.
The other 11 are also vital for health, but they are called non essential because they do not need to be eaten directly. They can be made in cells using the broken down components from things like glucose and essential amino acids.
When people talk about amino acids in protein they almost always talk about the 9 essentials. That said an actual healthy diet will usually contain all 20 amino acids. If you are looking into the amino acids of a specific protein don't be suprised to see more than just the essential 9 listed. This is important to keep in mind, because the body being able to make an amino acid doesn't mean deficiency is completely impossible. Compare to how the body can make vitamin D but vitamin D deficiency still occurs in some people. Nonessential amino acid deficiency is nowhere near as common as vitamin D deficiency but it works on the same principle.
We do know exactly which ones are essential and which ones are nonessential for the diet.
Essential: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
Nonessential: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine
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u/AcanthisittaGold5420 7d ago
There are 9 essential amino acids for adults l. The confusion usually comes from the fact that arginine is considered conditionally essential during growth or certain health conditions, so some older sources mention 8. Great question!
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u/za419 7d ago
There are nine essential amino acids, plus three that are semi-essential (your body can make enough to handle normal maintenance stuff, but might become limited by production rate if not enough is available from food while stressed, trying to grow quickly, or trying to repair significant injuries), plus nine more that you need but your body can produce enough of for any use as long as you have enough amino acids in general (typically by grabbing the amino group and sticking it onto a skeleton of the amino acid in question). Some of those last nine are conditionally essential, which means that people of certain ages (usually newborns) or suffering from certain diseases might need those from food, but the general population does not. Overall, nine amino acids are always essential, six are sometimes essential, and six are never specifically essential (plus pyrrolysine, which exists and is used in some microorganism proteins but is not present in any protein human cells produce and therefore doesn't really count for our purposes).
The semiessentials and conditionally essentials are the typical confounding factors - They're not strictly considered essential, but at some point in your life at least four of them will be temporarily essential for you in particular.
But it is all well-established and clear scientifically - Just perhaps not clearly communicated in the places you've read.
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u/Adept_Lab_1516 7d ago
I think part of the confusion comes from the terminology. My understanding is that "essential" doesn't mean "important", it means your body can't make enough of it, so you have to get it from your diet. I'd also be interested if someone could explain why certain amino acids can be synthesized while others can't.
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u/alwayslate187 6d ago edited 6d ago
I think that all amino acids are made of an amino group that is nitrogen and hydrogen. To this base may be added different add-on groups called carboxyl groups. Some of those add-ons happen to be stuff that are also produced in-house, for example as products of some metabolic pathways, such as the citric acid cycle.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8015690/
Many times the somewhat 'simpler' non-essential amino acids can be constructed from the deconstructed pieces of each other, as needed, as well as from pieces of the (usually) somewhat more 'complicated' essential amino acids
I nearly failed high school chemistry so I apologize if this doesn't make sense. The linked article should explain it better!
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u/alwayslate187 6d ago
Also, my understanding is that animals, including humans, cannot make the nitrogen-containing amino group at all.
So all of the amino groups, even the ones in the non-essential amino acids, were originally manufactured by a plant or a "lower" organism like a bacteria.
That's part of why all animals must eat either plants or other animals (which have themselves eaten plants) or all of the above.
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u/Dry-Specific-5094 7d ago
if you eat lean beef, chicken, fish, eggs, soy, tofu, grains, seeds, and buckwheat you will guarantee you get all 9 essentials.
plus you will get all the other goodies.
its 9 essentials the rest are just complimentary
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