Amino acid supplements: arginine, taurine, lysine, glycine, carnitine, theanine and glutamine explained

Amino acids are the building blocks of protein, and several of those sold as supplements are not even used to build protein. This guide covers seven: arginine, taurine, lysine, glycine, carnitine, theanine and glutamine. For each you get what it is, which foods contain it and how much our products give per daily portion on the label.

One rule shapes the whole text. The EU has authorised no health claim for any of these seven, so we say nothing about what they do in the body. What we can do is help you read a label and compare packs fairly.

What amino acids are

Protein is made of 20 amino acids. Nine of them are essential: the body cannot make them, so they must come from food. Lysine is one of the nine. Arginine, glutamine and glycine are often called conditionally essential, because the body makes them but may not always make enough. Taurine, carnitine and theanine are a different group. The body makes taurine and carnitine itself, theanine comes mostly from tea, and none of the three is a building block of protein.

Most people get their amino acids from ordinary food. EFSA set the population reference intake for protein at 0.83 g per kg of body weight a day for adults (2012), and the amino acids arrive with that protein. A supplement with one amino acid is not protein and does not replace it.

Seven amino acids in one table

Amino acid	What it is	Where it is in food	In our range, per daily portion on the label
Arginine	Conditionally essential, protein building block	Meat, fish, dairy, nuts, seeds, pulses	3000 mg (capsules and powder)
Taurine	Not a protein building block, made by the body	Meat, fish and seafood; little in plant foods	1500 mg (capsule), 3000 mg (powder)
Lysine	Essential, protein building block	Meat, fish, eggs, dairy, pulses	2000 mg (1000 mg tablets) or 1500 mg (500 mg tablets)
Glycine	Conditionally essential, protein building block	Meat, fish, gelatin, collagen-rich cuts	3000 mg (capsules and powder)
Carnitine	Made by the body from lysine and methionine	Mostly red meat; less in fish and dairy	840 mg L-carnitine in a capsule, 1360 mg in the powder serving
Theanine	Not a protein building block	Mostly tea leaves	200 mg (1 capsule)
Glutamine	Conditionally essential, protein building block	Meat, fish, eggs, dairy, plant proteins	4633 mg per 5 g serving, 1 or 2 servings

The figures are what the labels state, not what anyone needs. They differ widely because each product sets its own portion. Our whole selection is in the amino acids category, and training-related products are also gathered under sports supplements.

Amino acids in food

Meat, fish, eggs and dairy contain all nine essential amino acids, and so do soya and a few other plant proteins. Pulses, nuts and seeds supply many of them and are especially good sources of arginine and lysine. A diet with protein at every main meal covers the amino acids that food can supply. Tea is the everyday source of theanine.

Our amino acids one by one

Arginine: OstroVit capsules give 3000 mg per 3 capsules (packs of 150 or 300), and the powder gives 3000 mg per 3 g serving, 70 servings in 210 g.

Taurine: one OstroVit capsule holds 1500 mg and a pack has 120. The powder gives 3000 mg per 3 g serving, 100 servings in 300 g.

Lysine: NOW Foods 1000 mg tablets come in packs of 100 or 250, with a label portion of 2 tablets. The 500 mg tablets have a portion of 3 tablets, 1500 mg.

Glycine: NOW Foods capsules hold 1000 mg each, 3000 mg in the portion of 3, with 100 capsules per pack. The powder gives 3000 mg in 3 g (three quarters of a level teaspoon).

Carnitine: the OstroVit capsule is 1250 mg of tartrate, 840 mg of it L-carnitine, 60 capsules per pack. The powder serving is 2 g, 105 servings in 210 g.

Theanine: one OstroVit capsule holds 200 mg of L-theanine and 100 mg of inulin, 90 capsules per pack. A second product combines 200 mg of L-theanine with 300 mg of L-tyrosine.

Glutamine: the OstroVit orange powder gives 4633 mg per 5 g serving, 100 servings in 500 g. The label says two servings on training days and one on rest days.

How to read an amino acid label

1. Find the amount of the amino acid itself in mg, per serving and per daily portion. The weight of a capsule or of the pack tells you little.
2. Check how many capsules or tablets make a portion. Our arginine and glycine capsules are labelled per 3 capsules, our taurine and theanine per 1 capsule.
3. The prefix L- marks the form found in nature and in protein. Glycine and taurine have no L or D version, so their names carry no L.
4. Look at the salt. L-carnitine tartrate 1250 mg holds 840 mg of L-carnitine, and the powder serving of 2000 mg tartrate holds 1360 mg. Lysine is often sold as hydrochloride, and our NOW Foods label states the L-lysine amount, 2000 mg per 2 tablets.
5. Read the capsule shell. OstroVit arginine, taurine and carnitine capsules are gelatin. The OstroVit theanine capsule is plant-based (HPMC).
6. Flavoured powders contain sweeteners. Our glutamine powder lists sucralose and acesulfame K.

Taurine and the EFSA opinion on energy drinks

Taurine often comes up next to energy drinks. In 2009 EFSA assessed taurine as an ingredient of those drinks and found the exposure from them not to be a safety concern. That opinion is about drinks, not capsules, and it is not an approval of any dose. For capsules and powders, the label portion is the limit to follow.

Who should ask a doctor first

What EU law lets us say

Regulation (EU) No 1924/2006 allows a health claim only after it has been authorised and listed in the EU register. We found none for arginine, taurine, lysine, glycine, carnitine, theanine or glutamine, so our product pages state amounts, ingredients and warnings and nothing about effects.

Every product card shows the amount of the active substance per daily portion and the price per day, so packs of different sizes and forms can be compared on the same terms. Check the best-before date and the distributor on the pack too, and keep the original box with the leaflet text.

How to choose between packs

1. Decide which amino acid you are looking at and note the amount per daily portion on the label.
2. Check the form: salt, capsule shell, flavour and sweeteners.
3. Compare the price per day at the label portion, not the price of the pack.
4. Count how long a pack lasts. At the label portion, 150 arginine capsules last 50 days, 120 taurine capsules 120 days, 60 carnitine capsules 60 days, 90 theanine capsules 90 days and 100 glycine capsules 33 days.
5. Tell a doctor or pharmacist about the product if you take medicines or have a medical condition.

FAQ

What are amino acids?

They are the building blocks of protein. Nine are essential and must come from food, the others the body can make.

Are amino acid supplements the same as protein?

No. A capsule with one amino acid supplies that substance only, while protein powder or food gives the whole set.

Which foods contain taurine?

Meat, fish and seafood. Plant foods contain little.

Is L-carnitine the same as L-carnitine tartrate?

Not by weight. The tartrate is a salt: 1250 mg of it holds 840 mg of L-carnitine. Compare the L-carnitine line.

Can I take several amino acids together?

Add up the portions on every label, stay within each one and ask a doctor or pharmacist if you take medicines.

Do you claim what these amino acids do?

No. The EU has authorised no health claim for them, so we describe amounts and labels only.

Sources

• EFSA: Dietary reference values for protein (2012)
• EFSA: Taurine and D-glucurono-gamma-lactone as constituents of energy drinks (2009)
• Regulation (EC) No 1924/2006 on nutrition and health claims
• EU register of nutrition and health claims
• NIH Office of Dietary Supplements: Carnitine fact sheet

Content reviewed by Inese Kalniņa, dietitian.