L-tryptophan

Grades and forms

L-tryptophan is used in food supplements as the free amino acid, a white to off-white crystalline powder. It is not a salt, so 1 mg of powder carries 1 mg of L-tryptophan before you correct for the assay on the certificate of analysis. Its use in EU food supplements is governed by national rules rather than an EU positive list.

Manufacturers buy bulk L-tryptophan powder mainly in two kinds of grade. One is a food-grade material. The other is tested against a pharmacopoeia monograph, which some contract manufacturers require for their quality system. The specification sheet states which standard a lot meets. Ask for the grade you need in the quote form.

Three points usually decide the choice:

• Documentation: whether your customers or auditors require pharmacopoeia testing, or accept a food-grade specification.
• Production route: L-tryptophan is commonly made by microbial fermentation, and your file may need statements on the process and the organism used.
• Physical properties: flow, particle size and bulk density affect capsule filling and blending, and they vary between lots and processes.

SoleChem sends the specification sheet and the certificate of analysis with its quote, so you can compare these points before ordering.

EU regulatory status of L-tryptophan

Directive 2002/46/EC harmonises only vitamins and minerals, through the substances listed in Annexes I and II. L-tryptophan is an amino acid, so it does not appear on those lists. Its use in food supplements falls under the national rules of each member state on “other substances”.

Those national rules differ. Some member states may set specific conditions or maximum amounts for L-tryptophan. Others may assess products case by case, including where a product sits on the border with medicinal products. Check the rules of every market you plan to sell in with its competent authority.

Regulation (EC) No 1925/2006 lets the Commission restrict or prohibit “other substances” through its Annex III. Confirm the current Annex III entries before you finalise a formulation.

Novel-food status depends on the substance and can depend on its production process. Check it under Regulation (EU) 2015/2283 and the Union list of novel foods. Our guide to novel food status of supplement ingredients explains the procedure.

For any claim wording, consult the EU Register of nutrition and health claims and our health claims guide.

Formulation notes

Label-claim arithmetic. Because L-tryptophan is used as the free amino acid, the calculation needs no conversion factor. Divide the declared amount by the assay, expressed as a decimal, from the certificate of analysis. Then add any overage your stability data supports; the overage calculator handles both steps. A 250 mg declaration at a 100 % assay needs 250 mg of powder before overage.

Capsules. Fill weight is the main constraint, since the whole declared amount is active material. Poor flow can cause fill-weight variation, so a glidant such as silicon dioxide is often added. L-tryptophan works in gelatin or HPMC shells; see ingredients for capsules.

Tablets. Crystalline amino acids rarely compress well on their own. Formulators usually add a filler-binder such as dicalcium phosphate, and some use granulation. Trial compression with the lot you will buy, as physical properties vary.

Powders and drinks. L-tryptophan has limited water solubility and a bitter taste. In drink powders it tends to disperse rather than dissolve fully, and flavour masking is usually needed.

Stability. The indole ring in tryptophan is sensitive to light and oxidation, and the powder can discolour on exposure. Store and pack it in closed, light-protective containers. Like other amino acids, it can undergo Maillard browning with reducing sugars under heat, which matters in gummies and baked formats.

L-tryptophan often appears alongside other amino acids such as L-tyrosine and glycine. Check that each amino acid in a blend is permitted in every target market, since national rules treat them individually.