Alpha lactalbumin

Protein

What is it

Alpha-lactalbumin is the second most abundant protein in cow's milk whey, after beta-lactoglobulin, and is the main protein in human breast milk. It is particularly rich in tryptophan and cysteine, which are amino acids of interest for mood, sleep, and glutathione production.

Evidence for 3 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Muscle protein synthesis

Good Evidence

As a high-quality complete protein, alpha-lactalbumin supports muscle protein synthesis comparable to other whey fractions.

Sleep quality

Limited Evidence

Small studies suggest evening alpha-lactalbumin can improve sleep onset and morning alertness, particularly in people prone to stress-related sleep disturbance. Evidence is limited.

Mood under stress

Limited Evidence

Acute studies show small improvements in cognitive performance and mood ratings under stress, attributed to increased tryptophan availability. Effects are modest.

How it works

Alpha-lactalbumin provides a complete amino acid profile with notably high content of tryptophan (about 5-6%, the highest among common dietary proteins), branched-chain amino acids, and cysteine. The high tryptophan-to-large-neutral-amino-acid ratio favors tryptophan transport across the blood-brain barrier, where it is converted to serotonin and ultimately melatonin. Cysteine is a precursor to glutathione, the body's major intracellular antioxidant. Alpha-lactalbumin also yields bioactive peptides during digestion with reported effects on immunity, sleep, and stress response in preliminary studies.

Dosage

There is no specific RDA. Sleep and mood studies have used 10-40 grams per day, often given in the evening. As part of total whey protein, no separate dose is required. DSLD label data did not include a median dose.

When and how to take it

WHEN: For sleep and mood research applications, taken in the evening (1-2 hours before bed). For general protein purposes, at any time of day. HOW: Mix with water or non-acidic beverages; combine with carbohydrate in the evening to enhance tryptophan uptake.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Alpha-lactalbumin isolate

Specialty supplement for sleep and mood purposes.

Highly purified; rich in tryptophan.

Hydrolyzed lactalbumin

Used in some sports and medical formulations.

Pre-broken to peptides for faster absorption.

Safety

Generally well tolerated. Allergy to cow's milk protein is the main contraindication. Excessive intake can cause GI upset.

Who should be cautious

People with cow's milk allergy should avoid. Infants under 1 year should not be given cow's milk-based protein supplements as their main nutrition. Otherwise safe in pregnancy and lactation at typical intakes.

Interactions

Generally low interaction risk. As with other proteins, may slightly reduce levodopa absorption if taken simultaneously.

Food sources

Cow's milk (whey fraction)

Amount
~0.5-1 g per cup
%DV
—

Whey protein powder

Amount
~3-5 g per scoop
%DV
—

Human breast milk (primary protein)

Amount
Variable
%DV
—

Frequently asked questions

Is alpha-lactalbumin natural?⌄

Yes, it is one of the natural proteins in milk. It can be isolated to higher concentrations for specific applications.

Can it help me sleep better?⌄

Some small studies suggest a modest benefit, particularly under stress. Effects are not dramatic and individual responses vary.

References

Alpha lactalbumin on Wikidata — Wikidata link

Alpha lactalbumin on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Alpha lactalbumin (PubMed search) — PubMed link

Track Alpha lactalbumin with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.