Written by the Spacemilk team · Last updated October 2026

Yeast protein is protein isolated from baker's yeast (Saccharomyces cerevisiae), the single-celled organism behind bread, beer and wine. It's a single-cell protein: neither plant nor animal. The yeast is grown in water through fermentation, then the protein is separated, filtered and dried, leaving no live or active yeast. Yeast protein is a complete protein with a perfect protein quality score (PDCAAS 1.0), the same as whey and egg, and it has no dairy. Its research base is promising but newer and smaller than whey's. This guide covers the whole picture and links to a deeper guide on each topic.

What is yeast protein?

Most protein powders come from animals, such as whey from milk, or from plants, such as pea or soy. Yeast protein comes from a third place: a single-celled fungus. Yeast isn't a plant and isn't an animal, so protein made from it is called a single-cell protein.

	Whey	Pea	Yeast protein
Comes from	Milk (animal)	Yellow peas (plant)	Baker's yeast (single-celled fungus)
How it's grown	Dairy herds	Crops in soil	In water, through fermentation
PDCAAS	1.0	About 0.89	1.0
Dairy	Yes	No	No

Yeast protein isn't the same thing as yeast. It's the protein inside the yeast cell, separated from everything else. That's also why it isn't nutritional yeast, which is the whole cell, deactivated and dried into flakes. The full comparison is in Nutritional yeast vs yeast protein.

Spacemilk is the first protein made from baker's yeast. Each serving of Spacemilk Complete Protein delivers 20g of complete protein.

Where did single-cell protein come from?

People have been fermenting with yeast for thousands of years. Using yeast as a protein source in its own right is newer, but not new:

• World War I. Germany used torula yeast in soups and sausages during the war, when food was short (Jach et al., 2022, Metabolites).
• The 1970s. Microbes were grown at industrial scale as a protein source, mostly for animal feed. One lesson from that era: microbial cells are rich in nucleic acids, so protein meant for people needs processing to reduce them (Ritala et al., 2017, Frontiers in Microbiology).
• Today. Isolating the protein, rather than eating the whole cell, is what makes yeast protein practical as a protein powder: more protein per scoop, a neutral taste, and far less of the cell's nucleic acid.

How is yeast protein made?

At a high level, there are five steps:

• Grow. Baker's yeast is grown in water in stainless-steel fermentation tanks, fed sugar cane molasses plus vitamins and minerals.
• Break down. Gentle heat and the yeast's own enzymes break the cells open and release the protein.
• Separate. A high-speed centrifuge separates the protein from the rest of the cell.
• Pasteurize and dry. The protein is pasteurized, so no live yeast remains, then spray-dried into a powder.
• Test. Every batch of Spacemilk is independently third-party tested before it ships.

There's no cropland and no soil involved, and the protein comes from non-GMO baker's yeast.

How good is yeast protein? Nutrition and protein quality

A complete protein contains all nine essential amino acids your body can't make on its own. Yeast protein does, and it scores 1.0 on PDCAAS (Protein Digestibility Corrected Amino Acid Score), the highest score possible. A comparison of six proteins measured yeast protein at a PDCAAS of 100% in growing rats, matching whey and ahead of soy, wheat and pea (Cao et al., 2025, Food Chemistry).

Protein	PDCAAS
Yeast protein (Spacemilk)	1.0
Whey	1.0
Egg	1.0
Soy	0.98
Pea	0.89

Per 100g of protein, Spacemilk carries 46.9g of essential amino acids (whey: 45.7g), and over 21% of its protein is BCAAs (leucine, isoleucine and valine), comparable to whey. Whey has more leucine per gram; yeast protein has more valine, arginine and glycine. The detail is in Yeast protein vs whey and Yeast protein vs pea protein.

Per serving	Unflavored	Original	Vanilla	Chocolate
Protein	20g	20g	20g	20g
Calories	100	110	110	120
Total carbohydrate	3g	4g	5g	6g
Fiber	1g	1g	1g	3g
Sugar	0g	0g	0g	0g
Total fat	1.5g	1.5g	1.5g	1.5g

From Spacemilk's Nutrition Facts panels.

What does the research say about yeast protein?

Protein helps build and repair muscle, whatever the source. The strongest human evidence for yeast protein specifically is one trial: yeast protein, the protein in Spacemilk, was shown in a 2024 double-blind randomized controlled trial to match whey for building lean muscle and strength in men over 40 doing resistance training. The placebo-controlled trial gave 79 men 40g a day for eight weeks (Briskey et al., 2024, Journal of Food and Nutrition Research).

Laboratory and animal studies fill in the rest of the picture:

• Protein quality. PDCAAS of 100%, matching whey, with essential amino acid content close to whey and well above soy, pea and wheat (Cao et al., 2025).
• Digestibility. Comparable to whey in a laboratory model of human digestion (Caron et al., 2025, Food Research International), and 97.66% in another lab model, close to whey isolate (Qiao et al., 2025, Food Chemistry).

The honest limits: these studies tested yeast protein as an ingredient, not Spacemilk as a finished product. The muscle trial enrolled men over 40 only. And whey has decades more research across many more people. Our Science page keeps the full list of studies.

Is yeast protein easy to digest?

On digestibility itself, yeast protein performs about the same as whey in lab studies. What makes Spacemilk easy to digest is what's left out: no dairy or lactose, no sugar alcohols, no gums like xanthan or guar, and no plant material. It's formulated to be low in FODMAPs. Many customers describe it as light on their stomach. If other powders have bloated you, read Protein powder for a sensitive stomach. If you're eating less on a GLP-1 medication, read Protein on a GLP-1 medication.

Is yeast protein safe?

Baker's yeast is one of the most familiar organisms in food: people have eaten it in bread and beer for thousands of years.

For Spacemilk specifically:

• No live or active yeast. The protein is separated from the yeast and pasteurized.
• Every batch third-party tested by an independent FDA-registered lab for heavy metals, including lead, plus microbials, pesticides and allergens. Every result is published on our testing page, where you can match the lot code on your bag.
• Nothing artificial: no artificial flavors, sweeteners, colors or preservatives.

Can you have yeast protein with allergies, a yeast allergy or candida?

Spacemilk is free from all 9 major allergens: dairy, soy, gluten, eggs, tree nuts, peanuts, fish, shellfish and sesame. Every batch is tested for gluten, dairy, soy and peanuts, and every lot tests under 5 ppm gluten, against the FDA's 20 ppm gluten-free line.

Yeast isn't one of the nine, so we call it out separately. A true baker's yeast allergy is extremely rare, but if you have one, check with your allergist first: the yeast is removed, but the protein is yeast-derived. If you're following a candida protocol, Spacemilk has 0g sugar and no live or active yeast; check with your provider. More in Can you have yeast protein with a yeast allergy or candida?

Is yeast protein high in purines?

Whole yeast is. Yeast cells are rich in nucleic acids, which is where purines come from. Spacemilk is an isolate, not whole yeast, and our process includes a step that reduces the yeast's nucleic acids. A serving contains about 38mg of purines, less than a typical 100g portion of chicken, fish or beef. If you have gout or high uric acid, talk to your doctor first. The numbers are in Yeast protein, purines and gout.

Is yeast protein sustainable?

Spacemilk is grown in water, not farmland, and has about a 95% lower carbon footprint than beef protein. We haven't commissioned a full lifecycle study, so we don't claim more than that.

What does yeast protein taste like, and how do you use it?

Isolating the protein leaves the savory, nutritional-yeast flavor behind. Spacemilk is made to be smooth and creamy, not chalky:

• Unflavored: neutral, and disappears into recipes. One ingredient: yeast protein isolate.
• Original: mild and lightly sweet, like a milk alternative.
• Vanilla: tastes like a classic vanilla milkshake.
• Chocolate: like the milk at the bottom of a bowl of chocolate cereal, made with real cocoa.

The flavored versions are sweetened with Reb M, a sweetener fermented from rice, and thaumatin, and get their body from a small amount of konjac fiber. Mix a scoop into 10 to 12 oz of water, milk or a smoothie, or stir it into coffee, oats or yogurt. It's heat stable, so it works in pancakes, muffins and other baking.

Who it's for, and who should check with a doctor

Yeast protein may suit you if you want a complete protein without dairy, you're avoiding major allergens, you eat vegan, whey or plant proteins haven't sat well with you, or you're looking for an easy way to reach your protein goal when your appetite is low. Getting enough protein becomes more important as we age; read Protein for older adults.

Another protein may suit you better if you want the highest leucine per gram or the longest research record (whey), or the lowest price per serving.

Check with your doctor or allergist first if you have a known yeast allergy, gout or high uric acid, a condition that affects how much protein you should eat, such as kidney disease, you're pregnant or nursing, or you're choosing a protein for a child.

Frequently asked questions

Is yeast protein good for you?

It's a high-quality protein: complete, with a PDCAAS of 1.0 and all nine essential amino acids, and Spacemilk delivers 20g per serving with 0g sugar. Whether it's right for you depends on your diet and health, so if you have a medical condition, ask your doctor.

Is yeast protein vegan?

Yes. It's 100% animal-free. It isn't a plant protein either: yeast is a single-celled fungus, which is why yeast protein is called a single-cell protein.

Does yeast protein contain live yeast?

No. The protein is separated from the yeast and pasteurized during production, so there's no live or active yeast in Spacemilk.

What is single-cell protein?

Protein produced from single-celled organisms such as yeast, rather than from animals or plants. Yeast protein from baker's yeast is one kind.

Is yeast protein as good as whey?

For protein quality, both score PDCAAS 1.0, and yeast protein was shown in a 2024 trial to match whey for lean muscle and strength alongside resistance training. Whey has more leucine and a much longer research history. See Yeast protein vs whey.

Where can I try it?

Shop Spacemilk Complete Protein, and find more answers in our FAQ. Your first order is covered by our 30-day guarantee: if it's not right for you, choose a replacement, store credit or a refund.