What's in 100 Grams of Yeast Protein?
Yeast protein powder is one of the most concentrated protein ingredients you can buy. A typical unflavoured product delivers 70–80 g of protein per 100 g — the same ballpark as whey concentrate — with the rest made up of small amounts of fat, carbohydrate, fibre, minerals and moisture. It is also naturally free of lactose, gluten and soy, which keeps its ingredient label unusually short.
| Nutrient | Typical per 100 g |
|---|---|
| Energy | ~350–400 kcal |
| Protein | 70–80 g |
| Fat | ~5–8 g |
| Carbohydrate | <10 g |
| Fibre | ~5–10 g |
| Lactose | 0 g |
These are typical ranges for finished powders; exact values vary by brand and formulation. The energy figure (~350–400 kcal/100 g) is comparable to whey isolate, so yeast protein does not cost you extra calories for the same protein dose.
Protein Content: 70–80 g per 100 g
The headline number is the protein content. At 70–80 g per 100 g, yeast protein sits in whey-concentrate territory and only slightly below whey isolate, which typically reaches around 90%. More important than the raw number is quality: yeast protein scores a PDCAAS of 1.0, the maximum score, meaning its amino acid profile is both complete and highly digestible. High concentration plus perfect digestibility is a combination few ingredients achieve.
Essential Amino Acids: A Complete Profile
Yeast protein contains all nine essential amino acids — histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In fact, essential amino acids make up roughly 47% or more of yeast protein's total amino acids, slightly ahead of whey protein at about 46%. That matters because EAA content, not total protein, is the strongest driver of muscle protein synthesis.
| Amino acid (g / 100 g protein) | Yeast protein | Whey |
|---|---|---|
| Total essential amino acids | ~47+ | ~46 |
| Total BCAAs | ~21–22 | ~24 |
| Leucine | 8.8–9.9 | 10.9–11.1 |
| Cysteine | 0.8 | 2.1 |
| Methionine | 2.0 | 2.0 |
The table shows the amino acids that matter most for muscle and health. Values are typical published figures for yeast protein concentrate versus whey protein; ranges reflect product-to-product variation.
BCAAs and Leucine: The Muscle Signals
Branched-chain amino acids — leucine, isoleucine and valine — make up roughly 21–22% of yeast protein. Leucine is the most important of the three: it is the primary trigger for muscle protein synthesis. Yeast protein delivers 8.8–9.9 g of leucine per 100 g of protein, which is high in absolute terms and only modestly below whey's 10.9–11.1 g. For comparison, most plant proteins sit at 6–7 g of leucine per 100 g of protein.
Because a typical 25 g scoop of yeast protein provides roughly 2–2.5 g of leucine, it comfortably clears the ~2–3 g per meal threshold associated with a maximal muscle-building response — one reason fermentation-derived proteins have been shown to support muscle gains comparable to whey when total protein intake is matched.
Cysteine: The One Weak Spot
No protein is perfect, and yeast protein's weakest amino acid is cysteine. It provides about 0.8 g of cysteine per 100 g of protein, versus about 2.1 g in whey. Cysteine is a conditionally essential amino acid and a building block of glutathione, the body's main antioxidant. Two things soften this weakness. First, yeast protein's methionine (2.0 g per 100 g protein, identical to whey) can be converted into cysteine by the body. Second, at typical intakes you still receive meaningful amounts of cysteine, and any shortfall is easily covered by other foods. Still, if you build your diet around yeast protein exclusively, pairing it with a cysteine-richer protein such as whey or egg is a reasonable strategy.
Fibre: A Protein Powder That Feeds Your Gut
Unlike whey, yeast protein brings fibre to the table. Yeast cell walls are rich in beta-glucans and mannan oligosaccharides, which survive processing into the finished powder, leaving roughly 5–10 g of fibre per 100 g — several grams in a typical scoop. These fibres act as prebiotics, feeding beneficial gut bacteria, and add to the satiety that makes yeast protein useful for weight management.
B Vitamins: A Natural Bonus
Yeast is one of nature's richest sources of B vitamins, and yeast protein retains much of that heritage. Finished powders typically provide useful amounts of thiamin (B1), riboflavin (B2), niacin (B3), vitamin B6 and folate (B9), along with biotin. One caveat: Saccharomyces cerevisiae does not naturally produce vitamin B12, so if you see B12 on a yeast protein label it has been added during fortification. For anyone on a plant-heavy diet, the B-vitamin content is a welcome side benefit.
How to Read a Yeast Protein Label
When comparing products, look at three numbers. First, protein per 100 g — this tells you the concentration, and 70 g and above is good. Second, protein per serving — usually 20–25 g in a standard scoop. Third, the amino acid breakdown if printed: total EAAs, BCAAs and leucine are the numbers that predict muscle-building value. And check the ingredient list for added flavours, sweeteners and fillers — a high-quality unflavoured yeast protein should list little more than the yeast protein concentrate itself.
Bottom Line
Gram for gram, yeast protein matches whey on digestibility, edges it on essential amino acid density, and beats it on fibre and B vitamins — with the single caveat of a lower cysteine content. At roughly 350–400 kcal and 70–80 g of protein per 100 g, it is a complete, nutrient-dense protein that fits comfortably into a calorie-controlled diet.