Whey protein

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By Nikola · Precision Nutrition L1 · Updated 5 November 2026

Whey protein is one of the two main protein groups in cow’s milk, about 20% of milk protein with casein making up the rest, sold as a powder in concentrate, isolate or hydrolysate form. It is a complete, fast-digesting protein rich in leucine, likely why it is the most researched protein around resistance training. EFSA puts the adult reference intake at 0.83 g of protein per kg of body weight a day, and NIH ODS gives 1.2-2.0 g per kg for athletes. One 32 g scoop gives about 25 g of protein, roughly what you get from half a chicken breast.

What the research says

• Muscle with resistance training – strong evidence for protein. Numerous clinical trials show that enough protein improves the response to training and recovery (NIH ODS). Whey isolates and hydrolysates appear to be the most studied proteins before and after training (ISSN, Jäger 2017). Whey is about 11% leucine, casein 9.3%, and in one study 22 g of hydrolysed whey isolate raised muscle protein synthesis more than casein at rest and after training.
• Total daily protein beats timing – moderate evidence. A meta-analysis found that protein taken within an hour before or after exercise did not significantly increase strength or muscle size, and the window after training can last up to 24 hours (NIH ODS). Your daily total matters more than the post-gym shake.
• Older adults – moderate evidence, short-term studies. In 37 older men, 40 g of whey protein isolate was needed to maximise muscle protein synthesis (ISSN). These were lab measurements over hours, not long-term muscle gains.
• Keeping muscle while losing fat – moderate evidence for protein. In a calorie deficit, 2.3-3.1 g of protein per kg a day may help resistance-trained people keep lean mass (ISSN).
• What the EU allows. Regulation (EU) 432/2012 has no claim for whey itself. Protein claims apply: “Protein contributes to a growth in muscle mass”, “to the maintenance of muscle mass” and “to the maintenance of normal bones”, for foods that are at least a “source of protein”, meaning at least 12% of their energy comes from protein (Regulation (EC) 1924/2006).
• What is not shown. Powder is not necessary: athletes can probably meet their needs from food, and intakes above recommended amounts add no benefit (NIH ODS).

Dose and forms

Group	Protein a day	Source
Adults, all ages	0.83 g/kg (about 58 g at 70 kg)	EFSA PRI
Pregnancy	+1 g, +9 g, +28 g in the 1st, 2nd and 3rd trimester	EFSA
Breastfeeding	+19 g in the first 6 months, +13 g after	EFSA
People who train	1.2-2.0 g/kg (NIH ODS); 1.4-2.0 g/kg (ISSN)	for reference

EFSA found too little data to set a tolerable upper intake level for protein and considers intakes up to twice the reference intake safe. Per serving, the ISSN suggests about 0.25 g per kg, or 20-40 g, every 3-4 hours, with 700-3,000 mg of leucine.

• Concentrate (WPC). Whey with enough non-protein parts removed to reach at least 25% protein. A typical WPC80 has 80-82% protein, 4-10% lactose and 4-8% fat; low-protein WPC34 still carries 48-55% lactose (ADPI standards).
• Isolate (WPI). At least 90% protein, with typically 0.5-1.0% lactose and 0.5-1.0% fat (ADPI). Because so much lactose is removed, people with lactose intolerance can often take isolates safely (Hoffman and Falvo 2004).
• Hydrolysate (WPH). Concentrate or isolate in which enzymes or other agents have cut part of the protein chains, leaving a mix from intact proteins down to free amino acids (ADPI).

Food sources

Food first: you can reach most protein targets with ordinary meals.

Food	Protein, 100 g	Portion	Protein per portion	kcal per portion
Whey protein powder	78.1 g	1 scoop, 32 g	25.0 g	113
Chicken breast, roasted, meat only	31.0 g	½ breast, 86 g	26.7 g	142
Lentils, boiled	9.02 g	1 cup, 198 g	17.9 g	230
Greek yogurt, plain, nonfat	10.2 g	1 pot, 170 g	17.3 g	100
Eggs, whole, raw	12.6 g	2 large, 100 g	12.6 g	143
Cottage cheese, 2% fat	10.4 g	113 g (4 oz)	11.8 g	92
Feta cheese	14.2 g	1 wedge, 38 g	5.4 g	101

Source: USDA FoodData Central, SR Legacy, checked 5 November 2026: whey protein powder FDC 173180, chicken breast FDC 171477, lentils FDC 172421, Greek yogurt FDC 170894, eggs FDC 171287, cottage cheese FDC 172182, feta FDC 173420. Portions are USDA household measures (2 eggs = 2 × 50 g); values per portion are calculated and rounded. The whey record is a generic whey-based powder; your product’s label may differ.

A pot of Greek yogurt and two eggs give about 30 g of protein, as much as a scoop plus a bit. A cup of lentils also brings about 16 g of fibre. Sirene, the Bulgarian white cheese, is close to feta: useful, but high in fat and salt. Powder makes sense when meals fall short or you need protein on the go.

Side effects and interactions

• High protein in healthy people. NIH ODS reports no safety concerns up to about 2.0 g per kg a day. Diets with two to three times the RDA did not appear to harm kidney function, cause kidney stones or reduce bone health over several months.
• Lactose. The NHS lists protein shakes among foods that can contain lactose. If you are lactose intolerant, a concentrate may bring tummy pain, bloating, wind or diarrhoea; an isolate is less likely to.
• Medicines. If you take regular medication, ask your pharmacist.

Who should avoid it

• People with cows’ milk allergy. Whey is a milk protein, and cows’ milk is one of the common food allergens (NHS). Isolate and hydrolysate are still milk.
• People with chronic kidney disease. Some people with CKD need moderate protein so waste does not build up, while people on dialysis may need more (NIDDK). Work out the amount with your dietitian or doctor before adding a powder.
• People with lactose intolerance. Prefer an isolate, and get advice from your GP or a dietitian before cutting out dairy (NHS).

How to choose a good product

• Protein per serving. Grams of protein per scoop tell you more than the front label.
• Type. The ingredient list says concentrate, isolate or hydrolysate. Choose isolate if lactose bothers you.
• Short ingredient list. Watch for added sugar and proprietary blends that do not list amounts (NIH ODS).
• Independent testing. NSF Certified for Sport, Informed-Choice and BSCG test products for banned substances; certified products carry the logo and are listed on the certifier’s website (NIH ODS).

FAQ

How much protein do I need a day?

EFSA sets 0.83 g per kg of body weight a day for adults, about 58 g at 70 kg, with extra in pregnancy and breastfeeding. If you train regularly, NIH ODS gives 1.2-2.0 g per kg. Most people can reach this with food; powder only fills gaps.

What is the difference between whey isolate and concentrate?

Isolate has at least 90% protein and typically 0.5-1.0% lactose. A common concentrate (WPC80) has about 80% protein and 4-10% lactose. Both are complete milk proteins; isolate suits people sensitive to lactose.

Is it safe to drink whey protein every day?

For healthy adults, yes, within normal protein intakes: NIH ODS reports no safety concerns up to about 2.0 g of protein per kg a day, and EFSA considers up to twice the reference intake safe. Skip it with a cows’ milk allergy; with kidney disease, ask your doctor first.

Related entries and articles

• High-protein diets
• Creatine and collagen
• Greek yogurt, eggs and lentils
• Sirene (Bulgarian white cheese)
• High-protein vegetarian breakfast ideas
• Greek yogurt and pomegranate parfait

Sources

1. USDA FoodData Central, SR Legacy: Beverages, Protein powder whey based (FDC 173180); Chicken, broilers or fryers, breast, meat only, cooked, roasted (FDC 171477); Lentils, mature seeds, cooked, boiled, without salt (FDC 172421); Yogurt, Greek, plain, nonfat (FDC 170894); Egg, whole, raw, fresh (FDC 171287); Cheese, cottage, lowfat, 2% milkfat (FDC 172182); Cheese, feta (FDC 173420). fdc.nal.usda.gov
2. EFSA NDA Panel (2012). Scientific Opinion on Dietary Reference Values for protein. EFSA Journal 10(2):2557. efsa.europa.eu
3. Jäger R, et al. (2017). International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition 14. doi:10.1186/s12970-017-0177-8. europepmc (ebi.ac.uk)
4. NIH Office of Dietary Supplements: Dietary Supplements for Exercise and Athletic Performance, Fact Sheets for Health Professionals and for Consumers. ods.od.nih.gov
5. Hoffman JR, Falvo MJ (2004). Protein – Which is Best? Journal of Sports Science and Medicine 3(3):118-130. jssm.org
6. American Dairy Products Institute: Whey Protein Concentrate Standard; WPI Standard v4.0 (2023); Whey Protein Hydrolysates definition. adpi.org
7. Commission Regulation (EU) No 432/2012 (protein claims) and Regulation (EC) No 1924/2006, Annex (source of protein). legislation.gov.uk
8. NHS: Lactose intolerance (reviewed 8 July 2026) and Food allergy (reviewed 20 August 2026). nhs.uk
9. NIDDK: Healthy Eating for Adults with Chronic Kidney Disease (reviewed January 2025). niddk.nih.gov

This page is for information only and is not medical or dietary advice.