Protein powder: how much per kg, when to take it, which type

Protein powder: what an athlete needs to know.

The 30-second answer

If you lift and do cardio on the side, aim for 1.7 to 2.2 g of protein per kilo of body weight per day, split across 4 to 5 servings. Whey is not magic, it is just a convenient tool.

The 30-minute anabolic window? A myth. Protein that wrecks your kidneys? A myth. Plant protein inferior to animal protein? At a sufficient dose, false. Here is why.

Do you need to supplement?

Let's be clear from the start: your body makes no difference between the protein in a chicken breast and the protein in a whey shake. Both are broken down into amino acids in your gut before being absorbed. Powder is just a convenient, concentrated format.

Supplementing becomes useful in five concrete cases:

1. Your daily needs are high and hard to cover with meals alone. An 80 kg athlete aiming for 2 g/kg needs 160 g of protein. That is the equivalent of 700 g of lean meat or 26 eggs a day. Good luck.
2. You are strict vegetarian or vegan, so your sources are less dense.
3. You are cutting: your relative needs go up while your calories go down.
4. You don't have time for a proper post-training meal.
5. You are over 60 and need a precise dose per meal to switch on muscle protein synthesis.

On the other hand, if you already eat 1.6-2 g/kg from a varied diet, one more shake will do nothing for you.

How much: the 1.6-2.2 g/kg target explained

The number you will see everywhere is 1.6 g/kg/day minimum. It was not pulled out of a hat. It is the "breakpoint" identified by Morton et al.: above that dose, lean mass gains plateau.

In practice:

• For 80 kg: 128 g/day minimum, 160-175 g optimal
• For 70 kg: 112 g/day minimum, 140-155 g optimal
• For 60 kg: 96 g/day minimum, 120-130 g optimal

And depending on your profile?

If you only lift: 1.6-2.2 g/kg/day. The official position of the International Society of Sports Nutrition (Jäger et al., 2017) confirms that range.

If you run or do endurance: for a long time, 1.2-1.4 g/kg was thought to be enough. A study by Kato et al. (2016) using a more precise measurement method (indicator amino acid oxidation) showed that needs are closer to 1.65-1.83 g/kg. That is 30% above the classic recommendations. Long cardio burns more amino acids than was thought.

If you do both (concurrent training): aim for 1.7-2.2 g/kg/day, the top of the strength range. You stack the needs of muscle recovery and the extra breakdown from cardio.

If you are cutting: you need more to avoid losing muscle. Helms, Aragon and Fitschen (2014) recommend 2.3-3.1 g/kg of lean mass, roughly 1.8-2.7 g/kg of body weight. The Longland et al. (2016) study showed that at 2.4 g/kg in a calorie deficit, you gain 1.2 kg of muscle while losing 4.8 kg of fat. At 1.2 g/kg, it does not work.

What if I eat more? Is it dangerous?

No. Antonio et al. (2016) had trained men eat 3.4 to 4.4 g/kg/day for a year. Result: no extra benefit, but no toxicity either, whether renal, hepatic or lipid. The 2.2 g/kg "ceiling" is statistical (above it, more is just useless and expensive), not a physiological limit.

When: the "anabolic window" is a myth

Ever heard that you absolutely must take your whey within 30 minutes of training, or "you lose your gains"? That is false.

Aragon and Schoenfeld (2013) blew up that myth more than ten years ago. The window, if you can call it one, lasts 4 to 6 hours around the session, not 30 minutes. Better: post-training anabolic sensitivity can last up to 24 hours (Burd et al., 2011).

Schoenfeld et al. (2017) directly compared 25 g of whey before and after training over 10 weeks. Result: no difference in hypertrophy or strength.

The hierarchy, in order of importance:

1. Total daily intake (by far the most important)
2. Distribution across the day (4-5 servings)
3. Protein quality (essential amino acid profile)
4. Immediate timing (anecdotal except in specific cases)

The one timing that works: before bed

Here the science is solid. Luc van Loon's lab in Maastricht showed that casein taken 30 minutes before bed increases overnight protein synthesis (Res et al., 2012). Over 12 weeks, Snijders et al. (2015) confirmed greater gains in strength and muscle mass.

Distribution: the 4-serving rule

Areta et al. (2013) compared three ways of splitting 80 g of whey over 12 hours:

The rule that comes out of it: 4 to 5 servings of 0.3-0.4 g/kg every 3-4 hours. For 80 kg, that is about 25-30 g per serving.

Which type: whey, casein, plant?

Whey: the fast reference

Whey is 20% of milk protein. It is what absorbs fastest (peak at 60-90 min) and the richest in leucine, the amino acid that "switches on" muscle protein synthesis. You need 2.5 to 3 g per serving to trigger the response. 25 g of whey contains exactly 2.5-3 g. That is why it is the post-training reference.

There are three formats:

• Whey concentrate (WPC): 70-80% protein. The default choice. Good value for money (€20-35/kg). Contains 4-8% lactose.
• Whey isolate (WPI): ≥ 90%. Almost lactose-free. Relevant if you are intolerant or on a strict cut. More expensive (€40-55/kg).
• Whey hydrolysate (WPH): pre-digested, ultra-fast absorption. Bitter taste, high price (€50-80/kg). Marginal benefit in healthy people. For 90% of people, it is marketing.

Witard et al. (2014) established that 20 g of whey post-training maximizes muscle protein synthesis in young adults. Macnaughton et al. (2016) added a nuance: after a full-body session, 40 g beats 20 g (+20%). So adjust to the volume of muscle you trained.

Casein: the slow one

Casein is the remaining 80% of milk protein. Its structure forms a clot in the stomach, which slows digestion: amino acids are released over 5 to 7 hours. That is what makes it the ideal pre-sleep weapon.

Pick micellar casein (cold-filtered) over caseinates (sodium or calcium), which are partly denatured.

Plant protein: the gap is closing

For a long time, plant protein was looked down on as "incomplete" or lower quality. Recent science strongly nuances that.

Pea isolate is limited in methionine, but Babault et al. (2015) compared pea, whey and placebo in 161 men over 12 weeks. Result: identical biceps gains between pea and whey.

Rice is limited in lysine, but Joy et al. (2013) compared 48 g of rice and 48 g of whey over 8 weeks. Result: equivalent gains in lean mass, strength and power. At a sufficient dose, the weaker profile is compensated for.

A pea + rice blend (60/40) rebuilds a complete profile by using the two sources' complementarity.

Soy is the only plant protein considered "complete". And no, it does not lower testosterone: the Reed-Messina (2021) meta-analysis of more than 40 clinical trials concludes no effect on testosterone, estradiol or SHBG in men.

The most convincing study remains Hevia-Larrain et al. (2021), which followed strength-trained vegans and omnivores for 12 weeks, all at 1.6 g/kg/day. Result: identical gains in lean mass, in strength, and even at the microscopic level (type I and II muscle fibers).

Collagen: useful, but not for muscle

Collagen has no tryptophan and little leucine. It does nothing for muscle growth. On the other hand, Shaw et al. (2017) showed that 15 g of gelatin + 50 mg of vitamin C, 60 minutes before training, doubles collagen synthesis (useful for tendons and joints). Clark et al. (2008) documented a reduction in joint pain over 24 weeks at 10 g/day. Collagen complements a complete protein, it never replaces one.

What about BCAAs?

Shelve them. Wolfe (2017) showed that isolated BCAAs do not stimulate muscle protein synthesis for long: the other essential amino acids become limiting. If you eat 1.6 g/kg/day of protein, they are useless. The details are in our article BCAAs: do you need them?.

Cardio + lifting: the interference effect

If you do both, you may have heard of the interference effect: cardio "eats" your lifting gains. That is partly true, but heavily nuanced.

Why it happens

Cardio activates an enzyme (AMPK) that inhibits mTOR, the muscle protein synthesis pathway (Coffey & Hawley, 2017). If you do sprints right before your squats, you cut into your ability to build muscle.

How to limit the damage

Space out the sessions. Robineau et al. (2016) showed that with 6 to 24 hours between cardio and lifting, strength gains are preserved. If you have to do both on the same day, lift before cardio. We cover how to organize the sessions in Combining cardio and strength training.

Eat more protein. Shamim et al. (2018) put athletes on a 12-week concurrent training program at 2.0 g/kg/day. Result: strength and lean mass gains were no longer lower than those of a lifting-only group. Protein cancels out the interference.

Is it safe? The myths to bury

"Protein wrecks your kidneys"

Origin: a 1982 hypothesis made about people with kidney failure, wrongly extended to everyone. The Devries et al. (2018) meta-analysis of 28 studies and 1,358 participants concludes: no harmful effect on kidney function above 1.5 g/kg/day or 100 g/day in healthy people. Antonio et al. (3.4-4.4 g/kg for a year): no problem.

"Protein leaches calcium from your bones"

Shams-White et al. (2017), a meta-analysis commissioned by the US osteoporosis foundation, concludes a neutral to slightly positive effect on bone density.

"Too much whey gives you acne and gas"

Acne can appear in some people because of the hormonal effects of dairy protein (IGF-1): it varies. Digestive trouble is mostly linked to lactose (switch to isolate or plant protein) or to sweeteners (sucralose, etc.).

How to pick a good protein

1. Check the protein percentage per serving. Calculate: grams of protein ÷ grams of powder per serving. Aim for more than 75% for WPC, more than 90% for WPI.
2. Short ingredient list. Be wary if you see glycine, taurine, alanine or creatine near the top of the list: it is often amino spiking (artificially inflating the protein content).
3. Milk origin. Ireland, France, New Zealand and Germany are quality standards.
4. Third-party labels: Informed Sport, Informed Choice, NSF Certified for Sport. They guarantee batch testing.
5. Compare per gram of protein, not per kilo of product. On the French market in 2025: WPC at €0.025-0.04/g of protein, WPI and casein at €0.04-0.06/g, WPH at €0.06-0.10/g, plant proteins at €0.03-0.05/g.
6. Watch out for heavy metals. The Clean Label Project (2024-2025) report found that 47% of products exceeded California's (very strict) thresholds for lead. Organic plant proteins are the most contaminated (farm soils naturally richer in them). Not a big deal for occasional use, but it matters if you have it every day.

What to mix it with

• Water: fastest absorption. Ideal around training.
• Semi-skimmed milk: slows digestion (the milk's casein does its job). Relevant as a snack, or before bed if you have no pure casein.
• Never boil whey. You denature it and it clumps. Add it after cooking, to a warm porridge.

Practical summary

For an average hybrid athlete (lifting + cardio):

• Aim for 1.7-2.2 g/kg/day of total protein
• Split into 4-5 servings of 0.3-0.4 g/kg
• Each serving brings 2.5-3 g of leucine (≈ 25-30 g of whey or 35 g of plant protein)
• Reference stack: certified whey concentrate + 30-40 g of micellar casein before bed
• If vegan: pea + rice blend or soy isolate, aim closer to 1.8-2.4 g/kg
• Space lifting and cardio at least 6 h apart when possible
• On a cut: go up to 2.3-3.1 g/kg of lean mass

The bottom line

What matters is not in the shaker, it is in the consistency of your overall intake. Whey is only a tool to reach your daily target: useful, convenient, but not magic.

This article presents the current scientific data. For a personalized program, consult a healthcare professional.