Protein powder: types, differences and which one to choose (and whether you need it)

Protein powder is the best-selling supplement and the most misunderstood. It is not a steroid in a tub or a shortcut: it is concentrated protein from milk, soy, pea or rice, for reaching your daily protein when food is not enough. There are real differences between types (protein and leucine per gram, digestion speed, quality score), but they are smaller than the tubs suggest. Here they are, with the studies on the table. Before choosing a tub, be clear about one thing: protein powder only makes sense if you do not reach your daily target with food. In the most cited meta-analysis on protein supplements and strength training (49 trials, 1,863 people), above roughly 1.6 g of protein per kg of body weight per day there was no further gain in lean mass, whether the protein came from a shake or a plate. If you already eat enough chicken, eggs, legumes and dairy, save your money; if you fall short, powder is the most convenient way to close the gap. If you are not sure which case you are in, start with how much protein you need per day.

Types of protein powder: how much protein and how much leucine

The leucine column is the most useful one: leucine is the amino acid most closely linked to switching on muscle protein synthesis, and the practical reference is what 25 g of whey protein provides, about 2.7 g. A team at Maastricht University analysed commercial powders and calculated how much protein from each source is needed to match that leucine.

Whey: concentrate, isolate or hydrolysed

Whey is the protein in the liquid left over when milk is curdled to make cheese; the rest of the protein in milk, around 80%, is casein. Sports concentrates usually contain 70–80% protein and keep some lactose and fat. Isolate is filtered to over 90%, removing almost all the lactose and fat. Hydrolysed whey comes partly pre-digested and is sold as faster-absorbing, but it costs considerably more, and what decides your results is your total daily protein, not the speed of one shake. For reference, the USDA’s generic entry for whey protein powder gives 78 g of protein and 352 kcal per 100 g: a 30 g scoop is about 23 g of protein and 106 kcal.

Casein: the slow protein

Casein curdles in the stomach and leaves it gradually. In the classic experiment (Boirie and colleagues, 1997), with a single dose of each, whey caused a large but short-lived rise in blood amino acids and stimulated whole-body protein synthesis by 68%; casein produced a moderate, prolonged plateau, stimulated synthesis by 31% but slowed protein breakdown by 34%, and the net balance over the following 7 hours was better with it. That is why it is used before bed: in the Maastricht studies, protein taken before sleep raised overnight muscle protein synthesis, although at least 40 g was needed for a clear effect. You do not need a special tub: most of the protein in a yogurt or a glass of milk is already casein.

Plant protein: soy, pea, rice and blends

Plant proteins start with two disadvantages: fewer essential amino acids per gram and, often, a shortage of one in particular. In the Maastricht analysis, essential amino acids made up 43% of whey protein versus 30% of pea protein and 28% of brown rice protein; pea is low in methionine and rice in lysine. You make up for it with a little more protein or by mixing sources. In the lab, whey stimulates muscle protein synthesis over the following hours slightly more than soy, probably because of its leucine; but what matters is muscle after weeks of training, and there the results are reassuring. More detail in vegan protein: sources and how to combine them.

• Soy: a meta-analysis of 9 trials (266 people) found no differences in strength or lean mass between supplementing with soy and with whey or other animal proteins.
• Pea: in a 12-week trial with 161 young men taking 25 g twice a day, the biceps grew just as much with pea as with whey; compared with placebo, pea only stood out in those who started out weaker. Three of the authors worked for the manufacturer of that protein.
• Rice and blends: there are fewer trials; the sensible option is to mix pea and rice, which complement each other.
• Soy and hormones: a meta-analysis of 41 clinical studies found no effect of soy protein or its isoflavones on men’s testosterone or oestrogen levels.

Protein quality: what PDCAAS and DIAAS mean

They are the two official quality scores for a protein. PDCAAS, recommended by the FAO and WHO in 1989, multiplies the score of the scarcest amino acid by the protein’s overall digestibility and is capped at 100%, so it cannot tell apart proteins that exceed the reference pattern. In 2013 an FAO expert consultation recommended replacing it with DIAAS, which measures the digestibility of each essential amino acid and is not capped, with these cut-offs: 100 or more, excellent quality; 75 to 99, good; below 75, it cannot be claimed as a quality protein source. Published figures vary a lot depending on the product and the age pattern used:

• A 2020 compilation of dozens of measurements, using the pattern for children aged 6 months to 3 years (stricter than the adult one): casein 117, soy 91, whey 85, pea 70 and rice 47. Mixing pea and rice, the highest calculated score was 84, with 41% rice.
• A 2023 University of Illinois study, measured in pigs: whey isolate, 100 or more for people over 3; pea and rice concentrates, below 75.

How much and when: what the studies say

What matters most is your total daily protein. In a meta-analysis on protein timing (23 studies on hypertrophy), once the amount of protein each group ate was taken into account, taking it right around training did not change the results. The International Society of Sports Nutrition notes that the effect of training on muscle lasts at least 24 hours and that studies usually use doses of 20–40 g (or 0.25 g per kg) with 0.7–3 g of leucine, spread every 3–4 hours. None of this is a prescription for you: your amount depends on your weight, your goal and what you already eat. To estimate it, use the daily protein calculator and see how much you are short before thinking about powder.

BCAAs and collagen: where the money goes

BCAAs (leucine, isoleucine and valine) are sold as if they were enough to build muscle, but a 2017 review found no study in humans that measured their effect on muscle protein synthesis when taken alone by mouth, and in the two that gave them intravenously, synthesis went down: without the other essential amino acids, muscle has nothing to build with. Collagen is another trap: in a McMaster University trial with 22 women aged around 69, 30 g of whey twice a day for 6 days raised muscle protein synthesis, while the same amount of collagen did not raise it significantly. And before buying a “mass gainer”, read the label: many mostly add carbohydrates, which you can add yourself with oats or a banana.

Safety: kidneys and heavy metals

In healthy people, a high-protein diet has not worsened kidney function in trials (see the FAQ below); if you have kidney disease, the amount is decided with your doctor. On heavy metals, a university analysis of 36 protein powders sold in Ireland found acceptable levels of potentially toxic elements, although the authors warn that excessive, prolonged intake could slightly increase the risk and recommend not exceeding the serving the manufacturer indicates.

How to choose a good product

• Check the grams of protein per 100 g: in a whey concentrate, 70–80 g is normal
• The first ingredient should be the protein (whey, casein, soy, pea…), not sugars or thickeners
• Little added sugar: compare per 100 g, not per “serving”, which each brand defines its own way
• If lactose does not agree with you: isolate or plant protein
• Compare the price per gram of protein, not per tub
• A brand with quality controls; be wary of suspiciously low prices and miracle absorption claims

Practical summary: if you are short on protein at the end of the day, a shake fixes it in 30 seconds; if you already get there with food, it adds nothing. Use Renzy to find out which group you are in before spending on supplements. The takeaways: (1) protein powder is convenient food, not a requirement: if you reach your protein by eating, you do not need it; (2) whey concentrate for most people, isolate if lactose does not agree with you, casein for a slow dose at night, and soy, pea or a blend if you do not eat dairy; (3) what counts is your total daily protein, not the brand, the exact timing, BCAAs or collagen.