Protein powder

Protein powder is food in a tub. It helps only when your meals do not reach your protein target, and it works best with strength training.

At a glance

Our verdict	Only when meals fall short of your protein target. A powder is just a convenient food.
Best use	Protein when meals fall short
How sure the evidence is	Moderate with training; Low for GLP-1 users
Cost a month	About $39 to $60 (whey, one serving a day)

Written for adults in Canada. It explains the evidence; it is not advice for you personally. Last reviewed 20 October 2026.

Supplement Check

Is it right for you?

Most people already eat enough protein. Your check counts your protein meals, sets your target by weight and age, and checks your kidneys before suggesting any powder. Our Supplement Check looks at:

Kidney disease, kidney stones, kidney function below normal (eGFR under 60), or kidney function not known
Milk allergy
Whether your meals already reach your protein target (3 or more protein meals a day)
Pregnancy and breastfeeding
Drug-tested athletes. We ask by example, because few people know the term
Every medicine you take

Coming soon. The Supplement Check and the Online Health Assessment open once our safety testing is complete.

$59 when it opens, paid once. Adults 18 and over, anywhere in Canada. While the service is new, Dr. French reads every report himself, and your report arrives within 3 working days. More about the Supplement Check

Tell me when it opens

What it is

Concentrated protein from milk (whey), peas, soy or other sources, made into a powder to mix with water or food. Whey (milk) protein isolate is our default. A leucine-matched pea or soy isolate is used for a milk allergy, a vegan diet, or when whey upsets the stomach; it gave the same results as whey in a 12-week trial. [1] If no powder suits, the second line is essential amino acids.

Any product we suggest must hold a Health Canada licence (NPN) and be third-party tested. For drug-tested athletes it must also be on the NSF Certified for Sport or Informed Sport register.

Structure of Protein powder — Structure: PubChem (public domain).

How it acts

Muscle is built from the essential amino acids in protein, with leucine as the trigger. [2] Strength training is the signal to build; protein supplies the material. A powder does nothing that the same protein from food would not do.

Outline of a person showing where Protein powder acts in the body

What it is used for, and what the evidence says

Used to reach a protein target when meals fall short, mainly for people who strength-train, older adults and people losing weight on GLP-1 medicines.

Use	What the trials found	How sure we are
Adults doing strength training	49 trials, 1,863 people: added protein gave 0.30 kg more lean mass and 2.49 kg more on a one-lift maximum. No further lean-mass gain above about 1.6 g of protein per kg of body weight a day, and smaller effects with age. [3]	Moderate
Plant protein against whey	Soy and whey matched for leucine gave the same muscle growth (+1.54 kg in both groups) and strength over 12 weeks of training (48 people finished). [1] Whey beat leucine-matched collagen for muscle size over 10 weeks, so not every protein is equal. [4]	Low to Moderate
People on GLP-1 weight-loss medicines	Lean mass made up about 39% of the weight lost on semaglutide 2.4 mg [5] and about 25% on tirzepatide. [6] No trial has compared protein doses in these users. A joint expert advisory recommends 1.2 to 1.6 g/kg a day, anchored to goal or adjusted weight; [7] 25 to 40 g and about 2.5 to 3 g of leucine a meal is advised. [8] In a small group of users, more protein went with more muscle kept. [9]	Low
Strength training during weight loss, older adults	Dr. French recommends strength training to every GLP-1 user and older adult. In 6 trials of older adults with obesity on a diet, strength training prevented 0.82 kg of lean-mass loss, about 94% of it. [10] In 160 dieting older adults over 6 months, lean mass fell 2 to 3% with strength or combined training against 5% with aerobic exercise alone, and strength rose 18 to 19% against 4%. [11]	Moderate
Older adults generally	Resistance exercise added about 1.1 kg of lean mass (49 studies, 1,328 people), less in the oldest. [12] Protein without training has much less to work with.	Moderate

How sure we are: High means further research is very unlikely to change the answer; Moderate, it might; Low, it may well change; Very low, we are very unsure. These follow the GRADE method that guideline panels use.

Benefits

With strength training: about 0.3 kg more lean mass and 2.5 kg more on a one-lift maximum (moderate certainty), the same as eating that protein as food. [3]
Convenient when appetite is small (older age, weight-loss injections) or meals are short of protein.
No extra benefit above about 1.6 g/kg a day. [3]

Risks and side effects

Stomach upset (bloating, cramps, diarrhoea) from whey in some people; a plant powder usually suits them.
Milk allergy (hives, swelling, wheeze or vomiting after milk): no whey.
Feeling too full or sick, common on weight-loss injections: essential amino acids are smaller in volume.
Kidneys: in kidney disease the protein target is lower (0.8 g/kg) and is set by a doctor or kidney dietitian.
Banned substances for athletes: 38% of 66 high-risk sport supplements bought online contained undeclared doping substances. [13] Uncertified muscle products are the risk.
Waste: protein above the target is not used to build muscle.

Interactions with medicines

Protein does not change how the liver clears medicines: no enzyme induction or inhibition is known for amino acids. The interactions are with absorption.

Medicine	What can happen	What to do
Levodopa (carbidopa-levodopa, Sinemet, Duodopa, benserazide-levodopa)	Protein competes with levodopa for absorption and entry into the brain	Take levodopa at least 30 to 60 minutes before protein; your prescriber sets the timing
Quinolone and tetracycline antibiotics	Our check prints a spacing line on protein powder, as on minerals	Quinolone 2 hours before or 6 hours after; tetracycline 3 hours apart; or pause the powder during the course
Bone medicines (bisphosphonates), HIV integrase inhibitors	Spacing line, as above	Bisphosphonate first thing with plain water, powder at least 2 hours later; integrase inhibitor as your HIV prescriber directs

Who should not take it

Kidney disease, kidney stones, kidney function below normal (eGFR under 60), or kidney function not known: no powder from the check; the protein target is set by a doctor or kidney dietitian.
Milk allergy: no whey; a pea or soy powder instead.
Meals already reach the target (3 or more protein meals a day): no powder needed.
Pregnancy and breastfeeding: food protein first.
Drug-tested athletes. We ask by example, because few people know the term: a national or provincial team, carded athlete or Canada Games; university or college sport (U SPORTS, the CCAA, NCAA); junior hockey (QMJHL, OHL, WHL); a professional or minor-professional league (AHL, ECHL and others); or anyone told they can be tested. “Not sure” counts as yes. Then only a product on the NSF Certified for Sport or Informed Sport register, batch-tested, and the report goes to Dr. French before release. Never pre-workout, “test booster”, fat-burner or “proprietary blend” products.
Under 18: outside the Supplement Check.

Dose and timing

Food first: protein at every meal (meat, fish, eggs, dairy, legumes, tofu). We ask how many of your meals include a palm-sized portion, or a cup of milk, yogurt or cottage cheese. A powder is suggested only when that is fewer than 3.
Daily targets: about 1.6 g/kg with strength training; 1.2 to 1.6 g/kg on a GLP-1 medicine, worked out from your goal weight; 1.0 to 1.2 g/kg from food at 50 and over; 1.2 to 1.5 g/kg over 65 with illness; 0.8 g/kg in kidney disease, set by a doctor.
Powder dose: about 20 g of protein a day, no more than 40 g, to close the gap. Aim for 25 to 40 g of protein a meal. [8]
Which powder: whey isolate; a leucine-matched pea or soy isolate for milk allergy, vegan diets or whey intolerance; essential amino acids only if no powder suits.
With strength training on 2 or more days a week: weights, bands or body weight, every major muscle group.
Store as on the label, sealed.
How to tell it is working: protein reaching the target on a 3-day food record; strength and body composition steady or rising at 8 to 12 weeks.

What we know about Canadians

Canadian adults eat about 80 g of protein a day on average, two-thirds of it from animal foods. Against the official requirement (0.66 g/kg a day) few fall short; the group most often below it is women over 70, at about 1 in 10. [14] Many experts in the care of older people now advise 1.0 to 1.2 g/kg a day; no Canadian survey has reported how many fall below that higher figure, so we cannot say.

Canada has no count of people on GLP-1 medicines, but public drug plans spent $807 million on semaglutide in 2024, the single largest driver of growth in public drug spending. [15]

Most at risk: women over 70, people with a poor appetite or living alone, people losing weight (including on GLP-1 medicines), and plant-only diets.

How sure are we: moderate. National nutrition survey (2015, about 13,600 people) for the official requirement; no Canadian data for the higher targets.

An honest comparison: muscle and strength

Same outcome, cost a month in Canadian dollars.

Option	Effect	How sure we are	Cost a month (CAD)
Protein powder (whey), only if meals fall short	The same as the food protein it replaces [3]	Moderate	About $39 to $60
Creatine 3 to 5 g with training	+1.10 kg lean mass with resistance training; part of it is water [17]	Moderate	$10 to $20
Resistance training, 2 to 3 sessions a week	Older adults: about +1.1 kg lean mass; [12] strength +24 to 33% [16]	Moderate to High	$3 to $5 (bands) to $21 (budget gym)
Enough protein from food, to about 1.6 g/kg a day, with training	+0.30 kg lean mass, +2.5 kg one-lift maximum [3]	Moderate to High	$20 to $30 of extra food
None	No medicine is indicated to build muscle without a deficiency (testosterone only for proven low testosterone)	—	—

Read honestly: nothing comes close to strength training. Protein adds a little to training, and a powder adds nothing that the same protein from food would not.

Our verdict

Recommended only when your meals fall short of your protein target (fewer than 3 protein meals a day), and best with strength training. That most often means older adults with a small appetite, people on GLP-1 weight-loss medicines, and people training hard who cannot eat enough. Everyone on a GLP-1 medicine, and every adult 50 and over, is advised to do strength exercise on 2 or more days a week, whether or not they take a powder.

Not for anyone with kidney disease or unknown kidney function until a doctor sets the target. Drug-tested athletes use only NSF Certified for Sport or Informed Sport products.

Protein with strength training adds a little muscle and strength, with moderate certainty, and no more above about 1.6 g/kg a day. A powder is just a convenient food: it adds nothing that the same protein from a meal would not. Most Canadians already meet the official requirement, so our check asks how many protein meals you eat before suggesting any powder, rather than selling one to everyone who trains. Dr. French's rulings: strength training for every GLP-1 user and older adult; essential amino acids for anyone who cannot take a powder; drug-tested athletes asked by example and given certified products only.