Supplement Explainer
01How Much Protein Actually Drives Muscle Growth
The single best-studied question in sports nutrition is how much total protein you need when you're lifting weights. A 2018 systematic review and meta-analysis in the British Journal of Sports Medicine (Morton et al.) pooled 49 randomized controlled trials with 1,863 participants and found that adding protein to a resistance-training program increased fat-free mass by about 0.30 kg and one-repetition-maximum strength by about 2.49 kg on average compared with training alone — but only up to a breakpoint: intakes beyond about 1.6 grams per kilogram of body weight per day produced no further gains in fat-free mass.
A 2018 review by the same group (Morton & Phillips, Nutrients) noted the confidence interval for that breakpoint extended up to about 2.2 g/kg/day, which is why you'll often see a practical target of roughly 1.6–2.2 g/kg/day for hypertrophy. That's about double the standard Recommended Dietary Allowance of 0.8 g/kg/day for healthy adults, per the NIH Office of Dietary Supplements. And keep perspective: the analysis concluded resistance training itself is by far the more potent stimulus than the protein on top of it. Powder is a tool for hitting your daily target, not a substitute for the workouts.
02The Leucine Trigger: Why One Amino Acid Matters
Not every gram of protein counts equally for muscle protein synthesis (MPS), the process that repairs and builds muscle after training. The essential amino acid leucine acts as a signal that switches MPS on, and researchers commonly cite roughly 2–3 grams of leucine per meal as the threshold for a strong response.
A 2012 study in the Journal of Physiology (Churchward-Venne et al.) demonstrated the concept neatly: adding about 3 grams of free leucine to a small, suboptimal protein dose (6.25 grams) produced a muscle protein synthesis response similar to a full 25-gram protein dose alone. Hitting the leucine trigger at a meal can matter as much as the raw gram count.
Whey protein is naturally high in leucine, which is part of why it became the default gym protein. Morton et al. also noted that servings of roughly 0.25 g/kg (about 20 grams for an 80 kg person) alongside regular meals may be a sensible way to structure the day. And here's why this matters for plant eaters: most single plant proteins carry less leucine per gram, so the leucine math is exactly where blends earn their keep.
03Whey: The Fast Protein
Whey is one of the two proteins in cow's milk (about 20% of milk protein), left over as a liquid when cheese is made. Its defining trait is speed. In the landmark 1997 PNAS study by Boirie et al., whey produced a rapid, sharp rise in blood amino acids — peaking around one hour, near baseline within four — and stimulated whole-body protein synthesis by about 68%.
Whey is complete and naturally leucine-rich — roughly 10–11% of its protein weight, so a typical 25-gram scoop delivers close to 2.5 grams of leucine, near the commonly cited per-meal trigger point. Labels offer concentrate (~70–80% protein, more milk sugars), isolate (90%+ protein, lower lactose), and hydrolysate (pre-broken peptides). Same milk protein; pick by budget and lactose tolerance.
04Casein: The Slow Protein
Casein makes up about 80% of the protein in milk and behaves like whey's opposite. In stomach acid it coagulates into a gel-like clot, slowing gastric emptying — and the Boirie et al. 1997 PNAS study measured exactly that: a slow, sustained plateau of blood amino acids that stayed elevated through the full seven-hour window.
The interesting finding is that casein's effect looked different rather than weaker. It stimulated protein synthesis by about 31% (less than whey's 68% spike), but it inhibited whole-body protein breakdown by about 34%, something whey did not do. Over seven hours, net leucine balance was more positive with casein. Less breakdown plus sustained delivery is the logic behind casein's popular use before bed, when you won't eat again for hours. Some researchers suggest pre-sleep doses may need to run higher, around 30–40 grams, but that evidence is still developing — consistent total daily protein is the far better-established factor.
05Plant Proteins and Blends
Plant proteins can support muscle building, but the details matter more. The NIH Office of Dietary Supplements notes that soy protein is short on the essential amino acid methionine, rice protein lacks isoleucine, and because all essential amino acids are needed to stimulate muscle protein synthesis, it recommends combining complementary sources. That's the whole case for blends: pairing pea with rice, or soy with another source, fills in the gaps each one has alone.
A 2015 randomized, double-blind, placebo-controlled trial in the Journal of the International Society of Sports Nutrition (Babault et al.) gave 161 young men either pea protein, whey protein, or placebo for 12 weeks alongside resistance training (25 grams twice daily). Muscle thickness gains in the pea group matched those in the whey group, and the authors concluded pea protein could serve as an alternative to whey.
The practical takeaway: if you're plant-based, look for a blend with a full amino acid profile on the label, and consider a slightly larger serving to make up for the lower leucine per gram. A blend that gets you near 2–3 grams of leucine per serving is doing the job the leucine research describes.
06Whey vs Casein vs Plant: Head-to-Head
Here's how the three compare on the factors the research actually measures. Evidence on long-term superiority of any single type is mixed — the Morton et al. 2018 meta-analysis found protein source played a minor role, if any, next to total daily intake.
| Factor | Whey | Casein | Plant blends |
|---|---|---|---|
| Digestion speed | Fast — sharp amino acid peak around 1 hour (Boirie et al., 1997, PNAS) | Slow — sustained release up to ~7 hours via stomach clotting (Boirie et al., 1997, PNAS) | Varies by source; pea behaves as an intermediate/fast protein in digestion studies |
| Leucine content | High (~10–11% of protein); ~25 g delivers near 2.5 g leucine | High but slightly lower than whey per gram | Lower per gram (e.g., ~8% for pea); blends compensate through quantity and variety |
| Amino acid completeness | Complete — all essential amino acids | Complete — all essential amino acids | Complete only when blended (e.g., pea + rice); single sources may lack methionine or isoleucine (NIH ODS) |
| Key research effect | Stronger acute muscle protein synthesis spike (+68% in Boirie 1997) | Suppressed protein breakdown (−34% in Boirie 1997); more positive net leucine balance over 7 hours | Matched whey for muscle thickness gains over 12 weeks (Babault et al., 2015, JISSN) |
| Typical use case | Post-workout or any meal; dairy-tolerant lifters | Evening or between long meal gaps | Dairy-free, lactose-intolerant, or plant-based diets |
One note on combinations: a blend of whey and casein — or a "time-released" milk protein blend — is simply milk's natural ratio packaged as a powder, and there's no strong evidence it outperforms either protein alone for hypertrophy. Pick the one you'll actually use consistently.
07Timing, Serving Size, and Smart Buying
The famous "anabolic window" — the idea that you must drink a shake within minutes of your last set — has not held up well under controlled research. A 2013 meta-analysis in the Journal of the International Society of Sports Nutrition (Schoenfeld, Aragon & Krieger) found protein within one hour of training was linked to slightly more hypertrophy, but the effect all but disappeared after adjusting for total daily protein intake — the timing groups were simply eating more protein. Total intake was the strongest predictor of muscle hypertrophy.
A 2017 follow-up by Schoenfeld, Aragon and colleagues found resistance-trained men taking 25 grams of whey immediately before versus immediately after training for 10 weeks saw similar muscle and strength changes. The "window" appears hours wide, not minutes — especially if you've eaten protein in the few hours before training. The NIH Office of Dietary Supplements summarizes major sports nutrition bodies' guidance as about 0.3 g/kg of high-quality protein within 0–2 hours after exercise and then every 3–5 hours: a flexible framework, not a stopwatch.
On serving size, the IOC consensus statement on dietary supplements (Maughan et al., 2018, International Journal of Sport Nutrition and Exercise Metabolism) lists typical protein supplements at 20–50 grams of protein per serving. Use the label's protein-per-scoop line — not the scoop size — and count it toward your daily total rather than on top of it.
Finally, buy tested. Supplements don't require FDA approval before sale, so independent certification is your quality control. Look for the NSF Certified for Sport® seal — over 295 banned substances screened, label accuracy verified, recognized by USADA, MLB, the NHL, and the CFL — or the Informed-Sport seal, which certifies every product batch was screened for banned substances by the LGC anti-doping lab. Red flags: proprietary blends that hide ingredient amounts, outrageous muscle claims, and prices far below the rest of the shelf.
William's Natural Foods at 12249 San Pablo Ave, Richmond, CA 94805 carries whey, casein, and plant-blend protein powders — ask our staff to walk you through the leucine content and amino acid profiles side by side so you can compare what's actually in the tub.
Frequently Asked Questions
Is whey protein better than plant protein for building muscle?
Whey has a higher leucine content per gram and a stronger acute muscle protein synthesis response in single-meal studies. But over weeks of training, the gap narrows: in a 12-week trial (Babault et al., 2015, Journal of the International Society of Sports Nutrition), pea protein matched whey for muscle thickness gains. If your plant powder delivers a complete amino acid profile and roughly 2–3 grams of leucine per serving, the research suggests it can do the job.
Do I need a shake immediately after my workout?
Probably not on a stopwatch. A 2013 meta-analysis (Schoenfeld, Aragon & Krieger, Journal of the International Society of Sports Nutrition) found that any timing benefit disappeared once total daily protein intake was equalized, and a 2017 study found pre- versus post-workout protein produced similar gains. What matters most is hitting your daily protein target across several protein-containing meals.
How much protein powder should I take per day?
Think in terms of your total daily target, not the scoop. Commonly cited research targets for hypertrophy are about 1.6–2.2 grams of protein per kilogram of body weight per day (Morton et al., 2018, British Journal of Sports Medicine). If your meals already get you there, extra powder adds calories without adding muscle. Typical label servings provide 20–50 grams of protein per serving, so count whatever you use toward the daily total.
Is protein powder safe for my kidneys?
For healthy adults, high-protein diets providing two to three times the RDA have not been shown to harm kidney function, according to the NIH Office of Dietary Supplements' review of the evidence. But if you have kidney disease — or take medications — talk with your healthcare provider before adding protein powder.
What's the difference between whey concentrate, isolate, and hydrolysate?
It's a matter of filtering and lactose, not a different protein. Concentrate is roughly 70–80% protein by weight with more milk sugars; isolate is filtered to 90%+ protein with much of the lactose removed, making it friendlier for lactose-sensitive people; hydrolysate is pre-digested into smaller peptides for faster absorption. All three come from the same milk protein, so pick based on budget and tolerance.
Should I take casein before bed?
It's a reasonable strategy, not a rule. Casein clots in the stomach and releases amino acids slowly for up to about seven hours (Boirie et al., 1997, PNAS), which matches the overnight fasting window. Some researchers suggest pre-sleep servings may need to be a bit higher (around 30–40 grams), but the evidence on pre-sleep protein timing is still developing — consistent total daily protein intake is the far better-established factor.
Still Have Questions? Come Talk to Us In Store
Supplements are personal — talk to a real person before you buy.
- Visit us at 12249 San Pablo Ave, Richmond, CA 94805.
- Ask our staff — tell us your goals and we'll help you compare options.
- Call ahead at (510) 232-1911 if you want us to check stock before you come.
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Protein powders are generally well tolerated, but talk with your healthcare provider first if you have kidney disease, take prescription medications, are pregnant or nursing, or have a milk/dairy allergy or lactose intolerance — whey and casein are milk proteins. Very high protein intakes from food plus supplements have limited long-term safety data, per the NIH Office of Dietary Supplements. These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease.