Protein Supplementation and Requirements
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Active people training for strength or hypertrophy benefit from meaningfully more protein than sedentary people -- the ISSN puts most exercisers at 1.4-2.0 g/kg/day and resistance-trained people in a calorie deficit at 2.3-3.1 g/kg/day, above the 1.4-1.8 g/kg ceiling once assumed.
Current guidance (2026)
The ISSN position stand on protein and exercise (Jäger et al. 2017, still the current version) says 1.4–2.0 g/kg/day is sufficient for most exercising people to build and maintain muscle, and that 2.3–3.1 g/kg/day may be needed to maximise lean-mass retention in resistance-trained people during a calorie deficit (with some evidence that more than 3.0 g/kg/day may help fat loss in trained people). A 2018 meta-analysis of 49 trials found muscle gains from resistance training plateaued at about 1.6 g/kg/day, with a 95% confidence range up to about 2.2 g/kg/day (Morton et al. 2018), so some people benefit from more than 1.6. All of this sits above the 1.4–1.8 g/kg/day ceiling this module originally cited (Lemon, 1995). For context, the general-population federal goal in the 2025–2030 Dietary Guidelines is 1.2–1.6 g/kg/day, and the Dietary Reference Intakes RDA (a deficiency floor) is 0.8 g/kg/day.
The kidney-function caution has not held up for people with healthy kidneys: the ISSN stand reports that published reviews consistently find no indication of liver or kidney harm from higher protein intakes in athletes and active people, while people with kidney failure do benefit from protein restriction. The caution remains legitimate specifically for people with existing renal impairment.
Whey and casein protein powders are well supported as effective, convenient ways to hit a protein target. The ISSN stand calls supplementation a practical way to ensure adequate protein quality and quantity while limiting calories, while noting that whole foods can meet the requirement -- "not proven safe or effective" reflected legitimate uncertainty in the 1990s but is dated for these products today. The FDA-regulation point (supplements aren't reviewed like drugs before sale) remains accurate and is a separate, still-valid caution about quality control and unsubstantiated claims generally.
What still holds from the original source: protein calories beyond what the body uses don't build extra muscle by themselves, and whole foods can meet these targets without supplementation.
Key facts
- ISSN (2017): 1.4–2.0 g/kg/day for most exercising people; 2.3–3.1 g/kg/day for resistance-trained people in a deficit. Morton 2018: gains plateau ~1.6 g/kg/day (95% CI up to ~2.2).
- DGA 2025–2030 general goal 1.2–1.6 g/kg/day; DRI RDA 0.8 g/kg/day (deficiency floor).
- The kidney-damage concern from high protein intake hasn't held up for people with healthy kidneys; it remains a real caution specifically for pre-existing renal impairment.
- Whey/casein protein powders are well-supported as effective, convenient ways to hit a protein target -- not "unproven."
- Protein calories beyond what's used don't build extra muscle by themselves; whole foods can meet these targets without supplementation.
- Supplements remain FDA-unregulated (not reviewed like drugs before sale) -- a real, separate caution about quality control and marketing claims, distinct from whether the protein itself works.
- Sedentary requirement (DRI RDA): 0.8 g/kg/day. Example: a 57-kg sedentary adult needs about 46 g/day.
Connections
- Macronutrient Distribution Guidelines — protein's share of total calories.
- High-Protein Diets — protein and weight loss.
- Sports Nutrition Overview — one of the four focus topics.
- Sports and Energy Bars — companion sports-nutrition topic; bar protein content.
Historical source context
The section below preserves the original 1990s-sourced material verbatim, for citation fidelity -- it predates the current guidance above and should not be read as the current position. See "Current guidance (2026)" for what changed and why.
Protein is a building block for new muscle tissue and helps repair damaged muscle; a lesser role is to supply energy during intense exercise. People who exercise — especially those just starting to train — need 50 to 100 percent more protein than their sedentary counterparts (Coleman & Nelson Steen 1996). However, most Americans typically eat more protein than they need. The average daily intake for sedentary adults is approximately 100 grams per day, or 1.4 g of protein per kilogram of body weight (1 kg = 2.2 lb).
Requirements (original, 1990s source):
- Sedentary (no regular exercise): 0.8 g per kg. Example: a sedentary female weighing 125 lb (≈57 kg) needs 46 g of protein per day (57 × 0.8). Seventy percent should come from high-quality sources (lean meats, fish, eggs, low-fat dairy) — satisfiable with one cup of milk, one cup of yogurt, and 2–3 oz of lean meat; grains, starches, nuts, seeds, and legumes (including soy) provide the rest.
- Active (runs/cycles/swims/works out ≥3×/week): 1.2 to 1.4 g per kg (Lemon 1995). A 125-lb active female needs roughly 70–80 g/day — about 23–35 g more than her sedentary counterpart.
- Building muscle / actively weight training: 1.4 to 1.8 g per kg per day (Lemon 1995) — this ceiling is dated; see "Current guidance (2026)" above for the current ISSN ranges (1.4–2.0 g/kg/day; 2.3–3.1 in a deficit). Building 1 lb of muscle requires an additional 100 g of protein, met by adding 15 g per day for one week (an extra 2 oz of lean meat per day).
Bigger, not better (original framing): Any extra protein not used is ultimately stored as fat. Protein is broken into amino acids; if unused, these are broken down further and used as energy or stored as fat. Many weight lifters overdo supplementation and get stronger only because they've gained weight — bigger but no leaner. Excess protein by-products can contribute to dehydration and, long-term, can compromise kidney function -- this kidney claim is dated, see "Current guidance (2026)" above. High-protein diets are usually high in fat, leaving little room for carbohydrates; inadequate carbohydrate intake means poor muscle glycogen storage and premature muscle fatigue.
Recommendations (original framing): Amino acid / protein supplements provide extra protein at great financial expense (some clients spend up to $200/month), and were not proven safe or effective at time of original writing -- see "Current guidance (2026)" above; they are not currently regulated by the U.S. FDA. Nonfat dry milk is an inexpensive, high-quality alternative (¼ cup = 11 g); soy-based protein powders help strict vegetarians.
Sources
- Position standJäger R et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr 2017;14:20 Published 2017 · DOI 10.1186/s12970-017-0177-8 · Accessed 2026-10-13
- Meta-analysisMorton RW et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018;52(6):376–384 Published 2018 · DOI 10.1136/bjsports-2017-097608 · Accessed 2026-10-13
- GuidelineDietary Guidelines for Americans, 2025–2030 — accessible (Section 508) version (USDA/HHS) Published 2026-01-16 · Accessed 2026-10-13
- GuidelineInstitute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press Published 2005 · DOI 10.17226/10490 · Accessed 2026-10-13
Corrections (1)
- 2026-10-13 — Current-guidance section reconciled against the ISSN 2017 protein stand (still the current ISSN version). Corrected the attribution of '~2.2 g/kg/day' to ISSN: the stand says 1.4–2.0 g/kg/day is sufficient for most exercising individuals, with 2.3–3.1 g/kg/day possibly needed to retain lean mass in resistance-trained people during hypocaloric periods (and >3.0 g/kg/day possibly aiding fat loss); ~2.2 g/kg/day is the upper 95% confidence limit of the Morton 2018 meta-analysis plateau (1.62 g/kg/day). Kidney and supplement statements now quoted to the ISSN stand (no indication of hepato-renal harm in healthy exercising people; supplementation a practical way to ensure protein quality and quantity, whole foods also sufficient). Added the 2025–2030 Dietary Guidelines' general protein goal (1.2–1.6 g/kg/day) and the DRI RDA (0.8 g/kg/day) as dated sources. Historical 1990s section left verbatim.
See how this applies in practice, with honest limits on what the plan changes.
Educational content only — not medical advice. Always consult a qualified professional for individualized guidance, especially around injury, pregnancy, or medical conditions.