Quick answer: The Recommended Dietary Allowance (RDA) for protein — 0.8 grams per kilogram of body weight per day — was set as a deficiency floor, not an optimization target. Most active adults benefit from 1.2 to 1.6 grams per kilogram, and adults over 65 typically need 1.0 to 1.2 grams per kilogram to help preserve muscle mass.
For decades, the U.S. protein guideline has been a single number printed on the back of a cereal box. Today, a growing chorus of researchers, sports nutritionists, and physicians argues that number is outdated — too low for active adults, too low for adults over 65, and built on methodology that newer studies have shown to systematically underestimate true protein needs. This post breaks down where the Recommended Dietary Allowance came from, why nutrition researchers think it needs revisiting, and what current research from the International Society of Sports Nutrition (ISSN) and recent peer-reviewed reviews actually recommends for most adults.
What the RDA actually means (and what it doesn't)
The RDA for protein was set at 0.8 g/kg by the U.S. Institute of Medicine (IOM), based largely on nitrogen-balance studies done in young, sedentary adults. Its purpose is narrow: to identify the minimum intake needed to prevent overt deficiency in 97.5% of healthy adults. It is not an optimization target, and it was never meant to define how much protein supports muscle preservation, recovery, or healthy aging.
That distinction matters. A 2023 review published in Nutrients titled "Is It Time to Reconsider the U.S. Recommendations for Dietary Protein and Amino Acid Intake?" argued that the original nitrogen-balance methodology systematically underestimates true protein needs, and that newer techniques such as the indicator amino acid oxidation method consistently produce higher values across multiple populations.
Why researchers say the protein RDA is outdated
The case for revising the RDA rests on three lines of evidence. First, the original calculations relied on a method (nitrogen balance) that newer research has shown to be insensitive at the higher intakes most relevant to health outcomes. Second, studies in active adults, older adults, and adults in calorie deficits all show benefits to muscle, recovery, and body composition at intakes well above 0.8 g/kg. Third, age-related muscle loss (sarcopenia) appears to respond meaningfully to protein intakes in the 1.0 to 1.2 g/kg range, and the current guideline does not address this at all.
The ISSN's position stand on protein and exercise recommends 1.4 to 2.0 g/kg/day for adults engaged in regular training, and notes that intakes up to roughly 1.6 to 1.8 g/kg appear to maximize muscle protein synthesis (MPS) without diminishing returns in most populations. For adults over 65 — a group at high risk of muscle loss — recent reviews recommend 1.0 to 1.2 g/kg as a baseline, with higher intakes during illness or recovery.
How much protein do you actually need?
Protein needs vary by body weight, age, activity level, and goals. The table below summarizes where current research sits, drawing on ISSN position stands and recent peer-reviewed reviews.
| Population | Daily protein intake | Source |
|---|---|---|
| Sedentary adult (RDA floor) | 0.8 g/kg | U.S. Institute of Medicine |
| General active adult | 1.2 – 1.6 g/kg | Recent meta-analyses |
| Endurance training | 1.0 – 1.6 g/kg | ISSN position stand |
| Strength / power training | 1.6 – 2.0 g/kg | ISSN position stand |
| Adults over 65 | 1.0 – 1.2 g/kg | Geriatric nutrition reviews |
| Calorie deficit / fat loss | 2.0 – 3.1 g/kg | ISSN position stand |
For a 70 kg (154 lb) adult, that translates to roughly 84–112 g per day at the moderate-active end, versus the 56 g implied by the RDA. The gap is substantial, and it widens for anyone training hard or trying to preserve muscle while eating fewer calories.
Why most Americans fall short — even when they "meet" the RDA
Average American protein intake looks fine on paper: roughly 16% of daily calories come from protein, and most adults exceed 0.8 g/kg. But that average hides important gaps. Data from the National Health and Nutrition Examination Survey (NHANES) shows protein intake declines with age, and 7 to 9% of older women consume below even the Estimated Average Requirement (EAR) — the bare-minimum threshold that sits below the RDA. Younger women and adults who default to carb-heavy snacks often fall short of the 1.2–1.6 g/kg range that supports muscle, satiety, and metabolic health.
Distribution matters too. Most Americans front-load carbohydrates at breakfast and lunch and concentrate protein at dinner. Research suggests muscle protein synthesis responds best to roughly 25–40 g of high-quality protein at each of three to four meals, spaced 3–4 hours apart, with at least 700–3,000 mg of leucine per serving to trigger the anabolic response.
How to hit your protein target without overhauling your diet
Three practical levers move the needle. Anchor each meal with a complete protein source (eggs, Greek yogurt, fish, poultry, tofu, legumes, lean beef) rather than treating protein as a side. Bridge between meals with snacks that actually deliver protein — most "healthy" snacks are mostly carbohydrate or fat, with token protein. And prioritize protein quality: complete sources with a full essential amino acid profile and adequate leucine drive muscle protein synthesis far more efficiently than incomplete or low-leucine alternatives.
Bars like Marmels were built around this gap — a 60 g dark chocolate bar with 12 g of high-quality whey isolate and grass-fed bovine collagen, sweetened with organic coconut sugar rather than the sugar alcohols and seed oils common in the protein bar aisle. It is not a meal, but it is a useful tool for closing a protein gap between meals or after a workout.
Frequently Asked Questions
Is 0.8 grams of protein per kilogram enough?
For a healthy, sedentary adult with no athletic or aging-related concerns, 0.8 g/kg — the current Recommended Dietary Allowance — is enough to prevent clinical protein deficiency. It is not enough to optimize muscle preservation, satiety, or recovery. Most current sports nutrition and geriatric nutrition guidelines suggest active adults and older adults need 1.2 to 2.0 g/kg, depending on training status and goals.
Why is the RDA so much lower than what athletes are told to eat?
The RDA was designed to identify the minimum intake that prevents deficiency in nearly all healthy adults — a public health floor. Sports nutrition recommendations are based on a different question: how much protein supports muscle protein synthesis, recovery, and performance? Different question, different answer. Both numbers can be technically correct depending on what is being optimized for.
How much protein do I need after 40?
Protein needs gradually rise with age because older muscle is less responsive to dietary protein, a phenomenon called anabolic resistance. Research generally supports 1.0 to 1.2 g/kg for adults over 65, and many geriatric nutrition reviews suggest a similar trajectory beginning in the 40s and 50s, particularly for adults aiming to preserve muscle, bone, and metabolic health.
Can you eat too much protein?
For healthy adults with normal kidney function, intakes up to 2.0 g/kg are well-tolerated in the published literature, and short-term intakes up to 3.1 g/kg during fat loss have not been shown to cause harm in resistance-trained subjects. Adults with existing kidney disease should follow guidance from their physician.
What is the difference between the RDA and the EAR?
The Estimated Average Requirement (EAR) is the intake estimated to meet the needs of half of the healthy population — currently 0.66 g/kg for protein. The Recommended Dietary Allowance (RDA) is set higher, at 0.8 g/kg, to cover 97.5% of healthy adults. Both are deficiency-prevention thresholds, not optimization targets, which is why neither tracks closely with sports nutrition or healthy-aging recommendations.
How do I know if I'm getting enough protein?
A practical starting point: track your intake for three days using a food log or app, and compare it to 1.2–1.6 g/kg of your body weight in kilograms (your weight in pounds divided by 2.2). If you fall short, anchor each meal with a complete protein source and add a high-protein snack between meals to fill the gap.
The RDA is not wrong — it is just answering a different question than most people think it is. If your goal is to feel full longer, preserve muscle as you age, or recover well from training, current research consistently points to intakes well above 0.8 g/kg. For more on what makes a protein source bioavailable, explore the science behind protein quality.
