How much protein do you really need after 40?

If you've ever Googled "how much protein do I need", you've probably seen the same number quoted everywhere: 0.8 grams per kilogram of body weight per day. That number comes from the Recommended Dietary Allowance (RDA), and according to research published in peer-reviewed nutrition journals, it may not be adequate for adults over 40.

This article breaks down what the actual scientific literature says about protein requirements as we age, why the older "one-size-fits-all" guidance falls short, and what targets emerge from current research.

The phenomenon researchers call anabolic resistance

Anabolic resistance is a term used in the research literature to describe a reduced muscle protein synthesis response to dietary protein in older adults compared to younger adults.[3]

In plain language: when a 25-year-old eats a chicken breast, their muscles respond strongly by building new muscle tissue. When a 55-year-old eats the same chicken breast, that signal is weaker. A 2017 perspective paper published in Advances in Nutrition described the proposed factors that may contribute to this reduced response, which include reduced physical activity, changes in amino acid absorption, and altered muscle signaling pathways.[4]

The research suggests this is one reason older adults may need more total protein, and possibly more protein per meal, than younger adults to achieve the same muscle-building stimulus.

What the research actually shows

The standard recommendation (RDA)

The current Recommended Dietary Allowance for protein is 0.8g per kg of body weight per day. This figure was established to prevent deficiency in healthy adults, but a growing body of research suggests it may not be optimal for muscle preservation, particularly in older populations.

For Australian readers, the NHMRC's Nutrient Reference Values for Australia and New Zealand set comparable Recommended Dietary Intakes of 0.84g per kg for adult men aged 19 to 70 and 0.75g per kg for adult women in the same age range. These rise to 1.07g per kg for men and 0.94g per kg for women over the age of 70.[9] Like the US RDA, these values were calculated to prevent deficiency rather than to optimise muscle preservation in active or older adults.

What newer research suggests

A 2025 study published in Frontiers in Nutrition involving 126 older women aged 60–75 compared protein intakes of 0.8g/kg/day versus 1.2g/kg/day over 12 weeks. The higher-protein group showed measurable improvements in muscle mass composition, handgrip strength, and knee flexion compared to the standard intake group.[1]

The researchers concluded that "a protein intake of at least 1.2g/kg body weight/day should be considered as part of a targeted nutritional intervention for preventing muscle deterioration, maintaining functional independence, and reducing the risk of falls and frailty in older adults."[1]

A separate 2025 study used an analytical technique called indicator amino acid oxidation (IAAO) to measure protein requirements in older adults with sarcopenia. The estimated average requirement came out to approximately 1.21g/kg/day, with a recommended nutrient intake of approximately 1.54g/kg/day, significantly higher than the standard RDA.[2]

Protein per meal: the threshold matters

Total daily protein is only part of the picture. Research suggests that how protein is distributed across meals may also matter, particularly in older adults.

A review published in PubMed Central reports that older adults (over 60 years) require meals with approximately 30g of protein, providing around 2.8g of the amino acid leucine, to stimulate muscle protein synthesis. The same paper notes that younger adults (under 30 years) produce a more linear muscle protein synthesis response across a wider range of protein doses.[5]

Other research recommends older adults consume approximately 0.4g of protein per kg of body weight per meal, or roughly 30g per meal, to overcome anabolic resistance.[6]

The role of leucine

Leucine is one of the essential amino acids found in protein-containing foods. Research has identified leucine as a key trigger for the cellular signaling pathway (mTORC1) that activates muscle protein synthesis.[7]

A 2012 study found that supplementing older adults' meals with 4g of leucine three times daily for two weeks increased muscle protein synthesis rates.[7] However, longer-term leucine supplementation studies have shown mixed results, with not all studies finding significant improvements in muscle mass or strength.[4]

What this suggests, based on the available evidence, is that meeting the per-meal protein threshold matters, and choosing protein sources with adequate leucine content (animal proteins, soy, and dairy tend to be higher in leucine than most plant proteins) may help.

Practical protein targets

Based on the body of research described above, here's how the numbers translate to actual food:

A 70kg (154lb) adult over 40

• Standard RDA: 56g protein/day (0.8g/kg), likely a minimum, not an optimum
• Research-supported lower target: 84g protein/day (1.2g/kg)
• Research-supported upper target: 105 to 112g protein/day (1.5 to 1.6g/kg)

An 80kg (176lb) adult over 40

• Standard RDA: 64g protein/day
• Research-supported lower target: 96g protein/day
• Research-supported upper target: 120 to 128g protein/day

What 30g of protein actually looks like

For reference, approximately 30g of protein is found in:

• 120g (4oz) of cooked chicken breast
• 120g (4oz) of cooked lean beef
• 150g (5oz) of cooked fish (salmon, tuna)
• 5 large eggs
• 200g (7oz) of Greek yogurt + 1 scoop of whey protein
• 200g (7oz) of firm tofu
• 2 cups of cooked lentils

Important context and caveats

A few things the research is clear about, and a few things it isn't:

• Resistance training is part of the picture. Higher protein intake without any form of resistance exercise is less effective for preserving muscle than higher protein combined with strength training.[8]
• Individual variation exists. The numbers above are population-level estimates from research studies. Your needs may vary based on your health status, activity level, body composition, and goals.
• Kidney disease changes the picture. Adults with chronic kidney disease may need to limit protein intake. Higher protein intakes for healthy adults have not been shown to cause kidney damage, but anyone with existing kidney issues should consult their doctor before increasing protein.
• The research is ongoing. Studies on optimal protein intake for older adults continue. The figures cited here reflect current evidence as of 2025, but recommendations may be refined as more data emerges.