How Much Protein Do You Actually Need After 40?

I want to start with the number that annoyed me most.

The official Australian recommendation for a woman aged 51 to 70 is 46 grams of protein a day. That's 0.75 grams per kilo. It's the same number given to a 25-year-old. And when you read the NHMRC's own working, which almost nobody does, because it's a PDF from 2006, they concede that "adults older than 53 years appeared to have 25% higher requirements for maintenance than younger adults."

They noticed. They just applied the increase from age 70 instead.

So a 55-year-old woman is being handed a number that the guideline's own evidence says is too low for her, and nobody has updated it in twenty years.

But here's where most articles about this lie to you

The easy version of this piece would tell you that Australian women are protein-deficient. It's a great hook. It's also false, and it takes about ninety seconds to fact-check.

According to the ABS national nutrition survey, the median Australian woman eats 75 grams of protein a day, and 98.5% of Australians get enough by the official measure. Among women aged 30 to 49, the proportion falling short is 0.3%. You are almost certainly not deficient.

So what's the actual problem?

The RDI was built to stop you getting sick. It was never built to keep you strong. Those are different questions with different answers, and the gap between them is where the real story lives.

What's actually happening to your muscle

You'll have read that you lose 3 to 8 per cent of your muscle per decade after 30. I went looking for the study behind that figure and couldn't find one. It circulates through review papers and supplement marketing, citing each other in a loop.

Here's what the good longitudinal data actually shows, and it's more interesting.

In women over 75, muscle mass declines around 0.64–0.70% a year. But strength declines at 2.5–3% a year. You lose strength three to five times faster than you lose size.

That's the finding worth sitting with. The problem isn't that your arms get smaller. It's that the muscle you still have stops working as well. Which is exactly how it feels, the shopping bags get heavier, the jar lids get tighter, and you can't point to anything that looks different in the mirror.

The Health ABC study added a detail that should end the "just eat more" school of thought: women who gained lean mass did not gain strength with it. Getting bigger doesn't make you stronger. Only training does that.

And menopause?

Smaller than you've been told, and in a different place than you'd expect.

SWAN - which followed 1,246 women through the transition, which makes it the best data we have, found lean mass shifting from +0.2% a year before menopause to −0.2% a year during it. That's a real change. It is not a collapse.

Fat mass, meanwhile, went from +1.0% a year to +1.7%. The rate nearly doubles.

So the body-composition change you're noticing in your forties is mostly fat arriving, not muscle vanishing. Which matters, because it points you at a different solution.

Why the same meal stops working

This is the mechanism that makes midlife protein different, and it has a name: anabolic resistance.

Pooled data from six studies found that after an identical 20g dose of protein, younger muscle raised its protein synthesis rate substantially while older muscle managed about 16% less. Same protein. Weaker response.

The leucine research shows it starkly. In one classic study, a small dose of amino acids at normal leucine levels produced a significant response in young people and no significant response at all in older ones. Push the leucine up, and the older group's response came back.

So it isn't that you need more protein because you're old. It's that you need more per sitting to cross the same threshold.

The 30-gram threshold, and why more isn't better

One study did something clever. It gave people either 113g of lean beef (30g protein) or 340g (90g protein) and measured what happened.

Both doses raised muscle protein synthesis by around 50%. Tripling the protein produced no further increase, in young or old.

Which is the argument against the way most of us eat: nothing at breakfast, something at lunch, an enormous protein hit at dinner. The excess at dinner doesn't get banked. It's just expensive.

Roughly 25 to 30 grams per meal is where the research clusters. Below it, in older muscle, you may get very little. Above it, you're not getting extra.

So where's the gap? Breakfast.

This is the statistic that genuinely surprised me.

In US national survey data covering adults over 50, the proportion hitting 25g of protein at each meal:

Only 1% of women managed 25g at all three meals.

Ninety-five per cent of women over 50 start the day below the threshold their muscle needs to respond. Toast. A banana. Coffee and whatever's in the cupboard. Then they wonder why they're ravenous at three in the afternoon.

That's US data — no equivalent Australian meal-level survey exists. But the eating pattern it describes will be familiar to any Australian woman who has ever had a morning.

What 30 grams of protein actually looks like

Breakfasts that actually get there:

• 3 eggs + 40g cheese + a slice of toast - 31g
• 1 tub high-protein yoghurt + a scoop of protein powder - 36g
• 2 eggs + a tub of high-protein yoghurt + a tablespoon of peanut butter - 33g
• Porridge made with milk + 2 tbsp peanut butter + chia - 27g

None of that is a lifestyle overhaul. It's mostly the difference between eating breakfast and having something with your coffee.

A good unflavoured collagen powder is a useful shortcut here, 14 grams of protein that disappears into coffee, porridge or yoghurt without changing the taste of anything. Not because collagen is magic, but because it turns a 10-gram breakfast into a 25-gram one with no cooking involved.

The part the supplement industry would rather you skipped

Here is what happens when researchers actually test protein in postmenopausal women.

A 2024 trial put 55 women through twelve weeks in four groups: training plus high protein, training alone, protein alone, and control. Both training groups gained lean mass - +1.4kg and +1.2kg respectively. Essentially identical. The extra protein added nothing measurable. Only the training-only group lost fat mass.

A ten-week trial giving 40g of whey around resistance sessions found strength and muscle thickness improved significantly, and no difference between whey and placebo.

Four further trials comparing 1.2g/kg against 0.8g/kg alongside training: lean mass increased similarly in both groups, every time.

And protein without training? A six-month trial at 1.6g/kg versus 0.8g/kg in women over 65 found no increase in lean mass, strength or physical performance. None.

Which is, I'll admit, a slightly awkward thing for a website that also writes about supplements to say. But you can't build trust by only mentioning the studies that suit you.

What protein genuinely does do

It keeps you full. In a controlled feeding study, raising protein to 30% of intake and then letting people eat freely reduced spontaneous intake by 441 calories a day, without anyone counting anything. (Small study, 19 people, no control group. Treat it as an illustration, not a promise.) Higher-protein diets also preserve lean mass during weight loss, which is the whole game if you're trying to lose fat without losing strength.

It does not hurt your bones. This one deserves correcting, because the myth is still live on Australian government health pages. The Victorian Better Health Channel currently warns that high protein "can prompt excessive loss of the mineral calcium, which can increase your risk of osteoporosis."

A systematic review spanning forty years and 127 papers found no association between protein intake and osteoporotic fracture risk in any direction. A separate meta-analysis found higher protein slightly improved lumbar spine bone density. The acid-ash hypothesis is dead. The web page didn't get the memo. More on bone density here.

What I'd actually do

Fix breakfast first. It's where 95% of the gap is and it's the easiest meal to change. Aim for 25–30g before you think about anything else.

Aim for roughly 1.2g per kilo. That's about 84g for a 70kg woman, a bit above the median, well above the RDI, and comfortably below the point where you're just buying expensive food.

Spread it across three meals. The evidence for this is decent rather than overwhelming, but it's a practical way to actually reach your total, and it's certainly no worse.

Lift something heavy, twice a week. This is the non-negotiable one. Everything above is scaffolding for this.

Get your kidneys checked if you haven't.

And if you take one thing from this: the number on the guideline was designed in 2006 to stop you getting ill, using a formula the authors themselves admitted underestimates women over 53. It was never designed to keep you strong.

Strong is a different target. You have to aim at it deliberately.

Frequently asked questions

This article is general information, not medical advice. If you have kidney or liver disease, are pregnant or breastfeeding, or are managing a health condition, speak to your GP or an Accredited Practising Dietitian before making significant dietary changes.