The official answer is 0.8g per kilogram of body weight per day. For a 70kg person, that's 56g. You'd hit that with a chicken breast and a cup of Greek yogurt.
The problem is 0.8g/kg is the minimum required to prevent protein deficiency - not the amount that supports muscle maintenance, metabolic health, immune function, or healthy ageing. For most adults, especially active ones and anyone over 50, the actual target is considerably higher.
Why the Official Guideline Is Too Low
The 0.8g/kg figure comes from nitrogen balance studies - measuring the minimum protein intake at which the body isn't losing more protein than it's taking in. It's essentially a floor, not a goal.
Research from the International Society of Sports Nutrition (ISSN), published in the Journal of the International Society of Sports Nutrition, puts optimal protein intake for active adults at 1.4-2.0g/kg per day. Even for sedentary adults, several large studies suggest 1.2g/kg is a more appropriate minimum for long-term health.
The gap between 0.8g and 1.4g/kg doesn't sound big. For a 70kg person it's the difference between 56g and 98g daily - nearly double.
How Much Protein You Actually Need (By Goal)
For General Health (Sedentary Adults)
Target: 1.2-1.4g per kg of body weight
At this level, you're supporting muscle maintenance, immune function, enzyme production, and tissue repair adequately. Below this, the body starts cannibalising muscle for protein over time - a process that accelerates after 40.
For Active Adults (3+ workouts per week)
Target: 1.4-1.8g per kg of body weight
Exercise increases protein turnover. Muscles break down during training and rebuild during recovery. Without enough dietary protein, that rebuilding process is compromised. This applies to all forms of exercise - not just strength training.
For Building Muscle
Target: 1.6-2.2g per kg of body weight
The ISSN's 2017 position statement found that intakes above 2.2g/kg produce no additional muscle-building benefit for most people. The sweet spot for maximising muscle protein synthesis is 1.6-2.2g/kg, spread across at least 3-4 meals.
For Adults Over 50
Target: 1.6-2.0g per kg of body weight
This is one of the most underreported nutritional findings of the last decade. Muscle protein synthesis becomes less efficient with age - a phenomenon called "anabolic resistance." Older adults need more protein per meal to achieve the same muscle-building response as younger adults.
A 2018 meta-analysis in the British Journal of Nutrition found that older adults consuming 1.6g/kg of protein per day maintained significantly more muscle mass over 6 months compared to those eating 0.8g/kg.
For Weight Loss
Target: 1.8-2.4g per kg of body weight
Higher protein during a calorie deficit preserves muscle mass. Muscle is metabolically active tissue - losing it slows your metabolism and makes regaining weight more likely. A high-protein deficit diet also reduces hunger more effectively than a high-carb one, through the action of satiety hormones GLP-1 and PYY.
Practical: What Does This Look Like in Food?
Here's roughly how much protein is in common foods:
| Food | Serving | Protein |
|---|---|---|
| Chicken breast (cooked) | 150g | 46g |
| Salmon fillet | 150g | 36g |
| Greek yogurt (full-fat) | 200g | 20g |
| Eggs | 2 large | 12g |
| Cottage cheese | 200g | 23g |
| Lentils (cooked) | 200g | 18g |
| Chickpeas (cooked) | 200g | 15g |
| Tofu (firm) | 150g | 18g |
| Whey protein powder | 1 scoop (30g) | 22-25g |
A 75kg active person targeting 1.6g/kg needs 120g of protein daily. That's achievable across three meals without supplements - but it requires protein to be a deliberate part of every meal, not an afterthought.
Does Protein Timing Matter?
Somewhat. The old idea that you need to consume protein within 30 minutes of training (the "anabolic window") has been largely debunked for most people. The more important variable is total daily intake.
That said, there's reasonable evidence for spacing protein across meals rather than eating it all in one sitting. Muscle protein synthesis is maximised by meals containing roughly 0.4-0.5g of protein per kg of body weight, repeated several times throughout the day. One giant 120g protein meal is less effective than 30-40g four times.
For practical purposes: aim to include a meaningful protein source at every meal and don't skip it at any one of them.
Do You Need Protein Supplements?
No. But they're useful when hitting a target through food alone is inconvenient.
Whole food complete protein sources - meat, fish, eggs, dairy, soy, quinoa - are the base. Supplements fill gaps. If you consistently hit your target from food, you don't need them. If your schedule makes it genuinely hard to hit 140g from meals alone, a protein shake is a practical solution, not a shortcut.
The difference between plant and animal protein matters slightly at the margins - animal proteins tend to have a higher leucine content (the amino acid most directly linked to muscle synthesis) and are more bioavailable. But with adequate total intake, most people who eat predominantly plant protein do fine.