「经济学人」How much protein do you really need?

Unless you are older or want bigger muscles, you’re probably getting enough

Fats and carbohydrates, eat your hearts out—protein is the macronutrient of the moment. Rich people love the stuff. They treat it like ambrosia. Are they onto something?

Having protein on your plate is important. It is made up of amino acids, of which the body needs 20 types in order to grow, produce hormones and stay healthy. Nine of these amino acids must come from food. The World Health Organisation recommends 0.83 grams of protein a day per kilogram of body weight (g/kg) for healthy adults to maintain muscle and tissue health.

Elderly folk may be better off eating more, since muscles wither with age and older bodies are less efficient at absorbing protein. A review published in Nutrients in 2021 suggested that a ratio closer to 1.2g/kg, together with resistance training, could help limit muscle shrinkage in older people. Children and teenagers, who are still growing, may also want more than the minimum, depending on how active they are. A paper from 2020 suggested that pregnant and breastfeeding women need double the recommended amount to maintain muscle mass and feed their child.

More protein can also help you lose weight. Protein takes more energy to digest than carbs and fats and makes you feel fuller for longer. To build muscle mass, the International Society of Sports Nutrition has recommended a daily protein intake of between 1.4g/kg and 2g/kg, combined with resistance training. A meta-analysis published in Sports Medicine in 2022, though, found that eating more than 1.6g/kg does not lead to further muscle growth.

Where should the protein come from? Powders (dried extracts of milk, pea or soya) are popular and convenient—chugging protein as a drink is easier than gnawing on steak. A randomised controlled trial in 2013 found that whey protein, made from milk, was especially good at building lean body mass for exercising adults. Even if you’re a couch potato today, you can bulk up using this supplement, according to a review published in 2014 in Sports Medicine, as long as you also lift heavy in the gym.

Yet advocates of a traditional balanced diet argue that because alternative sources of protein such as powders and bars often contain too many sugars, flavourings, emulsifiers and other additives, they are less healthy than food-based protein. Eating whole foods may also be a better route to building muscles after a workout, according to a review published in Nutrients in 2018, because of the added benefits of naturally occurring micronutrients such as calcium, vitamin D and iron.

Followers of a Western diet, typically rich in meat, dairy and pre-packaged foods, tend to exceed the minimum protein requirements without trying. This includes vegetarians and vegans, according to a review published in Nutrients in 2019. Most Americans get more than the recommended amount of protein because of their fondness for meat.

The risks of overdoing it on protein are debated. Some nutritionists warn of the potential for kidney damage, but a 2018 meta-analysis concluded that this is only a concern for people with existing kidney trouble. The greater risk may come from protein-rich diets which rely heavily on red meat and ultra-processed foods that can also contain the saturated fats associated with ill health.

In places where food is plentiful, measuring your protein by the gram may not be worth it. Unless you’re looking to bulk up, a regular diet is ample.(Jun 6th 2025)

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