How much protein do I really need?

No matter the diet, everyone needs protein. Athletes consume it for recovery, bodybuilders down it to bulk up, and most diets have a minimum protein requirement. But more isn’t necessarily better when it comes to any nutrient, including protein.

So how much protein do you really need?

Protein basics

Protein is a large molecule that plays critical roles virtually everywhere in your body, including the muscles, bones, skin, hair, organs, and body tissues. It’s perhaps best known for helping repair cells and body tissue, but it also plays a vital role in many important bodily processes, like fluid balance, immune response, vision, and the production of hormones, antibodies, and enzymes.

When you eat foods with protein, your digestive system breaks the protein down into amino acids, then your body combines the amino acids to carry out different bodily functions, like building muscles or transporting nutrients. Most amino acids can be synthesized by the body, but there are nine essential amino acids that the body can’t make on its own (lysine, histidine, threonine, methionine, valine, isoleucine, leucine, phenylalanine, and tryptophan). These must come from high-protein foods.

Popular and widely known food sources of protein include meat, poultry, fish, eggs, and dairy. But plants are also great sources of protein. Protein-rich plant foods that boast other health benefits—like added vitamins, minerals, and phytonutrients—include beans, lentils, nuts, seeds, and soy foods.

In addition to carbohydrates and fats, protein is one of three macronutrients that the body requires in sizable amounts to function properly. But what is a “sizable” amount of protein, and does it differ for people of different ages, body types, fitness levels, or nutrition goals?

General protein requirements

The Institute of Medicine’s recommended daily allowance (RDA) of protein is 0.8 g for every kg of body weight, regardless of age. To find your weight in kilograms, divide your weight in pounds by 2.2. For example, a 130-lb woman should aim for at least 47 g of protein per day (130/2.2(0.8)=47) and a 150-lb man should aim for at least 54 g daily (150/2.2(0.8)=54).

But, according to a review published in Nutrients, this RDA for protein should be viewed as the minimum amount needed to meet your basic nutritional requirements. In other words, it will keep your body running, but shouldn’t serve as an optimal daily protein goal. Registered dietitian Nancy Rodriguez, PhD, RD, professor of nutritional science at the University of Connecticut, told the Harvard Health Blog that consuming up to twice the RDA of protein is a safe range for the average active adult.

However, this amount differs for people of different ages. Recent studies confirm that aging adults have higher protein needs because of the risk of sarcopenia, or age-related muscle loss. After age 30, people lose between 3% to 5% of their muscle mass per decade, which puts them at greater risk for falls and fractures. Increased protein intake helps restore, or at least maintain, healthy muscle mass. For healthy individuals over the age of 65, the adjusted recommendation is 1.0-1.2 g of protein per kg of body weight. In this case, a 130-lb woman should eat 59-70 g of protein per day, while a 150-lb man should consume 68-81 g daily.

Protein requirements for weight loss, muscle gain

There’s evidence that eating a high-protein diet can aid weight loss efforts by suppressing appetite and increasing satiety. One clinical study published in the International Journal of Obesity included 65 overweight women randomly assigned to either a high-protein, a high-carbohydrate, or a control diet. After 6 months, those following a high-protein diet (where protein comprised 25% of total energy intake) had lost significantly more weight than those in the other two groups. In addition, more high-protein dieters lost more than 10 kg (22 lb) than any other group.

While guidelines for high-protein diets for weight loss vary widely, research published in The American Journal of Clinical Nutrition suggests that dieters should aim to consume between 1.2-1.6 g of protein per kg of body weight. For a 130-lb woman, that’s 71-95 g, and for a 150-lb man, that’s 82-109 g per day.

As for muscle gain, numerous studies have found that protein supplementation can facilitate muscle building when combined with regular strength training. A meta-analysis published in the British Journal of Sports Medicine reviewed nearly 50 studies to conclude that protein supplementation, coupled with resistance exercise training, helped make muscles bigger and stronger. When muscles are stressed during exercise, small tears are created in the tissues. Those tissues not only require new protein to repair, but will absorb extra protein that is consumed, increasing their mass.

To increase muscle mass in conjunction with regular exercise, the American College of Sports Medicine (ACSM) recommends that a person eats between 1.2-1.7 g of protein per kg of body weight per day. For a 130-lb woman looking to gain muscle mass and strength, that’s 71-100 g, and for a 150-lb man, that’s 82-116 g.

Notably, the ACSM states that this level of protein intake can be met through diet alone and doesn’t require supplementation.

“Whole foods are always the best option, rather than adding supplements,” Angela Pipitone, RD, a registered dietitian with Johns Hopkins Institute of Genetic Medicine, said in an interview with NPR. She added that the FDA has less stringent regulatory guidelines for supplements, so a product promising high protein might also contain higher sugar and other mystery additives.

What should you do?

Whether your goal is weight loss or muscle growth, overloading on protein is not going to get you there.

“The body only digests and absorbs a certain amount of protein at every meal,” said Jim White, RD, a registered dietitian and exercise physiologist, in an interview with The New York Times. “You can eat 300 grams of protein a day, but that doesn’t mean you’ll put on more muscle than someone who takes in 120 grams a day.”

Research on optimal protein consumption is ongoing, but staying within twice the RDA for protein (0.8 g per kg of body weight) appears to be a safe bet. Individuals with higher-protein needs are generally older adults, extreme athletes, and people recovering from surgery. 

Before you plan to increase your protein intake, consider your current diet. If you’re supplementing with protein powders and bars, swap them for high-quality whole foods like lean meats, fish, chicken, nuts, and legumes. If you’re already consuming a variety of plant and animal proteins alongside regular exercise, you’re probably already reaching your daily protein needs (and your health goals). As long as you opt for lean, whole protein sources whenever possible and run the calculations based on your age, weight, and health goals, your protein needs will be satisfied.