Optimum Nutrition

Key Points

• Protein timing matters — spreading intake every 3–4 hours supports continuous muscle growth and recovery.

• Both men and women need similar protein amounts, with higher intakes useful during heavy training or dieting.

• Protein quality counts — whey and mixed sources (for plant-based diets) are most effective for muscle building.

• The standard RDA of 0.8 g/kg is too low for athletes, who benefit from 1.4–2.0 g/kg daily protein.

Introduction

Most people know that the daily protein goal is around 0.8 grams per kilogram of body weight. This number is called the Recommended Dietary Allowance (RDA). It helps prevent problems from not getting enough protein. But if you exercise a lot or want to get stronger, this amount may be too low.

Why Protein Helps Exercise

When you work out, especially with weights, your muscles get tiny tears. This sounds bad, but it is how muscles grow stronger. Protein, which is made of building blocks called amino acids, helps fix and rebuild muscle. Muscles grow when building is greater than breaking down. Exercise starts this process, and protein from food keeps it going.

One amino acid called leucine is extra powerful. It “switches on” muscle building. Foods like milk, eggs, meat, and soy have a lot of leucine. A meal with 20–40 grams of protein is enough for most people to trigger muscle growth.

Do Athletes Need More?

Yes. Research shows that athletes do better with 1.4 to 2.0 grams per kilogram per day. For example, a 70-kilogram person would need 98 to 140 grams of protein each day. If you don’t know your protein number, check out Optimum Nutrition’s protein calculator to get an estimate of your daily protein goals. It is also important to spread protein across meals because the muscle boost only lasts a few hours. Eating protein every 3–4 hours helps muscles grow more.

Athletes training hard, trying to lose fat, or doing long-distance sports may even need up to 2.2 grams per kilogram per day. This extra protein helps protect muscle during tough times.

What About Women?

Most early studies looked only at men, but newer studies show that women need about the same amount. Hormone changes during the monthly cycle or with birth control do not really change protein needs. Women can follow the same guideline of 1.4–1.6 grams per kilogram per day, with the higher end being better during heavy training or dieting.

Protein Quality Counts

Not all proteins are equal. Whey protein, which comes from milk, is digested quickly and has a lot of leucine, so it is very good for muscle growth. Milk proteins usually work better than many plant proteins, though plant proteins can still work well if you eat enough and mix different types. Plant-based athletes need to plan carefully, but they can still get the protein they need.

The Bottom Line

The usual protein guidelines are too low for people who exercise a lot. The RDA prevents sickness from lack of protein but is not designed for peak performance. Active people should aim for two to three times more than the RDA. Eating 1.4–2.0 grams per kilogram per day, spread across meals, with good quality protein sources, is the best way to recover, grow, and perform better.

References

• Phillips SM. 2006. Dietary protein for athletes: from requirements to metabolic advantage. Appl.Physiol Nutr Metab.

• Phillips SM. 2012. Dietary protein requirements and adaptive advantages in athletes. Br.J Nutr.

• Morton RW, Murphy KT, McKellar SR et al. 2018. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med.

• Phillips SM. 2009. Physiologic and molecular bases of muscle hypertrophy and atrophy: impact of resistance exercise on human skeletal muscle (protein and exercise dose effects). Appl Physiol Nutr Metab.

• Phillips SM. 2017. Current Concepts and Unresolved Questions in Dietary Protein Requirements and Supplements in Adults.

Written by:

Prof. Stuart Phillips, PhD

Known as the “Protein Professor,” Prof. Phillips is a Distinguished University Professor at McMaster University and Tier 1 Canada Research Chair in Skeletal Muscle Health. His research focuses on exercise, aging, nutrition, and body composition, and he has been recognized as one of the world’s top 1% most-cited scholars from 2018–2023.

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