Protein is one of the three macronutrients, alongside fats and carbohydrates, required for proper body functioning. These large, complex molecules are composed of smaller units known as amino acids, linked together in long chains. Found in every living cell, protein is a fundamental component that plays a part in virtually every process within the body. Without adequate protein, the body’s ability to grow, repair, and maintain itself would be compromised.
The Role of Protein in the Body
Proteins are often described as the “building blocks” of the body. They form the primary structural components of tissues such as muscles, skin, hair, and internal organs, constantly being repaired and replaced through a process called protein turnover. Collagen, for instance, is a fibrous protein that provides strength and elasticity to connective tissues like skin and tendons. Similarly, actin and myosin are proteins directly involved in muscle contraction and movement.
Beyond their structural roles, proteins act as versatile “worker molecules” facilitating countless biochemical reactions. Enzymes, which are specialized proteins, accelerate metabolic reactions, ranging from nutrient breakdown to energy production. Some proteins also function as hormones, acting as chemical messengers that transmit signals between cells, tissues, and organs to coordinate biological processes. Proteins also contribute to immune function by forming antibodies, which bind to foreign particles like viruses and bacteria. Furthermore, they assist in maintaining proper fluid balance and pH levels in the blood.
Determining Daily Protein Needs
The amount of protein an individual needs daily varies significantly based on several factors. For a sedentary adult, the general Recommended Dietary Allowance (RDA) is approximately 0.8 grams of protein per kilogram of body weight per day. This means a person weighing 70 kilograms (about 154 pounds) would need around 56 grams of protein daily to meet basic requirements and prevent deficiency.
However, individual needs increase with higher activity levels. For those engaged in light physical activity, protein requirements might be slightly elevated. Endurance athletes, such as long-distance runners, need between 1.0 to 1.8 grams per kilogram of body weight daily. Strength and power athletes, including weightlifters and bodybuilders, require even more, with recommendations ranging from 1.4 to 2.2 grams per kilogram of body weight to support muscle growth and recovery. For instance, a 90-kilogram (around 198-pound) strength athlete aiming for muscle gain might target 126 to 198 grams of protein daily.
Age also plays a role in protein requirements. While the official RDA for older adults remains the same as for younger adults, emerging research suggests that individuals over 50 may benefit from higher intakes, 1.0 to 1.6 grams per kilogram of body weight per day. This increased intake helps counteract age-related muscle loss, known as sarcopenia, and supports overall physical function. For specific health goals like weight loss, a higher protein intake, around 1.5 to 2.2 grams per kilogram of body weight, can help preserve muscle mass while reducing overall calorie intake due to increased satiety.
To estimate your own need, multiply your body weight in kilograms by the appropriate protein factor. For example, a 60 kg (132 lb) sedentary adult would aim for 60 kg 0.8 g/kg = 48 grams of protein daily. An active individual or older adult would use a higher multiplier. It is advised to distribute this protein intake evenly throughout the day across meals.
Sources of Protein
Proteins are readily available from a wide array of food sources, broadly categorized into animal-based and plant-based options. Animal-based proteins are complete proteins because they contain all nine essential amino acids the human body cannot synthesize.
Examples of complete animal-based proteins include:
Lean meats like chicken, turkey, and beef.
Fish and seafood, such as salmon, tuna, and sardines.
Eggs, offering approximately 6 grams of protein per large egg.
Dairy products like milk, yogurt, and cottage cheese.
Plant-based proteins are diverse and contribute significantly to daily protein needs. These include legumes such as lentils, chickpeas, and various beans. Tofu, tempeh, and edamame, derived from soybeans, are notable plant-based sources that provide complete protein. Nuts and seeds, including almonds, peanuts, and chia seeds, offer protein. Grains like quinoa are also unique among plant sources as they contain all nine essential amino acids, making them a complete protein.
Many plant-based proteins are considered “incomplete” because they may lack one or more essential amino acids. However, this does not pose a problem for most individuals consuming a varied diet. Eating different incomplete protein sources throughout the day, known as “complementary proteins,” ensures the intake of all essential amino acids. For instance, combining rice (low in lysine) with beans (low in methionine) within the same day creates a complete protein profile. This flexibility allows individuals following vegetarian or vegan diets to meet their protein requirements by consuming a diverse range of plant foods.
Timing Protein Intake
While the total daily protein intake holds more significance for overall adaptation and muscle maintenance, the timing of protein consumption plays a role, particularly around exercise. The concept of an “anabolic window,” suggesting a narrow timeframe post-workout for protein intake to maximize muscle growth, has been discussed. Current understanding indicates that this window is broader than once thought, extending several hours before and after exercise, especially if a pre-workout meal was consumed.
A practical approach for most individuals is to distribute protein intake evenly throughout the day. Consuming approximately 20-40 grams of high-quality protein at each main meal, roughly every three to five hours, optimizes muscle protein synthesis and promotes satiety. This consistent supply of amino acids supports continuous muscle repair and growth, rather than relying on a single large dose. For older adults, spreading protein intake across meals with about 25-30 grams per meal is beneficial to counteract age-related muscle loss.
Understanding Protein Supplements
Protein supplements, such as powders, bars, and ready-to-drink shakes, offer concentrated forms of protein. Common types include whey and casein, as well as plant-based options like soy, pea, and rice protein. These products provide a convenient way to increase protein intake without consuming large volumes of whole foods. Whey protein, for example, is quickly digested and absorbed, popular for post-workout recovery.
For most individuals who meet their protein needs through a balanced diet of whole foods, protein supplements are not necessary. A “food first” approach is recommended, as whole foods provide a broader spectrum of nutrients beyond just protein, including vitamins, minerals, and fiber. However, there are specific circumstances where supplements can be beneficial.
Supplements can be useful for athletes with high protein requirements difficult to meet through food alone, or for individuals with busy schedules who need a quick and convenient protein source. They also assist older adults or those recovering from illness or injury with increased protein needs or difficulty consuming regular meals. When choosing a supplement, select products from reputable brands and consider the protein type and amino acid profile, especially for those with specific dietary preferences or goals.