What, when, why, and how
Most of us associate protein with building muscle, but this nutrient has many other health benefits. Discover why protein is so important, and how to know if you’re getting enough.
Protein has crucial roles throughout your body: it’s a necessary component of enzymes, it’s key for nutrient transport, and it’s vital for your immune system. But how much protein do you really need, and which type—animal or plant based—is best?
Unlike carbohydrates and fats, which are primarily used for energy, proteins are structural nutrients. They’re used as fuel only as a last resort. This means that proteins are a part of your muscles, of course, but also a component of your skin and bones. In fact, after taking away water, protein accounts for 75 percent of your body weight.
Proteins are made up of blocks called amino acids, much like a child’s building set. Blocks of various shapes and sizes are constructed and reconstructed into different patterns according to your body’s needs. There are 20 amino acids, but from a nutritional perspective, nine are considered indispensable (or essential). This means that your body can’t construct them from other blocks that are lying around, so you have to eat them.
In contrast, your body is able to create dispensable (or non-essential) amino acids under most circumstances. Conditionally indispensable amino acids are those that you can make under the right conditions but frequently not in sufficient quantities or at appropriate times to meet your needs, such as when you’re sick or stressed.
Animal sources of protein, including dairy, eggs, fish, meat, and poultry, provide all the indispensable amino acids and are therefore considered high quality proteins. On the flip side, animal protein, especially red meat, boosts our intake of saturated fats and cholesterol, while at the same time potentially increasing our total daily energy (calorie) intake.
Soy and quinoa also provide every indispensable amino acid, but they contain nowhere near the same quantities as animal proteins. Other plant sources of protein, on the other hand, provide an assortment of indispensable amino acids. Beans, lentils, and other legumes are good sources of amino acids, as are these nuts and seeds:
Vegetables are also important protein sources. Along with amino acids, they offer a healthy dose of other nutrients to support your health: a 1/2 cup (125 mL) serving of asparagus, for example, provides 2 g of protein. Fruits provide little protein.
Health benefits seem to differ depending on the protein source. One study, for example, found that animal protein was associated with lean muscle mass, but that plant protein was associated with muscle strength. In another study, increased dairy protein intake was associated with higher bone mineral density (BMD). Women who consumed high levels of plant protein had lower fracture risk at their given BMD, likely due to the other nutrients in these foods.
In other words, for the best health benefits, try to enjoy your protein from a variety of sources. Because your body does not have a mechanism to store excess dietary proteins, unlike carbohydrates and fats, aim to spread your protein intake throughout every meal and snack.
|brown rice||1 cup||5 g|
|chicken||1/2 chicken breast||27 g|
|cocoa powder||2 Tbsp||2 g|
|eggs||2 eggs||12 g|
|kidney beans||1/2 cup||21 g|
|spirulina||1 Tbsp||4 g|
|walnuts||1/4 cup||5 g|
Protein is essential for developing and preserving healthy bone and muscle mass. Obviously, exercise is crucial for muscle development, but the focus here is on nutrition. After a meal, dietary amino acids increase muscle protein synthesis, while the hormone insulin helps to deliver nutrients to muscles through an increase in blood flow. In adults, eating a meal stimulates muscle creation (anabolism) and inhibits muscle breakdown (catabolism), with the result of an increase in muscle mass.
Unfortunately, as we get older, not only does muscle protein synthesis become less sensitive to dietary amino acids, but insulin action also becomes impaired. As a result, there is an imbalance between anabolism and catabolism during the day, which eventually leads to a net loss of muscle (also known as sarcopenia). This shortfall translates to an annual 1 to 2 percent loss of muscle mass for adults over age 50. Muscle strength declines by 3 percent per year after age 60.
Whether or not you have body-building aspirations, muscle strength is a critical factor in determining independence as you get older, particularly when considering tasks such as sitting and rising from the toilet. Weak muscles can also lead to more falls and injuries.
Protein makes up about half of our bone volume and one-third of our bone mass. Because many of the collagen fragments released during bone breakdown can’t be reused, bones require a daily influx of dietary protein for bone remodelling. Research shows that protein intake of less than 12 percent of total daily calorie intake is associated with increased risk of bone fracture in men and women over age 50.
Each day, adults should consume 0.8 g of protein per kilogram (or 0.36 g of protein per pound) of body weight. After age 65, however, we should aim for 1.2 g of protein per kilogram of body weight daily, with at least 25 to 30 g of protein at each meal.
Consider what you eat along with your protein, too. Added sugars accelerate age-related loss of muscle mass, possibly by disrupting insulin and aggravating the weakening of muscle protein synthesis. In other words, sugar will eat away at your muscle mass.
Athletes and those who simply want to age in a healthy way can turn to protein powders or supplements to add variety or increase intake. If you decide to take a protein supplement for a health-boosting top-up, remember that even in supplement form, protein has a satiating effect that may have you pushing back earlier from the table. While eating less may help you with your weight goals, be sure that you don’t undo the good you’ve done by inadvertently eating less dietary protein.
|casein||dairy||digests slowly; promotes satiety and weight loss; aids overnight muscle recovery when consumed before bed|
|hemp||plant||helps prevent and treat hypertension; increases endurance; provides essential omega-3 fatty acids|
|soy||plant||provides all indispensable amino acids; may be cancer protective|
|whey||dairy||increases muscle protein synthesis; contains the most leucine (an amino acid that aids muscle recovery); digests quickly, making it appropriate for older adults; may be cancer protective|