Protein, whether derived from animal or plant sources, is important to health. It provides the essential amino acids that our bodies need to maintain, grow and repair muscle and other tissues. Proteins also help our bodies produce hormones, digestive enzymes and hemoglobin. Our bodies also need protein to produce hair and fingernails, control brain signals and boost immunity.
Some amino acids are essential
Our bodies use amino acids, the building blocks of protein, to create the structures necessary for growth and energy production (metabolism). We manufacture four nonessential amino acids internally, which include alanine, asparagine, aspartic acid, and glutamic acid regardless of the food we eat. We need other amino acids, called conditional amino acids. They are arginine, cysteine, glutamine, glycine, ornithine, proline, serine and tyrosine. During times of stress and illness, we may need to consider supplementing this group.
However, there are nine amino acids, known as essential amino acids, that we must get through the protein-rich foods we eat every day in order to remain healthy.
- Tryptophan helps the body regulate mood and sleep.
- Valine helps muscles turn food into energy and helps heal tissues.
- Lysine helps the body change fatty acids into energy and produce hormones, antibodies and enzymes.
- Methionine helps the body produce the sulfur it needs for metabolism and the production of red blood cells.
- Leucine increases muscle mass and helps muscles recover after a workout. It also helps blood-sugar regulation, healing and brain function.
- Isoleucine regulates blood sugar.
- Threonine helps the body produce collagen and antibodies.
- The three forms phenylalanine, D-phenylalanine, L-phenylalanine and DL-phenylalanine are important for regulation of the nervous system.
- Histidine is important for metabolism.
These amino acids are available in a variety of vegetable and animal-based foods. But, which source is best?
What are the benefits of animal protein?
Animal protein from meat, poultry, fish, eggs, milk and whey are known complete proteins, which means they contain all the essential amino acids.
Many dark-meat proteins also contain zinc and iron, which the body absorbs easily. These minerals are also found in egg yolks.
If you are on a low-carb diet, animal-meat protein should fit into your diet nicely. However, you should be aware that animal proteins often contain more saturated fat and cholesterol than vegetable proteins. For a good source of low-fat animal-protein, you may want to consider wild-caught salmon, which is also high in Omega-3 fatty acids.
If you are a meat eater, you may want to limit your intake of beef to three or fewer six-ounce servings per week to reduce the fat and cholesterol in your diet.
What are the benefits of vegetable or plant-derived protein?
Plant proteins may lower your intake of dietary cholesterol and saturated fat.
Often a person who relies on plant-derived proteins will have a lower body mass index, lower blood cholesterol levels and lower blood pressure than his or her carnivorous friends.
However, people eating solely vegetables, legumes and nuts for their daily intake of protein need to be aware that very few vegetables provide all nine amino acids. For this reason, vegetable or plant-based proteins are referred to as incomplete proteins.
There are some exceptions to that rule such as soy, quinoa, and hempseed. According to the American Dietetic Association's position paper on vegetarian diets, eating an assortment of plant proteins during the day can maintain balanced nitrogen levels (a measure of protein) in the body. In other words, you can eat sources of complimentary plant-based proteins throughout the day instead of combining foods to create complete proteins at each meal.
How much protein should you eat each day?
The recommended daily allowance of protein depends on your gender, size, activity level and whether you are pregnant or lactating. According to the Harvard School of Public Health, the Institute of Medicine recommends that adults consume at least 0.8 grams of protein for every 2.2 pounds of body weight each day. For a 145-pound adult, that would be approximately 53 grams per day.
Women who are pregnant or lactating may need higher amounts of protein and should talk to their obstetricians about their dietary needs.
According to the International Society of Sports Nutrition, protein requirements are based on nitrogen balance and amino acid studies. People who exercise or train regularly need more dietary protein than people who do not. Physically active individuals may need between 1.4 and 2.0 grams of protein for every 2.2 pounds each day. To obtain this level of protein they may want to add a protein supplement to a nutrient-rich diet.
The best way to determine the amount of protein that you need is to consult with a dietitian or nutritionist.
What about high-protein diets?
While diets higher in protein and lower in carbohydrates can reduce weight quickly, they may not be sustainable for the long-term.
They work in the short-term because the body uses its carbohydrate and fat stores for energy. Limiting carbohydrates and fat while eating lean protein may prevent the body from using the protein stored in muscles and other cell tissues. However, a diet of this type may not be healthy for long periods.
The best diets balance protein from many sources. No matter what type of protein you choose, it is important to look at the nutritional value of the food that you eat to make sure that you are getting the vitamins, minerals and protein that your body needs.