Role of protein
Protein is an essential part of your nutrition. You need protein to build muscle, make essential enzymes and antibodies, connective tissue, hair, and many other structures. Proteins can also provide calories. How much protein do you need? It depends on your body weight, lifestyle, and whether you're trying to bulk up or lose weight. Not eating enough protein reduces muscle mass, increases the risk of fractures, and can affect skin, hair, and nail health. Too much protein can strain the intestines, liver, and kidneys. Along with the correct amount, the type and source of protein are important, too.
Protein is a macronutrient, meaning you need large amounts of it. Your body needs protein for growth, repair, and maintenance. Bones and muscles need a lot of protein. Protein is also an energy source — one gram of protein yields 4 calories. Some other roles of proteins:
- Proteins are also needed for the structures of various cells and tissues.
- Metabolic activities in the body need a variety of enzymes, which are proteins.
- Your immunity depends on antibodies, interleukins, and several other types of proteins.
- Hemoglobin, vital for carrying oxygen from the lungs to the tissues, is a protein.
- Cell signaling, muscle contraction, and many other activities depend on proteins.
How much protein do I need?
The recommended intake for protein is 0.8 grams of protein per kilogram of body weight. For example, if you weigh 60 kilograms, you need 48 grams of protein a day. This recommendation is for people with a sedentary lifestyle. If you have an active lifestyle, you need more. People with mild, moderate, and intense physical activity should consume 1.0, 1.3, and 1.6 grams of protein per kilogram body weight respectively.
Strength or endurance athletes should consume 1.2 to 2.0 grams of protein per kilogram a day. Highly trained athletes can take somewhat higher amounts. You should consume extra protein just after exercising to build muscle.
During pregnancy, you should increase your protein intake to at least 60 grams a day. This will provide 20% to 25% of your daily calories. If you're breastfeeding, you should have an additional 15 to 20 grams of protein a day.
Protein is a major part of your diet. About 10% to 35% of your energy should come from protein. If your calorie requirement is 2,000 calories a day, 200 to 700 should come from proteins. A higher proportion of protein foods helps if you're trying to lose weight. They make you feel full for longer.
Protein requirements increase with age and in severe illness. Older people should have 1 to 1.5 grams of protein per kilogram body weight a day. This helps counter the effects of aging and reduced activity. Older people also need more protein for wound healing and the ability to resist infections. People with severe illness may need as much as 2 grams per kilogram body weight a day.
Be careful if you have kidney disease. Chronic kidney disease impairs your ability to metabolize proteins. Consuming a lot of proteins could create a dangerous situation. Always talk to your doctor and dietician about your diet.
Is too much protein harmful?
Intakes up to 2 grams per kilogram a day are generally safe. Under normal circumstances, your body will use excess protein for energy. The breakdown of protein for energy releases nitrogen, which is converted to urea and ammonia. The liver, intestines, and kidneys participate in this process.
Eating too much protein increases the nitrogen load on these organs. Long-term over-consumption of protein can lead to liver and kidney injuries, metabolic abnormalities, fatigue, headache, seizures, and heart disease.
Protein is an essential nutrient for bone health. But excessive protein intake may cause demineralization of bone. Calcium is removed from the bones because of increased removal by the kidneys.
What are complete proteins?
Proteins that you eat are broken down in the gut into their basic components, amino acids. These amino acids are absorbed and used by various cells and organs to make proteins your body needs. There are twenty amino acids that human bodies use, and proteins that contain all of them are called complete proteins. Animal foods have complete proteins.
Among plant sources, quinoa, Quorn (a trademarked meat-free product) and soy protein are complete proteins. Other plant source proteins lack one or more of the amino acids. But eating plant proteins won't leave you deficient in amino acids. As long as you eat a diet with many types of plant protein, you'll get enough of all the amino acids.
Some amino acids can even be made in the body. The amino acids that your body can't make are called essential amino acids. Your diet must provide these. Again, eating a balanced diet with varied plant protein sources will provide all the essential amino acids.
Protein source and type
Protein in your diet is never alone. The foods classified as protein foods may contain about 15 to 30 grams of protein per 100-gram portion. The rest of the food will be fats, carbohydrates, water, and fiber. Foods also contain micronutrients like vitamins and minerals. Though protein is your focus, you should pay attention to the package of nutrients in your food.
Traditionally, meat was considered the best source of protein. But we now know that a diet very heavy in meat is not the healthiest. Even the leanest cuts of beef have significant amounts of saturated fats. Diets rich in red meat are also associated with colon cancer.
You don't need to stop eating meat but plan your meals to include proteins from different sources. Replacing dairy and meat (animal protein sources) with plant proteins like grains, nuts, and pulses (the edible seeds of legume plants such as lentils, beans, and peas) is better for health. This will give you a balanced mix of nutrients to stay healthy.
It's nice to know your protein requirements, but how do you meet them? Eating pure protein is neither possible nor desirable. Plan your meals to include a variety of foods that give your enough protein and a healthy mix of other nutrients.
- Most meat consumed is beef, which has significant amounts of fat. Always get lean cuts, and trim off the visible fat.
- Add beans, lentils, peas, and pulses to soups and stews.
- Try to add nuts and seeds to salads, pasta, and cereals.
- Skimmed milk provides all the protein and calcium of milk, with the fat removed.
Consume your protein in a variety of foods, including eggs, meat, dairy, poultry, beans, peas, nuts, seeds, and soy products. This will ensure you get a balanced variety of the other nutrients necessary for good health.
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Health Solutions From Our Sponsors
Annual Review of Nutrition: "Energy and Protein Requirements During Lactation."
British Heart Foundation: "Protein: What you need to know."
British Nutrition Foundation: "Protein."
Food & Function: "Dietary protein intake and human health."
Intermountain Health: "How Much Protein Is Simply Too Much?"
National Health Service: "The importance of protein in your diet,” “Overview - Bowel cancer."
University of California at San Francisco Health: "Eating Right Before and During Pregnancy."
U.S. Department of Agriculture: "Dietary Guidelines for Americans 2015-2020"
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