PROTEIN
Like carbohydrates and lipids, proteins are one of the macronutrients. Though protein provides your body with 4 kcals per gram, giving you energy is not its primary role. Rather, it’s got way too many other things going on. In fact, your body contains thousands of different proteins, each with a unique function. Their building blocks are nitrogen-containing molecules called amino acids. If your cells have all 20 amino acids available in ample amounts, you can make an infinite number of proteins. Nine of those 20 amino acids are essential, meaning you must get them in the diet.
Some proteins are enzymes, provide structure, provide antibodies, maintain body fluid, transport nutrients and other compounds, maintain acid base balance, back up source of energy.
Proteins in the Diet
Proteins in the body are constantly broken down and synthesised. Our bodies reuse most of the released amino acids, but a small portion is lost and must be replaced in the diet. The requirement for protein reflects this lost amount of amino acids plus any increased needs from growth or illness.
The Acceptable Macronutrient Distribution Range (AMDR) for protein for men and women age 19 and older is around 30% of total calories.
The Recommended Dietary Allowance (RDA) for protein for adults is 0.8 g/kg of body weight. Because of their rapid growth, infants have the highest RDA for protein at 1.5 g/kg of body weight. The RDA gradually decreases until adulthood. It increases again during pregnancy and lactation to a level of 1.1 g/kg. The RDA for an adult weighing 140 pounds (63.6 kg) is a mere 51 grams of protein, an amount many of us consume before mid-afternoon.
One population that needs special attention is the elderly. Though the RDA for older adults remains the same as for younger adults, some research suggests their needs may be 1.2 grams/kg body weight in order to prevent the common muscle loss and osteoporosis that come along with aging. Though this doesn’t require the elderly to eat large servings of food, they frequently have poor appetites and dental problems that make chewing difficult. Helping them meet their nutritional needs may take a little creativity and perseverance.
Vegetarian Diets
When you think of protein, like most people, you probably think of beef, chicken, turkey, fish and dairy products. Beans and nuts might come to mind as well. Most foods contain at least a little protein, so by eating a diet with variety, vegetarians and vegans can eat all the protein they need without special supplements.
A complete protein includes all of the essential amino acids. Complete proteins include all animal proteins and soy. Incomplete proteins lack one or more essential amino acids. Beans, nuts, grains and vegetables are incomplete proteins. Previously, registered dietitians and physicians advised vegetarians to combine foods that contained incomplete proteins at the same meal to give the body all the necessary amino acids it needed at one time. Today we know this is unnecessary. Your body combines complementary or incomplete proteins that are eaten in the same day.
If you eat a variety of foods, you will meet your protein needs. Recreational athletes rarely need protein supplements. Professional athletes should consult a registered dietitian.
Healthy regards
Gustavo Smeha
Personal Trainer
コメント