Proteins

All tissues and cells need protein. Proteins are very important for muscle building and keep hair, nails, skin and eyesight healthy. Proteins are used for transporting iron and oxygen in the blood and for the manufacturing of hormones, enzymes, stimulation of the immune system and other compounds that provide fuel for your body.

Protein is considered to be the most filling nutrient according to the energy it gives and also good for weight loss since it stimulates the fat burning hormone, glucagon. 10-20% of your daily calorie intake should be from protein.

Proteins are converted in the body into 22 building blocks called amino acids and divided into complete and incomplete proteins.

• Complete proteins contain 9 of the 22 amino acids that are essential to life and must be added to the diet. They are found in animal foods like meat, fish, milk cheese and eggs. Vegans and vegetarians can get shortages of the essential amino acids lysine and threonine if they are not observant. Lysine can be found in soy beans, chickpeas, kidney and oats. Threonine can be found in lenses, cereal, herbs and grasses. To avoid shortage it is easier if you drink milk, otherwise you must make sure that you eat various kinds of beans, lentils etc.

• Incomplete proteins contain the remaining 13 of the 22 amino acids and can be found in vegetables, cereals, soybeans, dry beans, peas and peanuts.

Protein deficiency is relatively rare in developed countries but people who are on a strict diet can be at risk. Symptoms of protein deficiency can be decreased muscle mass, fatigue, anemia, impaired immune function, decreased metabolism, reduced fertility, hair loss, premature aging, mood swings and memory problems.

If you eat too much protein the excess will be stored as body fat. If you eat too much animal protein it can lead to lack of calcium.

Dietary Reference Intakes (DRIs): Estimated Average Requirements for Groups

Life Stage Group	Protein Grams per Day
Children 1–3 years	11
Children 4–8 years	15
Males 9–13 years	27
Males14–18 years	44
Males 19–30 years	46
Males 31–50 years	46
Males 51–70 years	46
Males > 70 years	46
Females 9–13 years	28
Females 14–18 years	38
Females 19-30 years	38
Females 31-50 years	38
Females 51-70 years	38
Females > 70 years	38
Pregnancy 14–18 years	50
Pregnancy19-30 years	50
Pregnancy 31-50 years	50
Lactation 14–18 years	60
Lactation 19-30 years	60
Lactation 31-50 years	60

Source: Food and Nutrition Board, Institute of Medicine, National Academies