Amino Acid Classification

Of the 20 amino acids that make up all proteins, only 9 are considered "essential" in our diets because they cannot be made by our bodies and must be obtained from the foods we eat.

Essential in

Essential in Our

Nonessential

Our Diets

Diets Under Some Circumstances

in Our Diets

Histadine

Arginine

Alanine

Isoleucine

Cysteine*

Asparagine

Leucine

Tyrosinet

Aspartic acid

Lysine

Glutamic acid

Methionine

Glutamine

Phenylalanine

Glycine

Threonine

Proline

Tryptophan

Serine

Valine

*Cysteine can be synthesized from the essential amino acid methionine.

fTyrosine can be synthesized from phenylalanine when supplied in adequate amounts.

saturated fat, which increases the risk for coronary artery disease and some forms of cancer.

What if we eat too little protein? Few Americans are at risk of eating too little protein. However, individuals on severely restricted diets, those who are unable to eat, and those whose needs are increased because of illness or trauma may experience protein deficiency. To replenish the pools of essential amino acids that have been depleted, in order to make critical proteins such as enzymes and hormones, the body of a protein-deficient person begins to rob protein from muscle by digesting that protein to its constituent amino acids. Because muscle is needed for various vital functions (for example, diaphragm muscles for breathing and heart muscles for pumping our blood), the loss of large amounts of muscle protein can be fatal. Fortunately, the vast majority of people, even those who engage in regular, rigorous endurance exercise, can easily meet their need for protein by eating a balanced diet based on the Food Guide Pyramid.

The Bottom Line on Protein

Adequate protein is critical for growth, metabolism, and health, but eating more protein than we need will not build bigger muscles. Conversely, excess protein is converted to fat. Foods of animal origin are high in protein but may also be high in total and saturated fat. Lean meats and dairy products, fish, legumes, and grains are the best sources of protein.

36 Fat Burning Potent Foods

36 Fat Burning Potent Foods

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