Nutrition experts recommend that protein, as a source of amino acids, account for 10–12% of the calories in a balanced diet. However, requirements for protein are affected by age, weight, state of health, and other factors. On average, a normal adult requires approximately 0.36 grams of protein per pound of body weight. Using this formula, a 140-pound person would need 50 grams (or less than 2 ounces) of protein per day. An appropriate range of protein intake for healthy adults may be as low as 45–65 grams daily. Some athletes have higher amino acid requirements.1 Most American adults eat about 100 grams of protein per day, or about twice what their bodies need and at least as much as any athlete requires.
Foods of animal origin, such as meat and poultry, fish, eggs, and dairy products, are the richest dietary sources of the essential amino acids. Plant sources of protein are often deficient in one or more essential amino acids. However, these deficiencies can be overcome by consuming a wide variety of plant foods. For example, grains are low in lysine, whereas beans provide an excess of lysine. It was previously believed that, in order for vegetarians to obtain adequate amounts of protein, all of the essential amino acids had to be “balanced” at each meal. For example, a grain and a bean had to be consumed at the same meal. However, more recent research has indicated that, while consuming a proper mix of amino acids is important, it is not necessary to consume them all at the same meal.2
The vast majority of Americans eats more than enough protein and also more than enough of each essential amino acid for normal purposes. Dieters, some strict vegetarian body builders, and anyone consuming an inadequate number of calories may not be consuming adequate amounts of amino acids. In these cases, the body will break down the protein in muscle tissue and use those amino acids to meet the needs of more important organs or will simply not build more muscle mass despite increasing exercise.
Interactions with Supplements, Foods, & Other Compounds
Amino acids include several different nutrients, each of which has the potential to interact with drugs. Look up the unique interactions for each and discuss the potential benefits and risks of your current medications with your doctor or pharmacist before adding amino acids:
As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.
Many Western diets provide more protein than the body needs, causing excess nitrogen to be excreted as urea in urine. The excess nitrogen has been linked in some studies with reduced kidney function in old age. Some, but not all studies have found that when people have impaired kidney function, restricting dietary intake of protein slows the rate of decline of kidney function.3
Excessive protein intake also can increase excretion of calcium, and some evidence has linked high-protein diets with osteoporosis,4 particularly regarding animal protein.5 On the other hand, some protein is needed for bone formation. A double-blind study showed that elderly people whose diets provided slightly less than the recommended amount of protein suffered less bone loss if they consumed an additional 20 grams of protein per day.6 A doctor can help people assess their protein intake and needs.
Amino acids include several different nutrients, each of which has the potential for side effects. Look up the unique side effects for each and discuss the potential benefits and risks with your doctor or pharmacist:
1. Lemon P. Is increased dietary protein necessary or beneficial for individuals with a physically active lifestyle? Nutr Rev 1996;54(4 Pt 2):S169–75 [review].
2. Young VR, Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr 1994;59(suppl):1203S–12S.
3. Sitprija V, Suvanpha R. Low protein diet and chronic renal failure in Buddhist monks. BMJ 1983;287:469–71.
4. Heaney R. Protein intake and the calcium economy. J Am Diet Assoc 1993;93:1259–60 [review].
5. Abelow BJ, Holford TR, Insogna KL. Cross-cultural association between dietary animal protein and hip fracture: a hypothesis. Calcif Tiss Int 1992;50:14–8.
6. Schürch MA, Rizzoli R, Slosman D, et al. Protein supplements increase serum insulin-like growth factor-I levels and attenuate proximal femur bone loss in patients with recent hip fracture. Ann Intern Med 1998;128:801–9.
The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2014.
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