How Much Protein?

By Paulette Lambert, RD, CDE Director of Nutrition California Health & Longevity Institute

Protein is a hot topic in nutrition and the marketing campaigns of food products, generating myriad “high-protein” foods in the marketplace as well as continued questions from consumers as to dietary recommendations. Despite the continued push among food pro­ducers to create protein-rich offer­ings, according to the US Depart­ment of Health and Human Services Dietary Guidelines for Americans, the reality is that “inadequate pro­tein in the US population is rare.”1

So what should we know about the role protein should play in our diet? Do we really need as much as many food companies would have us believe?

For years the recommended daily allowance (RDA) has been 0.36 grams (g) of protein per pound of body weight (a woman weighing 125 pounds, for example, would require 45 g of protein per day).2 Current protein standards, however, are based on studies conducted with younger adults, many of which were completed 50 years ago. Now, with increased interest among the aging adult population in updated guide­lines that are appropriately specific to age and weight, recommenda­tions are being reviewed and revised.

In the past year, the Interna­tional Osteoporosis Foundation and the European Society for Clinical Nutrition and Metabo­lism reviewed the latest research and have come to this conclusion: to preserve muscle mass and stay healthy longer, older adults (60-plus years) should increase their protein intake from 0.36 to 0.54 g per pound of body weight.3,4

Age-appropriate recommenda­tions are important because we lose muscle mass as we age—1 percent per year after age 30 and twice that much by age 70—a process known in medical terminology as sarcope­nia. Muscle mass not only makes you look fit but it is critical for movement, everything from basic functions like walking up and down the stairs and carrying grocery bags to exercise and other desired recreational pur­suits. Loss of muscle mass can limit your lifestyle and can cause fragility in old age.

Research into the full range of benefits that sufficient protein provides is ongoing. The Women’s Health Initiative observational study, which followed 24,000 women age 65 or older for three years, con­cluded that the women consuming 0.54 g of protein per pound of body weight daily resulted in 32 percent less likelihood of becoming frail and was related to an increase in muscle strength.5 Some short-term studies have shown that having a consistent intake of protein throughout the day, at each meal, can make the differ­ence in how much muscle synthesis occurs; those who had adequate pro­tein throughout the day did better than those who had little and then a lot at one time.6 Other research showed that getting more than the recommended daily amount of 0.54 g per pound did not result in more muscle gain or an increase in strength.7

Additional research is also reflect­ing the role protein can play in weight loss. Preliminary studies show that adequate protein intake of 0.36 to 0.54 g had a modest effect on decreas­ing the appetite, but a high-protein diet resulted in no greater weight loss than one including just adequate protein when both diets included the same number of calories. Other stud­ies have investigated concerns that too much protein can cause cancer, bone loss, or kidney disease; at this point research suggests that that is not the case.8,9,10,11

We are clearly still learning from ongoing research about all the dif­ferent ways that protein intake can affect our health. As studies continue to deliver additional information, the following guidelines can serve as a basic plan for incorporating protein in our diets.

  • Aim for 0.5 g of protein per pound of body weight after age 60.
  • Avoid excessive amounts of animal protein, which can increase risk factors for heart disease and can be a source of extra calories that cause unwanted weight gain.
  • Choosing plant-based protein and limiting intake of animal protein is generally a good idea; it not only improves your health but benefits the planet as well.
  • You do get small amounts of protein from grains and vegetables (approximately 15 20 g per day), so factor that into your total protein needs each day.
  • One ounce of protein is equivalent to 7 g.
  • In terms of consuming meat, fish, poultry, and dairy, 7 to 8 ounces is recommended for most women, and 10 to 11 ounces is recommended for most men.

And remember, though protein intake plays a big role in building necessary muscle mass as you age, it is critical to incorporate strength train­ing into your exercise routine (three times per week); diet alone will not ensure that you maintain the muscle strength you need to live a healthy, active life.

References

  1. Dietary Guidelines for Americans 2010. US Office of Disease Prevention and Health Promotion website. Available at: http://www.health.gov/dietaryguidelines/dga2010/dietaryguidelines2010. pdf. Accessed December 29, 2014.
  2. Nutrition for Everyone: Protein. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/nutrition/everyone/basics/protein.html. Accessed December 29, 2014.
  3. Mithal A, Bonjour JP, Boonen S, et al. Impact of nutrition on muscle mass, strength, and performance in older adults. Osteoporosis International. 2013;24(5):1555-66. doi: 10.1007/s00198-012-2236-y.
  4. Gjessing PF, Constantin-Teodosiu D, Hagve M, Lobo DN, Revhaug A, Irtun Ø. Preoperative carbohydrate supplementation attenuates post-surgery insulin resistance via reduced inflammatory inhibition of the insulin-mediated restraint on muscle pyruvate dehydrogenase kinase 4 expression. Clinical Nutrition [early online publication]. December 11, 2014. doi: 10.1016/j.clnu.2014.12.004.
  5. Beasley JM, LaCroix AZ, Neuhouser ML, et al. Protein intake and incident frailty in the Women’s Health Initiative observational study. Journal of the American Geriatrics Society. 2010;58(6):1063-71. doi: 10.1111/j.1532-5415.2010.02866.x.
  6. Mamerow MM, Mettler JA, English KL, et al. Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. Journal of Nutrition. 2014;144(6):876-80. doi: 10.3945/jn.113.185280.
  7. Symons TB, Sheffield-Moore M, Wolfe RR, Paddon-Jones D. A moderate serving of highquality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects. Journal of the American Dietetic Association. 2009;109(9);1582-86. doi: 10.1016/j.jada.2009.06.369.
  8. Latest Research: The Expert Report. American Institute for Cancer Research website. Available at: aicr.org/research/research_science_expert_report. html. Accessed December 29, 2014.
  9. Cao JJ, Johnson LK, Hunt JR. A diet high in meat protein and potential renal acid load increases fractional calcium absorption and urinary calcium excretion without affecting markers of bone resorption or formation in postmenopausal women. Journal of Nutrition. 2011;141(3):391-97. doi:10.3945/jn.110.129361.
  10. Kerstetter JE, O’Brien KO, Insogna KL. Dietary protein affects intestinal calcium absorption. American Journal of Clinical Nutrition. 1998;68(4):859-65.
  11. Beasley JM, Katz R, Shlipak M, Rifkin DE, Siscovick D, Kaplan R. Dietary protein intake and change in estimated GFR in the Cardiovascular Health Study. Nutrition. 2014;30(7-8):794-99. doi:10.1016/j.nut.2013.12.006.
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