Protein Needs of Mature Adults

Research is beginning to show that certain nutrients might play a role in slowing sarcopenia. Protein is one of them. Eating extra protein will not enlarge muscles, but in 1995, a Tufts University study raised the question whether muscle loss in later years could be partly due to a chronic protein deficiency among older people.

Researchers found that older women who ate protein at half the recommended level lost lean tissue after just 8 weeks and showed declines not just in muscle function but in immune response as well. Women whose diets were adequate in protein had no such declines. The body has to compensate for everyday protein losses from skin, nails, hair, sweat, and body fluids, explains Carmen Castaneda-Sceppa, MD, Ph.D., head of the Nutrition, Exercise Physiology, and Sarcopenia Laboratory at Tufts. She noted that if daily protein intake is not enough, the body uses muscle as a resource for amino acids, the building blocks of protein. Poor protein intake does not just contribute to muscle loss from within; it also prevents proper muscle maintenance due to the absence of adequate building materials.

The idea that a chronic lack of protein depletes muscle reservoirs in older people makes sense, especially when you consider that many seniors are eating less protein than they should. In fact, an estimated one in three people over the age of 60 eats less than the current recommendation of 0.36 grams of protein per pound of body weight (or 0.8 g/kg). This would be 54 grams a day for a 150-lb person. Some research suggests that older people need even more protein than originally thought.

One study at Tufts, for instance, advised adults over the age of 55 to eat about 0.45 grams per pound (or 1 g/kg), which is the equivalent of 68 grams for a 150-pound person. This greater need might be due to a lower efficiency of dietary protein utilization (Wardlaw, 1999).

Experts are still debating the “correct” protein intake for older adults. In any case, make sure seniors are getting at least the current recommended amount of 0.36 g/lb of body weight to thwart off depletion of lean tissue in the body.

For decades, there has been controversy regarding whether a diet rich in protein is good for bone or detrimental to bone. A 2003 study investigated just that. Scientists considered the association between protein intake and change in bone mineral density in a group of women and men aged 65 and older. Half of the participants received a calcium/vitamin D supplement and the other half received a placebo pill.

The results of the study demonstrated that the women and men who had a diet rich in protein had the most favorable change in bone density over a 3-year period. What is interesting is that this beneficial effect was only seen in the group that also received the calcium/vitamin D supplement. Those individuals who consumed a diet rich in protein but who did not supplement with calcium and vitamin D did not receive a benefit from the protein rich diet. In fact, the protein-only group had an increase in fractures over the three-year study period.

How much protein is needed to receive this benefit? In the aforementioned study, the women and men who benefited most were those whose protein intake averaged about 20% of calories, or approximately 87 grams of protein a day. However, caution is warranted because numerous studies have shown that a high protein diet (over 30% of calories) is detrimental to bones.

About the Author

Tammy Petersen, B.S., M.S.E., is the Managing Partner for the American Academy of Health and Fitness. She has written two books on adult fitness and designed corresponding training programs. Tammy’s educational background includes Bachelor of Science degrees in marketing and economics from Pittsburg State University, Pittsburg, Kansas. She holds a Master of Science in Education in the area of health and fitness, with an emphasis in geriatrics, from the University of Kansas, Lawrence, Kansas.

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