Pay Attention to Protein Intake

Thursday, June 21, 2007 - 5:51pm

By Donna Feldman, MS, RD

As people age, metabolism slows and health concerns increase. Diets are tweaked to lower fat and calories and increase fiber, calcium, and antioxidants. For many seniors, protein is the last thing on their list of health concerns. Changes in taste preferences and decrease in appetite limits consumption of high protein foods like meats. If this sounds like you, maybe it's time to do a quick check-up on your protein intake. There is evidence that aging may increase protein needs.

Am I getting enough protein? 

How do we know how much protein is enough? By measuring nitrogen. The building blocks of protein and amino acids all contain nitrogen. When protein is metabolized, the nitrogen is released and flushed out by the kidneys. Comparing nitrogen IN (protein intake) with nitrogen OUT (in urine) is the standard method of determining whether a person is getting the right amount of protein.

Ideally, for adults, nitrogen-in matches nitrogen-out. If you are losing less nitrogen than you are consuming in food, you are retaining protein. This is normal for kids who are growing or for someone is building muscle by increasing exercise. Losing more nitrogen than you consume means protein-rich tissue, like muscle, is breaking down. There are many possible causes for this, such as illness, stress, or chronic inactivity. For older people, gradual, long-term decline in muscle mass, or sarcopenia, is cause for concern. It is difficult for anyone to rebuild lost muscle tissue, especially frail elderly people. Some researchers believe increasing recommended protein intake for seniors can reverse this decline.  Not everyone agrees that this is the solution.

What's the evidence for more protein?

The current recommendation for protein intake for healthy adults is 0.8 g protein per kilogram of body weight per day. This number was determined using studies on healthy young adults. Nitrogen balance studies on older adults have conflicting results. Some show that protein utilization is less efficient in elderly subjects and that higher intake would be beneficial. One researcher suggested the recommendation should be 1-1.3 g/kg for older people.1 Others disagree, claiming the 0.8g/kg recommendation is fine for all adults. One point that everyone can agree on is this: Older people are more likely to be affected by illness, loss of appetite, and unknown effects of medications, and these factors may have adverse effects on protein intake and protein metabolism.2, 3

Another very important piece of this puzzle is physical activity. "Use It Or Lose It" should be your motto as you age. Muscles need the stimulation of activity to stay healthy. No amount of extra protein will compensate for lack of activity. Exercise, including aerobic activity like walking, biking, or swimming, as well as weight training, is critical to avoid the gradual decline in muscle mass.

How much protein is enough?

To meet the current recommendation of 0.8 g/kg/day, a 180-pound man would need 65 grams of protein and a 135-pound woman would need about 50 grams. An ounce of lean meat, chicken, or fish has about 7 grams, a cup of either non-fat milk or soy milk has 8 grams, an egg has 6 grams, and an ounce of cheese 6-7 grams. If the man ate two 4-oz servings of meat per day plus an egg or a glass of milk, then his total protein would be more than 65 grams once the smaller amounts in all the other foods like bread, cereals and vegetables were added in. These servings might sound modest, but keep in mind, this amount must be eaten every day. If appetite decreases and taste preferences change, protein intake can easily fall below even the minimal amount. A diet that emphasizes softer, easier-to-chew items like bread, pasta, cooked vegetables, juices, and sweets could easily end up being low in protein.

Protein check-up

If you are generally healthy and active, don't panic. A quick assessment of your protein intake will show whether you need to increase your intake of high-protein foods. Use the rough estimates for protein in food above, check labels for protein on packaged food, and consult the web for additional information. Include adequate high-quality protein foods every day to ensure you are getting at least the recommended intake, about 50 grams for most women and 65-70 grams for most men.

Conclusion: maintain muscle mass as you age by eating protein and performing physical activity

It is hard to rebuild lost muscle tissue. Pay attention to your protein intake and physical activity so you maintain your muscle mass. When it comes to maintaining muscle mass as you age, an ounce of prevention is well worth the effort.

1. J.A.Morais. J Nutr Health Aging. 2006 Jul-Aug;10(4):272-83.

2. J Gerontol A Biol Sci Med Sci. 2001 Nov;56(11):M724-30.

3. American Journal of Clinical Nutrition, Vol. 77, No. 1, 109-127, January 2003.