Protein Requirements Go Up as We Age
Protein is required for a wide variety of body functions. The amino acids in dietary protein are also essential components in most hormones and all of the body’s enzymes, making protein intake a vital part of a healthy diet. The current recommended Daily Value is 0.8 gm of protein per kg (2.2 lb) of body weight per day for everyone regardless of age. New evidence indicates, however, that this is not enough for older individuals.
Twelve men and women, ages 56 to 80, stayed at the Tufts University Human Nutrition Research Center for 11 days, during which they consumed either 0.8 or 1.6 gm of protein per kg daily. They did not exercise during this period. The nitrogen-balance results were then extrapolated to calculate the real need. The researchers found that older people require 1 gm per kg to stay in positive nitrogen balance 25% more than young adults even though muscle mass tends to decline with age. This suggests that the body becomes less efficient at utilizing protein as the years progress.
Low-Protein Diet Reduces Strength and Immunity
Low protein intake is a common occurrence among senior citizens. The second National Health and Nutrition Examination Survey found that up to 25% of American women over the age of 55 consume less than 30 gm of protein per day. This has led nutritionists to examine the relationship between protein intake and the losses in lean body mass and immune function that are prevalent in this age group.
Six elderly women consumed a low-protein diet with 0.45 gm of protein per kg of body weight per day for nine weeks. The meals combined meat-free solid food with a milk-based drink. The results of this protein deficiency were devastating: Mean body-cell mass decreased by 8%, while the response to a delayed hypersensitivity skin test (a measure of immune function) dropped by 50%. Muscle strength also declined: There was a 12% decrease in the 1-RM for the bench press. The researchers said that the findings raise the question of whether changes that have been attributed to aging are actually due to chronic protein deficiency.
Age-Related Decline in Absorption
Everyone needs to consume enough amino acids to meet his or her metabolic requirements, and dietary protein is the only way to get it. But several studies have shown that many older individuals do not get enough. This occurs for two reasons: reduced intake and less efficient utilization by the body. Whether it’s for economic reasons or to reduce cholesterol, protein consumption tends to decline with age. Yet while you should cut back on the expensive, fat- and cholesterol-laden Porterhouse steaks, there are other protein sources that are less costly and virtually cholesterol-free. These include protein powders made from whey, casein, egg white and/or soy, and they give you all of the benefits of protein without the negatives.
The second main reason why older people don’t get enough protein is that protein requirements go up with age. “The digestive capacity of most people is comparable throughout life,” notes Wayne Campbell, PhD, of the Department of Foods and Nutrition at Purdue University. “The difference is what happens to the amino acids after they leave the intestines. There is a definite age-related decline in the percentage of amino acids that is absorbed into the splanchic region of the liver, so less is available for the muscles and organs to use.” Studies show that only 50% of consumed protein makes it into the bloodstream of older individuals dramatically less than the 75% that enters the blood of young people. The remaining protein is broken down in the liver, oxidized and excreted through the kidneys.
To make matters worse, there is an age-related shift in protein metabolism in favor of nonmuscle tissue. “The data show that the rate of muscle-protein synthesis in older sedentary people goes down by as much as 40%,” says Campbell, “even though total-body rates of protein building and breakdown do not vary much with age.” The good news is that weight training can stop this metabolic shift. Once the stimulus of weightlifting is introduced, the rate of muscle-protein synthesis goes up to the level of younger people. So your muscles are up to the task of getting bigger and stronger at any age as long as you challenge them and give them a reason to develop.
How to Get Enough
With the stakes this high, you really need to make an effort to consume enough protein. Yet while it may seem complex, measuring your protein intake is not that difficult. Here’s a simplified system that is sufficiently accurate to keep you on track. All portions are uncooked and skinless.
1/2 lb of chicken breast, turkey breast, lean ground
sirloin or salmon: 50 gm
1/2 lb of halibut or snapper: 45 gm
1/2 lb of cod or haddock: 40 gm
1 6-oz can albacore tuna: 35 gm
1 cup low-fat cottage cheese: 30 gm
6 extra-large egg whites: 25 gm
1 scoop protein powder: 17 to 25 gm depending on scoop size
1 cup milk (cow or soy) or 1 oz nonfat cheese: 10 gm
Part of a Balanced Diet
To hold on to the muscle you need to live actively, be sure to consume some protein with each meal. And be sure to eat enough carbs as well, because if you don’t, your body will oxidize some of your protein intake for fuel instead of using it for its intended muscle-building function.
Also, vary the protein sources you consume. Each source has its own unique blend of amino acids, so variety not only adds spice to your life, it also ensures that you get enough of the essential aminos. With your protein intake under control, you can look forward to healthy, strong muscles that will let you do the things you really enjoy in life.