CONSUMING a diet high in animal protein could prevent higher-level functional decline in aging individuals, according to results of a new study published in the Journal of the American Geriatrics Society.
The research comes at an appropriate time as the world's population is not only escalating but also aging: By 2050, the number of people ages 65 years and older is estimated to be just fewer than 1.5 billion, or 65% of the global total.
With life expectancies increasing in many countries, the number of older people with declining cognitive and physical abilities is also rising.
Functional decline can have profound effects on the health and well-being of older individuals — by preventing them from conducting normal daily activities and living healthy lifestyles — as well as their caregivers, in addition to draining health care resources.
The new research was conducted by Dr. Megumi Tsubota-Utsugi with the National Institute of Health & Nutrition in Japan and her colleagues at Tohoku University and Teikyo University in Japan.
"Identifying nutritional factors that contribute to maintaining higher-level functional capacity is important for prevention of future deterioration of activities of daily living," Tsubota-Utsugi said.
The study involved 1,007 Japanese adults who resided in a community dwelling and whose average age was 67.4 years old.
Each individual was assessed for physical, psychological and social function impairment, as well as for measures related to activities of daily living. The assessment could identify individuals with a high risk of developing disabilities.
At the start of the study, researchers had participants complete a food questionnaire. Seven years later, the same individuals completed the same questionnaire.
The participants were divided into four groups according to their intake levels of total protein, animal protein and plant protein.
After examining the intake results to determine an association with higher-level functional decline, no consistent association was observed between plant protein consumption and future higher-level functional decline in either men or women.
However, the study determined that elderly men who consumed animal protein daily had a 39% decreased chance of experiencing higher-level functional decline, although the same result did not hold true for older women consuming animal protein.
Still, Tsubota-Utsugi explained that animal protein can play an important role in the diet of aging populations.
"Along with other modifiable health behaviors, a diet rich in protein may help older adults maintain their functional capacity," Tsubota-Utsugi noted.
At any age, daily food choices play a vital role in health. Since total calorie intake is important for maintaining a healthy lifestyle, it is essential to focus on nutrient-dense foods — those that provide the most nutrition per calorie.
In general, proteins help the body build and repair tissue, along with fighting infection. Any extra protein is utilized by the body for energy.
Animal proteins — meat, dairy and poultry products — are nutrient-dense foods that also contribute B vitamins, vitamin E, iron, zinc and magnesium to the diet. Consuming leaner forms of meat and poultry can reduce the intake of solid fats.
Based on a 3 oz. serving of nutrient-rich animal proteins:
* A skinless chicken breast can provide 23 g of protein at 110 calories;
* A lean pork chop can provide 23 g of protein at 153 calories, and
* A cut of lean beef can provide 25 g of protein at 180 calories.
In comparison, a 3 oz. vegetarian burger provides 11 g of protein at 115 calories.
Therefore, among the 3 oz. protein options listed, it would take a minimum of two servings of a plant-based protein source to equal the same amount of protein in animal-based sources — and this does not reflect the additional nutrients poultry and meat can provide in one serving.
Based on the 2010 U.S. Department of Agriculture dietary guidelines, the recommended daily amount of proteins consumed by adults who get 30 minutes of daily activity actually decreases with age.
For example, the guidelines recommend that men ages 19-30 should eat 5.5 oz. of protein per day, while men older than 30 are encouraged to consume 5 oz.
According to the Agricultural Research Service's 2012 "Nutrient Intake from Food," U.S. males over 60 years of age are consuming, on average, 2.62-3.14 oz. of protein per day, while women of the same age are eating 2.12-2.36 oz., which is lower than the actual daily dietary guidelines.
In 2011, Tufts University, in coordination with USDA, adapted MyPlate for older adults that recommends consuming fewer calories but not necessarily fewer nutrients (Infographic). In particular, those dietary guidelines recommend consuming 5-7 oz. of protein, depending on a person's activity level and specific dietary requirements.
"Although calorie needs decline with age due to a slowdown in metabolism and physical activity, nutritional requirements remain the same or, in some cases, increase," explained Alice H. Lichtenstein, senior scientist and director of the Cardiovascular Nutrition Laboratory at the USDA Human Nutrition Research Center on Aging.
Recent research has suggested that, over time, people's ability to absorb or process protein may decline with age. Therefore, the amount of protein required may need to increase with age.
In addition, results from the "Health, Aging & Body Composition Study" suggested that eating animal protein — not plant protein — is associated with lean mass change in elderly people.
Animal proteins are considered to have a higher biological value than plant proteins because they provide essential amino acids that stimulate muscle production — a key to reducing future higher-level functional decline.
As indicated in the results of the Japanese research, the association between increased animal protein intake and reduced future higher-level functional decline was observed in men because the loss of skeletal muscle over time was greater for males. In addition, men who consumed less animal protein tended to eat more energy, carbohydrates and carbohydrate-containing foods such as rice, bread and pasta.
Overall, the researchers said to their knowledge, this is the first longitudinal cohort study of the relationship between animal protein and functional decline.
The results support the conclusion that, in general, eating less animal protein may contribute to future functional decline in people ages 60 and up, but more research is necessary to explain the response difference between men and women.