Scientists have long studied whether changing what we eat can help us stay healthier as we grow older.
A study from the University of Wisconsin School of Medicine and Public Health suggests that reducing one common part of dietary protein, called isoleucine, may influence both health and lifespan.
The research was led by Professor Dudley Lamming and published in the journal Cell Metabolism. The experiments were carried out in mice, so the findings do not yet show that people will receive the same benefits.
Isoleucine is an amino acid, one of the small building blocks the body uses to make proteins. It is considered essential because the human body cannot produce it and must get it from food.
Many protein-rich foods contain isoleucine, including meat, eggs, dairy products, and soy. The nutrient is needed for normal growth, tissue repair, and other important body functions, which means people cannot simply remove it completely from their diets.
However, researchers have become interested in whether the amount people consume matters for long-term health.
Earlier research has suggested that the balance of different amino acids in food may affect metabolism, body weight, blood sugar, and the biological processes involved in aging.
In the study, scientists gave mice diets containing different amounts of isoleucine and followed their health as they aged. Some mice received a diet with lower levels of isoleucine, allowing the researchers to compare them with animals eating a more typical amount.
The differences were striking. Male mice eating less isoleucine lived about 33% longer, while female mice lived about 7% longer than mice on the comparison diet.
The benefits were not limited to lifespan. The animals eating less isoleucine also showed several signs of better health as they aged, suggesting that the dietary change affected more than simply how long they survived.
One surprising result involved body weight. The mice on the reduced-isoleucine diet actually ate more food, yet they remained leaner instead of gaining extra weight.
This suggests that lowering isoleucine changed the way their bodies used nutrients and managed energy. The effect could not be explained simply by the animals eating fewer calories.
The researchers also found improvements in blood sugar control, an important part of metabolic health. Poor blood sugar control can contribute to insulin resistance and type 2 diabetes, conditions that become more common with age.
Male mice receiving less isoleucine also showed less age-related prostate enlargement. In addition, the researchers observed differences in tumor development, adding to evidence that nutrient balance may influence several diseases associated with aging.
The findings raise an intriguing question: could people benefit from eating slightly less isoleucine? The answer is not yet known, and researchers caution that results from mice cannot automatically be applied to humans.
Because isoleucine is essential, cutting it too sharply could cause nutritional problems. The possible goal would therefore be to find a healthy level rather than trying to eliminate the amino acid.
The scientists also examined information from people participating in a Wisconsin health survey. They found an association suggesting that people with lower body weight tended to consume diets containing less isoleucine, although this does not prove that isoleucine was responsible for their weight.
Human diets are much more complicated than controlled laboratory diets given to mice. Genetics, exercise, total calorie intake, medications, health conditions, and many other nutrients can all affect body weight and aging.
Future research will need to determine whether modest isoleucine reduction is safe and useful for people and which foods or dietary patterns might achieve it without causing nutritional deficiencies. Scientists are also interested in understanding the biological pathways through which isoleucine influences metabolism and aging.
That knowledge might eventually lead to treatments that change how the body responds to isoleucine without requiring people to follow highly restrictive diets. For now, the research offers an interesting new direction in the science of aging, but it is not a reason for people to drastically cut protein or essential amino acids on their own.
If you care about wellness, please read studies about nutrients that could combat inflammation in older people, and essential foods for healthy aging.
For more health information, please see recent studies about the link between processed foods and chronic diseases, and a simple diet change for a healthier life after 65.
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