Older adults can change important markers of aging in a surprisingly short period of time simply by changing what they eat.
New research from the University of Sydney found that Australians aged 65 to 75 who reduced dietary fat or animal protein showed signs of a lower biological age after just four weeks. Biological age is an estimate of how old the body appears based on its health and physiological condition, rather than the number of years a person has been alive.
The findings were published in aged cell and were led by Dr Caitlin Andrews from the School of Life and Environmental Sciences at the University of Sydney.
Although the results suggest that diet can relatively quickly influence health markers related to aging, the researchers emphasize that the findings are preliminary. Longer studies will be needed to determine whether the changes persist, whether they translate into a lower risk of age-related diseases, and whether similar effects occur in younger or different populations.
What really measures biological age
Everyone ages chronologically at the same rate, but biological aging does not necessarily follow the same schedule.
Two people of the same chronological age can differ considerably in cardiovascular health, metabolism, inflammation, and other measures of how well the body is functioning. These differences help explain why one person may remain relatively healthy and resilient later in life, while another develops age-related health problems earlier.
Scientists can estimate biological age by analyzing biomarkers, measurable characteristics of the body that provide information about health and physiological function. Researchers often use combinations of these markers to create a broader picture of how the body ages.
For this study, the team combined information from 20 different biomarkers, including blood levels of cholesterol, insulin, and C-reactive protein. C-reactive protein is commonly used as a measure of inflammation in the body.
Together, these measures were used to calculate the biological age score of participants in the Nutrition for Healthy Living study conducted at the University’s Charles Perkins Center.
Four different diets put to the test
The Nutrition for Healthy Living study included 104 participants who were randomly assigned to one of four diets.
Each diet provided 14 percent of total energy from protein. Two of the diets were omnivorous (half came from animal sources and the rest from plants), while the other two were semi-vegetarian (with 70 percent of the proteins coming from plant sources).
Within those groups, participants were assigned either a high-fat, low-carbohydrate diet or a low-fat, high-carbohydrate diet.
That produced four dietary groups: high-fat omnivores (OHF), high-carbohydrate omnivores (OHC), high-fat semi-vegetarians (VHF), or high-carbohydrate semi-vegetarians (VHC).
The BMI (body mass index) of the participants ranged from 20 to 35. All were non-smokers and non-vegetarians, and none had serious complications (e.g., type 2 diabetes mellitus, cancer, kidney or liver disease) or food allergies and/or intolerances.
Three diet groups showed younger biomarker profiles
The high-fat omnivore group did not experience any significant change in biological age calculated from their biomarker profiles. That diet was also the most similar to what the participants had been eating before the study began.
The other three groups, however, showed reductions in estimated biological age from their biomarker profiles.
The strongest statistical evidence appeared in the high-carbohydrate omnivore group. Those participants ate a diet in which 14 percent of energy came from protein, 28-29 percent from fat, and 53 percent from carbohydrates.
Taken together, the findings suggest that reducing dietary fat, animal protein, or both can influence aging-related biomarkers in older adults over a relatively short period.
However, a lower calculated biological age does not necessarily mean that the aging process itself has been permanently reversed.
Do the effects last?
Researchers do not yet know whether these changes in biomarker profiles will persist over time or lead to a sustained reversal of biological age.
They also cannot yet say whether the changes seen will ultimately reduce the risk of diseases associated with aging.
“Longer-term dietary changes are needed to assess whether dietary changes alter the risk of age-related diseases,” said Associate Professor Alistair Senior, from the School of Life and Environmental Sciences and the Charles Perkins Centre, who supervised the research.
Therefore, the study provides an early signal, rather than proof, that changing diet can extend life expectancy or permanently slow aging.
“It’s too early to say definitively that specific dietary changes will prolong life. But this research offers an early indication of the potential benefits of dietary changes later in life,” Dr. Andrews said.
“Future research should explore whether these findings extend to other cohorts and whether the changes reported are sustained or predict long-term outcomes.”