Four-Week Diet Changes Reduce Biological Age in Older Adults

Older Australians who reduce either dietary fat or animal-based protein show signs of reduced biological age, new research from the University of Sydney shows. Published in Aging Cell, the findings revealed 65- to 75-year-olds subjected to dietary intervention for just four weeks showed a reduction in 'biological age' based on their biomarker profile.

Scientists estimate biological age using biomarker profiles, measures of physiological function over time which are often considered a better indicator of overall health and potential longevity than chronological age. The research integrated data from 20 different biomarkers - including blood levels of cholesterol, insulin and C-reactive protein - to calculate a biological age score for participants in the Nutrition for Healthy Living study, undertaken at the University's Charles Perkins Centre.

In the Nutrition for Healthy Living study, 104 participants were randomly assigned to one of four diets, each deriving 14 percent of energy from protein. Two were omnivorous (half coming from animal sources and the rest from plants) and two were semi-vegetarian (with 70 percent of protein coming from plant sources). Within the omnivorous and semi-vegetarian categories participants were then assigned to diets either high in fat and low in carbohydrates or low in fat and high in carbohydrates, resulting in four categories of diet: omnivorous high-fat (OHF), omnivorous high-carbohydrate (OHC), semi-vegetarian high-fat (VHF), or semi-vegetarian high-carbohydrate (VHC). Participants' BMI (body mass index) ranged from 20-35. All participants were non-smokers, non-vegetarians and had no serious complications (e.g., type-2 diabetes mellitus, cancers, renal or liver disease) or food allergies and/or intolerances.

The OHF group, whose amended diets most closely resembled participants' baseline diets, showed no meaningful change in the 'biological age' of their biomarker profile. However, the biological age of the biomarker profile for those in the remaining three groups showed reductions. The reduction in biological age among the OHC group – those who ate omnivorous diets high in carbohydrates – was estimated with the highest degree of statistical confidence. This group's diet comprised 14 percent of energy from protein, 28-29 percent from fat, and 53 percent from carbohydrates.

It is unclear whether the impact of dietary changes on age-related biomarker profiles is enduring and results in sustained biological age reversal. The researchers said longer-term dietary changes are needed to assess whether dietary changes alter the risk of age-related diseases. They also cautioned that it is too soon to say definitively that specific changes to diet will extend your life, but the research offers an early indication of the potential benefits of dietary changes later in life. Future research should explore whether these findings extend to other cohorts and whether the changes recorded are sustained or predictive of long-term outcomes.