University of Sydney finds diet reduces biological age

University of Sydney researchers reported that a four-week diet change shifted biological-age markers in older adults, adding short-term human data to a field that often relies on longer observational studies or animal work. The findings, published in *Aging Cell* on May 12, came from a randomized trial of 104 adults aged 65 to 75. (sydney.edu.au) Researchers said participants who reduced dietary fat or replaced more animal protein with plant sources showed reductions in biological age based on biomarker profiles, while the diet that stayed closest to a typical high-fat omnivorous pattern did not. The study does not show that aging itself was reversed in a durable way. The paper said the observed changes may reflect short-term physiological responsiveness to diet rather than a changed long-run aging trajectory, and the authors called for longer trials to test whether the biomarker shifts translate into lower disease risk. (sydney.edu.au) ### What exactly did the researchers test? The University of Sydney said 104 participants were randomly assigned to one of four diets for four weeks, with each diet providing 14% of energy from protein. Two diets were omnivorous, with protein split between animal and plant sources, and two were semi-vegetarian, with 70% of protein coming from plants. Within each category, one diet was higher in fat and lower in carbohydrates, and the other was lower in fat and higher in carbohydrates. (sydney.edu.au) The four groups were labeled omnivorous high-fat, omnivorous high-carbohydrate, semi-vegetarian high-fat, and semi-vegetarian high-carbohydrate. The university said participants were non-smokers, non-vegetarians, had body-mass indexes from 20 to 35, and did not have serious conditions such as type 2 diabetes, cancer, renal disease or liver disease. (onlinelibrary.wiley.com) ### What do they mean by “biological age”? The researchers used 20 biomarkers, including cholesterol, insulin and C-reactive protein, to generate a biological-age score. The University of Sydney said biological aging varies between individuals and that biomarker profiles are often used as a proxy for overall physiological status and potential longevity, in contrast to chronological age, which simply counts years lived. (sydney.edu.au) The *Aging Cell* paper described the measure as KDM-derived delta age, a biomarker-based estimate that appeared responsive to dietary change within four weeks. The authors said that responsiveness could make it useful for tracking short-term shifts in physiological state, but they cautioned against reading it as proof of lasting age reversal. (sydney.edu.au) ### Which diet pattern performed best? Yahoo Health and the university’s summary both said the strongest improvements came from diets richer in complex carbohydrates and plant-based components. The omnivorous high-carbohydrate group showed a significant reduction relative to the omnivorous high-fat group, while the semi-vegetarian groups also showed reductions, though not every comparison reached statistical significance. (sydney.edu.au) The omnivorous high-fat group showed no meaningful change. University of Sydney researchers said that group’s revised diet most closely resembled participants’ baseline eating patterns, making it the clearest non-response group in the trial. (onlinelibrary.wiley.com) ### Why are the authors being careful about the claim? Dr. Caitlin Andrews of the University of Sydney’s School of Life and Environmental Sciences said the work offers a preliminary indication rather than a conclusive result. The paper said longer-term treatment would be needed to determine whether the measured changes predict lower age-related disease risk and whether similar effects appear in other age groups. (health.yahoo.com) The next step is in the journal record rather than a new intervention date: the *Aging Cell* paper, “Short-Term Dietary Intervention Alters Physiological Profiles Relevant to Ageing,” sets out the trial design and the authors’ call for longer-term follow-up. (onlinelibrary.wiley.com) (sydney.edu.au)