Reasons for a Simple Diet

August 22, 2025

Discover what research reveals about diet and healthy ageing

Fewer than one in ten individuals reach their seventies without developing at least one significant disease or impairment, according to recent research. Yet, scientists have uncovered that a straightforward diet can help middle-aged adults delay health decline as they grow older.

Researchers analysed data from more than 100,000 participants over a 30-year period and discovered that just 9.3 percent of older adults could be classified as genuinely “healthy.” Notably, members of this group shared common dietary habits, reinforcing the influence of nutrition on long-term risks for disease and physical, mental, or neurodegenerative conditions.

Those in the healthiest 9.3 percent typically consumed diets abundant in fruits, vegetables, whole grains, unsaturated fats, nuts, legumes, and low-fat dairy products. Conversely, individuals with diets high in sodium, sugary drinks, trans fats, red meat, and processed meats were least likely to be considered healthy.

“Healthy ageing” was defined as surviving to age 70 without any of 11 major chronic diseases and without cognitive, physical, or mental health impairments. These diseases included cancer (excluding non-melanoma skin cancers), diabetes, heart attack, coronary artery disease, heart failure, stroke, kidney failure, chronic obstructive pulmonary disease, Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis.

Published in the journal Nature Medicine, the study involved 105,015 middle-aged Americans, averaging 53 years old at the outset, who were followed for up to three decades. Their diets and any emerging health conditions were carefully tracked over time. Of all the participants, only 9,771 achieved “healthy ageing.”

Researchers compared eight different diet quality scoring systems, including Mediterranean-style and plant-based diets. They found the strongest association with healthy ageing among those who scored highest on the Alternative Healthy Eating Index, which rates consumption of six types of vegetables, whole fruit, whole grains, sugar-sweetened beverages, nuts, legumes, and red or processed meats. Additional nutrient-based scores included measures for trans and long-chain fats, sodium, and calcium.

The study authors observed, “Diet is the leading behavioural risk factor for death and chronic disease globally, and is the second such risk factor—after tobacco use—among older adults in the US.”

“Understanding how diet relates to healthy ageing is particularly important as populations age around the world. However, how dietary choices made in midlife impact health in later years remains to be fully understood.”

In conclusion, the researchers stated: “Our findings suggest that dietary patterns rich in plant-based foods, with the moderate inclusion of healthy animal-based foods, may improve overall healthy ageing and inform future dietary guidelines.”

What is a healthy diet?

Fruit and veg Mediterranean Diet Score tools suggest at least two servings of vegetables every day, and three of fruit. Variety, including leafy greens, is important.

Whole grains Minimise refined and processed grains.

Nuts Walnuts, almonds and hazelnuts are rich in nutrients.

Fish At least three servings of fish or seafood each week, with oily fish such as mackerel being an excellent source of omega-3 fatty acids.

Healthy fats Olive oil is a key part of Mediterranean diets, and high in monounsaturated fat.

Meat Prefer white meat such as chicken to red or processed meats.

Drink Low amounts of sugar-sweetened beverages, preferring water or milk. The Mediterranean diet typically includes a small daily glass of red wine, but doctors say there is no evidence teetotallers should start drinking alcohol.

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