People worried about memory and brain health often wonder what actually helps. A new study points to a familiar but important theme: long-term diet quality was linked to better signs of cognitive aging, and the strongest links showed up when healthier eating patterns were in place during midlife.
In a study published in JAMA Neurology, researchers followed 159,347 adults across three long-running US studies of health professionals. They tracked eating habits over many years, then looked at two early signals of cognitive aging: people’s own reports of noticeable changes in memory or thinking and, in a subset of older women, performance on telephone-based thinking and memory tests.
The researchers compared six different “healthy diet” scores. One was the DASH eating pattern, which was originally designed to help control blood pressure. Others reflected overall diet quality, health-focused plant-based eating and patterns associated with lower impacts on insulin and inflammation.
Across all six patterns, people whose diets more closely matched the healthier patterns were less likely to report signs of cognitive decline later in life. The strongest association was seen with the DASH pattern. In simple terms, people who most closely followed a DASH-style pattern had a much lower likelihood of reporting cognitive decline than people whose diets least resembled it.
The timing stood out. The associations were most pronounced when people ate healthier during midlife, especially ages 45 to 54. That matters because brain diseases develop over a long time. It also suggests this is not only a “what you do after retirement” story.
In the subset with objective cognitive testing, the differences were smaller but still pointed in the same direction. Higher DASH adherence was associated with slightly better overall cognitive scores. The authors described the size of that difference as roughly equivalent to being about three-quarters of a year “younger” in cognitive aging. That is not a dramatic shift, but it is meaningful in a study looking at subtle early indicators, not diagnosed dementia.
When the researchers looked at food groups, the patterns were consistent with the headline message. Higher vegetable intake and higher fish intake were linked to better cognitive outcomes, while red and processed meats were linked to worse outcomes. Some findings were less intuitive, including an association between higher nuts and seeds intake and higher reports of cognitive decline. That does not prove nuts or seeds are harmful. In studies like this, unexpected results can show up because foods cluster in different ways across real diets and because self-reported eating is never perfectly measured.
This study does not prove that changing your diet will prevent dementia. It is observational, meaning it can show associations but cannot confirm cause and effect. Diet was self-reported and the study participants were mostly white and highly educated health professionals, which may limit how well the findings apply to everyone.
Still, the results add to a growing body of evidence that long-term diet quality is linked to brain health.
The long-running health studies used in this research are supported by the National Institutes of Health. This specific analysis was also supported by the Zhejiang University Global Partnership Fund and the Alzheimer’s Association. The authors report that the funders had no role in the study design, data analysis or the decision to submit the manuscript. Two authors reported receiving NIH grants during the study period. No other conflicts were reported.