Study: A Healthy Diet May Be Undermined by Including Unhealthy Foods

Researchers at Rush University Medical Center have found that although eating well has a positive impact on health, including unhealthy foods in an otherwise healthy diet can diminish its benefits.

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Researchers at Rush University Medical Center have found that although eating well has a positive impact on health, including unhealthy foods in an otherwise healthy diet can diminish its benefits. In particular, they examined the effects of unhealthy foods when added to the Mediterranean diet, which is associated with slower rates of cognitive decline in older adults.

The observational study examined 5,001 older adults who were part of the Chicago Health and Aging Project, an evaluation of cognitive health in adults over the age of 65 conducted from 1993 to 2012. Every three years, study participants completed a cognitive assessment questionnaire and a questionnaire about the frequency with which they consumed 144 food items. 

The researchers examined the following factors: 

  • How closely each of the study participants adhered to a Mediterranean diet, which included daily consumption of fruit, vegetables, legumes, olive oil, fish, potatoes and unrefined cereals, plus moderate wine consumption. 
  • How much each participant followed a Western diet, which included fried foods, refined grains, sweets, red and processed meats, full-fat dairy products and pizza.  
  • The association between Mediterranean diet adherence and changes in participants' cognitive function, memory and perceptual speed.

Participants with slower cognitive decline over the course of the study were those who adhered closest to the Mediterranean diet, along with limiting foods in the Western diet. Conversely, those who ate more of the Western-associated foods had no beneficial effect of healthy food components (in terms of slowing cognitive decline).  

"Eating a diet that emphasizes vegetables, fruit, fish and whole grains may positively affects a person's health," said Puja Agarwal, PhD, a nutritional epidemiologist and assistant professor in the Department of Internal Medicine at Rush Medical College. "But when it is combined with fried food, sweets, refined grains, red meat and processed meat, we observed that the benefits of eating the Mediterranean part of the diet seems to be diminished. 

"The more we can incorporate green leafy vegetables, other vegetables, berries, olive oil, and fish into our diets, the better it is for our aging brains and bodies. Other studies show that red and processed meat, fried food and low whole grains intake are associated with higher inflammation and faster cognitive decline in older ages," added Agarwal. "To benefit from diets such as the Mediterranean diet, or MIND diet, we would have to limit our consumption of processed foods and other unhealthy foods such as fried foods and sweets."  

These results were published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association


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