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by Margery D. Rosen
Updated August 19, 2022
For years nutritionists have railed against the evils of three dietary villains — trans fats, sodium and added sugars — usually in terms of what they do to your heart and waistline. Now there's research showing these culprits can take a toll on the health of your brain, too.
Trans fats are processed fats added to foods to extend their shelf life. These fats are double trouble — they both raise blood levels of "bad" cholesterol and lower levels of "good" cholesterol. Still, the FDA announced on June 18, 2015, it is phasing out the use of partially hydrogenated oils, the primary source of trans fat in food, within about three years.
Gene L. Bowman, a brain nutrition researcher at Oregon Health & Science University, has done research that suggests trans fats are bad for the brain. When his team checked the blood levels of certain nutrients in 104 elderly participants, they found that those whose blood was high in trans fats had significantly lower cognitive performance and less total brain volume than those who ate a healthier diet.
Similarly, too much sodium can be just as bad on the brain as it is on the heart. A study by Canadian scientists has found that older people who eat too much salt and also fail to exercise are at increased risk for cognitive decline. According to the U.S. Department of Agriculture, if you're 51 and older or suffer from high blood pressure, your salt intake should max out at no more than 1,500 milligrams a day.
Most people get to 1,500 milligrams a day eating a normal, well-balanced diet, but can shoot past 1,500 milligrams loading up on processed and packaged foods like pasta sauces, soups and cookies and adding salt to food at the table.
Rounding out the deadly trio are sugars and simple carbs. So many studies have shown a link between dementia and obesity and high blood sugar at midlife that Alzheimer's disease has been dubbed "diabetes Type 3." Mayo Clinic scientists found that people age 70 and older who ate a lot of simple carbohydrates (found in refined flours and rice) and sugar were nearly four times more likely to develop mild cognitive impairment than those who ate a healthier diet.
Your body does need a certain amount of sugar (glucose) to function properly. But a diet packed with sugar and the simple carbs regularly sends blood glucose soaring. High glucose levels, in turn, block blood flow to the brain, depriving it of the energy it needs to generate new neurons. Too much glucose has also been implicated in the formation of the tangles of Alzheimer's disease.
While it may be costly and definitely not as tasty to cut out some of these foods, consuming them in moderation will go a long way for not just the brain but the whole body.
• “Nutrient biomarker patterns, cognitive function, and MRI measures of brain aging,” Neurology, December 2011. In this study, researchers compared the cognitive function and total cerebral brain volume of 104 older adults (average age of 87) with varying nutrient levels in their blood. Participants with high levels of trans fats in their blood were found to have lower cognitive function and less total cerebral brain volume than other participants. Read a summary of the study. (A fee is required to access the full study.)
• “Sodium intake and physical activity impact cognitive maintenance in older adults: the NuAge Study,” Neurobiology of Aging, April 2012. In this study, participants (ages 67 to 84) completed questionnaires to determine their sodium intake and physical activity level. Researchers then administered a mental examination to assess for cognitive function and repeated this test annually for three years. Participants in the low physical activity group who consumed relatively low amounts of sodium showed better cognitive performance over time compared to those who consumed higher amounts of sodium. There was no association between sodium intake and cognitive function over time for participants in the high physical activity group. Read a summary of the study. (A fee is required to access the full study.)
• “Relative Intake of Macronutrients Impacts Risk of Mild Cognitive Impairment or Dementia,” Journal of Alzheimer’s Disease, January 2012. In this study, 1,233 older adults (ages 70 to 89) were given a questionnaire to determine the percent of total daily calories they derived from protein, carbohydrate and total fat. Researchers then conducted testing for mild cognitive impairment every 15 months for a range of 2.5 to 3.9 years. The risk of mild cognitive impairment increased for those with high carbohydrate intake. As a population study, this research shows a correlation but does not prove cause and effect. Read a summary of the study. (A fee is required to access the full study.)