Trans fatty acids were banned in the U.S. as of June 2018, although some foods containing less than a half-gram of them can be labeled as containing zero. The World Health Organization has called for the elimination of trans fats worldwide by 2023. We’re still learning about the long-term negative effects of these fats, including new findings from Japan linking them to dementia.
Trans fatty acids (TFAs) are unnatural components of many processed fats, especially those that have been partially hydrogenated. Partial hydrogenation turns liquid oils into semisolid fats, much loved by manufacturers of processed foods for their longer shelf lives. Margarine, vegetable shortening, and most commercial baked goods contained these artificially hardened fats and, along with them, TFAs. We’ve long known that TFAs are bad for the heart and arteries. They increase total cholesterol; raise LDL (“bad”) cholesterol, and lower HDL (“good”) cholesterol. In addition, TFAs influence inflammation and probably have adverse effects on cell membranes and the immune system and may promote cancer and accelerate aging.
The link between TFAs and dementia was noted by Japanese researchers who measured blood levels of elaidic acid, the most common trans fat, in 1,628 men and women age 60 and older. None of the study participants had dementia at the time. Over the next 10 years, 377 of them developed some type of dementia. Those with the highest blood levels of elaidic acid were 50 percent more likely to develop any type of dementia and 39 percent more likely to develop Alzheimer’s disease than those with the lowest blood levels of this substance. (Because the study was observational, it could not prove cause and effect.) Lead researcher Toshiharu Ninomiya, M.D., Ph.D., of Kyushu University, noted that the effects of ingesting the small amounts of trans fats still legally permitted in foods is unclear.
An earlier study found an association between TFAs and sub-par performance in memory tests among young men (ages 20 to 45). Researchers at the University of California, San Diego, found that the more foods containing trans fats the men reported consuming, the worse their performance on 104-word memory tests. Results showed that for each additional gram of trans fat a man reported consuming, he misidentified an average of 0.76 words. Those whose consumption of trans fats was highest correctly recalled 11 to 12 fewer words than the participants’ overall average.
Study leader, Beatrice A. Golumb M.D., Ph.D., suggested that the oxidizing effects of trans fats may cause the death of brain cells essential to memory. She noted, however, that the study found only an association between high consumption of trans fats and poorer memory, not a cause-and-effect relationship.
Andrew Weil, M.D.
American Heart Association Meeting Report Abstract 15572, “Trans Fat Consumption is Linked to Diminished Memory in Working-aged Adults.” http://newsroom.heart.org/news/trans-fat-consumption-is-linked-to-diminished-memory-in-working-aged-adults, accessed November 19, 2014