A new study finds that people of 1914 may have had worse memory than people of 1814. The reason is partially hydrogenated oil - trans fats - that became a cheaper, healthier replacement for the saturated fats in butter. Crystallized cottonseed oil - Crisco - came onto the marketplace in 1911 and it revolutionized pie crusts but now the government says they should be banned and they now have a new reason why.

The reason is epidemiology and a new presentation at the American Heart Association's Scientific Sessions 2014. The authors found that 1,000 healthy men who said they consumed the most trans fats (self-reporting of things like doughnuts, crackers, movie theater popcorn, frozen pizza, coffee creamer, cake frosting) showed notably worse performance on a word memory test. The association was across things like age, education, ethnicity and depression. Correlation, meet causation.

The group included adults who had not been diagnosed with heart disease, including men age 20 or older and post-menopausal women. Participants completed a dietary questionnaire, from which the researchers estimated participants' trans fat consumption. To assess memory, researchers presented participants with a series of 104 cards showing words. Participants had to state whether each word was new or a word duplicated from a prior card.

They found:

  • Among men under age 45, those who ate more trans fats showed notably worse performance on the word memory test. The strength of the association remained even after taking into consideration things like age, education, ethnicity and depression.

  • Each additional gram a day of trans fats consumed was associated with an estimated 0.76 fewer words correctly recalled.

  • For those eating the highest amounts of trans fats, this translated to an estimated 11 fewer words (a more than 10 percent reduction in words remembered), compared to adults who ate the least trans fat. (The average number of words correctly recalled was 86.)

"Foods have different effects on oxidative stress and cell energy," said Beatrice A. Golomb, M.D., Ph.D., lead author and professor of medicine at the University of California-San Diego. In a previous study, we found chocolate, which is rich in antioxidants and positively impacts cell energy, is linked to better word memory in young to middle-aged adults. In this study, we looked at whether trans fats, which are prooxidant and linked adversely to cell energy, might show the opposite effect. And they did."

Oxidative stress is associated with the development of diseases such as heart disease and cancer.

Industrial trans fats are artificially produced to turn liquid oils into solids at room temperature and extend food shelf life. They can be found in margarines, fast foods, baked goods, snack foods, frozen pizza, coffee creamers and some refrigerated doughs. The Food and Drug Administration is taking further steps to reduce the amount of artificial trans fats in the U.S. food supply.

Analyses in younger women are needed to determine whether effects extend to this group, Golomb said.