My friend Mike is a very health conscious individual. He exercises almost religiously every day and generally watches what he eats--except on weekends and special occasions. At such times, when confronted with a delicious looking dessert like cake, cookies, etc. he feels he has license to indulge because he otherwise takes good care of his health. Inevitably, most of these foods contain something beyond sugar that should never even be consumed even in moderation and that is trans-fats.
A little history about trans-fats. They were originally synthesized as a response to the health concerns raised about saturated fats and their relation to heart disease. Trans-fats are created by the "hydrogenation" or adding of hydrogen under high pressure to an unsaturated fat. This creates a compound that has fewer double-bonds than polyunsaturated fats, but more than in saturated fats. Skipping past all the rest of the technical details, suffice it to say that scientists believed that these new fats provided a healthy alternative to saturated fats. They were wrong. Very wrong.
In the 1980, studies began to emerge that demonstrated an even higher than saturated fat incidence of heart disease among trans-fat consumers. One major study following thousands of nurses over decades found a strong linear correlation to heart disease. This meant that the more trans-fat they consumed the more heart disease they had. Other studies showed a strong relation to breast cancer, type 2 diabetes, and inflammation.
In fact, a review published in the New England Journal of Medicine concluded that merely limiting trans-fat is not enough. It needs to be completely eliminated from our diets. Even a slight increase, less than 2%, of trans-fat consumption leads to a significant increase in heart disease.
Although the direct cause of dementia is not yet well established, in animal studies, a strong association between trans-fats and cognitive impairment has been established. The amounts used in the study actually matched well against expected human consumption and therefore should give one pause for serious consideration.
Here's another problem for my friend Mike. I presume he is generally aware of the dangers of trans-fats and regularly checks packaging to avoid them. Here in the U.S., unlike in many other countries, trans fat levels of less than 0.5 grams per serving can be listed as 0 grams trans fat on the food label. Institutions, like cafeterias, are not subject to this requirement. Nevertheless, this 0.5 level is considered by most experts as still too high. (by the way, to know if a product contains trans-fats check the ingredients for the terms hydrogenated or partially-hydrogenated and avoid products with either of these ingredients.)
The other issue is that trans-fats are often used for shortening such as margarine and appear in many fried foods and foods listed as pareve (non-dairy). New York City, fully cognizant of the health risks posed by trans-fats, banned their use in amounts over 0.5% in all of its restaurants in 2008. Other states have been following suit.
Trans-fat also may be consumed in many animal products, like milk, in fluctuating amounts. The bottom line is that it is difficult to completely avoid them. That is why knowingly consuming them, even on weekends and occasionally, is a huge health mistake. I hope my friend Mike reads this and reconsiders his dietary choices. For that matter, I hope everyone does. By the way, saturated fats remain a health problem and should be equally avoided.