(NaturalNews) The trans fatty acids that naturally occur in certain dairy and meat products are not as unhealthy as those synthetically produced for processed foods and cooking oils, according to a study published in the American Journal of Clinical Nutrition.
While trace quantities of trans fats occur naturally in some animal foods, the vast majority are produced by partial hydrogenation of vegetable oils. These partially hydrogenated oils have longer shelf lives and increased flavor stability, which has made them popular in packaged foods and restaurants.
Because trans fats are well known to increase the risk of cardiovascular disease, they have been banned from restaurants in New York City, with other cities are contemplating similar laws.
In the TRANSFACT study, 24 women and 16 men were assigned to consume food containing a total of 11 to 12 grams of trans fats per day, either from natural or artificial sources. After three weeks on one of the two diets, the participants were given a one-week "washout period," then switched to the other diet for three weeks.
The researchers found that, as expected, artificial trans fats led to increases in LDL ("bad") cholesterol and decreases in HDL ("good") cholesterol. The natural fats, however, increased LDL cholesterol only in women. The natural fats did not decrease men's HDL levels, and actually increased those in women.
The study was not able to determine why the effects were so different in men and women
In an accompanying editorial, Walter Willett from the Harvard School of Public Health and Dariush Mozaffarian from Harvard Medical School critiqued the study, saying that the levels of natural trans fats consumed far outstripped those actually found in a standard, meat-eating diets. While comparing the two types of trans fats posed "an interesting scientific question," they said, "a control arm replacing trans fatty acids with non-hydrogenated fats would have made the study more informative."