Between 1980 and 2009, Americans’ consumption of trans fat dropped by about a third and intake of saturated fats declined as well, but both are still more common in daily diets than the American Heart Association (AHA) recommends, according to a new study.
“Other studies have previously shown a decline in trans fat intake over time, but our study is the first to look at such a long period of time,” lead author Mary Ann Honors of the Division of Epidemiology and Community Health in the School of Public Health at the University of Minnesota in Minneapolis.
“Trans fat intake declined by over one third, which was great to see,” Honors said by email.
The 12,500 people enrolled in the Minnesota Heart Study described in detail what they had eaten over the previous 24 hours in a series of six surveys over a 30-year period.
Researchers compared their reported types and amounts of nutrients with recommendations from the 2010 Dietary Guidelines for Americans and AHA recommendations.
Over time, total fat, saturated fat and trans fat declined, but remained above recommended levels.
Total fat declined from an average of 39 percent of daily calorie intake to 33 percent.
Trans fatty acids declined from 2.9 percent of calories to 1.9 percent for men.
That means trans fat intake decreased by 32 percent for men and 35 percent for women, on average.
The AHA recommends keeping trans fats, found in partially hydrogenated oils and noted on nutrition labels, to one percent or less of total calories consumed.
Saturated fats, found in fatty beef, lard, butter and coconut oil, declined as well but still accounted for more than 11 percent of daily calories for men and women in 2009, according to the results in the Journal of the American Heart Association.
The AHA recommends limiting saturated fat to between 5 percent and 6 percent of total calories.
Consumption of the healthy omega-3 fatty acids found in fatty fish like salmon, mackerel and herring, remained steady – but lower than recommendations – over the study period.
These fats can be good for the heart, reducing blood pressure and triglyceride levels.
The study examined trends in fat consumption, not the reasons behind them, but there could be several explanations for the decline, Honors said.
“For example, Food and Drug Administration regulations now require the trans fat content to be included on the Nutrition Facts Panel of packaged foods, making it easier for consumers to identify foods containing trans fats and to avoid those products,” she said.
“In addition, many food manufacturers have begun to reduce the trans fat content of their products, resulting in fewer trans fat-containing food products in the marketplace.”
Trans fats are naturally found in low amounts in some foods, including meats, she noted, but the majority of trans fats that people consume are from processed foods.
“The evidence is compelling enough to aim for the elimination of trans fats entirely,” said Rajiv Chowdhury, a senior research associate in Global Cardiovascular Health in the School of Clinical Medicine at the University of Cambridge in the UK. “There is also an increasing realization that trans fats are potentially even worse than saturated fats for cardiovascular health.”
Saturated fats, on the other hand, need to be studied further as the current evidence indicates that their health effects may vary widely based on type and source, he said by email. The saturated fats available in dairy products may not be harmful, said Chowdhury, who was not involved in the new study.
“Because researchers have found that consuming trans and saturated fats may increase cardiovascular disease risk, it may be particularly important for individuals with an elevated risk of cardiovascular disease to avoid these nutrients and follow the recommendations,” Honors said. “Diet is one important avenue for reducing cardiovascular disease risk.”