CABI Blog

Trans fats. I keep seeing them in the news: New York restaurants have banned them, McDonalds as well, but how much effect is this likely to have on the public’s health? In my opinion attention would be better focussed on the daily diet not on eating out and on saturated fat not trans fat.

Trans fats are most common in baked foods, chips and margarines. They were developed to replace saturated fats and have useful properties that extend the shelf life of foods. However, like saturated fats they increase low density lipoprotein but they also lower high density lipoprotein and so raise heart disease risk more than saturated fats for a similar intake. So they are not good for the health, that’s for sure but then neither are saturated fats and we eat far more of them.

Since the drawbacks of trans fats have been discovered the food industry has been replacing them. US trans fats intake has therefore been steadily decreasing over the years from around 8.3 g daily in the early nineteen eighties to 3 g in the early nineties. They make up less than 2.2% energy intake. In the UK intake is even less at 1.2% energy (National Diet and Nutrition Survey).

Saturated fats intake is greater-around 30 g or more per day in the US or about 11 percent of energy (year 2000 data). (http://0-www.cdc.gov.mill1.sjlibrary.org/mmwr/preview/mmwrhtml/mm5304a3.htm). The American Heart Association  recommends that people aim for a saturated fat intake of 7-10% of energy in the US.  So there is more improvement needed here.

In general bans on trans fats in food eaten in restaurants are not going to have a huge effect on trans fat intake, because people mostly don’t eat out all the time. (Having said that apparently New Yorkers get one third of their calories from food eaten in restaurants!). Banning trans fats in processed food generally as has happened in Denmark would still have a better effect than targeting restaurants. The effect of a trans fat ban also depends on what the trans fat is replaced with. A return to using saturated fat would not be a step forward!

See continuation for selected abstracts from CABI.

If you want to search the terms are: trans fatty acids and saturated fatty acids or saturated fats.

Dietary levels of trans-fatty acids: basis for health concerns and industry efforts to limit use.
Hunter, J. E.
Nutrition Research, 2005, Vol. 25, No. 5, pp. 499-513, 30 ref.

Dietary trans-fatty acids at sufficiently high levels have been found to increase low-density lipoprotein cholesterol and decrease high-density lipoprotein cholesterol compared with diets high in cis monounsaturated or polyunsaturated fatty acids. The dietary levels of trans-fatty acids necessary to do this appear to be approximately 4% of energy or higher to increase low-density lipoprotein cholesterol and approximately 5% to 6% of energy or higher to decrease high-density lipoprotein cholesterol, compared with control diets essentially trans-free. In response, the food industry is working on ways to eliminate or greatly reduce trans-fatty acids in food products. Current efforts focus on 4 technological options: (1) modification of the hydrogenation process, (2) use of interesterification, (3) use of fractions high in solids from natural oils, and (4) use of trait-enhanced oils. Challenges to the food industry in replacing trans-fatty acids in foodsare to develop formulation options that provide equivalent functionality, are economically feasible, do not greatly increase saturated fatty acid content, and meet the regulatory deadline of January 1, 2006.

Trans, saturated, and unsaturated fat in foods in the United States prior to mandatory trans-fat labeling.
Satchithanandam, S.  Oles, C. J.  Spease, C. J.  Brandt, M. M.  Yurawecz, M. P.  Rader, J. I.
Lipids, 2004, Vol. 39, No. 1, pp. 11-18, 15 ref.

The purpose of this study was to determine the trans-fatty acid (FA) content of a wide range of foods prior to the effective date (1 January 2006) of the new regulation on declaration of trans-FA in nutrition labels of conventional foods and dietary supplements. AOAC Official Method of Analysis 996.01 was modified for the analysis of trans-FA in noncereal products. Food products for analysis were selected on the basis of market share and data from the USDA’s 1994-1996 Continuing Survey of Food Intake by Individuals. Foods were purchased from local supermarkets, weighed, hydrolysed, converted to FAME (fatty acid methyl ester), and analysed by GC. The results showed that trans-FA (g/100 g fat) ranged from 0.0-48.8 in bread, cake, and related products; from 14.9-27.7 in margarines; from 7.7-35.3 in cookies and crackers; from 24.7-38.2 in frozen potatoes; from 0.0-17.1 in salty snacks; from 0.0-13.2 in vegetable oils and shortenings; from 0.0-2.2 in salad dressings and mayonnaise; and from 0.0-2.0 in dry breakfast cereals. Serving sizes for the foods included in this survey ranged from 12-161 g, and trans-FA levels ranged from 0.0-7.2 g/serving. The significant differences in trans-FA content in products within each food category are due to differences in the type of fats and oils used in the manufacturing processes.

Trends in the trans-fatty acid composition of the diet in a metropolitan area: the Minnesota Heart Survey.
Harnack, L.  Lee, S.  Schakel, S. F.  Duval, S.  Luepker, R. V.  Arnett, D. K.
Journal of the American Dietetic Association, 2003, Vol. 103, No. 9, pp. 1160-1166, 43 ref.

Objective: In this study, we examine trends in dietary intake of trans-fatty acids from 1980-82 to 1995-97 using data collected as part of the Minnesota Heart Survey (MHS). Design: The MHS is an ongoing observational epidemiological study among independent cross-sectional probability samples of adults. Twenty-four hour dietary recalls were collected on a subset of participants. To obtain trans-fatty acid intake estimates, the dietary recall records were recalculated using the University of Minnesota Nutrition Coordinating Center Food and Nutrient Database. Subjects/setting: The survey population included noninstitutionalized adults aged 25 to 74 years residing in the Minneapolis-St. Paul metropolitan area in Minnesota, USA. Statistical analysis: Mean intake estimates were generated for each survey, and a generalized linear mixed model was used to test the null hypothesis of no difference in the age-adjusted sex-specific means between 1980-82, 1985-87, 1990-92, and 1995-97. Results: Downward trends in dietary intake of trans-fatty acids were found between 1980-82 and 1995-97. For example, for men mean intake of total trans-fatty acids declined from 8.3 g per day in 1980-82 to 6.2 g per day in 1995-97 (P<0.001). Represented as a percentage of energy, similar declines were seen with mean intake of total trans-fatty acids decreasing from 3.0% of total energy in 1980-82 to 2.2% of total energy in 1995-97 (P<0.001). Applications/conclusions: It seems that intake of trans-fatty acids is on the decline. Consideration should be given to additional changes in the food supply and consumer food choices that may result in further reduction in consumption of trans-fatty acids.