Trans fatty acid intake and risk of disease

TRANS FATTY ACID INTAKE AND CHD.

 

On a per calorie basis, trans fatty acids increase the risk of CHD more than any other macronutrient, conferring a substantially increased risk even at low levels of consumption (between 1 to 3% of total energy intake).

 

Even a small rise in energy intake from trans fatty acids can cause a large increase risk. A meta-analysis of four prospective cohort studies that included data from 140,000 subjects showed a 23% increase in CHD incidence when energy intake from trans fatty acids increased by just 2%. So dramatic is the impact of trans fatty acids on CHD risk, another study showed that the positive association between levels of trans fatty acids in adipose tissue (a biomarker for dietary intake) and CHD risk was diminished after 1996, when trans fatty acids where eliminated from margarines sold in Australia and the population’s consumption levels decreased.

 

The potential benefits of reducing of reducing consumption of trans fatty acids from industrial sources on the incidence of CHD in the United States has been calculated. On the basis of predicted changes in total and HDL cholesterol, CHD events could be reduced by between 3 and 6 percent. If the influence of trans fatty acids on other risk factors such as inflammatory effects is considered,CHD events could be reduced by 10–19% (equivalent to between 72,000 and 228,000 CHD events each year). This reduction could be even greater, if healthier cis unsaturated fatty acids, including omega-3 fatty acids, are used to replace trans fatty acids.

 

 

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Impact of Modifying the Trans Fat Content of Foods on Dietary Intakes

From its deliberations and review of material, the Task Force concluded that the Danish approach - a 2% limit on the industrially produced trans fat content of oils or fats used in foods - would not be the most appropriate course for Canada.

 

 

A higher limit, which included all sources of trans fat, would be more feasible to implement and could still yield a significant health benefit to the Canadian population.

 

Before making its final recommendation regarding a limit on the trans fat content of foods, the Task Force asked Health Canada to model the impact of a variety of potential recommendations and limits on trans fat in foods and the resultant intakes across the Canadian population, grouped by age and sex.

 

The first step was to estimate the current baseline intake of trans fat for the Canadian population, taking into consideration as much as possible the changes that had occurred in the trans fat content of processed foods since the dietary intake data were collected in the late 1990s. This modelling indicated that the baseline average daily consumption of trans fats for the Canadian population would range between 3 and 9 grams. This range reflects lower intakes than previously estimated (5 to 13 grams). However, it is consistent with the increased availability of "trans fat free" foods on the market during the last year.

 

Next, three scenarios were developed to assess the impact on dietary intake of limits on the trans fat content of foods. In all three scenarios, the trans fat content of all oils, breads and salad dressings sold at retail was set at a maximum of 2% of total fat, while the trans fat content of foods containing only naturally occurring trans fat was not limited. Where the scenarios differed was in the maximum allowed trans fat content of all other foods, which was set at 3%, 4% and 5% of total fat respectively.

 

If an upper limit of 5% on trans fats were applied to all foods that are significant sources of industrially produced trans fats, the average trans fat intake of Canadians would decrease by at least 55%. Most of the industrially produced trans fats would be removed from the Canadian diet, and about half of the remaining trans fat intake would be of naturally occurring trans fats. At this level, the average daily intake of trans fats for all age groups would represent less than 1% of energy intake, consistent with the recommendations of the World Health Organization.

 

If an upper limit of 4% were applied, the modelling indicates that the average trans fat intake would decrease by an additional 2-3%. In reality, much of this additional reduction would also happen with a 5% limit since most products, once reformulated, would contain smaller amounts than the regulated limit. A reduction of the upper limit to 3% would have even less of an impact.

 

Consequently, throughout its deliberations, the Task Force has been concerned that consumption of saturated fats should not increase significantly as a result of limitations on trans fats.

 

There is no reason to believe that limiting trans fat intake would cause the intake of saturated fats to increase above the current combined intake of trans and saturated fats. The targeted scan of the food supply completed by Health Canada and Food & Consumer Products of Canada for the Task Force suggests an improvement in the fatty acid profile of key food categories such as margarines and snack foods, which should largely compensate for increased levels of saturated fats in a few food categories.

 

In each of the following food categories, analysis of foods demonstrated that partially hydrogenated fats had been replaced mostly by cis-mono- and cis-polyunsaturated fats: breads, margarines, shortening, breaded meats, granola bars, french fries, crackers, chips and nachos. These food categories represent a major portion of the foods identified as key sources of trans fats in the 1990s.

In some food categories such as cookies and oriental noodles, the amount of saturated fat was generally higher in the reformulated products; however, the amount was mostly lower than the combined amount of saturated and trans fats found in products that still contained partially hydrogenated fats.

 

A minority of "trans fat free" products had a saturated fat content above the combined trans and saturated fat content of similar products containing partially hydrogenated fats (e.g. a sandwich cookie, a liquid coffee whitener and a snack pudding). However, even then, it was sometimes possible to find other products in the same food category with a better fatty acid profile. Clearly, some manufacturers have been able to reformulate with healthier alternatives without increasing saturated fats. These data show that for a large number of food categories it is feasible to replace partially hydrogenated oils with healthier alternatives.