The food industry has aggressively decreased the level of saturated fats in processed foods, but such a switch has not been easy since solid fats play an important role in the shelf-life and acceptability of foods.4 For example, the textural properties of dairy, meat, and some plant foods such as chocolate, are very dependent on their solid fat content. More specifically, solid fats impart creaminess, lubrication and melt-away, the feeling of solid fat converting to liquid oil in the mouth (e.g. margarines and spreads). Solid fats are also important in baked goods because they increase the incorporation of air into products to produce fluffy textures (cookies) and inhibit gluten formation to produce flaky textures. Simple substitution of unsaturated for saturated fats is also a problem because unsaturated fats will become rancid, causing food waste.
The current reduction of saturated fats in the diet reflects a long term trend to change the type of fats in foods. For example, before the wide-spread availability of vegetable oils, most foods were produced with animal fats such as butter, lard and tallow (the original fat in fast food French fries). However, in the late 1950s and early 1960s, nutritionists thought that cholesterol consumption was related to heart disease so the food industry decreased the utilization of animal fats in many foods. Since solid fats play so many important roles in foods, something had to replace the animal fats and in this case it was mainly tropical oils (palm, coconut and palm kernel). Tropical fats are solid because they are also high in saturated fatty acids (e.g. coconut oil is 85% saturated fatty acids). However, additional research in the early 1980s suggested that saturated fats were closely associated with heart disease so the food industry switched to partially hydrogenated fats. Partially hydrogenated fats had several advantages because they are solid at room temperature but can be made so that their unsaturated fatty acids levels are high, and partial hydrogenation can be used to remove α-linolenic acid from soybean oil making it much less prone to developing rancidity. Subsequent research then found that trans fatty acids formed by hydrogenation increased LDL cholesterol like saturated fatty acids but also decreased "good" HDL cholesterol, thus making them potentially worse than saturated fatty acids.2
The potential health risk posed by trans fatty acids resulted in mandatory inclusion of trans fatty acids on the nutrition fact panel starting in 2006. This prompted food manufacturers to severely reduce the utilization of hydrogenated fats in foods. This action resulted in a large decrease (>60%) in trans fat consumption in a very short time. In 2013, the FDA removed the “generally recognized as safe” recognition from partially hydrogenated fat to further decrease trans fatty acids in the food supply.3This change was made because despite the labeling law, some foods continued to use partially hydrogenated oils. Removal of partially hydrogenated fat from food needs to be done by 2016 unless companies get FDA approval. FDA has estimated that further removal of trans fats could prevent an additional 20,000 heart attacks and 7,000 deaths from heart disease each year. Unfortunately, there is no evidence that removal of the very low levels of trans in the diet will actually improve health.
Now that partially hydrogenated fat is no longer allowed in foods, the food industry must again find a fat replacement. Intersterified fats and high oleic oils are the likely candidates to do so.
References:
1. Vieira, S.A.; McClements, D.J.; Decker E.A. Challenges of utilizing healthy fats in foods.
Adv Nutr. 2015 May 15;6(3):309S-17S.
2. McClements DJ, Decker EA. Eds.: Srinivasan D, Parkin KL, Fennema OR. Fennema's food chemistry. 4th Edn. Boca Raton CRC Press/Taylor & Francis; 2008;Chapter 4.Lipids; p 155-216.
3. Kritchevsky D. History of recommendations to the public about dietary fat. J Nutr. 1998; 128(2):449S-52S.
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