Expert opinion

All of the consulted experts agreed that there is sufficient evidence to consider the total/HDL cholesterol ratio as the primary biomarker for assessing the effects of dietary fats on coronary heart disease.

 

A marker of inflammation such as C-reactive protein might be a stronger biomarker; however, there is currently a lack of data on the effects of dietary fats on plasma levels of this biomarker.

 

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Effect on serum cholesterol and lipoprotein levels of replacing partially hydrogenated oils with oils rich in monounsaturated fats

 

There was general consensus that replacing partially hydrogenated oils (containing both trans and saturated fats) with oils high in cis-monounsaturated fatty acids would have positive effects on lipoproteins and coronary heart disease risk. The reduction in risk would, however, depend on baseline trans and saturated fat intakes.

Polyunsaturated fatty acids, including alpha-linolenic (omega-3) and linoleic (omega-6) acids, are also important components of a cholesterol-lowering and more healthful diet. However, the benefits depend to some degree on consuming an appropriate balance of these fatty acids.

 

Comments from the Expert Committee on Fats, Oils and Other Lipids suggest that, while changes to the diet to reduce trans fats are not likely to alter current intakes of omega-3 polyunsaturated fatty acids, these changes may potentially increase the intake of omega-6 polyunsaturated fatty acids to undesirable levels.

 

Thus the use of oils high in cis-monounsaturated fatty acids rather than omega-6 polyunsaturated fatty acids should be considered when choosing substitutes for trans and saturated fats in food products. The goal should be to replace, as much as possible, trans and saturated fats with monounsaturated fats and maintain adequate intakes and a proper balance of omega-6 and omega-3 polyunsaturated fatty acids.

 

Comparison of trans fats and saturated fats on risk factors for coronary heart disease
There is evidence from both metabolic and epidemiological studies that saturated fats (at least those from dairy products and meat) increase the risk ofcoronary heart disease. However, there was general consensus among the experts that trans fat is a more important risk factor than saturated fat for coronary heart disease.

 

Some manufacturers have already succeeded in eliminating most of the trans fats without increasing saturated fats by using cis-monounsaturated fats in certain food categories. In Europe, the transition from partially hydrogenated frying oils to frying oils and margarines high in cis-monounsaturated fats and low in saturated and trans fats shows that replacing trans fats in fast food, spreads and cooking oils or fats is feasible.

 

The primary product category that may require the use of a hard fat is baked goods, although this does not apply to every food within this category. At present, the only viable alternative to partially hydrogenated fats in baked goods appears to be fats and oils containing a significant proportion of saturated fatty acids. However, the use of saturates in baked goods should not lead to an overall increase in saturated fat intake as the use of saturates plus trans fats in other categories has been decreasing.

 

Research from both prospective cohort studies and metabolic studies found that high intakes of trans fat (5.7-11% of energy intake) are more harmful to health than high intakes of saturated fat (14-20% of energy intake), whether the outcomes measured are coronary heart disease events themselves or cholesterol-related biomarkers of such risk. However, no research has been done to determine whether trans fats are more harmful than saturated fats at low levels of intake (1-3% of energy intake).

 

Relative effects of different types of saturated fats on coronary heart disease risk
Evidence to date on the relative effects of individual saturated fatty acids is sparse. The few randomized metabolic studies that do exist suggest that different saturated fats have varying effects on the total/HDL cholesterol ratio, depending on their individual effects on levels of LDL and HDL cholesterol. Lauric, myristic and palmitic acids, for example, appear to raise LDL cholesterol, while stearic acid either has no effect or slightly reduces LDL cholesterol. All four saturated fatty acids increase HDL cholesterol to different extents, which could be interpreted as counterbalancing their effects on LDL cholesterol. However, while low HDL levels have been linked to increased risk of coronary heart disease, it is not known whether increases in HDL, resulting from saturated fat consumption, have a protective effect.

 

There is currently no scientific agreement on the relative health effects of saturated fatty acids from plant sources, whether they are derived from natural fats or fully hydrogenated fats. Data are also lacking on the relative effects of liquid oils interesterified with saturated fats or fats high in saturated fatty acids on the risk factors for coronary heart disease. Thus experts consider it prudent to ensure that substitutes for partially hydrogenated oil not lead to large increases in the intake of saturated fats, whether they are derived from natural fats or fully hydrogenated fats.

 

Net health benefit of replacing partially hydrogenated oils, in some instances, with solid dietary fats that are high in saturated fats
All the invited experts, including those providing written feedback, agreed that butter and other animal fats are not a good replacement for partially hydrogenated oils. Butter has been shown to have a greater adverse effect on the total/HDL cholesterol ratio than all the other solid dietary fats (e.g. palm oil, palm kernel oil and coconut oil) as well as margarines and shortenings with low to moderate levels of trans fats.