The 2010 Dietary Guidelines Advisory Committee (DGAC), a group of experts and scientists, is convened every 5 years to advise the government on nutrition policy.
The government takes their recommendations into account when revising their nutrition advice to the general public. Some of the best known communications tools used by the USDA and FDA include the food pyramid and the nutrition facts panel, present on all retail packaged foods. In the case of saturated fat, the current government dietary intake recommendation is 10% of the diet or less. Earlier this year the DGAC published their final report, which included recommendations for dietary intakes of different kinds of fat. Their main conclusions were – (1) reduce saturated fat from the current level of approx. 12% of the diet to 7%, and (2) substitute saturated fat with unsaturated fat, but not with carbohydrates.
Calling for a reduction in saturated fat to 7% of the diet is not new and can be categorized as "more of the same". For example, the final report of the previous DGAC (convened in 2005) made the same recommendation (specifically referencing people with high cholesterol): "For adults with an elevated LDL cholesterol (≥ 130 mg/dL), less than 7 percent of calories from saturated fatty acids is recommended." (the government kept their recommendation at 10% for the whole population). However, the 2010 DGAC had the benefit of new human nutrition research not available in 2005. Two large studies that measured the relationship between food intake and risk of heart disease were recently published. With about 130,000 participants in each study and up to 25 years in duration, these were promoted as the last word on the effect of saturated fat on heart disease. But both of these studies showed that saturated fat had no effect on risk of heart disease – it neither increased nor decreased it! On first glance this might appear very surprising. After all, for decades saturated fat has been labeled as "cholesterol raising", an effect that is supposed to increase heart disease risk. But on closer evaluation, the cholesterol raising effect is not that simple. It is only valid for the so-called "bad" cholesterol (LDL) but the opposite is true for "good" cholesterol (HDL) – higher levels of good cholesterol actually reduce risk of heart disease.
Therefore in order to predict how saturates affect risk of heart disease, we need to understand how saturated fat affects serum levels of both good and bad cholesterol. Many such human studies have already been carried out over the last 20 years and almost all of them agree: saturated fat raises good cholesterol more than anything else you can eat. Yes, saturates also raise bad cholesterol, but the good more or less cancels out the bad, and predicts that saturates will have little effect on risk of heart disease. Therefore the recent findings that saturates have no effect on actual heart disease should not come as a surprise. But it certainly is surprising that the 2010 DGAC recommendations are "more of the same." Their saturated fat recommendation – just 7% of the diet for the whole population - is even more restrictive than before. This in spite of convincing new data showing saturated fat is not as bad as previously believed.
However, the 2010 DGAC did make a new recommendation: substitute saturated fat with unsaturated fat, but not with carbohydrates. This statement implies that simply lowering saturated fat intake will not lower risk of heart disease. Rather, in order to get any benefit from reduced saturated fat intake, an equal weight of unsaturated fat must be simultaneously consumed. This certainly falls into the category of "a radical shift in thinking." The practical implications for this recommendation are enormous.
Does this mean that for years our efforts of cutting back on saturated fat have had no effect on heart disease? In most cases the answer must be yes!
The majority of saturated fat in the American diet comes from meat and dairy products. Over the years saturated fat in these products has been gradually cut back using reduced or low fat milk and lean cuts of meat. But the missing saturated fat was almost never replaced by unsaturated fat. How can unsaturated fat be added to a lean cut of meat? In processed foods saturated fat was mostly replaced by trans fat and carbohydrate – not only did this have no benefit, it may have done harm. Since the 1970’s saturated fat intake in men decreased by about 14% and increased in women by 3% - on average a significant decrease. Incidence of heart disease has not decreased. Our only conclusion can be that 20 years of recommendations to reduce saturated fat intake have had no beneficial effect on risk of heart disease.
Accepting that the earlier saturate fat intake recommendations were ineffective, can the new 2010 DGAC recommendations deliver a big drop in the incidence of heart disease in the American population? The quick answer is: no. Their recommendation would require a reduction of 5% saturated fat intake PLUS a simultaneous increase in 5% unsaturated fat intake for every man, woman and child in the country. This saturated fat reduction is equivalent to about 65% of all meat and dairy products consumed in the American diet today – a target that is extremely unrealistic. But reduction of saturated fat per se has little or no affect on risk of heart disease. The DGAC requires that 5% unsaturated fat must be added back somewhere in the diet. Even with all liquid milk converted to zero fat and 100% trimming of all meats, how can the necessary unsaturated fat be incorporated back into these products? In the case of baked goods and snack foods, a solid fat is needed for most of these products, so substitution with liquid oil is usually not an option. Focusing on saturated fats with this new approach will likely have little or no benefit on risk of heart disease, but the risk of more unforeseen consequences is very real.
The 2010 DGAC recommends substitution of saturated fat with unsaturated fat. But even the word "unsaturated" is fraught with potential problems. Unsaturated fat in food is composed of both polyunsaturated fat and monounsaturated fat that are chemically distinct and have different biological activities. There is substantial evidence that polyunsaturated fat intake reduces risk of heart disease as shown recently by two large human studies (see above).
But the same studies showed that monounsaturated fat had no effect on heart disease, similar to saturated fat. Therefore it is uncertain that substitution of saturates with monounsaturates will actually provide any benefit. Even though the benefits of polyunsaturated fat are clearly positive with respect to risk of heart disease, it is not clear what unforeseen health consequences could arise from a proposed significantly higher dietary intake. Polyunsaturates are readily oxidized compared to other fats and react with oxygen both inside and outside the body. The resulting breakdown products are known to damage protein and DNA.
Such damage could increase incidence of age related diseases such as arthritis and some cancers. In addition, polyunsaturated fats are biologically active and are converted into hormone-like substances in the body that affect a broad range of metabolic processes. Significantly increasing polyunsaturated fat intake could disrupt these processes in a positive or negative way.The 2010 DGAC recommendation could result in up to a 70% increase in consumption of polyunsaturated in the US diet. We have no idea how such a large increase in dietary polyunsaturated fat would alter oxidative stress, or critical metabolic processes.
Our attempt to control the disease state of the American population through dietary guidelines has so far been a dismal failure, likely doing more harm than good. The current 2010 DGAC recommendations are both more of the same combined with a shift in thinking that offer no hope of improving the situation. Continuing to focus on single ingredients such as saturated fats can only lead to more unforeseen consequences. Our resources will be better utilized by promoting consumption of healthy food groups in combination with a healthy lifestyle.