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It’s high time to end the war on dietary fats

 

Is the battle of low-fat diets finally over? I recently read with interest the May 2011 edition of the Journal of the American Dietetic Association, which included an extended feature on the historically controversial issue of the role that dietary fat plays in our health and weight. Entitled The Great Fat Debate: A Closer Look at the Controversy — Questioning the Validity of Age-Old Dietary Guidance, the series is a summary of a live debate that occurred at the 2010 ADA Food and Nutrition Conference and Expo, featuring several leading public health authorities and researchers with varying opinions on the role of fats in our diet.

If you were alive and vaguely conscious through most of the 1980s and ’90s, you probably heard more than your share of low-fat diet marketing. During that time, low-fat foods and diet regimens proliferated, centred on the belief that eating fat not only made us fat, but it increased our risk of disease, especially of the heart. (I distinctly remember hearing a couple of weight-conscious university students brag about getting their fat intake to as close to zero grams per day as possible —_a slightly extreme, and all-too-common way of thinking at the time.)

Since the mid-1990s, however, a small but growing group of researchers and health advocates started questioning the validity of the anti-fat claims, largely based on emerging evidence that certain types of fat, especially the essential omega-3 polyunsaturated fatty acids (also known as PUFAs), were not just harmless, but actually healthful. Other types of fat, including the monounsaturated fats (MUFAs) that make up a key part of the Mediterranean diet, were also exonerated.

Even with the growing acceptance of the “some-fats-are-good-for-you” hypothesis, however, there were still a cluster of fats that were — and continue to be — thought of as nutritional no-no’s: trans fat, the synthetic fat produced through the process of hydrogenation; and saturated fats, or the so-called four-legged fat derived mostly from animals, but also from coconut and palm oil. Both types of fat, along with cholesterol to varying degrees, have been deemed verboten on the grounds that they can clog our arteries.

Despite the rise of so-called “good fats,” total fat intake also remains a public health target, even to this day. Current guidelines recommend a dietary fat intake of 20 to 35 per cent of our calories, and Canadian food labels use 65 grams of total fat as a target for someone consuming a 2,000 calorie per day diet. (Most dietary guidelines also recommend that saturated fat be limited to 10 per cent of our calories, or about 20 grams per day, while it is generally agreed that trans fats should be limited as much as possible.)

As outlined in the ADA piece, however, there is a surprising lack of hard data to tie dietary fat intake to our risk of disease. As noted by researcher Dr. Walter Willett of Harvard’s School of Public Health, societies with dietary fat intakes of up to 40 per cent of total calories do not necessarily have a higher risk of heart disease. Similar studies on cancer risk (especially of the breast) and type 2 diabetes have also been unable to demonstrate a cause-and-effect link between dietary fat and disease. Moreover, even studies on high-fat diet and body weight have shown that low-fat diets can be harmful to our waistlines, especially if the fats were replaced with carbohydrates of the white and refined variety, such as bagels, muffins, sugary drinks, white rice and pasta.

Even the well-worn recommendations that we should limit saturated fats are showing signs of age. First, since saturated fats are not all the same — the saturated fats in coconut oil, for example, are structurally and metabolically different from those in cheese, which are different from those in lard — there is growing concern that painting all solid fats with the same brush may have been short-sighted. While there is reasonable consensus that replacing saturated fats with the MUFAs and PUFAs found in olive oil, nuts, seeds and avocados makes good sense for heart health, there is also evidence that replacing fats of any kind with refined carbohydrates may do our hearts more harm than anything else.

Beyond the grams-of-fat, or type-of-fat debate, however, there is also a growing focus on the need to move away from nutrient-specific guidelines to whole food-based recommendations. Among the take-away points issued by the ADA included recommendations for dietitians to “talk food not chemicals,” and “balance calories with an emphasis on reducing starch, sugars and refined carbohydrates, and not healthy fats.” The authors also noted that “the evidence against saturated fat may not be as strong as dietary guidelines have interpreted, but what is clear is that PUFAs and MUFAs are healthy fats.”

After decades of encouraging consumers to read labels for lower-fat-this, or higher-fibre-that, the ADA feature recommended that we consider the entirety of a person’s diet, rather than fixating on single nutrients: “Dietary patterns are more important than single dietary components,” was among the final recommendations. While the haze of the low-fat era will undoubtedly linger for some time to come, it seems that we are on the verge of finally moving away from some age-old recommendations that have more than worn out their welcome.


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This entry was posted on Thursday, June 30th, 2011 and is filed under Healthy Food Online. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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