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Monday
Feb182013

The Truth about Vegetable Oils and Cardiovascular Health

We all know the refrain by now: vegetable oils are good and saturated fats are bad. Right? Actually, no. We’ve discussed how saturated fat has been wrongfully accused of causing heart disease and weight gain (see Saturated Fat: Wrongfully Accused?, Fat, Carbs and Cardiovascular Disease and Myth Busting: Fat). In fact, there’s growing awareness in scientific circles that saturated fat isn’t bad. There’s also increasing concern that the fats recommended to replace saturated fat, the polyunsaturated fats common in vegetable oils, may be not only an unnecessary but an unhealthy substitute.

Currently, many public health organizations regularly recommend the replacement of saturated animal fats or saturated plant-based fats (e.g. coconut) with vegetable oils like corn, soybean, sunflower and safflower oil, which contain a high proportion of omega-6 fatty acid linoleic acid. Recommendations like this date back to the 1960s, when flawed research showed associations between saturated fat consumption and heart disease in a small number of cultures. A more global view of saturated fat consumption and heart disease made this association fall apart but not before public health organizations grabbed hold of the notion that “saturated fat is bad.” You can read more about the history of how we got here in Gary Taubes’ fantastic New York Times article, What if It’s All Been a Big Fat Lie? or his book Good Calories, Bad Calories.

In an updated analysis of study results originally used in previous decades to support the use of vegetable oils, researchers have recovered unreported data that shed new light on the saturated versus polyunsaturated picture. Their paper, published this month in the British Journal of Medicine, adds to evidence that recommendations to consume more vegetable oils may cause the very thing people think they prevent--heart disease and mortality.

Experts analyzed evidence from research dating back to the 1960s and 70s. The original study used two groups. One group stuck with their normal diet at the time, which included 6% of their daily calorie intake from linoleic acid and 16% from saturated fat. The other group was told to modify their diet so they could increase their omega-6 intake to 15% of their daily calorie consumption and reduce saturated fat to less than 10%. One group maintained a relatively low omega-6 intake and were free to eat animal-based saturated fat. The other group lowered their intake of animal fats and increased their vegetable oil consumption. According to conventional recommendations, the second group should have fared much better with a reduced risk of cardiovascular disease and death.

For whatever reason, the original researchers didn't report on cardiovascular disease outcomes, although they did report that those who replaced the saturated fat with vegetable oil had an increased all cause mortality. In this 2013 updated meta-analysis, researchers went back and reviewed the data for all cause mortality, cardiovascular disease and coronary heart disease risk and found all three got worse by replacing saturated fat with vegetable oil!

Two other studies, published in 1965 and 1989 provided similar findings to this one.

Since the 1960s, our exposure to vegetable oils has grown significantly. One of the most prevalent vegetable oils in our food supply is soybean oil, which is found in the majority of today’s processed foods. A steep rise in soybean oil consumption started in the 1960s, about the same time we were told to consume more vegetable oils in place of saturated fat. To add to this precipitous slide, this was also the time we began eating a lot more sugar and relying on processed foods in place of homemade whole food meals.

Reducing Vegetable Oil Consumption

Clearly, the results of this research suggest we should limit the role of these conventional vegetable oils in our diets. Fortunately, you can easily reduce your intake of omage-6 fats with a couple easy changes to your diet. First, eat fewer processed foods. The three most common vegetable oils, corn, soybean and canola oil are common in processed foods. (Alhough canola oil is not high in omega-6 fats, it is a highly processed oil which can contain a lot of inflammation-promoting oxidized fats.) If you occasionally eat some processed foods, be sure to check labels and avoid these oils whenever possible. Using a daily fish oil supplement or increasing your fish intake can help bring your omega-6 and omega-3 ratio toward a healthier balance.

Second, be aware that these conventional oils are unstable fats and oxidize with heat--either through cooking or heated processing, which is the standard industry practice. You don’t need a processed oil for cooking. Instead, cook with saturated and monounsaturated fat-rich oils. Butter, ghee, coconut oil and leftover grease from animal foods are the most naturally stable forms of fat to cook with, especially at higher temperatures. Olive oil can be used for sautéing but isn't good for use at high temperatures. Try unprocessed, cold-filtered nut oils for seasoning and other non-heated preparations. For a full list of oils to use and avoid, check out Chapter 8 in Eat Well Live Well.

It’s frustrating when research and public health messaging don’t align. It can be easy to get confused about what you should eat and what you shouldn’t, but if you stick with whole foods in your diet and use the Healthy Way of Eating as a guide, you can easily avoid the food products and substances that wreak havoc on your health. Unfortunately, what’s most ubiquitous in the food supply and prevalent in the grocery store aisles isn’t always the healthiest. Hopefully, public health recommendations will catch up with new (and old!) insights. In the meantime, when you inform yourself with the science behind the headlines, you’re empowered to make the best choices for your health--in the present and the future.

Share your comments and questions about the BMJ research and healthy fats.

Written by Tom Nikkola - Sr. Director of Nutrition & Weight Management

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

 

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