08 July, 2011
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Canola Oil Side Effects
The heated controversy over canola oil and its safety for human consumption makes it challenging for consumers to find the truth about this popular vegetable oil. While the U.S. Food and Drug Administration for decades has had the oil on its list of products generally recognized as safe, naysayers argue that canola can cause a wide array of serious side effects. As is often the case in disputes such as this, the truth lies somewhere in between.
Critics of canola oil are quick to point out that it is derived from rapeseed, many species of which contain high levels of erucic acid, a substance that in large amounts can be toxic to humans, according to Mayo Clinic nutritionist Katherine Zeratsky, a registered and licensed dietician. While the allegations about rapeseed and erucic acid have a kernel of truth, they overlook certain realities. Most importantly, canola oil is extracted from hybrid cultivars of rapeseed--now actually recognized as canola plants--that were bred specifically to reduce erucic acid content. “Canola plants have very low levels of erucic acid,” Zeratsky says. That said, consumers should moderate their use of this oil because it is always possible to get too much of a good thing.
Dangers of High Omega-6 Fatty Acid Intake
Canola oil is a rich source of omega-6 polyunsaturated fatty acids, or PUFA, which within limits are beneficial to human health. However, studies show that excessive consumption of this strain of fatty acids can be counterproductive. An Israeli study, published in the November 1996 issue of the Israeli Journal of Medical Sciences, investigated the high incidence of cardiovascular disease, hypertension, obesity, non-insulin-dependent diabetes and cancer among Israelis. Israel is a country where the consumption of omega-6 PUFA is 8 percent higher than in the United States and 10 to 12 percent higher than in most European countries. The study concluded that “rather than being beneficial, high omega-6 PUFA diets may have some long-term side effects, within the cluster of hyperinsulinemia, atherosclerosis and tumorigenesis.”
Not All Canola Oil is Created Equal
Andrew Weil, M.D., a pioneer in the field of integrative medicine, sees health benefits in canola oil when it is used in moderation, but he warns consumers that it’s important to buy oil that’s organic and expeller-pressed. “The lower-cost products sold in supermarkets have often been extracted with chemical solvents or high-speed presses that generate heat,” Weil cautions. “Both methods alter the oil's fatty acid chemistry in undesirable ways,” which can lead to adverse side effects. He also warns that high levels of pesticides are used by canola oil producers, opening the way for possible tainting of the finished product. He suggests that consumers check product labels carefully.
- Mayo Clinic: Nutrition and Healthy Eating: Canola Oil: Does It Contain Toxins?
- Israeli Journal of Medical Sciences; Diet and Disease—The Israeli Paradox: Possible Dangers of a High Omega-6 Polyunsaturated Fatty Acid Diet; D. Yam et al.; November 1996
- Weil: Q and A Library: Choosing Canola Oil
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