DEAR DR. BLONZ: A local natural foods store recently held a seminar on cooking oils. The talk favored olive oil over alternatives, but said that when you open any bottle of cooking oil, such as corn, safflower, canola or peanut, the oxygen in the air immediately begins spoiling the oil. They said this was a "hidden cause of disease." They advised refrigerating all cooking oils after opening. However, product labels make no mention of any need to refrigerate. What do you recommend? -- B.T., San Diego
DEAR B.T.: Of course it is true that air gets in when you open the bottle, and that the oxygen in the air participates in the oxidation reactions associated with spoilage. However -- and this is the key -- it's a slow process under normal conditions, and there is no basis or evidence to fear that your oil, or your body, is at risk.
You can keep oils at room temperature, but you should follow some simple guidelines: Stored oils should be kept out of the sunlight and away from heat. And always keep the container sealed when not in use. Avoid buying amounts in sizes greater than you typically use in three to four months. But if you do, consider splitting the large size into smaller portions, refrigerating the unused bottles until needed.
There's no problem with storing oil in the refrigerator, but if you decide to go that route, be sure to have a tight seal on the container to keep the oil from picking up any undesirable refrigerator odors. Some oils may become cloudy when refrigerated, but this disappears when they return to room temperature, and it's no reflection on the oil's wholesomeness.
Oils can go rancid if they are mistreated or stored in the wrong way. Rancidity does indeed occur when an oil reacts with oxygen, and aside from giving foods an "off" taste, the consumption of oxidized oil does represent a health risk. The greater the degree of unsaturation (double bonds), the greater the tendency to oxidize. Omega-3 oils, such as flax or fish oil, have more double bonds than other oils, so they are very susceptible to spoilage. This helps explain the nasty aroma of fish left at room temperature for an extended period of time.
Our body has to deal with unwanted oxidation on a regular basis, and we have a series of systems designed to handle it. There are antioxidants produced in our body, for example, which are supplemented by those we consume in our diet. Eating well makes it so that we don't have to sweat the small stuff.
DEAR DR. BLONZ: Since I began a new multivitamin, my urine has become very yellow. Is this normal? I drink plenty of fluids, so I am not dehydrated. Does the yellow urine indicate an excess of bilirubin, and is taking the vitamins a strain on my liver? -- T.F., Butte, Montana
DEAR T.F.: I will have to assume that you are in otherwise good health. You should be comforted by the fact that it is quite common for B vitamins to increase the yellowness of urine. It happens all the time. B vitamins are yellow, and they color urine as they pass out of the body via the kidneys. This is not a sign of strain on the liver or the production of excess bilirubin (a waste product from the breakdown of hemoglobin).
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