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).

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: Do fruits and vegetables put in a blender have the same fiber value as if eaten normally? -- D.D., La Jolla, California

DEAR D.D.: There is no problem with the blender, as the fiber and nutrient values are the same. You are eating the entirety of the same foods that went into the blender. The physical breakdown that takes place in the blender may end up causing the food to spend slightly less time in your stomach, but the net effect of the fiber should be the same. The same could not be said for a juicer, in which the fibrous bulk gets separated from the food and is not a part of the final product.

DEAR DR. BLONZ: It was my understanding that there is a considerable difference between soybean oil and palm oil. A popular whole-grain cracker lists in its ingredients "soybean and/or palm oil." If there is a significant nutritional difference between these two oils, isn't this somewhat deceptive? The product even has a red heart symbol, saying it may help reduce the risk of heart disease. Why are they allowed to use this seal if one oil ingredient is of questionable health value? -- M.M., Humbolt, California

DEAR M.M.: There is nothing deceptive about an ingredient statement indicating that a product contains soy and/or palm oil. That red heart seal on the product is likely based on the fact that the cracker is made from whole grains, and that the food is low in total and saturated fat. The numbers on the Nutrition Facts panel would have to be accurate irrespective of the oil or oils used.

Your concern about palm oil is misplaced. Palm oil is about 49 percent saturated, 37 percent monounsaturated and 10 percent polyunsaturated. You may have been thinking about palm kernel oil. Although from the same plant, palm kernel oil is quite different from palm oil: Palm kernel oil is around 82 percent saturated, 11 percent monounsaturated and 2 percent polyunsaturated. If you enjoy these crackers, the either/or oil ingredient should not be a reason to cross it off your list.

DEAR DR. BLONZ: Is there a vitamin or mineral that can reduce the dark circles under my eyes? -- K.K., Sedona, Arizona

DEAR K.K.: Darkness under the eyes can be brought about by a number of factors. Perhaps the most common cause is a natural thinness in the skin under the eyes. The skin isn't darker in that area, but it is thinner, which makes it easy to see the vascular bed underneath. This trait can run in families, and it doesn't necessarily reflect any health problem. If one is fatigued, under stress, or affected by allergies, the skin can lose its natural vascular glow; when this happens, the thin skin under the eyes can take on a paler tone and make the underlying vascular bed appear more prominent. I am sorry to say that aside from any vitamins you already take for your overall health, I have seen no evidence that specific vitamins or minerals can eliminate this problem.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I have gone through a situation you touched on in a recent column on cancer advances, and thought I'd respond. I, too, believe that the pharmaceutical companies are not on the cutting edge of finding a cure. There is so much money involved in the treatment industry, and Big Pharma rakes in billions. If a true cure were found, their profits would collapse substantially. Scientists, on the other hand, would rejoice if they found a cure, since they are not tied to the cash flow like pharmaceutical companies are.

But enough of that. As I write this, a close family member is dealing with terminal cancer. First there was surgery, then the painful "poisoning and burning" from treatments, by which the cancer was supposedly vanquished. Four months later? Stage 4. One round of chemo was followed by an "alternative approach." An acquaintance had endured the same type of cancer 15-plus years ago, went to Mexico for treatment, and has been cancer-free since. Off went my family member, and followed the protocol precisely, expecting that the cancer was then taken care of. Honestly, those very expensive treatments didn't slow it down at all. So now we wait for the inevitable, less thousands and thousands of dollars.

Aggressive malignancies leave very few survivors. Until medicine can decode each individual's genetics and then modify a treatment specifically for that person, cancer will continue to do its deadly deed. -- S.G., via email

DEAR S.G.: The very idea of cancer is an affront to our passion for life. With cancer, a combination of events allows a "nonself" growth to be treated as self and receive all the privileges of membership. The cancer's effective use of bodily resources, its continuous growth and spread, and its ability to skip detection as an invader provide a competitive advantage over normal cells. It has also led to the current strategy of radiation and chemotherapies, which put a careful dose of poison in the system so that the cancer's constant need for sustenance will bring about its earlier demise.

While there may be similarities among cancer types, each individual creates a different spin, and there lies the rub in finding an effective treatment. There is a fine line between providing the correct dose of the right agents to hobble the cancer and destroying the body in the process.

You confess disdain for "Big Pharma," but an equal dose should be directed at bogus alternative methods. They often claim a focus on providing support for our immune systems and allowing the body to successfully weed out the cancer, but this assumes the immune system can tell the difference between friend and foe. Once the cancer has set up shop, however, such enhanced support may also provide succor to the enemy.

Finally, I totally agree with your assessment that the missing element is an ability to genetically decode an invading cancer. We need to identify treatments based on a cancer's Achilles' heel. This will happen, and we are on the road there. Science, including "Big Pharma," is working on this. Your skepticism aside, cancer treatments have made remarkable advances in recent years. In the meantime, it is incumbent on all of us to live in a way that lessens our risks. Please convey my concerns to your family member.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.