DEAR DR. BLONZ: I recently had a good health report, but after starting a new multivitamin -- to up my intake of vitamin D and other essentials -- my urine has become noticeably bright yellow. Is it normal? Does this yellow urine indicate excess bilirubin, or a strain on my liver? -- L.G., Tulsa, Oklahoma

DEAR L.G.: It is pretty standard for specific vitamins to deepen the yellowness of urine, which is typically pale yellow. The B vitamins are not stored in the body, and several of them are yellowish compounds: Vitamin B2 (riboflavin) is known for this effect. Coloring from B vitamins in a basic supplement is not indicative of a strain on the liver, nor of the production of excess bilirubin (a yellowish waste product from the breakdown of hemoglobin).

Check this article on the significance of various urine colors at b.link/3y3ywf.

DEAR DR. BLONZ: I went to a cooking class that included a lecture on oils. The chef explained that when you open a bottle of cooking oil, such as corn, safflower, canola or peanut, it allows air to enter, and that the oxygen in the air begins spoiling the oil. As described in the class, this spoilage is not an immediate health danger, but is an unappreciated hidden cause of disease.

The message was that we must refrigerate all cooking oils after opening. However, I read the labels on bottles of vegetable oil, and they make no mention of any need to refrigerate. -- S.C., Anderson, North Carolina

DEAR S.C.: It is true that air gets in when you open the bottle, and that the oxygen can participate in oxidation reactions associated with spoilage. However, under normal circumstances, it's a slow process, and there is no reason to fear that your oil (or your body, for that matter) is at significant risk.

To safely store oils at room temperature, follow some simple guidelines: Oils should be kept out of direct sunlight and away from heat, and always keep containers sealed when not in use. If you buy more than you will likely use in a few months, split the large size into smaller portions, refrigerating the unused bottles until needed.

There's no problem storing oils in the refrigerator, but if you decide to go that route, be sure the container has a tight seal 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 is no reflection on the oil's wholesomeness.

Oils can go rancid if mistreated or stored in the wrong way. Rancidity occurs when oil reacts with oxygen, and aside from giving foods an "off" taste, the consumption of oxidized oil does represent a health risk. The greater an oil's degree of unsaturation (double bonds), the greater the tendency to oxidize. Omega-3 oils, such as fish oil, have four or five double bonds, making them more susceptible to spoilage as temperatures rise. This helps explain why discarded or unrefrigerated fish soon lends a unique, nasty aroma to a room.

Our body has to deal with unwanted oxidation regularly, and we have a series of systems designed to neutralize these events before they cause any problems. The antioxidants in many whole foods empower this first-alert system. Eating a whole-food, plant-based diet makes it so that we don't have to sweat the small stuff.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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 want your opinion about some online videos I have seen, which claim that acidic water is a health risk. The people in these videos use pH drops in popular brands of water and show that most are acidic. One exception, of course, is their "medical grade" alkaline water that they claim is best for health -- the only one that turns the indicator blue. After this comes a list of health conditions that are affected.

I know this is a serving of promotional nonsense, but I want to know if it is OK, and no less healthy, if the water we drink is not always alkaline. Also, how does this logic translate to whole foods that are acid or alkaline? -- W.F., New York City

DEAR W.F.: I receive frequent questions on this topic, perhaps because there is so much misleading nonsense out there about the impact of water pH -- the measure of its acidity or alkalinity -- and whether we harm ourselves by drinking the wrong stuff. It's a sales pitch attempting to cash in on the public's limited understanding of the topic.

The products on offer are not sodas or flavored waters, but plain waters with different minerals and natural carbonation combinations. The indicator drops in that video were probably qualitative, meaning they don't tell you if the water is a strong acid or base, but simply whether its pH is above or below 7.

The body has overlapping systems designed to maintain pH because essential chemical reactions can't occur if our pH is out of the accepted range. Diseases, conditions, medications, stress or anxiety, in addition to a poor diet, can create an unhealthfully acidic environment. But if you are adequately hydrated and have a healthful, balanced diet, there is no need to be concerned about water that might measure a bit acidic. The systems in our bodies are designed to compensate to keep things on track. We don't need to eat a more "alkaline diet;" the only real help the body needs is a healthful, plant-based whole foods diet and an active lifestyle.

Healthful foods, including fruits and vegetables, can be on the acidic side: Carrots (pH 6.1), asparagus (pH 6.3) and cauliflower (pH 5.6) would have all turned that indicator the "wrong" color. A typical vinegar used in salad dressing has a pH of about 3, and lemon juice has a pH of 2.3. The hydrochloric acid released in our stomach to break down foods is a very strong acid with a pH of 1.0.

On the alkaline (base) side, baking soda and egg whites have a pH of 8.0. A typical laundry bleach has a pH of 11.4, and the pH of ammonia used for cleaning is 12.0. (Check the pH of many substances at b.link/pdf75.)

A healthy body is adept at dealing with variances, and makes adjustments while foods are in the digestive system and then absorbed. The kidneys play a crucial role: The pH of our urine will change according to our state of health and any disease process that might be underway. It also reacts to what we have been eating, drinking or doing, and any medications we are taking. Aside from urine, our perspiration and breath also help to keep body pH in its optimal range.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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: My elderly mother is convinced that taking daily multivitamins causes weight gain. I have never heard of such a thing, and don't believe it. Is this possible? -- S.T., Oakland, California

DEAR S.T.: No. OK, there could be a weight-gain twist in an exceptional circumstance, such as a nutrient-deprived body that had wasted away a bit. In such a case, a multivitamin could provide the deficient nutrients and help return one to normal health, which could involve regaining the lost body weight.

But outside of a rare, specific case such as that? No.

DEAR DR. BLONZ: In a recent column, you responded to a question about nutrition while on dialysis. Thank you for the link you posted (b.link/3nucqh) regarding how a registered dietitian can help.

The renal nutrition plan is complex, and dietary recommendations can change monthly, based on the most recent lab results. This can be very confusing to individuals who might not understand unless they receive personal nutrition counseling from a dietitian familiar with renal dietetics.

Thank you for this helpful information. Now retired, I worked as a registered dietitian and certified diabetes educator. -- J.M., via email

DEAR J.M.: Thank you for these comments. As you know, the blood is what carries nutrients throughout the body. It also serves as the medium through which metabolic wastes produced by the cells get picked up, transported and eventually eliminated from the body.

It is essential to appreciate our kidneys' central role as the blood's cleansing filter; they are also responsible for fine-tuning the concentration of various substances in our bloodstream to desired levels. When they are not working correctly, close attention must be paid to what we put into the body -- which is where dietitians specializing in renal dietetics play their role.

DEAR DR. BLONZ: When using a blender, do you get the same amount of dietary fiber as the unblended food? I am having some work done on my jaw and will be shifting to a liquid diet while things heal. -- S.C., Oakland, California

DEAR S.C.: No problem with using a blender; the fiber value will be the same as long as the whole food gets consumed. The same goes for a juicer, but only one that does not discard the solids, which tend to be the source of insoluble fiber. Blenders and juicers can cause the food to spend slightly less time in your stomach, but the net effect of the fiber should be the same.

As for your particular situation, there are liquid fiber supplements on the market that can be used to fortify foods, but also to help those who can only eat through a straw. In your case, the idea of blending whole foods or using a liquid supplement can make sense.

Keep in mind that your digestive system and its muscles usually do what your blender will be doing; that can translate to some minor upsets until the whole system gets used to your new way of eating. A consult with your physician would be in order, as well as one with an associated dietitian, who can help you select a progression of foods to soothe the adjustment period and help with the healing process.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 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.