DEAR DR. BLONZ: How long should milk be kept after the carton has been opened? -- S.T., Ripon, Wis.

DEAR S.T.: Milk and other dairy products usually have a sell-by date stamped on the container. Fluid milk is a perishable and it will spoil. The date on the container is the last day on which the carton should be sold. Manufacturers use these dates to tell retailers how long to sell the product, and the dates include an allowance for normal home use. That means that a gallon container will typically have an earlier sell-by date than a quart container that comes from the same batch of milk.

Assuming it has been opened prior to the sell-by date stamped on the container, a conservative estimate is that homogenized milk should keep for about five days. The point is that the clock begins ticking as soon as the carton is opened. There is some flex here: The fresher the milk and the more time it spends at a chilled temperature, the longer it will remain wholesome. Of course, a carton opened 10 days before its sell-by date will last longer than one opened on the sell-by date.

Please understand that the sell-by date is not a guarantee of freshness or safety. The breakdown of food is a gradual process and does not take place on one particular day. You always need to keep containers chilled and tightly closed. Never return unused milk back to the container. The accuracy of any dating system relies on the proper handling of foods. If there's been any mishandling by the manufacturer, trucker, supermarket or consumer, the life and safety of the product will be compromised.

In the end, consumers must trust their eyes, nose and palate in addition to the numbers stamped on a carton. If you notice an "off" taste, smell or appearance in any food, forget the date and toss it out.

DEAR DR. BLONZ: You will probably get a number of emails on this matter, but a plantain is a fruit, even if it is eaten as a vegetable. Even though seedless, it develops in the reproductive system of the plant. A vegetable is any other part of the plant, i.e., root, stem, flower. -- J.R.

DEAR J.R.: My apologies for the gaffe; thanks for pointing it out.

DEAR DR. BLONZ: I recently purchased a jar of peanut butter that was clearly marked "NO TRANS FAT per serving" However, in the "Ingredients" column, it listed partially hydrogenated vegetable oils (cottonseed, soybean and rapeseed). Is it possible that a food could contain partially hydrogenated vegetable oils but not trans fats? -- G.G., San Jose, Calif.

DEAR G.D.: Only a fraction of the fats undergoing partial hydrogenation will become trans fats; that percentage is determined by the starting material and the degree of hydrogenation desired. If there is no more than 0.5 grams of trans fat per serving, a product can be labeled as being "free" of trans fats.

I know that the advice is to zero out our trans fat intake, and this is something I support, but at the level of less than one half of one gram per day, there is no evidence that trans fats would have a measurable negative impact on health. It could become an issue if multiple servings were routinely consumed.

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 suggest you might be misguiding your readers on homeopathy, and encouraging them to close a door on options to try before pharmaceuticals. I have a foot in each practice. I have a master's in nursing, and am a clinical nurse specialist in integrative health practices. I have 20 years' experience as an OR nurse, and now work in quality and patient safety.

While I was completing my master's degree, homeopathic remedies helped me manage my stress and anxiety levels. Calms Forte sleep aid is non-addictive and works wonderfully for me. I have a number of colleagues and staff coming in regularly to get arnica cream to relieve muscle tension and knots in their neck and shoulders. They are all amazed by how beneficial these products are. It's a wonderful thing to get relief from natural products, not to mention a very important option, as pharmaceuticals often have side effects. It's certainly a smart option to explore when dealing with chronic issues. Remember, never touch homeopathic pills; drop them in the cap and then pop them under your tongue. -- A.K.

DEAR A.K.: It's great when one experiences relief for stress, anxiety or sleep issues -- particularly if it does not require pharmaceuticals. My concern is the lack of objective evidence to support your optimistic assessment of homeopathy as a treatment modality. I question whether it merits endorsement by a health professional. Primary to my concern is the lack of competent and reliable evidence to support the underlying mechanism.

The power of belief in a person, product or practice can be an amazing adjunct to healing, one that science has yet to fully understand or quantify. The problem comes when one objectifies the results, attributing them to the product, for example, and then assumes that similar results will be experienced by all others who take the product.

I also feel obliged to ask about the basis for the directive "never touch the homeopathic pills." Where is the evidence to support this? I do recall once reading that "do not touch" does not apply to traditional tableted homeopathic products where the "active" ingredients are a part of the tablet. The directive against handling should only apply to pelleted products where the active ingredient is sprayed on the outside; I am guessing this is based on concerns that the "active" ingredient might be rubbed off, rendering the pellets less effective. It all seems a bit dubious considering the homeopathic theory where more dilutions equal greater potency. Finally, as regards your mentioning of the use of creams to relieve muscular tension, this can be reasonably explained by the physical action involved with their application.

I sincerely thank you for your note, but as you can see, I remain skeptical. As a scientist, I am open to persuasion when the evidence indicates it. Until then, presenting what is known and placing it in context is not a basis for concern that the readers of this column will be misguided.

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: The February 2014 Costco magazine had an article about brassica vegetables where it was said that boiled cauliflower is "devoid of nutrients." Isn't that a bit extreme? I love to eat it warm, and think the flavor is enhanced. I am not concerned about the vitamin C content from cooking, as I get that in many other foods, and I am sure the antioxidant chemicals are still present. I would like your opinion on this. -- T.B.

DEAR T.B.: I am pleased that pessimism prompted your note. That boiled cauliflower would be "devoid of nutrients" is nonsense, and it's unclear why such misinformation would appear. Heating does indeed reduce certain "heat labile" nutrients, and vitamin C is one that can be affected, but cauliflower has a great complement of healthful phytochemicals to offer.

Never forget that the nutrients in plant foods have become a part of their structure to assist in their growth, survival and reproduction. There is a broad variety of these beneficial substances in nature, and only by having a variety in our diet can we get the power of these substances on our team. Cooking, in many cases, helps enhance nutrient bioavailability. Check out the article in Scientific American that addresses this issue: tinyurl.com/nlvyyrk. Continue to enjoy your vegetables, fresh or properly cooked, and keep checking when you read something that sounds dubious.

DEAR DR. BLONZ: Please tell me about the benefits of sesame oil. Is it OK to use in salads and also to saute vegetables, chicken, meat and fish? Are there any reasons why I should not use it? I currently use extra-virgin olive oil and balsamic vinegar for my salads. -- J.P.

DEAR J.P.: Sesame oil is a healthful oil that is composed of approximately 40 percent monounsaturated fatty acids, 42 percent polyunsaturated and 14 percent saturated. It is source of tocopherols (such as vitamin E) and lignans, both of which act as protectants for the sesame seed. Pure sesame oil has a mild flavor and a high smoke point, making it ideal for high-heat cooking methods including those you mention. Toasted sesame oil, pressed from the toasted seeds, has a distinctive nutty flavor used to complement many dishes in Asian and other cuisines.

DEAR DR. BLONZ: When playing sports, we freeze half a bottle of water, then add water to it to keep it cold. We then refill the bottle as we drink it until the ice melts. I have read that this is a safe practice, and yet people tell me the plastic breaks down and can cause cancer. I use pre-bottled water from the store. -- D.O., Walnut Creek, Calif.

DEAR D.O.: The water bottles you buy at the store have been specifically designed for water. As long as the bottle is completely cleaned and allowed to dry between uses, there is no evidence that any problem exists. There is a bogus cancer-scare email going around with misinformation on this topic; go to tinyurl.com/cgq874 to sort fact from fiction.

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.