DEAR DR. BLONZ: You often refer to the "Nutrition Facts" label in your columns, but I have always wondered about the information listed. How are these figures arrived at, by whom, and how reliable are the values? -- A.W., Walnut Creek, California

DEAR A.W.: The accuracy of the information on the "Nutrition Facts" label is the responsibility of the company selling the food bearing the label. With few exceptions, all regulated foods must display nutrition information on the package or have that information available to consumers in other ways.

There are exceptions for small businesses with fewer than 100 full-time-equivalent employees or food product sales of less than 100,000 units annually. (For importers, the exceptions are: fewer than 10 full-time-equivalent employees and sales under 10,000 units annually.) Retailers are exempt if their annual gross sales are less than $500,000 or their gross sales of foods to consumers in the U.S. are less than $50,000. Nutrition labeling for fresh fish or produce is voluntary.

The information on nutrition labels is generally reliable, and is subject to periodic review. The FDA takes samples from store shelves to check for accuracy, and they allow up to a 20% difference between what's listed on the label and what is found in product analysis. Infractions can result in penalties such as fines and product seizures. Food companies, especially larger ones, have much at stake, as the penalties can be hefty. (For more on Nutrition Facts label accuracy, check b.link/z22pgnw.)

There are several consumer options if you have doubts. First, it helps to do a side-by-side comparison of similar products from different companies. Be sure to factor in serving size and the similarity of the top ingredients, which must be listed in order of decreasing prevalence. Another option is to check the company website, or contact the company directly.

There are now extensive food composition resources available online. The USDA's FoodData Central database can be accessed at b.link/7f92kh5. For a nutrition value calculator, including nutrient options in standard servings, adjusted serving sizes and totals for recipes, see b.link/avx5kqc.

DEAR DR. BLONZ: Since my husband's heart attack earlier this year -- which was caught early, and he is doing quite well, all things considered -- we have limited our fat intake to olive, avocado and canola oils. I find many "healthier" foods and desserts contain expeller-pressed canola oil. What is that? Is it hydrogenated? -- K.K., Palm Springs, California

DEAR K.K.: Expeller pressing is used to extract oil from an oil seed. This process utilizes mechanical pressure rather than a chemical solvent, resulting in cleaner oil -- no solvent residues -- higher in natural colors and flavors. It has nothing to do with hydrogenation. The mechanical pressure used for extraction can generate heat and decrease some nutrients, albeit to a minor degree. When looking for an expeller-pressed oil, consider opting for ones that keep things cool during extraction, referred to as "cold pressed."

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 appreciate that you answer questions about health claims made on social media. I am continually amazed when I want to learn about a condition and then find it can be treated successfully using a particular promoted product. It seems there are cures out there for everything, often promoted by doctors, but it is unclear whether these are doctors with genuine credentials. What bothers me is the lack of guardrails, and I wanted your comment on how all this continues to exist. -- S.K., Lombard, Illinois

DEAR S.K.: I am less concerned with who hawks the products, and more so with the products themselves. A laissez-faire attitude over the past few decades has spawned an unbridled atmosphere of health claims associated with nutritional supplements. Social media, often with an anti-science bent, has amplified the situation. While it is against the law to make unsubstantiated health claims, the Food and Drug Administration (FDA), Federal Trade Commission (FTC) and other consumer protection agencies don't have the resources to make any significant dent in the infractions.

Another element of uncertainty involves adding supplements alongside a doctor-prescribed medication regime. A 2017 study in the respected journal American Family Physician reported that nearly 25 percent of U.S. adults take supplements along with their prescription medications -- and possible interactions must be considered. (For more on drugs, supplements and potential interactions, see b.link/cvkx2c3.)

While consumer protection laws can vary between states, scientific literature has no such boundaries. The FDA, FTC, state agencies and other respected elements of the supplement industry wouldn't dispute the need for a mechanism to regulate claims that lack clinical evidence, but testing for safety and effectiveness can be a thorny issue. Manufacturers might have a lack of economic incentive to fund research if it involves non-proprietary substances -- because other companies selling the same substances could benefit from their results when published. Many companies offer "proprietary blends," but the missing link is clinical evidence showing that their product's blend works as they claim. Then there is the issue of bogus claims that escape any accountability. The burden of proof should rest with the companies profiting from supplement sales -- not consumer protection agencies inadequately funded for the task.

I would support a goal for the supplement industry to establish a self-policing policy to evaluate their health claims. A panel of independent scientists could be empowered to decide on the essential proof for any particular claim. A ratings system as simple as the red-yellow-green of a traffic light could link to a consumer-friendly database of evidence.

Having something like this on the product's label or website could empower consumers to patronize brands that favor consumer protection and education. In the meantime, I will continue to respond to my readers' queries.

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 am on Medicare and had a bone scan as a part of my annual wellness checkup, which showed that I have weak bones in the form of osteopenia in my hips and spine, but other areas were in the normal range. I was told to increase my calcium and vitamin D intake, which I am doing; in addition, I was given a list of exercises to help keep my bones strong. This test result came as a surprise, as I have no pain and have never had a broken bone. I will add the bone-strengthening exercises to my routine.

I also have high blood pressure that is being successfully treated with a calcium channel blocker medication. Is there any interaction between taking a calcium channel blocker and taking calcium as a dietary supplement I should be aware of? Neither my doctor nor pharmacist mentioned any such possibility. -- W.P., Raleigh, North Carolina

DEAR W.P.: I commend you and your physician for including a bone scan in your wellness checkup. We shouldn't wait until we're eligible for Medicare to get our bone strength tested. (Those on Medicare are entitled to a yearly wellness visit as part of their healthcare. For more on this, see b.link/aqdrzczc.)

The fact that you had no idea there were issues with your bone strength underscores the importance of undergoing such testing -- the sooner you diagnose and treat bone-strength issues, the greater the odds it can be stopped or even reversed. I understand your need to learn more, given that calcium is involved in both of your health situations, and you want both medications to function as intended.

Calcium channel blockers can be prescribed for hypertension (high blood pressure) because they prevent the contraction of certain smooth muscles surrounding the blood vessels. For the muscle around the vessel to contract, a small amount of calcium has to pass through a channel in the membrane (outer skin) of the muscle. Calcium channel blockers are so named because they slow the movement of calcium through these channels, thereby keeping the blood vessels relaxed. (For more on calcium channel blockers, see b.link/r5jfpw3.)

There is little connection between the calcium present in your system via your diet or your supplement and the ability of a calcium channel blocker to do its job. It should be interesting for you to track your bone strength in future testing. (Read more about bone-strengthening exercises at b.link/jgisklr.)

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.