DEAR DR. BLONZ: If using olive oil in foods, are the health benefits limited to extra-virgin olive oil? We found that the flavor of the extra-virgin oil we were getting was often too strong or bitter for our taste, so we switched to ordinary olive oil. What are we missing health-wise, if anything, by not using extra-virgin oil? -- O.F., Phoenix

Dear O.F.: Many different types of olives are used to make oil, each with subtle twists on a basic flavor theme. But even oil from the same olives can vary by where and how the olives are grown, harvested and processed. (More on the different varieties of olives used to make oil at b.link/we3azd.)

The extra-virgin style will always be the most intense, as it is the least processed. Extra-virgin also contains the highest amount of the phytochemicals of that olive variety; these protect the oil that's the vital initial energy source for a developing tree if the olive was planted.

Olive oil characteristics can vary, so consider visiting a store where they do olive oil tastings. Or, you might look online for stores that offer tasting notes for their various oils. It helps to try one or more of these to find a reviewer whose tastes align with yours. The bottom line is that, irrespective of extra-virgin oil's health assets, you don't want to use it in a dish if it doesn't work. Olives, like growing conditions, can vary from season to season. Some companies blend to achieve a consistent taste for their brand; this involves blending oils from different regions to achieve the desired characteristics.

We all want any olive oil we select to work for its intended use. You might consider hosting an olive oil tasting party where the host makes the selections, or one in which guests drop off their choices ahead of time for a blind-tasting event. It can be an enjoyable event, with host and guests gaining added knowledge. (For suggestions on how to put on such an event, see b.link/xpdvp4.)

DEAR DR. BLONZ: I love spinach in salads, but heard that large consumption of spinach would cause kidney stones. Is this true -- is there any relationship between spinach and kidney stones? I would really appreciate it if you could clear up my concern. -- M.Y., New York

Dear M.Y.: Not sure what your "large consumption of spinach" is; suffice it to say it should be one of many greens, not the only one you consume. Spinach is an excellent food -- one of my favorites, as well, and is unlikely to cause kidney stones to develop in an otherwise healthy individual. (More on kidney stones at b.link/3nn8k6.)

If your body has displayed any tendency to form oxalate kidney stones, spinach would be on your "foods to avoid" list. So how to proceed? Assuming you are in good health, there is no history of kidney stones in your family, and in discussions with your physician there have been no expressions of concern that you are at risk of developing kidney stones, it seems dubious to avoid spinach on the mere chance that you "might" form a stone.

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: Many people I encounter seem to take it as a given that cow's milk is not a healthy choice and that any other choice -- oat, almond, soy -- is better. I don't drink milk, but I do use it in coffee and cereal, and eat Greek yogurt and cottage cheese pretty regularly. My weight is very healthy, my vitals are normal, and I've never had any digestive issues with cow's milk, so I'm curious how right or wrong my friends are about their assumptions and whether any of that applies to my current diet. I should also mention that as a 70-year-old thin woman, I strive to keep my protein and calcium intake up. -- S.M., San Francisco

DEAR S.M.: Assuming there are no allergic or intolerance issues, I must disagree with the basic sentiment that cow's (dairy) milk cannot be a healthful choice. It provides several required nutrients, but dairy milk is not "essential" as the source of the nutrients. That same argument also applies to nondairy milks, as there is no current nutrition standard; they can, and do, vary by source and manufacturer. (For more on the nutritional difference between dairy milk and other "milk" choices, see b.link/cqz5mc.) Given the variety of wholesome foods available, completeness is not what we require in any individual food -- only in our diet as a whole.

I do not drink whole or low-fat milk, but I use half-and-half in my coffee and full-fat yogurt or kefir in my typical breakfast, which also includes fresh berries and high-fiber granola. As with most foods, I opt for organic when possible, but that also considers the environmental impact of what I eat, and the effect of my food choices on workers from field to plate.

I am there with you supporting your efforts to get the nutrients you need. Remember that routine physical activity is vital to the "use it or lose it" aspect of our muscles, bones and brain as we age.

DEAR DR. BLONZ: Does dairy cause inflammation in the body? -- L.K., via email

DEAR L.K.: Assuming one has no issues of allergy or intolerance to dairy, there is no evidence that milk, as part of an otherwise healthful diet, will cause inflammation. There is plenty of misinformation out there, and it has leaked into the underbelly of awareness -- albeit without evidence. One 2017 review study reported dairy had no pro-inflammatory effect in healthy adults or those with metabolic syndrome, obesity or diabetes. That paper actually reported a weak anti-inflammatory effect from certain fermented dairy products, such as yogurt and kefir. (More on this at b.link/t8qjwr.)

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 just turned 60, and I seem to tear tendons and ligaments with what I think is unusual regularity. I am fairly active -- walking and yoga daily, plus hiking on the weekends -- and I am beginning to fear my usual activities. I am not a "pills will fix everything" person, but after my last tear, I asked the doctor if there was something I could take to prevent future injuries. He suggested a collagen supplement. I know you are not a fan of supplements, so how can I get extra collagen into my diet? -- J.S., via email

DEAR DR. BLONZ: I see many promotions for drinkable collagen products, which are supposed to help maintain good skin and nails and slow the aging process. Is there truth to these claims? I thought that the body made its own collagen, and that there was no value in consuming it. If the body does indeed make collagen, what nutrients does it use (as those are the nutrients that I want to consume)? Aside from eating balanced meals, what supplements would you suggest to promote collagen production? -- K.O., via email

DEAR J.S. AND K.O.: These questions raise the issue of whether taking collagen as a supplement will improve the state of collagen-based tissues in the body. First, some background.

Collagen is the body's most abundant protein, making up about 6% of our weight. It is used to make skin, bones, nails and connective tissues. There are about 272 grams of collagen in every 10 pounds of body weight. Like other proteins, collagen is constructed of chains of amino acids (peptides) folded into the three-dimensional form for its intended uses. As it lacks tryptophan, one of our essential amino acids, collagen is not a complete protein. (Read more about protein folding at b.link/k3yyj4, and about collagen peptides at b.link/x3b43u.)

Assuming the diet provides the essential nutrients, a healthy body can make collagen as needed. This helps explain why, despite its many important roles, there is no specific collagen dietary requirement. As we age, though, the body produces less collagen, contributing to changes in appearance as our skin becomes thinner, drier and less elastic. Men and women alike experience a gradual decrease in collagen production, although women also tend to experience a drop at menopause.

Regarding collagen supplements, there is some evidence in their favor, but no reliable guarantee. Some small studies report improvements, while others do not. It is also unclear how long the collagen would need to be taken to achieve measurable effects. The impact of other factors -- such as diet, exercise, medications, exposure to the elements, and use of moisturizers -- would also need to be considered and measured.

The collagen present in food is insoluble, with low bioavailability. If you are considering collagen as a supplement, it might be best to opt for a hydrolyzed collagen product where the protein is partially broken down to enhance bioavailability. Like other digestible proteins, when hydrolyzed collagen is consumed, it will be exposed to stomach acid and enzymes to help split the collagen peptides into individual amino acids before absorption. One scoop of a typical collagen powder supplement will contain about 10 grams of protein.

In short, it is still unclear whether taking collagen as a supplement can benefit body structure and/or produce cosmetically significant changes to skin and nails. We are left with distinct possibilities, but no reliable certainty.

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.