DEAR DR. BLONZ: At a recent luncheon, there was a talk at our table about healthy foods we include in our diets. A couple of my friends went on at unusual length about the endless health and curative powers of mangosteen. This is not a fruit I am familiar with. I would appreciate any information you may have about this substance and products made from it. I was rather skeptical, and I will pass on your comments. -- S.T., Concord, California

DEAR S.T.: The mangosteen is a fruit native to Indonesia and southeast Asia, but it can be grown in other tropical climates, including Hawaii. Like any plant that manages to flourish under the oxidizing rays of a tropical sun, the mangosteen has evolved to produce a complement of antioxidant phytochemicals. As with most tropical fruits, this one can be an excellent addition to the diet, but it is not widely available in the domestic produce aisle. As for its possessing “endless health and curative benefits,” this is more marketing than a reflection of evidence-based science.

There may indeed prove to be something special in the mangosteen, but I could find no convincing evidence from clinical studies. Regarding the fruit itself, it’s supposed to have a unique, enjoyable flavor that has been variously described as sweet or slightly sour, with undertones of vanilla, strawberry and peach. I will keep an eye out for reliable scientific studies, and will report back if there are any promising developments.

We have been down this road before with various fruits, vegetables and herbs. The more respectable commodities put funds into research on the popular produce du jour, and then wait for results before any grand health claims are made.

The bottom line is that there is no shortage of healthful foods, and they all deserve consideration for a place on your plate. Health claims should never outpace the hard science. Proceed cautiously, especially if the plaudits from your friends are associated with the use of mangosteen as a dietary supplement and not a whole food.

DEAR DR. BLONZ: I have been told not to heat food in the microwave in hard, plastic containers, as the plastic secretes a cancer-causing chemical when hot. Is this true? -- M.S., via email

DEAR M.S.: The major issue here is: Are you using containers that are specifically designated as “microwave safe”? That being the case, you are almost certainly in the clear. There may be troubling substances in certain plastics, but we are talking about levels that are very low -- well below any level for concern. There is an FDA article on microwave cooking that includes a discussion of containers at tinyurl.com/yc8z6ydl.

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 support the importance of having whole foods in our diets. But I am troubled by constantly reading that the soil is depleted of minerals -- the same minerals we assume will be present in our foods. If that’s the case, the produce we eat might not be providing our bodies with the nutrients we need. However, it is my understanding that produce requires certain nutrients to grow to proper size, shape, color, taste, etc. Therefore, it seems illogical to me that the produce of today would not have the same nutrients as it would have had in previous eras with “non-depleted” soil. Please advise. -- S.T., Arlington Heights, Illinois

DEAR S.T.: You can think of plants as miners, pulling the mineral elements required for their growth out of the soil. Add water, energy from the sun, and the appropriate climate, and the game is on.

You are correct in your assumption that if a mineral needed by the plant is unavailable, the plant will fail to thrive; it is doubtful such produce would ever find its way to the market. That indeed makes it incorrect to think that today’s fruits, vegetables or grains would provide any less of the essential nutrients than the same varieties of these plants had provided in the past.

Mineral elements are key here, because unlike humans, plants synthesize their own vitamins. So vitamins will definitely be there, as required by the plant, and will be available for us after the food is consumed, digested and absorbed.

There is another layer to this question, however, as nonessential minerals in the soil can also end up in a plant. Whole foods grown in iodine- or selenium-rich soils, for example, can have more of these nutrients than the same type of food grown in soils with lesser amounts of these minerals.

What gets pulled in can differ from plant to plant and mineral to mineral -- even among different varieties of the same fruit, vegetable or grain. The plant’s overall nutrient content can also vary according to the time of the growing season and the length of time the plant has had to grow. This means that a plant picked green may not have the same nutrient content as one allowed to ripen on the vine.

It is difficult to speak with any statistical certainty, because we don’t have records of nutrient content from the produce of a hundred years ago. Based on what we know, however, it’s likely that the amounts would be comparable.

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 have kept up with a group of my high school friends through social media. Back then, we went out for the same sports and all had comparable body types, heights and weights. This past New Year, we made an agreement to measure and compare our caloric intakes, checking with online food composition tables. To our surprise, we found that we each eat just about the same number of calories every day. Despite all this, our weights and body shapes have now changed, in some cases rather dramatically. It was frustrating for me, as I have one of the larger waistlines in the group. How is it that people with similar caloric intakes can end up with such different weights? Four of us have been exercising together on and off for about 10 years. -- F.S., Brooklyn, New York

DEAR F.S.: Food composition tables, now available online through the U.S. Department of Agriculture (ndb.nal.usda.gov) and commercial sites (nutritiondata.self.com), provide information about what’s in the foods we eat. Remember that the calories they list for a given portion are nothing more than calculations of “potential energy.” The efficiency with which a fixed number of calories is utilized can vary from body to body. It’s similar to the way miles per gallon varies between the different models and conditions of automobiles.

For example, one’s basal metabolism -- the calories used while the body is at rest -- rises as the amount of muscle in the body increases. This is because muscle is “active tissue.” Fat tissue, by contrast, is not very active. Using the automobile analogy, this would be similar to how a car with an eight-cylinder engine burns more gas at idle than one with a four-cylinder engine.

Other factors include age, sex, genetic makeup, level of physical activity and the efficiency with which one digests and absorbs food. All these play into the way a given number of calories will affect a particular body at a particular period of life.

We get away with much during our youth, particularly if we are physically active. But if we scale back the exercise during our transition to adulthood, we will find our measurements advancing with the years. This becomes more likely if our dietary habits fail to change with the times. Exercise not only burns up calories, but can also increase the amount of muscle in the body, and that additional muscle mass burns more calories even when you are at rest.

As is true with most aspects of life, some people have to work harder to accomplish the same goal. Where weight is concerned, though, one’s value system should not get bogged down with comparisons to others. Rather, we should be focused on doing the best we can with what we’ve got -- or at least starting the process with that as our goal.

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.