DEAR DR. BLONZ: Our new home has some olive trees that are bearing fruit. We all know how healthy extra-virgin olive oil is for us, but do we get the same health benefits from eating olives? -- J.T., San Jose, California

DEAR J.T.: As you may have inadvertently discovered if you sampled the fruit, olives are quite bitter coming off the tree. To be eaten, they need to undergo a curing process to remove this bitterness, caused primarily by a phytochemical called oleuropein.

Curing typically involves a solution of salt or lye (sodium hydroxide). Both of these leave the olives quite high in sodium: 15 grams of olives (three to five of them, depending on size) contains about 115 milligrams of sodium -- not surprising given that the olives are stored in salty pickling brine before purchase. In a pimento-stuffed olive, the sodium can be twice that amount.

By contrast, when olives are used for oil, the harvested fruit goes directly to the presses without treatment. The fatty acid profiles are similar between eating olives and extra-virgin olive oil. The phytochemicals are mostly similar, with one exception being the intentional decrease of the bitter oleuropein in the eating olive.

It takes a lot of olives to equal a comparable serving of oil. For example, a tablespoon of olive oil (about 14 grams) would contain 120 calories. It would take about 22 large black-pitted olives to match that amount of oil, but that number of olives would contain 644 milligrams of sodium.

I do enjoy eating olives, and there are countless varieties and flavors, but you have to keep in mind that it’s a high-sodium food. You can give your olives a series of fresh-water rinses before serving to reduce the level of sodium.

If you are interested in this topic, there is excellent information from the University of California at Davis (tinyurl.com/zeqp2lh). This page provides reading on different olive types, the curing process, and information on curing with water, which would certainly make a dent in the level of sodium.

DEAR DR. BLONZ: I’ve been having a strange reaction to all dairy, including lactose-free products. I react as if I’ve had three cups of coffee or other caffeine products. I cannot sleep, and sometimes I get a headache. What am I allergic to? -- T.M., via email

DEAR T.M.: Get this checked out with your health professional at your earliest opportunity. It could be a reaction to the protein or some other substance found in dairy products -- but whatever the issue might be, this is NOT something you should let slide. Until it is all sorted out, it’s best to keep dairy products off the menu. This includes reading the ingredient statements of any processed foods you use. There are many dairy ingredients aside from the obvious; see the hidden dairy “cheat sheet” at tinyurl.com/y9tmbw75.

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: 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.