DEAR DR. BLONZ: How do imitation crab meats compare with regular crab in terms of omega-3 fats? I asked my local fish store and was told that imitation crab comes from pollock, and I heard this is a low-mercury fish. I don’t buy it to pretend that it is crab; I buy it because it’s the only way that I can find pollock locally. And it is generally inexpensive, so that makes it a good buy. But does the processing of the pollock -- including the coloring and the flavor infusion -- change any of the omega-3 levels? -- F.M., Tulsa, Oklahoma

DEAR F.M.: While a good source of protein, and low in mercury, pollock is considered a moderate to low source of omega-3 fats -- comparable, actually, to that found in crab. A 3-ounce serving of Dungeness crab contains 383 milligrams of omega-3 fats, while a similar serving of Alaskan pollock contains 418 milligrams. For comparison with other fish, this is about one-fourth the level found in wild salmon.

While pollock isn’t particularly high in omega-3s to begin with, turning it into imitation shellfish (also called surimi) will reduce the levels even further. To make the fish look and taste like crab or lobster, they are typically deboned, rinsed, minced, flavored, colored and reformed to resemble the muscle fiber and taste impression of the desired variety. It is not a process that’s kind to omega-3 fats. A 3-ounce serving of surimi made from pollock will contain only 26 milligrams of omega-3 fatty acids.

DEAR DR. BLONZ: What are the nutritional consequences of discarding the liquid that separates from yogurt in the container? Since discovering Greek yogurt on my trip to Greece last year, I find I prefer the thicker consistency. However, I like to achieve this by purchasing American yogurt, allowing it to settle and then removing the liquid. However, I’m unsure whether I am losing valuable nutrients with this practice. -- A.A., Denver

DEAR A.A.: The liquid on top is mostly water, but also contains whey. Whey contains a bit of protein, some carbohydrates and a few water-soluble nutrients, including calcium, that remain in solution.

The texture of Greek-style yogurt comes from being strained to eliminate extra liquid. More liquid gets removed with Greek yogurt than from pouring out the liquid from a standard type; this explains why, even if you pour off the liquid and spoon out a serving, you will find some water there the next time you open up the container. Greek-style yogurt has less calcium, but a higher proportion of protein per weight.

But all things considered, when compared with the overall healthfulness of yogurt, the nutritional consequences of going Greek or pouring off the liquid from a standard type is not significant. Go with the type that best pleases your palate. Another yogurt plus is that it’s often better tolerated than milk by those with lactose intolerance. This is explained by the fact that active yogurt bacteria produce a lactose-digesting enzyme.

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 very concerned: My recent wellness check revealed that my total cholesterol was 242. I’m a 37-year-old, 150-pound white male. My triglyceride level is 71, HDL is 88, LDL is 110 and my fasting glucose is 90. There is no history of heart disease in my family. I am an avid athlete, landscaper and marathon runner, and am even sponsored by a shoe company, having had some success in races. I have been doing daily runs at an intense level for over a decade.

Food-wise, I eat a balanced diet, and rarely eat meat and animal products. I’d like to know what you think is going on, and get your suggestions for lowering my numbers. -- J.F., Boston

DEAR J.F.: You describe great habits, and you eat well. I can’t offer medical advice, but if these numbers do not jibe with previous data, you can always ask your doctor for a retest. Numbers can vary from test to test, and from lab to lab.

Your HDL is in great shape, and your triglyceride number is also in the low-risk range. There are some doctors, however, who care only about your LDL value. It’s important to discuss this with your physician. Other tests, such as C-reactive protein (for heart disease risk) and hemoglobin A-1C (for blood sugar) can provide more information, if needed. In addition, there are many websites providing information about blood cholesterol. Check out Medline from the U.S. National Library of Medicine (medlineplus.gov, search “cholesterol”).

Regarding your exercise habits, it is not always in our best interests to push “intense” on a daily basis. Have you ever considered working with a trainer? Doing the same intense workout every day can overwork the body, and landscaping work demands that your joints remain in good shape. There might be some benefit to alternating your workouts, such as running every other day and doing complementary exercises, such as yoga, tai chi or resistance training, on the alternate days.

An unfortunate fact of life is that the body becomes less forgiving as we transition to midlife. Our habits determine when midlife begins and how long it lasts. It is likely that you have already gotten subtle reminders that youthful flexibility doesn’t last forever, even for one who maintains an active lifestyle. Even those who stay active need to refine their workouts as the years go by. This is not a bad thing, and by doing so, you can remain injury-free and at the top of your game. Let me know how things turn out.

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: Will meal-replacement bars work well for a multiday backpacking trip in the mountains? It will only be for a few days, and I am thinking of taking bars instead of freeze-dried food. Some bars try to be balanced meals, while others are only slightly better than snacks. Assuming I have plenty of water, do you foresee any problems relying on them for a few days at 10,000 feet? -- M.H., Indio, California

DEAR M.H.: My response assumes you are in appropriate shape for such a trek, that you have been fully acclimated to high-altitude hiking, and that the only issue is what you would be eating. That said, an approach based on real food would be preferable, as it offers a wider variety of flavors and textures.

You might find that after living off of meal bars for a few days, they’ll all begin to taste alike, and mealtime will lose its appeal. You could do a mix of bars and regular meals to see how it works out on the trail. But this is a short-term issue, so I can see no serious issues if you want to focus on sports bars.

Sample all prospects in advance, as you may not find all of them to be pleasing to your palate. You will be exhausted after hiking all day, and will want something satisfying to eat. Find an assortment that brings together sufficient energy (calories), high protein and a balance of nutrients. Select some designed for exertion and others designed to be meal replacements. Have a variety of products so that you won’t get bored.

Consider supplementing this selection with foods such as jerky, nuts and dried fruits. These will bring concentrated energy, nutrients and variety -- the latter providing a welcome hedonic boost. Add sufficient fluids, and you will be all set.

It’s only two or three days; the key is to bring along enough calories and nutrients to facilitate, rather than impede, the outing.

DEAR DR. BLONZ: Tell me a bit more about xanthan gum. I have a corn allergy, and recall you writing that xanthan gum is made from corn. It is my understanding that it is the end product of a fermentation process involving Xanthomonas campestris, which is mainly “fed” corn syrup as its source of sugar. These are gum-producing bacteria, which yield xanthan gum. As such, I am not sure it can be said to be made from corn syrup. -- S.F., Hayward California

DEAR S.F.: Much in the same way that we might think of beer as being “made from” grains, it is not that misleading to think of xanthan gum as coming from corn. That earlier column had been generated from a reader’s concern about a corn allergy, and I adapted the answer to fit that paradigm. To be more precise, consider that xanthan gum, a preservative used to help thicken and stabilize foods, is made “using corn.” It is refined, and this should, in theory, remove any corn protein. But that represents an unknown for any particular manufacturer, so I counsel avoidance -- or at least awareness and caution -- for those with a corn allergy.

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.