DEAR DR. BLONZ: I have cereal for breakfast most days, adding a tablespoon of ground flaxseeds to help add omega-3 fats to my diet. I have my own grinder and buy the seeds in bulk at my local market. A friend posed a question about whether I might be exposing myself to contaminants or germs because I do not wash the seeds before grinding. Is that something I need to worry about? Are there other options for purchasing and using flaxseeds? -- S.G., Las Vegas

DEAR S.G.: Food-grade flaxseed should arrive at the store clean and ready to eat. If they come in a package, there will be some form of freshness date, but when food is purchased from a bulk bin, the customer needs to exercise a bit more care. If you’re dealing with a food that will be cooked before consumption, that provides another element of safety, but that doesn’t apply to flaxseeds that are either eaten directly or simply ground before use.

Factors to consider with bulk-bin shopping are your knowledge and confidence in the store, as well as your inspection of the bulk-bin operation. Bulk containers should have seals to avoid dust, dirt and humidity. They should be positioned away from direct sunlight, and of a size that reflects the contents’ shelf life and the volume typically sold. Gravity-fed designs facilitate overall freshness, and they have the added feature of dispensing contents directly into the bag. Look around, and feel free to ask the manager how often the bulk bins are cleaned. If you are comfortable, and all seems fresh and clean, there is no inherent reason you can’t buy your food-grade flaxseed in bulk.

As to other options, soaking or washing flaxseeds prior to grinding raises issues, as the seeds will clump together: A soluble fiber gum comes off the seeds when soaked. If you want to rinse your flaxseeds, they should be dried completely before grinding.

Another option might be to purchase flax already ground. Proper storage is essential in that case, to avoid oxidation of the oils, given that the protective seed coat is no longer on the job. Some products may be packaged in a limited or controlled atmosphere, or be stored at cold temperatures. A well-sealed package is important in any case. One sold at room temperature, for example, is likely to have instructions to refrigerate after opening.

Opting instead for flaxseed oil will provide flax’s omega-3 fatty acids, but it also requires proper storage. A negative is that you will miss out on the other health assets in the whole flaxseed, including lignans and soluble and insoluble dietary fiber.

One final point: The main omega-3 of plant origin is known as ALA (alpha-linolenic acid, 18 carbons long). This fatty acid tends to be burned for energy, with only a small fraction getting converted into the longer omega-3s referred to as EPA (eicosapentaeneoic acid, 20 carbons long) and DHA (docosahexaenoic acid, 22 carbons long) that are found in fish and used by our body for different purposes. There is more info on flaxseeds and nutrition at the Flax Council of Canada: flaxcouncil.ca.

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: You recently wrote about imitation crab, or surimi, and I am curious about its nutritional value relative to the real thing. Even though it is made from fish, I wonder how much nutrition is destroyed in the manufacturing process. I am specifically interested in the relative amounts of protein, omega-3 fats, carbohydrates and sodium, and I try to avoid anything loaded with preservatives. -- J.K., Hayward, California

DEAR J.K.: Surimi is a type of processed seafood made up of less expensive varieties of fish, such as pollock, that are deboned, rinsed and minced until there’s nothing more than a bland and colorless mass. The surimi gets extruded into filaments that are woven together to resemble the texture and appearance of crabmeat muscle fibers, or other shapes.

Next comes flavoring and coloring. In addition to crab, surimi is used to form imitations of more expensive fish such as lobster, scallops or shrimp. The flavoring used is usually a concentrate made from real shellfish. This should serve as an alert to those with shellfish allergies: Surimi-based foods are not necessarily a safe alternative.

It may be difficult to tell the difference between surimi-based seafood salad and one containing the genuine article, especially if many other ingredients are present in the salad. Check the price, though, as surimi costs only a fraction of the price of genuine shellfish. And read the ingredient statement, which should be available from the clerk if you are purchasing bulk food from a deli counter.

Nonfish ingredients in surimi include sugar, carbohydrate-based binding agents, and flavorings (which may or may not include glutamate). Surimi is lower in fat than real fish, and it is not a significant source of the omega-3 fatty acids found in other types of seafood. A 3.5-ounce serving of surimi contains 10 grams of carbohydrate, while there is less than 1 gram in real crabmeat. The serving of surimi has about 12 grams of protein, compared with real crab’s 22 grams. Surimi is higher in sodium and lower in potassium than real crabmeat: Surimi contains 841 milligrams of sodium and 90 milligrams of potassium, versus crab meat’s 378 milligrams of sodium and 408 milligrams of potassium.

Surimi is not “loaded” with preservatives, and the flavoring is usually from natural substances. But as with most foods, there can be a variance in quality among the different brands. Read the ingredient statement to see what you are getting. You can find surimi-type imitation seafood in prepared salads in the deli case, but also in sealed containers in your store’s refrigerator or freezer section. Once opened, surimi should be consumed with a few days. Unopened, refrigerated packages can be kept for up to two months, and frozen surimi can be kept for up to six months. Check expiration dates for guidance.

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: Most fresh potatoes are not sold right out of the field, but are stored first -- sometimes for many months. Do they lose their nutritional value in storage? -- S.G., via email

DEAR S.G.: Fresh tends to be best, but if stored under proper conditions, potatoes do quite well with little nutrient loss. Cool, dry and dark conditions are the key, with “cool” defined as a range of 45-50 degrees F. Exposure to warmth or light will cause the potato to come out of its dormancy, begin to sprout and take on a greenish tinge. Potato sprouts or green parts are NOT to be eaten.

If stored correctly, mature potatoes will keep well for up to two months. Aside from their carbohydrate content, an average-sized potato (with skin) is a good source of vitamin C and potassium, and also provides a couple of grams of fiber, several B vitamins, magnesium, iron, phosphorous and zinc.

DEAR DR. BLONZ: My reading of food ingredient labels often reveals “modified food starches” somewhere on the list. I prefer to make foods from scratch, but this is not always possible. Are these ingredients I need to be concerned about? -- W.H., Charleston, North Carolina

DEAR W.H.: A modified food starch is a complex carbohydrate that has been chemically modified to change some of its qualities. These would include texture, the ease with which the starch dissolves, and how readily the starch can be digested. Modified food starches are used in processed foods as thickeners, as formulation aids (to help maintain a desired consistency or texture), as an anti-caking agent (to help keep powdered foods free-flowing), or as a humectant (an additive that absorbs and maintains a food’s water content). Typical foods that contain modified starches include sauces, pie fillings and gravies.

Modified food starches are usually synthesized from a naturally occurring food starch, and they are not considered to represent a health risk. Those sensitive to gluten, however, should avoid foods containing modified food starches unless specifically labeled as “gluten-free,” as the starch may have originally come from wheat or another gluten-containing grain.

DEAR DR. BLONZ: My son and son-in-law both suffer from kidney stones. Can you tell me what foods they should not eat? -- A.T., Phoenix

DEAR A.T.: Kidney stones are among the most painful conditions that people can have, and they can develop for a number of reasons. There are different types, so an essential first step is for each of your relatives to work with his physician to determine the type of stones he has, and what might be responsible for them. Don’t wait; find out what is going on. Once you have this information, there will be more specific steps to take. The therapy will depend on the type of stone being formed. About the only common advice is to drink plenty of water.

There is more information on kidney stones at the National Kidney and Urologic Diseases Information Clearinghouse: kidney.niddk.nih.gov

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.