DEAR DR. BLONZ: My husband has high blood pressure and is watching his salt intake. He doesn’t want me to add salt to our food, and he thinks he is being careful. But I am concerned about the hidden sodium in processed foods. How many milligrams of sodium are there in a teaspoon of salt? And how much should he be having per day? -- M.D., Berkeley, California

DEAR M.D.: There are approximately 2,325 milligrams of sodium in one teaspoon of salt. The Daily Value -- the set of nutritional guidelines developed for food labels -- uses an upper limit of 2,400 milligrams of sodium per day. The average sodium intake in the United States is between 4,000 and 5,000 milligrams per day.

The main concern about excess salt stems from its association with hypertension, or high blood pressure, which currently affects 1 out of every 3 adults. Hypertension is defined as blood pressure readings higher than 140 over 90. The first number (140, in this case) is the measure of the pressure in the arteries when the heart contracts, and the second number (90) is the pressure in the arteries as the heart relaxes between beats.

Hypertension is called the “silent killer” because there are no warning signs until problems such as heart disease, stroke, or kidney disease have already developed. The only reliable way to find out whether you have hypertension is to have regular blood pressure checks.

If your husband has high blood pressure and has been placed on a low-salt diet, you are correct in being concerned about hidden sodium. With the exception of sugar, we add more salt to our foods than any other condiment. About 10 percent of the salt we eat is naturally present in foods; 15 percent is added during cooking and at the table. That means 75 percent of the salt in our diet comes from processed foods.

Salt is added to processed food for a number of reasons. It can slow the growth of certain microorganisms; before refrigeration, salting was the only practical way to keep meat and fish from spoiling. Salt can also play a role in food texture: Processed meats such as bologna, hot dogs and lunch meats contain higher levels of salt because it helps form and maintain the gel-like consistency of these foods. Then, of course, there is salt’s role as a flavor enhancer. Salt can be delicious, but the key is to learn to enjoy foods’ natural flavors, not that which comes from the salt shaker.

There is definitely a relationship between salt intake and high blood pressure, but not everyone with high blood pressure will benefit to the same degree when reducing their intake of sodium. Research tells us that the most reliable way to help reduce elevated blood pressure is to lose excess weight, increase activity and decrease alcohol consumption. (Be sure to check with your physician before beginning any exercise program.)

There have been impressive numbers coming out of the DASH studies (Dietary Approaches to Stop Hypertension), showing how blood pressure can also be lowered by decreasing sodium intake and following a diet that’s low in total and saturated fat but rich in fruits, vegetables and dairy. Not surprisingly, the DASH diet was named again as the best overall diet (tinyurl.com/3j57mmw).

As regards processed foods, check the Nutrition Facts label to see the milligrams of sodium per serving. I suggest you begin making note of the processed foods you and your husband eat and keeping track of how much sodium they contain.

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: My daughter is sensitive to gluten, so I was wondering if glutamate will cause similar trouble. I cannot find anything helpful. One label, on a can of chicken broth, says: "Small amount of glutamate occurs naturally in yeast extract." Is this a likely problem? -- A.M.H., via email

DEAR A.M.H.: I am not aware of any connection between being sensitive to gluten and being sensitive to glutamate. These are completely different substances. Gluten is a unique mix of proteins found in the wheat family of grains, while glutamate is an amino acid found in all complete proteins -- in foods and in our bodies.

Yeast is a living organism that contains protein, so it is not surprising that it will contain some glutamate, along with other amino acids. However, yeast does not contain gluten. In short, sensitivity to gluten does not translate to sensitivity to glutamate.

DEAR DR. BLONZ: I put flax meal in my morning smoothies and sometimes on sandwiches and cereal. After opening a new package, should it be frozen or refrigerated? Would I be better off grinding my own from flaxseeds? Also: Is organic or gold flax any better than conventional? I consume about two tablespoons of it daily; is that too much? -- S.S., via email

DEAR S.S.: Flaxseeds should be stored in a cool place away from any direct sun or heat. Once ground, rely on refrigerated storage in a well-sealed container. Some already-ground flaxmeal is sold refrigerated, but if properly sealed (with little, if any, air, or with a controlled atmosphere in the package), the risk of oxidation is limited.

As regards grinding at home: As long as it's properly packaged and stored, there is no "better off" either way, so the choice would be yours. Always check for freshness dating on the package. I don't favor purchases from a room-temperature bulk bin.

Flax should have a mild, nutty flavor and aroma, so give it a sensory check when the package is first opened. This can provide a baseline for repeat assessments after the ground flax has been around for a while. If you detect "off" odors or flavors, that's a sign that it's time to toss it out (or put it in your compost bin). I also favor organic, not necessarily because of significant evidence that the organic flaxseeds are more healthful, but because I feel we need to encourage (with our purchases) this method of agriculture when possible. It benefits the land, and those who work in agriculture.

Ground flaxseed can add a flavor dimension and nutritional quality to other foods. There is no daily requirement for flax, so the amount you consume is up to you. Depending on the brand, a two-tablespoon serving of ground flaxseed will provide in the range of 3-4 grams of protein, 4 grams of carbohydrates, 6-8 grams of fat and 4-6 grams of dietary fiber.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 read that the minute a jar or bottle of cooking oil -- such as safflower, canola, peanut or olive -- is opened, oxygen enters and the oil starts to go rancid. Will refrigeration stop this? I know that people won't die from using unrefrigerated oils, but are there negative consequences, healthwise? I read the label on a bottle of canola oil and it said nothing about needing to be refrigerated. And what about fish oil in capsules? -- J.S., Phoenix

DEAR J.S.: Any oil can go rancid if stored in the wrong way. Rancidity occurs when the oil reacts with oxygen. Aside from having an odor and giving foods an "off" taste, the consumption of oxidized oil does represent a health risk.

With refined oils, there is only minimal risk in leaving oils at room temperature, provided you follow some simple guidelines. Oils should be stored out of the sunlight and away from any source of heat. Since air, and therefore oxygen, gets in whenever the container is opened, keep the container sealed when not in use. This doesn't mean you need to get frantic and cap the container instantly, but it does make sense to close it when you are done, especially if it takes you months to get through the entire container. If you buy more oil than you tend to use in a few months, consider splitting the large size into smaller portions and refrigerating the unused bottles until needed.

Whenever an oil is stored in the refrigerator, keep it well-sealed to prevent it from picking up any undesirable refrigerator odors. Some oils may become cloudy when refrigerated, but this disappears when they return to room temperature, and is not a reflection on the oil's wholesomeness.

It is an oil's points of unsaturation, the double bonds in its fatty acids, which are most vulnerable to attack from oxygen. This means that the greater the degree of unsaturation, the greater the tendency to oxidize. As produced in nature, oils are blends of fatty acids with varying degrees of unsaturation, but we tend to classify them by their predominant type. Monounsaturates, such as olive oil, mostly contain one double bond. Polyunsaturates, such as soy, corn and safflower, have two. These types are more stable, but they should also be well-sealed and stored away from sun and heat. With flaxseed oil, over half the fats contain three double bonds, so it should be chilled.

Fish oils have four or five double bonds, so they are among the most susceptible to oxidation, and should always be refrigerated when in bottles. As dietary supplements, however, fish oil tends to be dispensed in air-tight capsules, which can be kept at (cool) room temperature.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.