DEAR DR. BLONZ: I have shifted from animal sources to tofu as my primary source of protein. I am about 5 feet tall and I weigh 104 pounds. Is there anything about how tofu is made that I need to consider, and how much tofu should I have daily to satisfy my protein needs? I use tofu in a shake in the morning and add it to soups and salads. I scramble it, and I'm familiar with many other ways to prepare it. -- S.T., Tulsa, Oklahoma

DEAR S.T.: One serving of meat, poultry or fish is approximately 3 ounces, equivalent in size to a deck of playing cards. When trimmed of all visible fat, one serving would contain approximately 25 grams of protein. A cup of extra-firm tofu contains an equivalent amount of protein.

One way to estimate your recommended daily protein intake in grams per day is to multiply your weight in pounds by 0.36. A 104-pound body weight would require 37 grams of protein per day. (For more on protein recommendations, see b.link/hva5ju7.)

You indicate that tofu is your main protein source. Enjoying tofu is fine, but a single food should not serve as your dietary focus. Be sure to include other sources of protein. For vegetarians, these other sources might include nuts and seeds or a well-balanced diet containing grains and legumes, as these provide all the essential amino acids the body needs to make protein. For others, protein can come from fish, poultry and dairy, and red meat on occasion. The issue is not so much the source of the protein as the complement of other foods in the diet.

Tofu is made from soybeans that have been soaked, crushed, cooked and filtered. (For more on soybeans, see b.link/7y7jtya.) Calcium sulfate is then added, which causes the soy pulp to form a gel. The water is then removed as the soy is pressed into cakes. Tofu has a relatively high level of polyunsaturated fats, which can turn rancid when exposed to air -- especially warm air.

Fresh tofu must be packed in water and kept refrigerated. When purchasing fresh tofu, make sure it has been properly packaged and stored, and you should take it home in a well-sealed plastic bag that contains water. There are other options, one of which is to buy cakes of tofu in refrigerated, commercially sealed, water-filled packages; another is to buy tofu that is vacuum sealed in an aseptic package.

Discard tofu if the storage water becomes cloudy, if a slippery film develops on the surface, if you notice any unusual smells or if it takes on a pinkish tinge -- usually the effect of exposure to air. If the storage water is changed every day, fresh tofu can last up to two weeks in the refrigerator.

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: Do dried blueberries have the same antioxidant benefits as fresh ones? -- C.D., Albany, California

DEAR C.D.: Depending on the size and degree of hydration before harvest, a fresh blueberry is about 80% water by weight; a dried one is about 15% water (it may be less, depending on the degree of drying). With a dried berry, you get more nutrients and calories by weight (check the added sugars if they are sweetened). When dried, there will be a just slight loss of nutrients, but the loss of antioxidant substances is negligible -- nowhere near enough to dampen the flavor and nutritional value.

Dried blueberries are an excellent source of dietary fiber, and they contain the bountiful nutrients and beneficial phytochemicals found in fresh berries, so use fresh or dried -- whichever you prefer. I use fresh blueberries, preferably organic, in my morning breakfast, which includes plain whole-milk yogurt and a high-fiber granola.

When out of season, I rely on frozen blueberries. I always have dried fruits in the house, including cranberries, raisins, raspberries, cherries and blueberries, which I enjoy with various nuts (and a few dark chocolate chips) for my homemade trail mix, which also works as an office snack, allowing convenient access to flavorful, real food.

DEAR DR. BLONZ: One of my friends got his elevated cholesterol back in the desired range since he started taking a statin drug more than a year ago. Lately, however, he has become a bit lax in how he eats. Is there any reason, except perhaps for weight issues, why it would be best for him to stay away from foods that are high in cholesterol and fat if those statin pills keep his numbers in the good range? -- K.M.

Dear K.M.: I will offer general advice, as this is best discussed with a professional familiar with his family history and the specifics of his health situation. Medications prescribed to control an elevated blood cholesterol level should not be thought of as a license to eat and live in an unhealthful manner. Taking a statin or any cholesterol-lowering drug provides a means to correct a symptom of imbalance associated with an increased risk of disease.

Whether due to a genetic predisposition, poor diet or lifestyle factors, our blood cholesterol values become elevated for a reason. It makes little sense to think that a pharmaceutically lowered cholesterol level is the only fix needed. Such meds do not relieve us of the responsibility to treat our bodies with care. If you need the medication, by all means, use it. But wouldn't it be a worthy goal to make the appropriate changes to reduce or eliminate the need for the medication? (Read more about cholesterol in the blood at b.link/suaf5qb. See b.link/vq74z82 for an article on the impact of family history on heart disease and stroke.)

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 often refer to the "Nutrition Facts" label in your columns, but I have always wondered about the information listed. How are these figures arrived at, by whom, and how reliable are the values? -- A.W., Walnut Creek, California

DEAR A.W.: The accuracy of the information on the "Nutrition Facts" label is the responsibility of the company selling the food bearing the label. With few exceptions, all regulated foods must display nutrition information on the package or have that information available to consumers in other ways.

There are exceptions for small businesses with fewer than 100 full-time-equivalent employees or food product sales of less than 100,000 units annually. (For importers, the exceptions are: fewer than 10 full-time-equivalent employees and sales under 10,000 units annually.) Retailers are exempt if their annual gross sales are less than $500,000 or their gross sales of foods to consumers in the U.S. are less than $50,000. Nutrition labeling for fresh fish or produce is voluntary.

The information on nutrition labels is generally reliable, and is subject to periodic review. The FDA takes samples from store shelves to check for accuracy, and they allow up to a 20% difference between what's listed on the label and what is found in product analysis. Infractions can result in penalties such as fines and product seizures. Food companies, especially larger ones, have much at stake, as the penalties can be hefty. (For more on Nutrition Facts label accuracy, check b.link/z22pgnw.)

There are several consumer options if you have doubts. First, it helps to do a side-by-side comparison of similar products from different companies. Be sure to factor in serving size and the similarity of the top ingredients, which must be listed in order of decreasing prevalence. Another option is to check the company website, or contact the company directly.

There are now extensive food composition resources available online. The USDA's FoodData Central database can be accessed at b.link/7f92kh5. For a nutrition value calculator, including nutrient options in standard servings, adjusted serving sizes and totals for recipes, see b.link/avx5kqc.

DEAR DR. BLONZ: Since my husband's heart attack earlier this year -- which was caught early, and he is doing quite well, all things considered -- we have limited our fat intake to olive, avocado and canola oils. I find many "healthier" foods and desserts contain expeller-pressed canola oil. What is that? Is it hydrogenated? -- K.K., Palm Springs, California

DEAR K.K.: Expeller pressing is used to extract oil from an oil seed. This process utilizes mechanical pressure rather than a chemical solvent, resulting in cleaner oil -- no solvent residues -- higher in natural colors and flavors. It has nothing to do with hydrogenation. The mechanical pressure used for extraction can generate heat and decrease some nutrients, albeit to a minor degree. When looking for an expeller-pressed oil, consider opting for ones that keep things cool during extraction, referred to as "cold pressed."

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.