DEAR DR. BLONZ: We have been shifting away from meat and making more vegetarian dishes lately. We're considering eating tofu, and I have a few questions. How much fat and other nutrients are in tofu, and how long should soybean tofu be expected to last? What is going on when it starts to change color, and is it no longer safe to eat at that point? Does tofu interfere with minerals in other foods? -- S.T., Sun City, Arizona

DEAR S.T.: Unlike other legumes, the soybean is relatively high in fat content; about half the calories in tofu come from fat.

There are a lot of steps to get from the soybean to the tofu. After soybeans have been soaked, crushed, cooked and filtered, calcium sulfate is often added to the soy pulp, which causes it to form a gel. Excess water is then removed as the soy gets pressed into cakes.

There are minor differences among different tofu makers, and there will also be variations between degrees of tofu firmness. But as a general benchmark, just under half the calories in tofu come from fat. A half-cup serving of firm tofu made with calcium sulfate (nigari) supplies 88 calories, 10 grams of protein, 2 grams of carbohydrate and 5 grams of fat (43 percent polyunsaturated). Other nutrients include 2 milligrams of iron (11 percent of the Daily Value), and 253 milligrams of calcium (25 percent of the Daily Value for adults). The calcium comes primarily from the calcium sulfate used to form the tofu into cakes.

Because of its relatively high content of polyunsaturated fats (PUFAs), tofu is susceptible to oxidation when exposed to the air for an extended period of time; the warmer the air, the greater the risk. As such, most tofu is kept refrigerated in water, or is vacuum-packed. When you purchase tofu, make sure it's stored in a similar manner. Tofu should be discarded if the storage water becomes cloudy, if a slippery film develops on the surface, or if you notice any unusual smells or tastes. Also, the tofu should be discarded if it takes on a pinkish tinge -- usually the effect of exposure to air. If the water is changed daily, fresh tofu can last up to two weeks in the refrigerator.

Regarding minerals, as long as it is consumed in moderation, tofu and soy milk are versatile, nutritious foods. Soy does contain phytic acid (phytate), as do other legumes and grains. This substance has anti-nutritional properties, in that it can bind with certain nutrients like iron and zinc and inhibit their absorption. This is a direct, physical effect that takes place in the digestive system; the ability to bind is limited by the milligrams of phytate present.

Tofu and soy milk contain phytates, and regular cooking doesn't affect the phytic acid that much. One way to blunt the phytate effect is via fermentation. This can occur in grains, as a yeast changes flour into bread. With soybeans, phytate gets broken down when the beans are fermented into products such as natto or tempeh.

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 recently that some people did a chemical analysis of white wines and found them to have five to 10 times the amount of arsenic that is allowed in an equal amount of drinking water. I was all set to throw my stash out when a friend suggested that we drink far more water than white wine, ergo the arsenic intake would not be harmful. Please offer your thoughts. Sincerely, B.R., via email

Dear B.R.: This is an evolving issue where there may be uncertainty over who or what to believe. Here is a brief background, and a number of links for follow-up. To start with, arsenic is a naturally occurring element (chemical symbol: As) that is distributed throughout nature. It tends to be present at varying levels in geological formations and, as a result, it can also be found in groundwater. It then is naturally taken up by fish and plants, and can also be found in animals that consume them. Arsenic is also found in various commercial products, including wood preservatives, fertilizers, paints, dyes and semiconductors. Various industrial practices, such as smelting and coal burning, release arsenic into the environment. Arsenic is considered a potent poison because it can interrupt essential reactions in the human metabolism. Acute overexposures can be fatal, but chronic exposures at sub-toxic levels can also cause problems. The U.S. Department of Health and Human Services has an information page on arsenic exposure (tinyurl.com/btcrc3o).

The toxicity of arsenic depends on its chemical (oxidation) state. Inorganic arsenic, which is found in geological formations, mines and groundwater, is considered the most toxic. Organic arsenic, which represents the forms of arsenic that have been taken up by plants and animals and made a part of their biochemical substance, is less harmful. (Depending on the circumstance, a plant, fish or animal can contain both forms at the same time.)

The human body has a means, albeit slow, to eliminate unwanted arsenic. The most critical element, of course, is to avoid the possibility of an acute exposure to a dangerous level of any type of arsenic. If the body experiences chronic exposures at a lower level, such as from the water supply, the key is to avoid an intake of the more-toxic inorganic arsenic that exceeds the rate at which the body can send it on its way. The half-life of inorganic arsenic in the human body is about 10 hours, and about 70 percent leaves via the urine. The Environmental Protection Agency sets limits for arsenic in drinking water of 10 parts per billion (tinyurl.com/3eu8sws).

Back to your question about arsenic in wine: There are some lawsuits filed, and when you toss in the possibility of litigation, everyone tends to shut up, save those who have a personal interest in a certain slant on things. What to do in the meantime? I found a number of accounts worth reading. The first, by National Public Radio, is informative and provides needed perspectives (tinyurl.com/o8jwkjs). Another is from Snopes.com, a site that strives to inject objective perspectives into various "urban legends" (tinyurl.com/q485ext). For those interested in a more scientific approach, there is a fact sheet from the University of California at Davis with specific ranges and implications(tinyurl.com/krrbls8).

As one who enjoys a glass of wine, I will continue to follow this issue.

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 wanted to share my formula that has been working to slow, and even counter, my expanding waistline: Eat slowly, chew completely, relax and enjoy your food! That's it. I'm surprised no one has mentioned this very simple method. Except maybe it isn't so strange, when you consider that it costs nothing! -- M.D., Vallejo, California

DEAR M.D.: The road to weight loss tends to be a long trek, but your logic is definitely on track. Most of us fail to understand that it takes years, if not decades, to amass the unwanted pounds we are anxious to lose. We balk when it comes to the battle, and this opens the door for products promising a quick fix. Most offer nothing more than an effective sales pitch, and the only thing lost is our bank balance.

Here are some successful weight-loss steps I have gathered; you will see your "eat slowly" on the list.

-- Plan meals. Eat three meals a day and envision definite portions before you start the meal. If you're still hungry after the main course, fill up on salad, low-calorie vegetables, fruits and whole-grain breads.

-- Add more liquids to your diet, such as soups, low-calorie beverages and water. These can provide fullness and help cut down on calories.

-- Eat slowly, and pace your meals to a minimum of 20-30 minutes. The brain doesn't provide instant feedback that the body has taken in enough food, so if you eat until you feel stuffed, you've probably had too much.

-- Keep your activity level up. Try to introduce new activities often, such as riding a bike, or find a park, neighborhood or shopping mall in your area where there are good walking trails. Make walking and taking the stairs a part of your daily routine. When running errands, park far away from the entrance rather than hunting for the closest space.

-- Set up a schedule where you ride a bike or walk at least three times a week. Listen to music, podcasts or audiobooks, or watch something while you exercise. (I watch movies on my iPad while using the elliptical trainer at the Y. It makes the time -- and the stored calories -- slip away.)

-- Make a commitment and keep track of your efforts. Decide on a way to score your progress, and set up a series of incentive rewards for intermediate goals. Share your efforts with your partner, and consider telling others in your social circle who might have similar concerns. This will add support, along with social pressure to succeed.

-- Shift to a monthly weight check. Body weight is a sum of fat, muscle, bone and water, and does not always reflect changes in body fat. Understand that there will be periods during which your scale weight will not change, despite a continued adherence to your plan (and loss of body fat).

-- As you begin to lose weight, alter or replace clothes that no longer fit. You'll immediately know if lost pounds begin to reappear.

Self-directed individuals are more likely to succeed, so why not you? With patience, conviction and good planning, you can achieve positive results. But whatever happens, the above strategies will definitely result in a healthier you.

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.