DEAR DR. BLONZ: I drink lots of tea, mostly green and black (decaffeinated) with my meals. I am a vegetarian, and a nutritionist was concerned that I may be "losing" protein because the tannins in tea bind up the protein in my food. Is it true that tannins bind up proteins? Are there any teas that I would do better with? -- W.S., Madison, Wisconsin

DEAR W.S.: Tannins are naturally occurring plant substances that belong in the family known as the polyphenols. Certain tannins can indeed react and bind with proteins, but it should not be a concern since they tend to spread out their binding to other substances as well.

As teas go, black and oolong do contain relatively high levels of tannins, and green tea contains lesser amounts. To have a tea with low or no tannins, you will need to find one that is not made from leaves of the traditional tea plant (Camellia sinensis).

Protein can be affected by tannins, but a few cups of tea a day will not produce a worrisome protein-depleting effect. Most people -- including vegetarians -- eat more protein than their bodies require. (An interesting historical aside: Tannins derived from trees have long been used to react with the proteins in animal hides, and this process is integral to the "tanning" of hides into leather.)

Tannins can also affect the absorption of minerals such as iron and calcium, and this might be of greater concern. If you tend toward iron-deficiency anemia, it makes sense to avoid drinking a high-tannin tea with a key iron-rich meal. Calcium is less of a concern because there tends to be more of it in foods than there are tannins in tea.

For most people, an occasional loss of a few milligrams of an otherwise plentiful nutrient should not be a great concern. Tea has a number of healthful benefits, so enjoy.

DEAR DR. BLONZ: Can you explain the nutritional roles of zinc and copper? I heard it is not OK to have these at the same meal. -- U.A., San Francisco

DEAR U.A.: Zinc plays a role in many enzymes, including those involved in detoxification, sex-hormone production and wound healing. It is also involved in taste and smell. Copper helps in the formation of red blood cells, is essential for normal hair and skin, and is needed for normal respiration and the production of certain antioxidant enzymes.

Both are essential nutrients, and there is no problem taking recommended amounts at the same time. I think the source of your concern is based on the fact that too much zinc can deplete the level of copper in the body; likewise, if copper intake is excessive, the level of zinc can suffer. This antagonism only comes into play if there is an imbalance.

The take-home message, at least with zinc and copper, is that we shouldn't overdo it unless there is a medical reason to do so. At present, the Daily Value for zinc is 15 milligrams and the tolerable upper limit is 40 milligrams per day. For copper, the Daily Value is 2 milligrams and the tolerable upper limit is 10 milligrams per day. These figures are for adults 19 years of age or older. (For those not familiar with this term, "tolerable upper limit" is the highest level of intake that is likely not to pose any risk of adverse health effects in almost all individuals.)

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: After my last health exam, I've decided to make the move to a vegetarian diet. I currently eat pretty well, having meat no more than a few times a week and fish at least once. I have heard many things concerning the lack of protein and of one kind of vitamin B in typical vegetarian diets. Do these concerns have any validity? Should I be taking a certain supplement in addition to my multivitamin? -- H.M., San Diego

DEAR H.M.: Health statistics for groups of vegetarians include lower rates of heart disease, obesity, obesity-related diabetes, colon cancer, lung cancer, breast cancer, hypertension, osteoporosis, kidney stones, gallstones and diverticular disease. Though some gains are connected to the lifestyle that's frequently adopted along with the new eating habits, these findings are certainly impressive.

Protein is rarely a problem for vegetarians eating a varied diet. However, if you are going to adopt a vegan diet -- that is, one with no animal products at all (no meat, fish, dairy or eggs) -- sources of certain essential nutrients will be harder to find. These nutrients include calcium, iron, zinc, vitamin B12 (the "B" you were referring to), vitamin D and riboflavin. You can get all of these nutrients in foods, but if you want a supplement for added insurance, these nutrients are the ones to look for. Again, if you continue to eat dairy and eggs, this is less of an issue.

In general, becoming a successful vegetarian means learning which foods are required for a complete diet. These food selections and combinations become very important -- especially with children and pregnant or lactating women. There are resources you can consult for more specific information. Nutritiondata.com provides a convenient nutrition breakdown of many foods, and it can suggest those that are rich sources of specific nutrients. Other online resources include the Berkeley Wellness Letter, tinyurl.com/le7r7l9, and the National Institute of Health MedlinePlus page: tinyurl.com/kwm6j3.

DEAR DR. BLONZ: Please don't be offended, but I am curious about where you went to school and what you studied. You are called a nutritionist, but many people use this title. Do you have a degree in nutrition? Are you a registered dietitian? -- S.S., Phoeniz

DEAR S.S.: It's never a problem to answer these questions. You are correct that many call themselves nutritionists; unfortunately, there is little regulation associated with the term's use. It is definitely "buyer beware" when seeking advice.

I did my undergraduate study at the University of Wisconsin at Madison, where I studied psychology, and my graduate degrees are from the University of California at Davis. I earned a master's degree in nutrition, working on a problem involved with food toxicology. My doctorate was also in nutrition, and I did research on the role of insulin in the development of obesity. I am not a registered dietitian. There is a brief bio online at blonz.com/bio.htm.

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: Is there a best food for fiber? I want to increase my intake and want something convenient that does not taste like cardboard. -- S.S., Concord, California

DEAR S.S.: We should aim for about 14 grams of dietary fiber for every 1,000 calories consumed, but Americans tend to eat rather low on the fiber scale. Population studies continually find that an increased consumption of dietary fiber is associated with a lower risk of diabetes, coronary artery disease and obesity. The best foods in terms of convenience and fiber content would have to be breakfast cereals: Cereal fibers are associated with the most overall importance to our health. There's no better way to start the day than with a bowl of fiber-rich cereal topped by fresh fruit. That is what I do. I also consider making time for breakfast to be a valuable adjunct to health.

If fresh fruit is unavailable for your morning bowl of cereal, consider dried fruits. They are an often-overlooked fiber resource with a great variety of rich fruit flavors, and the fact that they are dried gives them an extended shelf life. Their concentrated sugars also allow you to reduce or eliminate other sweeteners on your cereal. Dried fruits also work in your child's lunch box, or as a quick office treat, making a between-meal power snack when combined with nuts.

Next we have nuts, seeds, vegetables and grains, with legumes (beans) and whole grains being particularly low in fat and high in fiber. What about fiber supplements? There are plenty out there, and they may be appropriate when certain health issues are involved. But why even think of a supplement when you have all the fiber you need in whole grains and fresh, whole foods, which are the precise types of foods you should be eating? For more on fiber, consult the National Institutes of Health collection at tinyurl.com/2qp9l2.

DEAR DR. BLONZ: Does sunscreen prevent the absorption of vitamin D? I walk daily for about 30 minutes, but depending on the weather, I am covered with a light sweater or sunscreen. I am over 60 and take a calcium supplement with 1,000 IU of vitamin D. Am I getting any vitamin D from my daily exposure, or should I be taking additional amounts in a supplement? -- P.F., Oakland, California

DEAR P.F.: Sunscreens come in various strengths, but in general they are specifically designed to prevent ultraviolet rays from penetrating your skin. It is these rays that are necessary for the body to make its own vitamin D. You do, however, seem to have your D covered. Is there a particular reason you are considering taking more? You can discuss this with your physician. There are blood tests to determine the level of vitamin D in your body. Read more on sunscreens at tinyurl.com/kp895ep. The National Institutes of Health has a list of articles on vitamin D at tinyurl.com/mmtlu68.

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.