DEAR DR. BLONZ: Is guarana better than caffeine, and is it habit-forming? My religious beliefs recommend that I keep away from caffeine. I am 67 years old and retired. Even after a good night's sleep, I suffer from tiredness as soon as I wake, as well as lower leg aches. -- M.J., Provo, Utah

DEAR M.J.: Guarana, in essence, is caffeine. The active ingredient might go under the name "guaranine," but that is just another name for caffeine. Guarana comes from a paste made from the crushed seeds of a woody shrub native to the Amazon region. Caffeine (guaranine), which belongs to the alkaloid family, is the principal active ingredient in guarana. There is a higher concentration of caffeine in guarana than in the coffee bean, the kola nut or cacao (cocoa). Guarana also contain trace amounts of other alkaloid compounds, most notably theophylline and theobromine.

Caffeine, regardless of source, can produce tolerance, psychological dependence and habituation when consumed on a regular basis. Withdrawal symptoms, including headache, drowsiness and fatigue, can occur when intake is stopped abruptly. Interestingly enough, abstinence from caffeine is a very common cause of headaches after one has gone through surgery, as presurgical routines usually require that one stop caffeine. One study published in the Mayo Clinic Proceedings found it beneficial to give a small amount of caffeine intravenously to patients undergoing outpatient surgery who were at risk for caffeine-withdrawal headaches.

Leg aches can be brought about by any of a number of situations. It may be that you would benefit from stretching and flexibility exercises, or there may be some specific medications or even herbs to try. It could even be the bed you sleep on. You need to find out whether there is anything medical going on before you begin looking for methods -- or substances -- to provide relief.

DEAR DR. BLONZ: Please explain the origin of carnauba wax. I find it on candied almonds and other foods. Does it represent a concern as a food additive? -- N.N., Pinole, Calif.

DEAR N.N.: Carnauba wax comes from the leaves of the South American wax palm. It is used as a wax or a glaze and it has "GRAS" status (generally regarded as safe). It is one of a number of such compounds used in foods. Aside from carnauba, there are the oil-based compounds petrolatum and paraffin. Shellac, another commonly used wax, comes from an Asian insect and is also used on candies, jewelry and floor waxes. Carnauba is also used in car wax.

Waxes are applied to hard-coated confections, such as candied chocolates and almonds, but they are also used with produce, including tomatoes, apples, bell peppers, avocados, cucumbers, sweet potatoes, all citrus fruits, peaches, pumpkins, eggplants, squash and nuts in hard shells. In produce, waxes are applied to retain moisture, limit flavor loss and enhance appearance. Waxes are not considered harmful and are only used in small amounts. For example, The Center for Produce Quality estimates that one pound of wax will cover 160,000 pieces of fruit or vegetables.

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: These days, many of us who are getting up there in age are taking several prescription drugs, as well as dietary supplements. What's the total effect of all these substances? I have not been able to locate a resource where one can input all that he is taking to see how it may interact. Neither of my medical doctors have a clue, but they would also like to know about such a tool. Pharmacies can process this type of information, but only as it relates to prescription drugs. Throw in glucosamine, calcium, MSM, chondroitin and others, and it seems like no one knows! What are your thoughts? -- V.S., via email

DEAR V.S.: When prescription and over-the-counter (OTC) medications come to the marketplace, they have to go through FDA-mandated screening for potential interactions. Such is not the case with dietary supplements. In today's regulatory environment, what we have is a host of ongoing laboratory experiments where we are the guinea pigs. To be sure, not every combination is going to cause problems, but the risk is certainly there.

Consider that medications and dietary supplements -- even "natural" ones -- need to be metabolized and eliminated from the body. When multiple items are in the queue for processing, it can affect the way the body does its job, which can result in abnormal blood levels of medications that need to be tightly controlled. This, in turn, can lead to unexpected -- and possibly dangerous -- effects. Matters become even more complicated when multiple prescription medications, pre-existing health conditions, alcohol and who knows what else are also on the scene.

I am not saying that all supplements should be avoided, but the time has come when responsibility falls upon us, the consumers. My advice is to learn as much as you can. The Interactions Checker on drugs.com includes prescription medications and many dietary supplement ingredients. You can add your profile of products, and it will tell you where the red flags are. This is a good place to check before adding anything else to your regimen. Don't forget pharmacists, as they have the latest resources to help answer questions. Whenever you start a new medication, take the time to consult with your pharmacist to see if there are any issues with what you are already taking.

DEAR DR. BLONZ: My husband and I just turned 80 and we try to watch what we eat. After dinner, while we read or watch TV, we enjoy a small dish of ice cream. Is there anything wrong with this? -- H.L., Pleasanton, Calif.

DEAR H.L.: It is tough to provide specific dietary advice not knowing anything about the rest of your diet or health histories. With this as a qualifier, and making the assumption that you are in good health with a good lifestyle, there is absolutely nothing wrong with having ice cream; the key is the sum total of what we have for the entire day. With few exceptions, it doesn't pay to get worked up about individual foods. You are in the eighth decade of life, so you must have been doing something right. I encourage you to enjoy each other and enjoy your lives.

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: If I purchase tuna that is packed in water, will I get the same level of omega-3 fat that I would if I got the tuna packed in oil? -- M.M., Logan, Utah

DEAR M.M.: As a general rule, the oil used for canned tuna is either soybean or canola oil, not fish oil. Tuna in oil will contain extra fat, but little in the way of extra amounts of the healthful omega-3 fats. A 3.5-ounce serving of light tuna in water (drained) contains 0.8 grams of fat and 0.3 grams of omega-3 fats. Contrast this with light tuna in oil (drained), which contains 8.2 grams of fat and 0.2 milligrams of omega-3 fats.

For higher levels of omega-3 fats, use the albacore (white) tuna. A 3.5-ounce serving of water-packed albacore (drained) contains about 3 grams of fat, of which 1 gram is omega-3 fats.

Light tuna is made from the yellow fin and skipjack varieties, which contain less of the omega-3 fatty acids than albacore. One additional note about tuna: Because tuna is relatively high on the food chain, it can contain higher levels of contaminants such as mercury. It remains a flavorful, healthful fish, but it also makes sense to take steps to make good choices. When buying tuna, consider opting for tuna caught via troll, or pole-and-line. This will tend to be stated on the label. Check with the Seafood Watch (tinyurl.com/d464hdm) for more on the different types of canned tuna.

DEAR DR. BLONZ: What are the things in plant-based foods that prevent minerals from being absorbed? I'm concerned because my main source of calcium comes from vegetables and grains. -- R.R., Oakland, Calif.

DEAR R.R.: The compounds that limit absorption are known as chelators (KEY-late-erz) in that they bind, or chelate, nutrients -- in this case, minerals such as calcium and zinc. The two most common chelators are phytate, found in some whole grains, and oxalate, found in many fruits and vegetables, but most notably spinach and rhubarb.

Zinc deficiency was first described in people consuming a high-phytate cereal grain diet. It does not represent a problem when the grains are a part of a yeast-leavened bread, because yeast contains an enzyme that breaks the bond between the phytate and the mineral. That is not the case with an unleavened bread such as pita bread. Indeed, zinc deficiency tends to be prevalent in parts of the Middle East where pita bread accounts for about 85 percent of calories consumed.

There are plenty of reasons to enjoy spinach, such as its valuable phytonutrients, but its oxalate content means it should not be considered a good dietary source of iron and calcium (although it is high in both). Usually about 10 to 25 percent of the calcium in foods can be absorbed, but a study in the April 1988 issue of the American Journal of Clinical Nutrition reported that only about 5 percent of the calcium in spinach was actually absorbed. A second study two years later in the same journal reported that the calcium absorption in a low-oxalate vegetable, such as kale, was comparable to that found with dairy products.

If vegetables and grains are the core of your diet, make sure you include a wide variety of different food sources. Fruit and vegetable sources of calcium without significant quantities of oxalate or phytate include broccoli, turnip greens, collards, kale, mustard, figs and almonds.

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.