I am a 22-year-old man who loves drinking cola. I suppose I am nearly addicted. I prefer the regular type and not diet, as that has a funny taste.I know it is fattening and causes tooth decay, and I want to gradually reduce the amount I drink. But in the meantime, is there a way to drink it that reduces the risk of tooth decay? B.N., Tel Aviv Judy Siegel-Itzkovich comments: The Mayo Clinic Health Letter recently gave advice on this subject: Drinking soda, especially cola - which contains a large dose of acids as well as sugar - is indeed bad for your teeth. It eats away at the protective enamel, causing tooth decay. But if you can't pass up an occasional cola, there are ways to minimize soft-drink-related damage to your teeth. Use a straw when drinking, as it may help by reducing the contact between your teeth and the beverage. Position the straw near the back of your mouth. One study indicates that a straw positioned near the front of the mouth can, over time, expose your front teeth to a significant amount of acid. Don't brush your teeth right after drinking soda. You may damage the enamel, which is weakened by the acid in carbonated beverages. Drink it down quickly, and wash it down with ordinary water if possible. If you sip sugar-sweetened drinks over a long period, you're increasing exposure to acid and the risk of damage leading to tooth decay. At my local supermarket, "sea salt with iodine" is being sold. Printed on the container is the message: "The Health Ministry recommends enriching the salt with iodine." I want to know what effect iodine has on health and is it possible to be allergic to iodine? R.D., Kfar Saba Olga Raz-Kessner, chief clinical dietitian of Tel Aviv Sourasky Medical Center, replies: Natural salt is very rich in iodine, but in the process of cleaning salt from unnecessary substances, all the iodine is "washed out" as well. Iodine is necessary for normal functioning of thyroid gland, and iodine deficiency causes goiter - a very dangerous condition. That's why it is necessary to add iodine to salt, which is the most important source of iodine in the diet. Allergy or sensitivity to iodine is related to chemicals - and not food products - containing iodine. I am having a problem with constipation and occasionally see blood in my stool. My doctor wants me to take a laxative, but I am hesitant because they can become habit forming and eventually less effective. I seem to need more fiber. Your column recently listed the foods that cause gas and those that don't. Can you list the foods that cause constipation and those that don't, especially among fruit and vegetables? Also, I was told that apples contain pectin which can make constipation worse. Is that true? A.G., Jerusalem Olga Raz-Kessner comments on this as well: There is more than one reason for constipation, so every case should be checked individually and properly by a gastroenterologist, especially if you have bleeding! But in general, to deal with constipation, there are a number of things you can do: Drink at least eight glasses of liquids a day. Eat small meals regularly, preferably every three to four hours. Eat vegetables, preferably without peeling their skin; boiled or stir-fried vegetables are good as well as fresh ones, and even better if you suffer from flatulence. Eat whole-grain products. You can eat apples, as pectin is very good for constipation. This problem is not caused by food itself; it is often a result of slow bowel movements or more serious problems, so there is no list of "constipation-producing" foods. It is good for you to eat vegetables and fruits, but too many fruits can be fattening. There is no need to be afraid of using laxatives, whether natural or chemical, if you don't overdo it. To find the right way to deal with your constipation after visiting a gastroenterologist, you should go to a clinical dietitian for advice. Rx For Readers welcomes queries from readers about medical problems. Experts will answer those we find most interesting. Write Rx For Readers, the Jerusalem Post, POB 81, Jerusalem 91000, fax your question to Judy Siegel-Itzkovich at (02) 538-9527, or e-mail it to email@example.com, giving your initials, age and residence.