DEAR DOCTOR K: I have high blood pressure. Should I take a potassium supplement?
DEAR READER: This is a great question, but before I answer, let me take a step back to explain the connection between potassium and blood pressure.
DEAR DOCTOR K: Many years ago, my doctor told me that men, like women, should take calcium supplements. So I have been. Now I hear that it's a bad idea. What do you think?
DEAR READER: All of us -- patients and doctors -- wish we had all the answers, and that the answers never changed. Unfortunately, the way the human body works, and malfunctions, is very complicated. To understand it, we conduct research. But no study is perfect, and the answers sometimes change as larger and better studies are conducted.
DEAR DOCTOR K: It seems like several years ago all my friends were taking antioxidant pills. Now I don't hear about antioxidants as much. Are they worth taking?
DEAR READER: Here's what we know, and here's what is still controversial. The cells of our body are full of chemicals interacting with other chemicals. In the process of getting the energy they need to survive and carry out their functions, cells naturally produce chemicals called "free radicals." Just as political free radicals can sometimes damage society, chemical free radicals can damage body tissues.
DEAR DOCTOR K: I'm a 65-year-old woman. My doctor says my bones are strong, and he wants to keep them that way. So, for years I've been taking a daily 1,200 milligram calcium supplement. Now I hear that might be too much. How much calcium do I really need?
DEAR READER: I've gotten this question from so many patients. As I assume is true for you, their bones have normal amounts of calcium. That is, they do not have osteoporosis (or "thin bones"). To prevent osteoporosis, they have been taking the recommended amount of calcium -- 1,000 milligrams (mg) a day for women ages 50 and younger and 1,200 mg for women over 50 -- in an effort to preserve their bones.
DEAR DOCTOR K: My new doctor recently told me I had pernicious anemia, that it had not been diagnosed by my old doctor and that his treatments would end my symptoms. What is pernicious anemia?
DEAR READER: The cause and treatment of pernicious anemia were discovered more than 80 years ago, here at Harvard Medical School. The discovery was honored with the Nobel Prize. Unfortunately, even today there still are people like you for whom diagnosis and treatment have been delayed. That's because, as I explain below, it can be a tricky condition to diagnose. With pernicious anemia, vitamin B12 cannot be absorbed by the intestines.
DEAR DOCTOR K: Heart disease runs in my family. Should I eat fish, or take fish oil supplements?
DEAR READER: Eating fish regularly reduces a person's risk of sudden death from heart disease. It's also brain-healthy. For that reason, I and most doctors recommend a regular diet of fish for people who have heart disease. And also for people like you where heart disease runs in the family. Fish oils are rich in omega-3 fatty acids, a kind of "healthy fat."
DEAR READERS: In yesterday's column I began to answer a reader's question about the different causes of vitamin B12 deficiency, and whether to treat them with shots or pills. Today, we continue a discussion of the many conditions that can interfere with the ability of the small intestine (the part called the ileum) to absorb vitamin B12 from the foods you eat. As we get older, some people have more trouble absorbing the vitamin B12 in their food during digestion. Vitamin B12 in food is like leaves on a tree: It needs to be shaken loose. Stomach acid (and another stomach chemical called pepsin) are what shake vitamin B12 loose from food, allowing it to be absorbed by the ileum.
DEAR DOCTOR K: I was recently diagnosed with a vitamin B12 deficiency. Can I take B12 supplements by mouth? Or do I need the shots?
DEAR READER: Tissues throughout the body need vitamin B12, especially in the brain, spinal cord and bone marrow, where blood cells are made. Vitamin B12 in the diet gets absorbed in the part of the small intestine called the ileum. There, it enters the blood. Vitamin B12 deficiency can cause anemia, and problems with the bones, brain and spinal cord. Low vitamin B12 levels in the blood basically have two causes: Either there is not enough B12 in the diet, or the B12 in the diet has trouble getting absorbed by the ileum. B12 is found naturally only in animal products like meat, fish, poultry, eggs and milk. Many cereals are fortified with it.
DEAR DOCTOR K: Whatever happened to the idea that vitamin C can boost your immune system and prevent colds?
DEAR READER: Vitamin C, also known as ascorbic acid, was promoted as a health supplement for decades. It is perhaps best known for its one-time reputation for preventing and treating the common cold. This idea was heavily promoted in the 1970s by one of the 20th century's most celebrated biochemists, Nobel laureate Linus Pauling. But Pauling did not win the Nobel Prize for his theories about vitamin C. Vitamin C is crucial for making collagen, the substance that lends structural support to tendons, ligaments, bones and blood vessels.
DEAR DOCTOR K: I'm a man in my 50s, and I've been feeling run-down. Is it possible I'm not getting enough iron in my diet?
DEAR READER: Many patients ask me this question. I think it has to do with an old commercial for a popular vitamin and mineral supplement to treat iron-poor "tired blood." Iron helps make hemoglobin. That's the molecule that grabs oxygen in the lungs and transports it around the body to release it as a source of energy to the cells in the body. The USDA recommends that adult men get 8 milligrams of iron per day in their diets.
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Dr. Anthony Komaroff is a practicing physician, Professor of Medicine at Harvard Medical School, and Editor in Chief of the Harvard Health Letter. Learn more »
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