Vitamins and Supplements

What is difference between vitamin D2 and vitamin D3?

DEAR DOCTOR K: My doctor advised me to take a vitamin D supplement. Why do I need vitamin D? Also, my pharmacy sells vitamin D in two forms: D2 and D3. What is the difference, and which one should I take?

DEAR READER: This is an area full of controversy because not enough research has been done. I typically recommend getting vitamins from food, but vitamin D is found naturally in only a few foods. Fatty fish is the main dietary source, and milk, many juices and breakfast cereals are fortified with it. We get most of our vitamin D from the sun: When sunlight strikes the skin, skin cells make vitamin D. But these days, people get a lot less sunlight than they used to.

Should I have my vitamin D level checked?

DEAR DOCTOR K: I've read several articles about the negative effects of a low blood level of vitamin D, but my doctor said I didn't need to have my level checked. Why not?

DEAR READER: Many of my patients are asking me the same question. Vitamin D has been in the news a lot in recent years, but we still don't have solid answers to many questions, including yours. There is strong evidence that people with a low blood level of vitamin D have higher rates of osteoporosis (thin bones).

How do you treat anemia?

DEAR DOCTOR K: My teenage daughter recently learned that she has iron deficiency and anemia. Why would her iron be low? What is the treatment?

DEAR READER: Anemia means that the blood does not have enough red blood cells. These cells carry oxygen from the lungs to the rest of the body. There are many kinds of anemia. In the United States, iron-deficiency anemia is the most common; it occurs when the body does not have enough iron to make red blood cells.

What can I do about my vitamin D deficiency?

DEAR DOCTOR K: I had some blood work done recently and was surprised to learn that I am deficient in vitamin D. How is this possible? What can I do about it?

DEAR READER: Vitamin D is an unusual vitamin. We get most vitamins from the foods we eat; our body can't make them. Unfortunately, vitamin D isn't found naturally in many foods. Fatty fish and milk (which is fortified with vitamin D) are the main food sources.

What could cause iron deficiency anemia?

DEAR DOCTOR K: I have iron deficiency anemia. What could have caused it? Also, my doctor wants me to take a daily 325 mg iron sulfate supplement. Is that dangerous? The recommended daily dose of iron is much lower.

DEAR READER: Most iron in the body is stored in red blood cells. If you don't have enough iron, it can lead to a low red blood cell count. Doctors call this iron-deficiency anemia, and it's more common in women.

Should I take extra folic acid to boost my immune system?

DEAR DOCTOR K: I'm a healthy woman in my 40s. Should I take extra folic acid to boost my immune system?

DEAR READER: Folic acid is, essentially, a vitamin. We all need vitamins. Indeed, the word "vitamin" was coined to refer to a substance that was essential to human life. The natural form of folic acid, folate, occurs in some foods, including vegetables, fruits, and dried beans and peas.

Do products claiming to boost immunity actually work?

DEAR DOCTOR K: I've seen many product labels that claim to boost immunity. Could they really help? Or should I be skeptical?

DEAR READER: Your immune system does a remarkable job of protecting you from bacteria, viruses and other microbes that can cause disease, suffering, even death. So it seems logical to want to give your immune system a boost. But the concept of boosting immunity actually makes little sense scientifically.

What are antioxidants?

DEAR DOCTOR K: What is an antioxidant? Should I be taking an antioxidant supplement?

DEAR READER: Something terrible often happens to medical scientists: A beautiful theory is murdered by a brutal gang of facts. The theory that vitamin pills with antioxidant powers — primarily vitamins A, C and E — could slow aging, fend off heart disease, improve flagging vision and curb cancer was beautiful and very plausible. As a result, some doctors urged their patients to take such vitamin pills daily.