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This week we respond to questions about caffeine and complications of diabetes.

Dear HOUSE Calls,

How much caffeine is safe to drink in a typical day?

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There is not a right answer for everybody. (We really like our coffee, so we are not likely to err on the low side here!)

There are a few important side effects of caffeine, and by and large, we recommend listening to your body. Caffeine can cause or contribute to reflux, heart rhythm abnormalities, high blood pressure, irritable bowel syndrome, bladder spasm, anxiety, and insomnia. Most of these problems people can identify pretty easily. If you drink two cups of coffee and feel fine, but drink 4 cups of coffee and have heart burn or diarrhea, you should take the hint.

Insomnia is one of the tougher symptoms with which to deal. People feel tired, so they have a cup of coffee in the afternoon, and 6 hours later they have trouble sleeping. Caffeine has a long half life, which means it stays in your body for a long time. I recommend that people who are having trouble sleeping try to eliminate caffeine after lunch.

Regarding high blood pressure (often called hypertension), research has shown that if your levels of caffeine intake are relatively even day to day, it won’t have much effect on blood pressure.

Sorry for the long answer. The short version: about 2-3 cups (8 oz.) of coffee are fine for most people.

Dear HOUSE Calls,

I have type 2 diabetes. I have heard it can cause people to go blind or lose a limb. How can it cause this type of thing?

That is a great question without a short answer. High blood sugar causes blockage and inflammation of small blood vessels throughout the body. This includes the blood vessels to the heart, eyes, kidneys, feet, and muscles. The damage to the blood vessels is the common reason for diabetes as the leading cause of adult blindness and kidney failure in the US as well as one of the leading causes of heart conditions.

The high blood sugar directly damages nerves, especially those in the feet and hands.

The issue with amputations is a little more complicated. As people with diabetes lose sensation in their feet, they are more likely to get sores that go undetected and get infected. Then, poor circulation caused by blood vessel damage contributes to this problem, making healing less likely and more difficult. Wounds that get too deep, especially when they involve the bones, are more likely to result in amputation to avoid wide spread and life-threatening infection.

While all of this is quite scary, when you take good care of your diabetes with help from your family doctor, the chance of these complications is drastically reduced.

HOUSE Calls is a weekly column by Dr. Adam Zolotor, Dr. Adam Goldstein, and Dr. Cristy Page on behalf of YOUR HEALTH™ and the UNC Department of Family Medicine.

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