DEAR DR. ROACH: I was under the impression that fat was the major cause of Type 2 diabetes. When fat clogs the arteries, it does not allow sugar, from any source (table sugar, potato or Twinkie), to pass through the clogged arteries, which in turn causes the insulin levels to be abnormally heightened. Is this right? I saw nothing of this in your article. — R.A.S.

ANSWER: In Type 2 diabetes, the underlying cause is a resistance to insulin and a decreased ability to move sugar into cells. The exact cause for insulin resistance is not yet completely worked out. The resistance to insulin causes the pancreas to release even more insulin, leading to high insulin levels, which affects fat metabolism, leading to a propensity to gain weight. However, the blockage in arteries from fat deposits is more likely a result of diabetes, and not its cause. Also, because of the resistance to insulin, blood sugar is higher than normal, especially after eating, which also tends to damage blood vessels, particularly small ones.

A diet low in simple carbohydrates, especially simple sugars, is critically important for people with Type 2 diabetes. Healthy fats, from nuts or olive oil, for example, slow absorption of sugar and tend to improve blood sugar control, along with good sources of protein. Carbohydrates from plant sources are absorbed much more slowly, and should be the major source of carbohydrate calories.

Diabetes has become epidemic in North America. The booklet on it provides insight on its diagnosis and treatment. Readers can order a copy by writing: Dr. Roach Book No. 402, 628 Virginia Dr., Orlando, FL 32803. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. ROACH: I read your column on vitamin D and the difference between the sun in Miami in summer and Boston in winter. I’m always confused when I read about the time needed to get the proper amount of exposure to the sun because the recommendations never explain how much of the body is exposed.

I assume the suggested time of six minutes of summer Miami sun is for a person in shorts and a short-sleeve shirt, whereas the time in Boston during the winter is for a person who is bundled up so that only the face is exposed.

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This very much seems like an apples-to-oranges situation. Is there a chart available to show the sky conditions (full sun, partial sun, cloudy, etc.) and percentage of skin exposed (face, extremities, full body) for different areas of the country? — K.L.

ANSWER: The major difference in the increased time necessary for vitamin D conversion in Northern areas has more to do with the angle of the sun. While it is true that more sun-exposed skin increases vitamin D production, the sunlight is so weak in wintertime that it cannot efficiently convert vitamin D precursors to active vitamin D in Northern climes.

The other major issue is the amount of pigment in the skin: the lighter the skin, the more efficient at converting vitamin D, which is why darker-skinned people are at higher risk for vitamin D deficiency. (Many biologists think that vitamin D synthesis was the major evolutionary pressure favoring light skin in humans after they migrated north from Africa, despite higher risk of skin cancer.)

UV light penetrates light cloud cover reasonably well, and sometimes clouds can focus UV rays so that the UV light can be 25 to 40 percent stronger than on a cloudless day. This is good news for vitamin D formation, but bad news for skin cancer, so light-skinned people need UV protection if they will be outside for more than a short period, even if it’s cloudy.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.


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