If you have chronic difficulty with temperature sensitivity, it's a good idea to talk to your doctor, who may run tests to see if you have any vitamin deficiencies.

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We all know someone who is always cold. Or always hot. You might be one of those people who wears shorts all year, even in the chilly winter months. Or maybe you always have a sweater stashed in your bag, even in the summertime. Regardless of which side you may fall on, all healthy humans maintain a body temperature of about 98.6 degrees Fahrenheit (37 degrees Celsius), give or take a smidge depending on the individual workings of your body and the time of day you're taking your temperature (it naturally fluctuates throughout the day). So, if we're all about the same temperature, why do some people feel so cold all the time?

First, let's rule out two conditions that may be causing you to reach for a sweater.

There are two diseases that may cause cold intolerance: Raynaud's disease and hypothyroidism, and both should be diagnosed by a health care professional. The symptoms of Raynaud's disease include cold, numb fingers and toes that may turn blue or white (it may also affect your ears and the tip of your nose). It's caused by a problem with how your blood circulates in your body -- during an attack (brought on by stress or cold temperatures) the arteries that bring blood to your skin narrow, and those narrow arteries can't deliver enough blood to the surface of those extremities. Raynaud's disease is very rare, though, and most of us who feel cold all the time are probably not suffering from the condition. Hypothyroidism, a condition where your thyroid gland is sluggish, however, is more common, and one of its classic symptoms is an intolerance to cold temperatures.

And now that we've ruled those out, what about the rest of us? What you might not realize is that your diet, not how many layers of clothing you may or may not be wearing, may be causing you to feel cold. Let's talk more about the vitamins and minerals that are important in keeping your temperature just right.