Summer is officially over. The kids are back in school. The Halloween/Thanksgiving food orgy is about to begin. Our preoccupation with sunscreen has been replaced by a search for last year’s mittens and scarves.

It won’t be long before the nip of Jack Frost brings folks in from outdoors craving a bowl of hot soup or a big steaming mug of hot chocolate or cider.

Everybody thinks that drinking hot liquid is what warms up a cold body, but the truth is that just coming inside where it’s warm is the most important thing. Drinking a thermos of hot coffee in a cold football stadium makes you feel warmer because the hot liquid increases blood flow to the skin. However, you might be surprised to learn that this actually results in somewhat greater body heat loss.

For the metrically challenged among you (and you know who you are), here is fair warning that we are about to engage in some “metrispeak”. Normal body temperature is usually about 37 degrees C (more or less 98.6 degrees F). Therefore, any food or liquid that you consume at room temperature (about 20 degrees C) would tend to lower body temperature and anything warmer than 37 degrees C would tend to raise it, but not by as much as you would think.

Believe it or not, the confusion comes from something with which we are all more than familiar — a calorie. Now pay close attention. At the end of this column, we want you to say: Hmmm, that’s interesting. I didn’t know that!

A calorie (with a small c) is a measure of energy expressed as heat. More precisely, it is the amount of energy needed to raise the temperature of a small amount of water (1 ml) by 1 degree C. The Calorie (with a large C) that nutritionists use is really 1,000 calories or one Kilocalorie (Kcal). One Kcal is the amount of energy needed to raise the temperature of about a quart of water by 1 degree C. The reason this is so difficult to understand is that people tend to use calorie (little c) to describe food energy as well as physical energy.

A cup of tea contains about 240 ml of liquid but essentially no food calories. The hottest temperature we can comfortably drink or eat is about 60 degrees C (140 degrees F). The difference between 37 degrees C (body temperature) and 60 degrees C is 23 degrees. If you multiply this by the 240 ml of liquid in the cup of tea, you get about 5,520 calories. This sounds like a lot of calories — especially for something we thought didn’t have any calories. In fact, if we were talking about Kcal, it would be equivalent to about 140 Oreo cookies.

However, to measure the amount of change in body temperature that could be caused by drinking 240 ml of very hot tea, we have to use calories, not Kcal, and 5,520 calories is only 5.52 Kcal (about 1/6 of an Oreo cookie), hardly worth mentioning at all. In order for the body to function and maintain a normal temperature, even at rest, it needs to take in about 50 to 70 Kcal per hour. This means that a cup of hot tea would only supply enough energy to run the body for about 5 minutes. Not much left over for heating the body up! By the same token, cold drinks in the summer won’t really cool you down, although you will feel cooler for a moment.