What cools you down, and what heats you up

Ever wonder if eating ice cream will really cool you down, or whether eating a spicy dish would be a better idea?

Well, look no further. We asked a group of top food scientists to help us solve these and a few other mysteries. Here are the answers.

Does ice cream really cool you down?

Even though ice cream doesn't really have to have a cooling effect for you to enjoy it, I guess it would be nice to know there is some benefit besides taste. "Anything ingested that is lower than actual body temperature will initially produce a cooling effect systemically," says Gerard E. Mullin, the director of gastroenterology at Johns Hopkins Hospital.

But don't reach for your ice-cream scoop just yet. About 15 to 20 minutes after you eat it, ice cream has the opposite effect. "This is because the parts of the body that are in contact with the ice cream are physically cooled by the contact as heat is transferred to the ice cream. However, as the digestive process kicks in, body temperature increases as the body works to digest and absorb the nutrients in the ice cream, as well as to store the calories," says Josephine Connolly-Schoonen, a professor of family medicine, Stony Brook University Medical Center.

"The body will physiologically respond to energy (i.e., heat) loss by increasing blood flow to the 'cool' region and bring the temperature back up to a physiological 'body temperature,' " (98.6 degrees), adds Barry G. Swanson, a professor and co-chair of Food Science and Human Nutrition at Washington State University. So, eating cold foods does not really change your overall body temperature.

How about an ice-cold beer to battle that summer heat?

Hmm ... Despite the ice-cold container, beer may not be the best choice to keep you cool. Alcohol creates dehydration. "It does this by inhibiting the release of the hormone vasopressin. Vasopressin (also known as antidiuretic hormone) is responsible for the reabsorption of water from the kidney tubules. Inhibition of the release of this hormone results in less water 'reabsorption' from the kidneys and hence more urine production, leading to dehydration," says Stephen J. Pintauro, a food scientist at the University of Vermont. "Additionally, alcohol requires energy to metabolize, and during the metabolism of alcohol, water is used," says Swanson. Which further adds to the issues of dehydration. And how does dehydration heat you up?

"Body temperature is affected by how well you hydrate your body, how much water you have in your muscles, blood and cells," says Lona Sandon, a professor of nutrition at the University of Texas Southwestern Medical Center at Dallas. Body fluids also serve other purposes. "The first purpose is to fill small blood vessels near the skin so blood can pass by the skin and lose heat to the environment. The second purpose is to generate sweat that wicks heat away as the sweat evaporates off the skin," says Schoonen. Therefore, if you do not drink enough fluid, and/or you're dehydrated, your body water levels will be low, and your body has a harder time staying at normal temperature. "Drinking plenty of fluids will help keep you cool," adds Sandon.

Does eating spicy foods cool you off?

Is that logical? Spicy foods cool you down? Well, spicy foods are more common in tropical countries — you know, where it's very hot. One reason for this might be the phenomenon called "gustatory facial sweating," which is common after eating hot peppers, according to Luke LaBorde, a professor of food science at Penn State University.

Spicy foods may actually make you feel warmer at first, and then you might feel cooler. According to Swanson, "The heat resulting from eating spicy foods is a pain response to select molecules. If you perspire from eating spicy foods and find yourself in a breeze, then your body will cool by evaporative cooling. Eating spicy foods often results in 'flushing' or a surge of blood to the skin, somewhere on the body. This regional increase in blood flow may result in increased temperature, and as the flushing dissipates, you may feel cooler."

Charles Stuart Platkin is a nutrition and public health advocate, author of "The Diet Detective's Count Down" (Simon & Schuster, 2007).