"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.
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The best way to cool your body is to stay hydrated. According to the Institute of Medicine of the National Academies, women should consume 91 ounces of water a day, and men need 125 ounces—a good deal more than the 64 ounces (8 cups) generally recommended. However, we get a significant portion of that from consuming food (nearly 35 percent) and liquids other than plain water.
Should You Avoid Swimming After You Eat?
"After you eat your body sends extra blood to the stomach and intestines to help with digestion," says Schoonen. In fact, according to Mullin there is actually a "pooling of blood in the digestive tract after eating." Therefore, there is less blood available to send to other body tissues such as muscles, and, according to Mullin, this can result in cramping. Also, "The larger the meal the more work your body needs to do afterwards to digest and process the nutrients. If you start swimming some serious laps after eating, the body would be stressed to send enough blood to both the digestive body parts and the working muscles, which also need more blood brought to them while exercising," Schoonen explains. This stress may affect the heart and lungs, or may cause muscle pain, since enough oxygen cannot be carried to the working muscles.
However, "Having a light meal and then a relaxing swim is not a problem," adds Schoonen. So, eat light and chill out.