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Salt for Sports

The key to retaining water during exercise is to take in salt to replace the salt you lose in your sweat. Until recently, many scientists did not appreciated how important salt is to retaining fluid in your body. Thirst is a late sign of dehydration. You lose water during exercise primarily through sweating, and sweat contains a far lower concentration of salt than blood. So exercisers lose far more water than salt, causing the concentration of salt in the blood to rise. A person will not feel thirsty until the concentration of salt in the blood rises high enough to trip off thirst osmoreceptors in the brain and it takes a loss of between 2 and 4 pints of fluid to do that.

You need to take salt to retain the fluid you drink while exercising. If you lose two pints of fluid, you can replace it with two pints of water if you also take salt, but if you don't take salt, it can take four pints of fluid to replace two pints of sweat because the water you drink will pass out through your kidneys. In one study, female competitive distance runners took in drinks with different concentration of salt during a four-hour run (British Journal of Sports Medicine, Volume 37, Issue 4, 2003). Ninety-two percent of those who took in plain water with no additional salt developed low blood levels of salt. Taking in fluid without also taking in adequate amounts of salt dilutes the bloodstream, so that the concentration of salt in the blood is lower than that in brain cells. This causes fluid to move from the low-salt blood into the high-salt brain causing the brain to swell which can cause seizures and death. Taking in extra salt during prolonged exercise increases thirst so you drink more fluids, and prevents blood salt levels from dropping so low that you become tired, develop muscle cramps, and can even die. You can keep yourself fresh during extended exercise by eating foods with salt and drinking frequently, before you feel hungry or thirsty. Once you feel hungry or thirsty, you will find it very difficult to regain your strength.


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Listen to my answers to these questions and lots more in HOUR 203 of The Dr. Gabe Mirkin Show


Dear Dr. Mirkin: Should I exercise when I have a cold or the flu?

Most doctors allow their patients to exercise when they have a cold, as long as they don't have a fever and their muscles don't hurt when they exercise. However, it's probably better to stop exercising altogether when you have an infection. You risk injury if you exercise when your muscles hurt at rest or when you start to exercise. When muscles are damaged, they release enzymes from their cells into the bloodstream and they fill with blood from broken blood vessels. One study reported markedly increased muscle damage during relatively minor exercise during an infection, with blood tests demonstrating increases in muscle enzymes and ultrasound tests demonstrating hemorrhage into the muscles.

You also should not exercise when you have a high fever. When you exercise, your heart has to pump blood to your muscles to supply them with oxygen. It also has to pump blood from your muscles to your skin where the heat is dissipated. When you have a fever, your heart has to work extra hard to get rid of extra heat. Furthermore, some viruses that infect your nose and throat can also infect your heart muscle. The combination of the extra work and an infected heart muscle could cause irregular heart beats. You won't lose much conditioning unless you take off more than a week.


Dear Dr. Mirkin: Is there any truth to all of the health claims made for vinegar?

Vinegar is an excellent preservative and a good household cleaner, but it is not a medicine or a weight-loss drug. Several popular books claim that vinegar prevents cancer and heart disease, lowers high blood pressure and helps you to lose weight, but here is no evidence to support any of these claims. One of the books explains that vinegar helps you to lose weight because oil and vinegar don't mix, so vinegar and your fat won't either.

Vinegar is nothing more than a mixture of 95 percent water and around 5 percent acetic acid, made from grapes, apples, rice, potatoes or other fermented plants. It is very low in calories, but the only way vinegar could possibly help you to lose weight is by causing you to eat lots of salads while you cut back on other sources of calories.

You can put vinegar in a footbath to help soften hard calluses. Because it is acidic, it prevents the growth of bacteria in a bottle and is used as a preservative to pickle a wide variety of foods. However, it has not been shown to prevent infection in humans. Vinegar is an excellent and cheap cleaning agent. You can mix equal parts vinegar and water and use it to clean a coffee pot, remove stains from clothing or dissolve rust spots.


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Recipe of the Week
Red Pepper Stew

List of Diana's Healthful Recipes


June 26th, 2013
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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