As published in the June 1998 issue of UltraRunning Magazine.
My introduction to nausea in an ultra took place in my first Ice Age Trail 50. At 42 miles I was feeling great, but came across a young woman leaning against a tree, miserable with dry heaves. She could not eat or drink anything. How can it be that a body that is short of energy and partially dehydrated is not able to take in food and drink? Having found solutions for energy and electrolyte maintenance during a run, I wanted to study the nausea that we often see in ultras. If we can understand and solve that problem, we will have come a long way to making our events more successful, and enjoyable. Feelings of nausea and vomiting can arise from a number of stimuli. There are many types of receptors in the body which constantly monitor the condition of the digestive tract, hydration, electrolyte status, and blood flow. These signals are analyzed in the brain, along with signals from the eyes, ears, and nose. Consider that sometimes in an ultra, just the mention or sight of food may cause nausea. The process of becoming nauseous and vomiting is quite complex. My own experience with nausea in ultras is rather limited, so I asked members of the Internet ultra lists to tell me of their experiences with the problem. Plenty of people responded, providing a representative picture of the problem. There are a number of things to consider:
- Pre-race mealFructose
- All-carbohydrate foods
- Motion sickness
- Hypersensitive stomach
- Electrolyte depletion
- Reduced blood flow to the small intestine
- Stress reaction
Let’s consider each starting with the simpler ones, and see what can be done to overcome them. Pre-race meal: Fortunately, there seems to be no relationship between the content of the pre-race meal and later nausea. However, uncooked food the day before a long run may cause diarrhea. Fructose: People vary their ability to absorb this simple sugar. Many people have considerable gastric distress, nausea, and diarrhea from taking in more fructose than they can handle. The best insurance policy is to take none during an ultra. All-carbohydrate foods: Carbohydrates are a key energy source for faster running, but most runners find an all-carbohydrate diet a mistake for 100-mile or 24-hour runs. Foods with protein and/or amino acids help control excess acidity in the stomach, while fats help keep the small intestine from becoming too acid. Motion sickness: A small percentage of runners are bothered by motion sickness. They get effective relief by using motion sickness bands. These bands put pressure on the underside of the wrist. Look for the bands where travel products are sold. Anxiety: Anxiety causes nausea in some people. A competitive situation or just worrying about making the cut-offs can be detrimental. Those who have this condition should try various forms of relaxation therapy. Hypersensitive stomach: For the very few people who have this condition, their best course is to find by trial and error those foods and drinks which will suit them. Some people swear by supplemental ginger, which is an old Chinese remedy for upset stomach. Dehydration: Water is needed for the digestive processes. If it is in short supply, the contents of the digestive tract cannot be properly absorbed, and nausea results. One common danger is that runners will be feeling fine and enjoying their run to the point that they will just forget to drink and eat properly. The eventual dehydration and flagging energy supply will make normal digestion impossible. When hunger builds, the concentration of the chemical neuropeptide Y rises in the hypothalamus. However, dehydration dominates hunger. Rising dehydration increases the corticotrophin-releasing hormone, which overrides the neuropeptide Y and inhibits hunger. If you get too dehydrated, your body will reject food until the dehydration is corrected. Electrolyte depletion: Sodium is needed for transport of some food components from the small intestine into the blood stream. If too much sodium is lost from sweating, and not replaced, digestion is impeded until the sodium is restored. Reduced blood flow to the small intestine: Related to the above is the condition where contents of the small intestine are not moved or absorbed because of reduced blood flow. If blood near the small intestine is in short supply, nausea and vomiting will result. Nausea is common when the temperature is hot and/or the runner is running a hard pace. When the runner is hot, blood flow is shunted away from the digestive tract to the skin for cooling. When the runner is running a hard pace, blood is shunted to exercising muscles. These conditions rob the digestive tract of the blood and energy needed for proper absorption of food. Once this condition is established, there is really no way out except to cool off, slow the pace, walk or sit. While it may be hard to accept, when conditions are not favorable, a runner must slow the pace to avoid a nauseous condition. Thus, a run-walk strategy may be advisable in hot weather. Cooling the head and neck with ice is also effective. Stress: After many hours of running, the level of stress hormones in the blood increases significantly. These hormones can have a major affect on hunger and digestion. Chemicals related to stress and low energy ( histamines, serotonin, dopamine, and adenosine ) are known to bring on nausea. Adenosine can accumulate in low-energy conditions and alter people’s sensations. What tasted fine at the start of a 100 miler may taste repulsive after many hours of hard running. Counteracting an ongoing reaction to stress is very difficult and time-consuming. There are drugs that can block various receptors for serotonin and histamines, but they likely have side effects that make them unsuitable for use in an ultra. Runners who are under-trained for the distance they are running are most vulnerable to stress reactions. The rise in stress hormone levels can be delayed by attending to fluids, electrolytes and energy intake starting early in the run. Once the stress hormones have built up in the blood stream, it takes many hours to days to get them back to normal levels. Novice runners seldom understand that the fluid and energy intake patterns that are tolerable in a 20 mile training run can be seriously inadequate for a 100-mile or 24-hour run. The saying, “eat before hunger, drink before thirst” is sound advice. In summary, some combination of dehydration, electrolyte depletion, and shunting of blood flow due to overheating cause most cases of severe nausea in an ultra. You can avoid the nausea demon in your ultras if you attend to your needs for water, electrolytes, easily digested foods, and avoid a pace too fast for conditions.
Copyright 1998 Karl King, all rights reserved.