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By Karl King
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 meal
Fructose
All-carbohydrate foods
Motion sickness
Anxiety
Hypersensitive stomach
Dehydration
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.
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