Summer Heat Stress – More Than Just Dehydration

Linda J. Dobberstein, Chiropractor, Board Certified in Clinical Nutrition

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Summer Heat Stress – More Than Just Dehydration
The month of August brings the “dog days of summer." For many, this means oppressive heat, trouble sleeping, and fatigue with the hot, sticky summer days. For adults and kids alike, appropriate precautions must be taken for dealing with hot weather. August means that high school, college athletes and even professional athletes are starting with two-a-day practices. Marching band practice, parade performances, soccer, baseball, 5Ks, and just the daily run with the dog also means increased physical stress in the hot, sultry summer days. Individuals whose job requires strenuous activity outdoors need to pay attention as well. We now have an increasing understanding of what heat stress does to the human body, and we need to take precautions.

The Basics

Adequate hydration is vital for surviving in blistering temperatures. The general rule of thumb for basic adequate hydration is to drink one half of your body weight in ounces of water. For example, if you weigh 150 pounds, then you need at least 75 ounces of water or fluids on a daily basis. Coffee, pop, alcohol, heavily caffeinated beverages, or thick beverages like a protein smoothie, kefir, etc. are generally not counted for basic hydration. Caffeine containing beverages can act as a diuretic – avoid them for hydration purposes. If you are thirsty, this means that you are past the initial stage of dehydration and need to be more aggressive in consuming water.

Hydration recommendations change if you participate in athletic activities. Shortly before exercise, it is recommended to drink at least 250-500 ml (8.5 -17 ounces) of water. During endurance exercise or training, a general recommendation is to ingest 200-250 ml water/6-8% carb/electrolyte mix every 15-20 minutes. Once you are done exercising, it is still vital to continue replacing fluids as you are still losing fluids after exercise stops. A simple way of checking hydration status is to watch your urine output. With adequate hydration, urine should be a clear or pale yellow with sufficient volume. Darker hues of yellow or amber especially in scanty amounts clearly indicate significant dehydration concerns.

For workers in hot environments, the recommended rate of rehydration is somewhat similar to athletes. If temperatures are below 113 degrees F, drink 250 ml or 8.5 ounces every 30 minutes. It is important to note that sodium loss in sweat varies greatly and is not significantly related with sweat rate. Becoming acclimated does reduce risk of sodium loss.


Symptoms of heat illness may be related with electrolyte disturbances, i.e. loss of sodium, potassium, and chloride. Symptoms of disorientation, dizziness, headache, fainting, irritability, confusion, nausea, fatigue, muscle cramps, increased systolic blood pressure and body temperature may occur. It is important to note that researchers have shown that potassium loss was substantially higher than sodium and chloride loss in individuals working in severe heat. Symptoms of potassium deficiency include muscle weakness, spasms, cramps, muscle stiffness, soreness, abdominal pain or cramping, constipation, heart palpitations, dizziness, fainting, frequent urination and extreme thirst. It is not just a coincidence that the symptoms of dehydration sound like potassium deficiency.

Heat Stress and Intestinal Permeability

Heat tolerance is more than just hydration and electrolyte balance. As important as this is, there are other nuances and concerns to be monitored. Studies over the last decade have identified overwhelming evidence of an inflammatory pathway process linked with heat stress. Researchers have recognized a complex interplay among heat stress, gut health, and inflammation. The physical activity causes increased gut permeability. Heat stress from the environment and the increase in body heat leads to a complex interplay among increased intestinal permeability, heat stress, coagulation cascade (blood clotting) and a systemic inflammatory response. This can lead to increased concerns with endotoxins leaking into the circulation. This can lead to poor recovery and general increased wear and tear, even in young, healthy athletes.

The physical heat stress also engages heat shock proteins. Heat shock proteins are molecular chaperones, which aide in the transport of proteins throughout the cell’s various compartments. These internal molecular compounds are protective to the cellular proteins. When heat shock proteins are released at high outdoor temperature levels, or due to internal heat stress, these protective agents become stressed and their work capacity decreases. They lose their ability to protect proteins inside of cells. This causes cellular proteins to become unraveled or unglued which then causes collapse of the cellular proteins and may even lead to death of the cell. This often damages the intestinal mucosal membrane and can lead to a systemic inflammatory response. This may cause fatigue, pain, weakness, and crashing and feel similar to dealing with the flu and a fever. The end result is feeling weak, fatigued, and wasted. Research published in the International Journal of Sports Physiology and Performance just weeks ago recommend nutritional countermeasures for all athletes to address increased intestinal permeability along with the standard measures of hydration and cooling support.

This concept of heat stress and increased intestinal permeability is not just related to humans. This concept has been seen in a variety of animals. It caused the same increased intestinal permeability and concerns with endotoxins and lipopolysaccharides toxins. This means that pet owners, along with farmers and ranchers, have to be even more diligent with their animals’ health with heat stress. Combine heat stress with conventional livestock practices including antibiotics, GMO grains, and low dose pesticide/herbicide (Monsanto) residues and the result is increased gut permeability, endotoxemia and overall unhealthy animals.

Heat Stress and Adrenals

There is also evidence that temperature tolerance may be worse at different times of the day for some individuals. Earlier this year, research published in the European Journal of Applied Physiology found that moderate heat stress in the AM (8:00) led to an increase in presyncope or near fainting more so than when heat stress occurred at 5:00 PM. This finding may be a bit perplexing as one would expect just the opposite as environmental temperatures are higher in the afternoon.

Clinically, the results may be interpreted as individuals dealing with fatigued or weakened adrenal glands. This, along with stressed autonomic nervous system responses, end up limiting reserves and blood pressure control. Cortisol patterns are often borderline low or low in the AM and functional neurological stress is present. The result is that blood pressure has a tendency to be low or there are low reserves for coping with orthostatic stress. Putting someone in this condition through an activity such as standing first thing in the AM for an extended period of time, in a warm or hot environment, causes vasodilation. Presyncope or syncope occurs when the physical activity persists beyond the body’s ability to cope with the heat stress and vasodilation. A similar example, but without the 24 hour cortisol diurnal variation, is the groomsman standing at the altar in a tuxedo in hot room under high stress and proceeds to pass out. The level of vasodilation and heat stress was too much bear.


This study has further practical implications. If you or your child has poor adrenal reserves and has high physical stress and heat exposure first thing in the AM, the stress of the activity may cause heat related illness. If your adrenal glands are compromised, it is absolutely vital to ensure adequate electrolyte intake (potassium, sodium, chloride, magnesium, and even calcium) and hydration prior to the work or practice. In addition, individuals dealing with adrenal fatigue are often salt wasters, i.e. they lose salt at a higher rate than others. As noted earlier, the amount of sweating does not determine the amount of sodium loss. Key indicators of salt wasting are salt lines on clothing after perspiration has dried, or if animals are drawn to you and love to lick your skin. They are using your skin as a “salt lick."

Before sending your child off to 7 AM practice, make sure they are adequately hydrated and have consumed mineral rich foods and something with salt. One quarter teaspoon of salt provides 500 mg. Consider using a small serving with the breakfast meal or loading up with it in the water bottle. The same principle applies to adults. Use nutrients such as pantethine, vitamin C, magnesium, potassium, and a B complex to help support healthy adrenal function.

Other nutritional support for heat induced illness and increased gut permeability is glutamine. Researchers clearly found that chronic glutamine supplementation reduced the exercise induced increase of intestinal permeability and suppressed the inflammatory activity of NF kappa B in blood cells. Whey protein has been shown to be more advantageous in rehydration and fluid balance restoration than a carbohydrate-electrolyte sports drink for athletes. Whey protein has also been shown to reduce the dysfunction of the heat shock proteins, thereby protecting the body’s proteins from inflammatory heat stress. Whey protein is also naturally rich in glutamine.

Don’t wait until you have a heat related illness to do something. Be proactive in supporting your body and your children before strenuous activity. Work on acclimation to the heat as well as proper nutritional support. The knowledge and understanding of increased gut permeability with heat stress and physical activity leads to a whole new level of heat related illness and implications. Don’t risk it. Take charge of your health today!

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