Race-Time Nausea and The Big Empty
Nausea is serious business in the endurance sports world. It can go well beyond just a little “upset stomach”. For some, it’s worse than the pain in your muscles and bones, worse than the shortness of breath, and more fatiguing the tiredness you feel deep down inside.
But what causes this feeling? Is it because the stomach is empty? Or because it’s full? Is the feeling coming from further along in the digestive tract? Is it because of something you ate? Or is it simply a brain mechanism?
Most likely the feeling is due to a combination of factors and is, to some degree at least, highly individualistic. Certainly at least one reason, though, is the degree of efficiency with which the stomach is able to empty itself.
Gastric (i.e. stomach) emptying is a complex process and is heavily regulated by many factors. It has to be this way. Your digestive system has quite a logistical task it must perform every time you eat. It must ensure vital nutrients find their way into the blood stream for the next step of processing. It needs to provide a protection against toxins and foreign organisms. All this while ensuring that any leftover material finds its way expeditiously out the other end. If it pushes things along too fast, essential nourishment bypasses absorption and you end up with a lot of diarrhea (with associated fluid losses). Too slow, and a back-up occurs which, when severe, can be life threatening.
As a result, your GI tract has an elaborate system of sensors and feedback in constant communication and coordination to make sure you get the most out of each meal while ensuring that this energy doesn’t go to waste during the times when you are not eating.
Part of that system is the process of gastric emptying. Your stomach uses a set of regulators to determine how fast it needs to empty out its contents into the small intestines. The details of this process go well beyond a single blog post. But I am going to highlight a few big factors here.
Before I get into that though, understand that ensuring efficient gastric emptying goes beyond just improving gut discomfort. You want the maximum amount of nutrients to enter your bloodstream as rapidly as possible during competition. When you need that boost during a race, you don’t want it to be two hours later, you want it ASAP. So gastric emptying has to take into account both optimal energy delivery as well as speed of emptying.
The first big factor with regards to gastric emptying is the osmolarity of the stomach contents (1, 3, 6, 13). Osmolarity, defined as the total number of solute particles per liter, has a strong influence on gastric emptying, with solutions of higher osmolarity taking longer to leave the stomach. This is very important to consider when unnecessary ingredients are being added to your supplement product.
Think of this when you look at products that take the “the more electrolytes, the better” kind of approach. Yes, to some degree at least, electrolytes are an essential part of your race day nutrition regimen. But how much is really beneficial? And do you need all of those electrolytes that are listed on the label?
The answer to the first question is still a very undecided subject in sports science. Many challenges and potential inaccuracies (8) exist when it comes to measuring electrolyte losses during endurance competition. And some research has shown that such supplementation really has no performance benefit (9). Regardless, what is pretty much universally accepted is that such needs are extremely variable from person to person and from situation to situation.
And what types of electrolytes are essential? Sodium is far and away the biggest player when it comes to regulating plasma volume. Outside of sodium, all other electrolytes (potassium, calcium, magnesium, among others) play a negligible role in maintaining fluid balance. Why then are they included? Such electrolyte levels generally go up during an endurance competition, not down, because you lose much more water than you do the electrolytes. Evidence is lacking when it comes to any performance benefit from supplementation of these electrolytes. And the effects on cramping are at best debatable (https://ultra26sports.com/electrolytes-separating-anectodes/).
So think about that when you are reading the labels. It’s not necessarily “the more, the better” as far as electrolytes go. And in certain cases, such as with potassium (3, 13) and calcium (13), more electrolytes leads to slower stomach emptying. Things get a bit more complicated with sodium, where gastric emptying improves with small concentrations and worsens with higher concentrations (13), but that’s beyond the scope of this post.
Similarly, the addition of protein to your in-race nutrition will also increase the osmolarity of your stomach contents. All the more so when the protein is already broken down into its constituent amino acids, including the subset known as “branched chain” amino acids (BCAAs). Breaking down protein into small bits prior to getting into your stomach greatly increases the osmolarity, which, by extension, can further slow gastric emptying.
Of course, again, all of this has to be weighed against the benefit you may get from including such ingredients. So you have to ask yourself, are you really gaining anything with the addition of such ingredients?
For protein or BCAAs, the answer appears to be NO when it comes to your “during” or in-race nutritional supplementation. There does exist evidence for such supplementation being a good thing before (10) or after (11) endurance performance. But when it comes to what to take during the competition itself, the evidence of benefit is lacking (12).
The evidence also doesn’t support various vitamins, anti-oxidants, herbals, minerals, etc etc etc. taken during a race. Again, if it doesn’t help, it is just slowing your stomach emptying without getting a benefit in return.
The second big factor when it comes to gastric emptying is energy content. The higher the energy content, the slower the rate of emptying (2, 5). This holds true for carbohydrates, fats, and proteins, as long as the energy content (i.e. calories) are kept constant (2). Conversely though, the amount of energy ultimately delivered into the bloodstream goes up when you have higher energy contained in the supplement (6).
So it’s a balancing act of sorts. How much slowing of gastric emptying are you willing to accept in order to get the higher amounts of energy into your bloodstream. For example, drinking pure water will empty out of your stomach quickly, but will deliver no energy. But drinking a solution with a very high energy content may deliver more energy, but will slow the stomach emptying down considerably. Somewhere in the middle is an acceptable compromise.
There are potentially ways around this, though. Maltodextrin, which has a lower osmolality than pure glucose, may have an advantage in providing energy into the bloodstream with a faster gastric emptying (4). And adding fructose has been shown to improve this further when compared to either maltodextrin or glucose alone (4, 7). This is presumably due to the feedback receptors in the duodenum not being sensitive to fructose the way they are sensitive to glucose. But this needs to be further evaluated with future research.
Many other factors also play a role in gastric emptying, beyond what is addressed here in this post. What is most important to remember, though, is that adding unnecessary ingredients is not helping you and is potentially only delaying the process of getting you the nutrients you need.
Understanding stomach emptying is an essential component to developing a sensible nutritional strategy for you in endurance competition. An appropriate blend of ingredients will ensure you are maximizing nutritional gains while minimizing nausea and stomach upset. Ultra 26 products are specifically designed to provide the optimal fuel to your body in the most efficient manner possible when your body needs it most. As always, just “MORE of what you need, NONE of what you don’t!”
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