Nutrition for Divers – More Than Just a Side Dish

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Saturday morning, 10:00 a.m. My buddy and I are doing a short technical dive to 60 meters. CCR, diluent 18/45. Planned bottom time: 15 minutes, followed by standard decompression.

As we ascend from the depth, I notice that he starts gesturing. Shortly after, he ascends a bit faster than I’m used to seeing him do. We stay in contact, adjust our pace, and complete all planned decompression stops correctly. After a total of 55 minutes, we finish the dive without further incident.

On the surface, he seems relieved but exhausted. He reports that shortly after leaving the bottom, he suddenly felt very nauseous. He felt like he was going to vomit and therefore wanted to end the dive as quickly as possible.

Upon inquiry, it turns out: He hadn’t eaten breakfast that morning. He felt “a bit of a heavy feeling in his stomach.” The night before, he had eaten sausages and cabbage.

This isn’t a dramatic incident. No decompression problem, no technical malfunction. And yet it’s a classic example of how seemingly trivial factors—in this case, diet—can influence a dive.

Nutrition as an Underestimated Factor

Nutrition is not one of the classic safety factors in diving, such as gas management or decompression planning. Nevertheless, it influences several physiological mechanisms that are highly relevant for divers—especially for technical divers who experience long dive times, decompression stops, and significant changes in pressure.

This is less about special diets or so-called “superfoods” and more about simple, physiologically sound basic principles. Many problems arise not from exotic mistakes, but from mundane oversights: arriving at the dive site dehydrated, starting a long dive on an empty stomach, or eating a heavy meal shortly before entering the water.

Hydration – the most important single factor

The most important nutrition-related factor in diving is likely hydration.

Even under normal conditions, divers lose fluid through immersion diuresis. Added to this are dry breathing gases, a cold environment, and the fact that fluid intake is not possible during a dive. Dehydration leads to increased blood viscosity and can impair microcirculation. Even though the exact mechanisms are complex, dehydration has long been regarded as a modifiable risk factor for decompression problems.

In practical terms, this means: Fluids should be consumed consciously and not only when thirst is felt. Anyone who waits to drink until they feel thirsty is usually already slightly dehydrated.

Do not dive on an empty stomach

Another common mistake is diving on an empty stomach. Many divers skip breakfast or drink only coffee during a morning dive due to time constraints.

Physiologically, this makes little sense. A fasting metabolism reduces performance and can increase sensitivity to cold. Especially during longer dives with decompression stops or in cold conditions, insufficient energy intake can lead to faster cooling, reduced concentration, and increased fatigue.

It therefore makes sense to eat at least a small, easily digestible meal even before an early dive. This isn’t about large portions, but rather a moderate energy intake that provides the body with a steady supply.

Avoid heavy meals before diving

The opposite is equally undesirable: a heavy or very high-fat meal shortly before diving.

Large meals lead to a full stomach and can increase the risk of gastroesophageal reflux (heartburn). Underwater, this is not only unpleasant but can also lead to nausea and vomiting. Additionally, digestion diverts significant amounts of blood to the gastrointestinal tract, which can subjectively lead to sluggishness and discomfort.

This can impair performance, especially during physical exertion or in cold environments.

Gas-producing foods – a physical problem

An often underestimated aspect is the selection of foods that tend to produce gas in the gastrointestinal tract.

Certain foods can produce gas through bacterial fermentation in the gut. Typical examples include legumes, cabbage, onions, or highly carbonated beverages. This gas formation is not only a comfort issue on land but can have significant effects underwater.

According to Boyle’s law, the volume of a gas increases as ambient pressure decreases. This means that gas present in the gastrointestinal tract or produced by fermentation expands upon surfacing.

This increase in volume can lead to stretching of the stomach and intestinal walls, causing a feeling of pressure, nausea, and, in extreme cases, vomiting. This can lead to significant problems, especially during long decompression stops or when wearing restrictive gear such as dry suits.

Therefore, it is advisable to avoid foods that cause excessive gas buildup the night before and especially before diving.

Energy Requirements – Particularly Relevant in Cold Conditions

Energy requirements during diving are also frequently underestimated. While a short warm-water dive requires little energy, technical diving in cold environments can result in significant energy demands. Cold is a key factor here: thermoregulation requires energy, and insufficient energy intake leads to hypothermia more quickly.

This is not only a matter of comfort but can also have operational consequences, as cold can impair cognitive performance and decision-making ability.

Multiple Dives and Liveaboard Trips

Between repeated dives, it is advisable to eat small, easily digestible meals and consistently replenish lost fluids.

This is particularly important on liveaboard trips or during intensive diving days with multiple dives—even in recreational diving. Multiple dives per day place repeated strain on metabolism, circulation, and thermoregulation.

Easily digestible meals are therefore beneficial here as well, as they provide a continuous energy supply without unnecessarily taxing digestion. This point should be given particular attention on liveaboards, where four or more dives per day are common.

Alcohol and Nitrogen Narcosis

Another point to consider is alcohol consumption. Alcohol has a diuretic effect and thus promotes dehydration. At the same time, it can impair sleep quality and cognitive performance. Alcohol can also be problematic the night before a dive, as its effects may still be relevant the next day.

Additionally, it should be noted that alcohol itself has a central nervous system depressant effect and thus functionally resembles the effect of nitrogen narcosis. Anyone entering the water under the influence of alcohol must expect that nitrogen narcosis will set in earlier and be more pronounced.

The combination of increased urination, impaired judgment due to alcohol, and narcotic effects under pressure is particularly dangerous from a safety perspective.

Long-Term Nutrition

In the long term, overall dietary habits also play a role. A balanced diet with sufficient amounts of vegetables, fruits, complex carbohydrates, and unsaturated fatty acids supports vascular function and reduces inflammatory processes. While these factors are not specific to diving, they influence the body’s overall physiological resilience.

Conclusion – simple rules, big impact

In summary, nutrition in diving is not a niche topic for nutrition enthusiasts, but rather a fundamental part of preparation.

No special diets or dietary supplements are needed—just common sense. Diving while properly hydrated, not starting demanding dives on an empty stomach, avoiding heavy meals, reducing foods that cause significant bloating, ensuring an adequate energy intake, and abstaining from alcohol are simple measures with potentially significant benefits.

Nutrition is therefore not a spectacular safety factor—but one that can be optimized with minimal effort and that can make a difference, especially during longer, repeated, or demanding dives.

And my buddy? – In his case, it was likely a combination of two factors: gas-producing food the night before, resulting gas formation in the gastrointestinal tract, the expansion of these gases during ascent, and skipping breakfast.

This combination most likely led to severe nausea and the urge to vomit—and thus to a surgically relevant problem underwater, even though everything proceeded correctly from a technical and decompression standpoint.