>An appreciation of fundamental concepts can help guide nutritional choices. Energy is primarily provided by fats (9 kilocalories per gram [kcal/g]), carbohydrates (4 kcal/g) and protein (4 kcal/g). Alcohol is high in calories (7 kcal/g), but in a healthy diet should be a negligible source of total calories.
>Diets that exclude major food groups are generally considered undesirable. While a healthy total intake can be maintained, it requires much greater effort with exclusionary diets. A recommended dietary balance is 10-15 percent protein, 25-30 percent fats and 55-65 percent carbohydrates. Saturated fats, primarily from animal sources, should constitute less than one-third of the total fats. Complex carbohydrates, starches and dietary fiber found in beans and grains, should vastly outweigh simple sugars such as glucose and fructose.
>Fats, sugars and sodium are used liberally to enhance flavor in processed food. Unsaturated fats may be partially or fully hydrogenated to improve cooking performance and enhance a product's shelf life. Problematically, the hydrogenation process also creates trans fats, agents now linked to several health concerns. Fortunately, the trans fat content has declined in prepared foods since the component was added to U.S. nutrition labels in 2006.
>"Caloric consciousness" and nutrition label reading can reinforce good dietary habits. Read the nutrition labels and look for foods low in fat, sugar and sodium, free of trans fat and high in dietary fiber and vitamins; products that appear very similar can differ significantly in nutritional value. An even better strategy than simply comparing labels is to focus diets on scratch-made, home-cooked meals.
>Nutritional status can affect diving performance in obvious or subtle ways. Obvious effects would include sudden fatigue or loss of consciousness resulting from extreme caloric restriction. Loss of consciousness has been reported in individuals trying to achieve dramatic weight loss and others simply not taking time to eat.
>Nutritional Considerations in Diving
>Adequate caloric reserves are necessary for appropriate thermoregulatory responses. The measure of "adequate," however, is often misunderstood. There are many misconceptions as to the demands of diving, referring both to physical work and thermoregulation. It does not take huge amounts of food to effectively fuel the most energetic dive in the coldest water.
>State of hydration is another important issue, but also one subject to misconception. Proper hydration promotes effective circulation that benefits thermoregulation and normal decompression health. However, dehydration is a far less important risk factor than the dive profile. Dehydration is probably unfairly blamed for the negative outcome of many extreme exposures. In addition, excessive hydration brings its own problems, such as potentially increasing the risk of immersion pulmonary edema.
- The experimental evidence specific to nutrition and diving is limited but interesting. For example, based on the available data, it does not appear that ingesting either caffeine or capsaicin (the active ingredient in hot peppers) enhances thermal protection.
- A single study describes a possible relationship between high total cholesterol levels and "bubble-proneness" following altitude decompression. Further work is required but the possibility of this being a real effect should encourage divers to maintain healthy (low) cholesterol levels.
- Observations that marine fish oils (primarily omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) might reduce blood platelet adhesiveness are tantalizing. Further work is required to confirm this effect and determine whether the biochemical insult of decompression stress could be reduced.
- Drinking alcohol in conjunction with diving is inappropriate given the potential for impaired decision making and/or symptom masking. However, animal studies suggest that potential biochemical interactions deserve further laboratory study.
- Questions regarding herbal supplements and decompression stress generally have not been critically investigated. Some supplements are known to interact with medical treatments, particularly anesthesia. It is speculative but possible that some may interact with the pressure environment or decompression stress in a meaningful way.
>Consumers are frequently faced with grandiose marketing claims that should be viewed cautiously. This is particularly true for products related to nutrition but outside Food and Drug Administration purview. Several have prompted questions from the diving community. Oxygenated water, for example, does not improve aerobic performance. Similarly, there is no evidence that any commercial drink will provide special protection against decompression sickness. Finally, high-calorie sport bars are not essential to meet the modest caloric demands of most diving activity.
>Nutrition Tips for Consumers
>Sound nutrition is an important tool in maintaining general health. Good nutritional practices, particularly when combined with regular physical exercise, can contribute to a long and enjoyable diving life. Developing the habit of making thoughtful dietary choices is the best place to start.
- Eat a variety of foods, favoring whole fruits, whole vegetables and whole grains.
- Avoid processed foods high in sodium, fat and calories and low in natural nutrients.
- Avoid trans fats.
- Replace whole fat with low-fat or nonfat milk and dairy products.
- Control calorie intake to manage body weight.
- Be physically active every day, limiting high-intensity exercise to nondiving days.
- If you drink alcoholic beverages, do so in moderation.
- If you use multivitamins, do so as a backup, not to replace good dietary habits.
- Be cautious in accepting nutritional health claims.