Pilot Health: Diet, Exercise and Lifestyle

An aviation medical examination checks a pilot against the standards at intervals of months or years. Whether the pilot is fit on the morning of a flight, and still certificated twenty years later, depends largely on habits that no examiner sees: what and when the pilot eats and drinks, how much exercise the pilot takes, body weight, smoking and caffeine.

These habits act on two time scales. In the short term, a missed meal, a day without enough fluid or too much coffee degrades attention and judgment in ways that resemble hypoxia and fatigue. In the long term, smoking, raised blood pressure and cholesterol, inactivity and excess weight lead to coronary artery disease, to which ATPL texts attribute about 70 percent of the deaths of pilots during their careers. EASA and FAA guidance give largely the same advice.

Health and the medical certificate

Between examinations, fitness is the pilot's own responsibility. Under EASA's Part-MED (MED.A.020) a license holder must not exercise the privileges while aware of any decrease in medical fitness that might make them unable to exercise those privileges safely, and must seek aeromedical advice on starting regular medication. The FAA's 14 CFR 61.53 forbids acting as pilot in command or as a required pilot flight crewmember while knowing, or having reason to know, of a medical condition that would make the pilot unable to meet the requirements of the medical certificate (see medical certification).

Many of the conditions that end flying careers are diseases of lifestyle. The FAA's Aeronautical Information Manual (AIM) lists myocardial infarction, angina pectoris and diabetes requiring medication for its control among the conditions that mandatorily disqualify a pilot, although a special issuance may still be possible. Coronary disease can progress without symptoms, and the FAA requires an electrocardiogram for a first-class certificate at the first examination after age 35 and every year from age 40.

Day to day, ATPL texts name the internal physiological factors a crew member must deal with before reporting for duty: hunger, thirst, fatigue, lack of sleep and pain. All but pain are normally within the pilot's control, and no duty should start with any of them unresolved. The FAA's IMSAFE checklist (illness, medication, stress, alcohol, fatigue, emotion) covers the rest of the self-assessment (see fitness to fly).

Diet, meals and blood sugar

Glucose is almost the only fuel the brain uses, so mental performance follows the blood sugar level. A normal blood glucose is about 100 mg per 100 ml. ATPL texts define hypoglycemia as a level below about 50 mg per 100 ml, while about 200 mg per 100 ml points to hyperglycemia. Low blood sugar follows skipped meals or fasting, and brings headache, stomach pains, lack of energy, nervousness, shaking, sweating, sleepiness, poor concentration and eventually fainting. The picture resembles early hypoxia, so a pilot may treat the wrong problem or dismiss it altogether, and low blood sugar also lowers tolerance to g. A snack relieves it in the short term.

The practical rules are simple:

• never fly on an empty stomach;
• make breakfast a real meal: ATPL texts recommend about 25 percent of the day's calories;
• carry food and water on a long flight or duty;
• avoid very large meals, especially carbohydrate-heavy ones, before or during duty, because they tend to increase drowsiness;
• eat a balanced diet of carbohydrate, protein and fat. The PHAK notes that a well-balanced diet keeps the body from consuming its own tissues for energy and helps prevent acute fatigue.

Food safety is part of diet for crews. ATPL texts name acute gastroenteritis from contaminated food or water as the most common cause of in-flight incapacitation, and gastrointestinal disorders as almost half of all incapacitations. Crews therefore allow about 90 minutes between eating and flying, long enough for the first symptoms of food poisoning to appear, and the two pilots eat different meals. A pilot with vomiting or diarrhea should not fly at all. Self-medication has its own trap: antacids containing sodium bicarbonate release carbon dioxide, which expands at altitude and can cause acute stomach pain.

Over a career, diet also bears on diabetes. In type 2 diabetes, usually in adults, the pancreas makes too little insulin or the body cannot use it effectively, and the principal causes are obesity, poor diet and a sedentary lifestyle. Since the FAA treats diabetes requiring medication as disqualifying, subject to special issuance, the diet that prevents it also protects the medical.

Hydration and dehydration

Dehydration is a critical loss of water from the body. The PHAK lists its causes in flying as hot flight decks and flight lines, wind, humidity and diuretic drinks: coffee, tea, alcohol and caffeinated soft drinks. Airliner cabins add very dry air, typically 5 to 15 percent relative humidity against the 40 to 60 percent that ATPL texts give for comfort, and long flights in hot weather or at high altitude increase the rate of water loss.

The first noticeable effect is fatigue; headache, cramps, sleepiness and dizziness are other common signs. If the fluid is not replaced, fatigue progresses to dizziness, weakness, nausea, tingling of the hands and feet, abdominal cramps and extreme thirst. Even mild dehydration slows reactions, reduces concentration and lowers tolerance to heat and to g.

Thirst is a poor alarm. Most people become thirsty only with a deficit of about 1.5 quarts, or 2 percent of body weight, and a small amount of fluid in the mouth switches the thirst off long before the deficit is made good. Pilots should therefore drink to a plan rather than on demand.

The PHAK suggests carrying a container to measure the day's intake and limiting caffeine and alcohol, both diuretics. On any long flight, water should be carried and drunk at frequent intervals, thirsty or not. Light-colored, porous clothing and a hat help under a canopy or roof window, and so does good ventilation.

Heat stress is insidious: the cockpit of a light airplane on the ramp can reach 100 °F (about 38 °C) or more. Heatstroke, the body's failure to control its temperature, may be recognized by the symptoms of dehydration, but it has also been recognized only when the victim collapsed.

Exercise and fitness

Regular exercise works on both time scales. The AIM lists it with rest, sleep and proper nutrition as a way of preventing acute fatigue. The PHAK counts lack of physical fitness among the physiological stressors that erode a pilot's reserve, alongside fatigue, sleep loss, missed meals and illness, and recommends a program of physical fitness, or time set aside for relaxation each day, to keep stress levels down (see stress). Individual tolerance to hypoxia also varies with fitness, as it does with smoking, fatigue and illness.

The long-term benefit is protection against coronary artery disease, but only if the exercise is regular and hard enough. ATPL texts specify exercise that raises the resting pulse rate by 100 percent for at least 20 minutes, three times a week, as in swimming, jogging, cycling, tennis or squash. Walking the dog or a round of golf is pleasant but brings too little cardiovascular benefit.

Weight and body mass index

Body mass index (BMI), also called the Quetelet index, relates weight to height: the weight in kilograms divided by the square of the height in meters. A pilot 1.80 m tall who weighs 85 kg has a BMI of 85 ÷ 1.80², about 26.2, which is overweight.

The WHO thresholds are the same for men and women. Some older ATPL texts quote slightly lower cut-offs for women, overweight above 24 and obese above 29. Obesity increases susceptibility to heart attack, hypertension, diabetes, decompression sickness and hypoxia at lower altitudes, and reduces tolerance to g.

Excess weight is also linked to obstructive sleep apnea (OSA), in which repeated pauses in breathing interrupt restorative sleep. The AIM calls OSA an important preventable factor in transportation accidents, associated with hypertension, heart attack, stroke, obesity and diabetes. It advises evaluation by a sleep medicine specialist for anyone with its symptoms, such as snoring, excessive daytime sleepiness and breathing pauses during sleep, a neck size over 17 inches in men or 16 inches in women, or a BMI above 30. OSA can be treated, and most treatments are acceptable for medical certification once shown to be effective.

There is no magic formula for losing weight: energy taken in as food and not used is stored as fat. ATPL texts state that the only practical way is to eat less from a balanced diet, and warn against crash diets, which fail in the long term and can produce dangerous symptoms, and against appetite suppressants taken without aviation medical supervision.

Smoking and caffeine

Smoking harms a pilot in flight as well as over a lifetime. Cigarette smoke contains carbon monoxide, which binds to hemoglobin some 200 to 250 times more readily than oxygen and forms carboxyhemoglobin, which carries no oxygen. ATPL texts put the carboxyhemoglobin of a smoker of 20 cigarettes a day at about 7 percent; the FAA's PHAK says that 3 cigarettes in rapid succession, or 20 to 30 in 24 hours, may saturate 8 to 10 percent of the hemoglobin's capacity. The AIM describes the effect as equivalent to already being at a cabin altitude of several thousand feet. The body needs up to 48 hours to rid itself of carbon monoxide. For the smoker:

• hypoxia begins at a lower altitude, and the time of useful consciousness is shorter;
• night vision, which depends on the oxygen-hungry rods, is degraded: ATPL texts give a loss of about 20 percent at 20 cigarettes a day, and the PHAK also puts the smoker's loss at 20 percent;
• tolerance to g is reduced;
• nicotine stimulates the secretion of adrenaline and is addictive;
• the risk of heart attack rises, together with lung cancer and breathing and circulatory problems.

The PHAK adds that tobacco causes diseases that can be medically disqualifying. Smoking is also prohibited whenever oxygen equipment is in use, because materials that barely burn in air can ignite in oxygen (see carbon monoxide).

Caffeine is the pilot's commonest stimulant. It helps tactically against sleepiness, but it masks the symptoms of fatigue without repaying the sleep debt (see sleep and circadian rhythms). The FAA's fatigue guidance, AC 120-100, gives a dose of about 200 mg an onset of 15 to 30 minutes and an effect lasting 3 to 5 hours. Its half-life is about 4 hours, its benefit fades with habitual use, and it disturbs both deep (stage 4) and REM sleep, so a late cup shortens the rest that would have fixed the problem. ATPL texts give a recommended maximum for aircrew of 250 to 300 mg a day, about two to three cups of coffee. Caffeine is also in tea, many soft drinks and some aspirin preparations, and as a diuretic it adds to dehydration.

Smoking, coffee and alcohol also share a role in stress. ATPL texts class them as symptom-directed coping, which relieves the symptoms of stress without touching its cause (see alcohol, drugs and medication).

Cardiovascular risk factors

Coronary artery disease is the long-term result of most of the habits above. Fatty deposits, to which cholesterol carried in the blood contributes, build up in the walls of the coronary arteries and narrow them. A narrowed artery may supply enough blood at rest but not under effort, causing angina; a blocked one causes a myocardial infarction, a heart attack, which can incapacitate a pilot suddenly. The disease can progress without symptoms (see circulatory system and cardiovascular health).

ATPL texts list the factors predisposing to a heart attack in decreasing order of importance:

1. family history (heredity)
2. age
3. previous cardiovascular problems
4. raised blood pressure (hypertension)
5. smoking
6. raised cholesterol
7. lack of exercise
8. diabetes.

The first three cannot be changed. The other five can, and each responds to the habits described in this article. The same texts describe the role of stress, obesity, alcohol and diet as less clearly understood.

Blood pressure is written as two figures in millimeters of mercury, such as 120/80. The higher, systolic figure is the pressure produced when the heart contracts; the lower, diastolic figure is the pressure that remains in the arteries between beats. Persistently raised pressure, hypertension, is a major risk factor for heart attack, and obesity increases susceptibility to it. Low pressure, hypotension, reduces g tolerance.

Treatment raises questions of its own. The AIM warns that blood pressure drugs, among others, can have side effects that impair judgment, alertness and coordination, and its safest rule is not to fly while taking any medication unless the FAA has approved it. Under Part-MED, starting regular medication obliges the pilot to seek aeromedical advice. Keeping blood pressure, cholesterol and weight in check through diet, exercise and not smoking is the surest way to avoid those questions.

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.