The six essentials of health

Updated October 2026 · 9 min read

The idea in one sentence

In the Canon of Medicine, Ibn Sina and the physicians before him taught that a healthy person stays healthy by managing a short list of daily factors, which the tradition calls الأسباب الستة الضرورية (the six essential causes). If they are balanced the body stays well. If one is badly out of balance, illness follows. Medicine is for when this has failed.

An honest note: the classical explanation used humoral theory, which we no longer use. But the list itself is surprisingly close to how doctors talk about prevention today, so it is a useful map. It also gives structure to the rest of our series, such as treating the whole person.

1. Air

The classical view. The air you breathe affects you all day, so the physicians paid close attention to the quality of air in the home, the town and the season. They preferred clean, moving air, away from stagnant water, rot and smoke.

Today. The World Health Organization treats air pollution as a major risk to health, linked to heart and lung disease. Practical steps: ventilate your home, avoid smoking and being around smoke, and exercise outdoors away from heavy traffic and on days when air quality is better. See living by the seasons for the effect of heat and climate.

2. Food and drink

The classical view. This is the largest part of the Canon's advice on preserving health. The physicians discussed what to eat, how much, when, in what order and with which drinks. They wrote at length about moderation, about not eating before the last meal was digested, and about matching food to the person and the season.

Today. Diet is one of the strongest factors in modern health. WHO recommends plenty of vegetables, fruit, legumes and whole grains, and limiting salt, sugar and unhealthy fats. The Qur'an also commands moderation in eating (7:31). We cover this in water and digestion.

3. Movement and rest

The classical view. Exercise keeps the body strong and firm, and rest allows recovery. Both are needed, in the right amounts for each person.

Today. Guidelines recommend about 150 minutes a week of moderate activity plus strength work. Rest and recovery matter just as much for muscle growth and for preventing injury. Read the full article, Ibn Sina on exercise.

4. Sleep and waking

The classical view. Sleep restores the body and settles the mind, but too much sleep makes you heavy and too little leaves you dry and weak. The physicians gave rules for the right amount and timing.

Today. Most adults need at least 7 hours a night. Poor sleep is linked to weight gain, low mood, weaker immunity and poorer recovery from exercise. See sleep and waking.

5. What the body expels and retains

The classical view. This essential covers everything the body takes in and lets go of: digestion and bowel movements, urine, sweat, and also things like bathing, menstruation and bleeding. In the classical system, a body that cannot clear its waste becomes ill, so regular elimination was a sign of good health, and constipation or retention was a warning.

Today. The "waste" theory is outdated, but the practical point stands: regular bowel movements, pale urine and healthy sweating are everyday signs of how the body is doing. Fibre, water and exercise keep the gut moving. Persistent constipation, blood in the stool, or a change in your usual pattern should be checked by a doctor.

6. The emotions

The classical view. The physicians called these the "accidents of the soul": anger, fear, grief, anxiety and joy. They taught that strong or lasting emotions affect the body, and that calm and cheerfulness protect it. A physician should treat the mind of the patient too.

Today. This is now well established. Long-term stress affects blood pressure, sleep, digestion and immunity, and good mental health is part of physical health. Prayer, remembrance (dhikr), time with family, walking outdoors and talking to someone you trust all help many people. If low mood or anxiety lasts for weeks, see a doctor or a qualified counsellor, just as you would for any other health problem.

How the six fit together

Why this order matters

Ibn Sina's point was that these six come before any pill. If a patient came with a complaint, the physician first looked at these daily habits. Modern evidence agrees that for most common long-term conditions, such as type 2 diabetes, high blood pressure and heart disease, improving diet, activity, sleep and stress is as important as any treatment. It is not a replacement for medicine when you are seriously ill. It is the foundation under it.

A one-week experiment

Pick one habit from each essential and track it for seven days. For example: a 20-minute walk outdoors, one extra glass of water, lights out by a set time, a 5-minute pause for prayer or breathing, and no food for 2 hours before bed. At the end of the week, note how your energy, digestion and mood have changed. Small, steady changes are easier to keep than a complete overhaul.

References

Classical sources: Ibn Sina, The Canon of Medicine, Book One (the six essential causes and the regimen of health); Galen, on the preservation of health.

Modern research:

• World Health Organization: Healthy diet
• World Health Organization: Ambient (outdoor) air quality and health
• World Health Organization: Physical activity
• World Health Organization: Mental health