Humans, like all living organisms, have basic needs that must be met in order to survive. While the specific needs may vary slightly from person to person, there are three primary necessities that all people require: air, water, and food.
Air
Air is the most immediate need for human survival. Our bodies need a constant supply of oxygen in order to respire and produce energy. Without air, humans will lose consciousness in just a few minutes and can suffer brain damage or death after just 3-4 minutes without oxygen.
On average, humans need to inhale about 5-6 liters of air per minute in order to supply the body with adequate oxygen. This amounts to about 11,000 liters of air per day. Of course, increases with physical exertion or health conditions.
The air we breathe is comprised of roughly:
- 78% nitrogen
- 21% oxygen
- 0.04% carbon dioxide
- 1% other gases
It is the oxygen that our cells use to produce energy in the form of ATP through respiration. Without a fresh supply of oxygen, our bodies’ cells cannot produce energy and our organs begin to fail.
How the Body Uses Oxygen
When we inhale, the oxygen we breathe travels down the trachea and into the lungs. In the lungs, the oxygen passes through tiny air sacs known as alveoli and diffuses into the bloodstream via capillaries surrounding the alveoli. Oxygenated blood then circulates through the body, delivering oxygen to cells throughout the body.
At the cellular level, oxygen is used in a series of chemical reactions known as cellular respiration which produces adenosine triphosphate (ATP) – the primary energy source for cells. The oxygen combines with glucose broken down from food to produce ATP. Without this oxygen, cells cannot produce enough ATP to survive.
Effects of Oxygen Deprivation
If the oxygen supply is disrupted or decreased, it can have serious effects on human health and survival:
- 1-2 minutes: Loss of consciousness
- 3-4 minutes: Brain damage begins
- 5-10 minutes: Death
Lack of oxygen is often associated with respiratory conditions like pneumonia, pulmonary edema, chronic obstructive pulmonary disease (COPD), and asthma. It can also occur at high altitudes where the air pressure is lower. Some health conditions like anemia and sleep apnea can also impair oxygen transport and uptake.
How Humans Acquire Oxygen
Because air is all around us, humans can acquire the oxygen we need by simply breathing. But sometimes supplemental oxygen is required:
- Medical oxygen devices like nasal cannulas or face masks provide extra oxygen to those with respiratory conditions.
- Ventilators mechanically push air into the lungs for those who cannot breathe effectively on their own.
- Hyperbaric oxygen chambers increase air pressure and oxygen saturation to treat issues like carbon monoxide poisoning.
As long as we are able to breathe and inhale an adequate supply of oxygenated air, our bodies can utilize this oxygen to produce energy and keep our cells and organs functioning. Air is essential to life, and particularly the oxygen component in air.
Water
After air, water is the next most critical human need for survival. Water makes up 50-75% of the human body and is needed for most essential functions. An average adult requires 2-3 liters of water per day from both food and drink to stay healthy and hydrated.
Water serves a number of vital roles in the body including:
- Transportation of nutrients and waste: Water moves nutrients through the blood and lymphatic system and helps eliminate waste through urine, feces, and sweat.
- Temperature regulation: Water helps regulate body temperature through sweat.
- Digestion: Water is essential for digesting food and metabolizing nutrients.
- Cushioning joints: Water provides cushioning and lubrication for joints and tissues including eyes, mouth, and nose.
- Maintaining blood volume: Water comprises over 90% of blood and helps maintain adequate blood pressure and circulation.
Without adequate water intake, the body’s ability to perform these vital functions becomes impaired. Even mild dehydration of 1-2% water loss can cause fatigue, dizziness, confusion, increased heart rate and impaired coordination and judgement.
Dehydration Effects
More severe dehydration develops when water loss exceeds 3% of body weight. Effects escalate and can become life-threatening:
| Dehydration Level | Symptoms |
|---|---|
| 3-5% water loss | Headache, weakness, anxiety, rapid breathing and pulse |
| 6-10% water loss | Difficulty swallowing, shrivelled skin, sunken eyes, loss of consciousness |
| 10-15% water loss | Swollen tongue, inability to walk, circulatory collapse, kidney failure |
| Over 15% water loss | Permanent organ damage, death |
Severe dehydration can develop rapidly in instances of intense sweating, vomiting, diarrhea, burns or bleeding injuries. Infants and children are particularly vulnerable to dehydration.
Acquiring Adequate Water
Humans acquire water through both beverages and food:
- Drinking water, juices, milk, tea, coffee, soda etc.
- Eating fruits and vegetables which have high water content.
- Consuming soup broths and jellies.
The Institute of Medicine recommends women consume 2.7 liters (91 oz) of total water per day and men 3.7 liters (125 oz). This can vary based on climate, physical activity level, health status, etc. Most people can meet their hydration needs by letting thirst guide their fluid intake, but some groups like athletes require more diligent hydration.
Food
The third essential human need is food. While air and water provide the basic requirements to sustain life, food provides the nutrients and energy that allow the body to perform essential activities and maintain health.
There are six primary nutrient groups that foods provide:
- Carbohydrates – Found in grains, fruits, vegetables. Provide glucose for energy.
- Proteins – Found in meat, eggs, beans. Build and repair tissues.
- Fats – Found in oils, butter, nuts. Provide energy reserves.
- Vitamins & Minerals – Found in fruits, vegetables, whole grains. Regulate body processes.
- Fiber – Found in plant foods, whole grains. Facilitates digestion.
- Water – Found in all drinks and foods with high fluid content. Maintains hydration.
Consuming adequate nutrition allows the body to:
- Maintain healthy organ function
- Produce energy for cells to perform work
- Build and repair tissues like muscle, skin and bone
- Fight off infection through immune activity
- Carry out essential biochemical reactions
Malnutrition
Insufficient food intake can cause malnutrition which impairs bodily function. Different forms of malnutrition include:
- Marasmus – severe calorie deficiency
- Kwashiorkor – severe protein deficiency
- Anemia – iron, B12 or folate deficiency
- Scurvy – vitamin C deficiency
- Rickets – vitamin D deficiency
- Beriberi – thiamine (B1) deficiency
These nutritional deficiencies can impair organ function, reduce immunity, hinder development, and eventually lead to death if not corrected. Malnutrition remains a leading cause of morbidity and mortality worldwide, especially in children.
Food Requirements
So how much and what types of food do humans require? Recommended intake varies based on age, sex, size, activity level and health status. General daily recommendations for adults per the U.S. Department of Agriculture include:
| Food Group | Recommended Intake |
|---|---|
| Fruits | 1.5 – 2 cups |
| Vegetables | 2 – 3 cups |
| Grains | 5 – 8 ounces |
| Protein | 5 – 7 ounces |
| Dairy | 3 cups |
Following these guidelines and eating a balanced diet with variety ensures adequate intake of macro and micronutrients. However, up to 11% of American households face food insecurity meaning limited access to sufficient affordable nutrition. Globally, around 9% of people are undernourished – a total of 702 million people. Ensuring adequate food for all humans remains an ongoing challenge.
Conclusion
In summary, humans require three essential things to survive and maintain health: air, water and food. Air provides the oxygen needed for cellular respiration and energy production. Water allows nutrients and waste to be transported, regulates temperature, enables digestion and maintains circulation. Food gives the body the carbohydrates, proteins, fats, vitamins and minerals it needs to build and fuel tissues and organs. Depriving the body of any of these three necessities for a sustained period will result in organ failure, malnutrition and eventually death. Meeting these fundamental human needs for air, water and food is critical not just for survival, but for enabling people to thrive and live healthy, productive lives.
