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Blood has fascinated mankind throughout the ages. Some cultures worship it, while some people faint at the very sight of it. So what do we really know about the fluid of life?
 To start off, there are about five litres of it coursing through the average adult’s arteries and veins, accounting for about seven per cent of a human’s body weight. It’s job is to transport oxygen and nutrients to every cell and carry away waste products produced by cells. It also delivers disease-fighting white blood cells to areas of the body under threat of infection.
Blood has four main ingredients – plasma, red and white cells and platelets.
Approximately 50 per cent of blood is plasma. Pale and straw-coloured, plasma is mostly water containing proteins, salts and hormones.
A single drop of blood contains about 5 million red blood cells. Shaped like a shallow bowl, these cells attract and pick up oxygen from the lungs, releasing it into tissues all around the body.
White blood cells make up only one percent of blood. They fight against unwanted visitors like bacteria, cancer cells, infections and foreign objects. An increase in the number of white blood cells is a sign of infection.
Platelets are cell fragments that clump together to clot blood. They help the body to stop bleeding after a skin wound.
Everyone belongs to one of four blood groups: A, B, AB or O. The four groups are distinguished from one another by markers, or antigens, found on the surface
of the red blood cells.
The body’s immune system uses these markers to recognise whether a particular cell is from our own body or is foreign. For a blood transfusion to be successful, the donor blood must be from the same blood grouping as the patient; otherwise the body will detect ‘invading cells’ and attack them.
Some other interesting facts about blood:
Nobel Prize winner Dr Karl Landsteiner discovered the four blood groups in 1900.
World Blood Donor Day is held each year on June 14. This date was selected by the World Health Organisation because it’s Landsteiner’s birthday.
One out of every 10 people admitted to hospital requires blood.
Around 80 per cent of New Zealanders will need blood or a blood product during their lifetime.
One blood donation can save the lives of up to three people.
A range of medical fact sheets are available on blood related topics in our Medical Library.
Good food for the blood
- Food that may discourage blood clots: garlic, onions, hot peppers, black mushrooms, ginger and cloves, vegetables, olive oil, seafood, tea
- Food that may lower blood pressure: celery, garlic, fatty fish (mackerel), vegetables, olive oil. Cutting down on salt is also known to help lower blood pressure. A good way to do this is to limit processed foods which account for about 75 per cent of the sodium (salt) in the food supply
- Food that may help prevent strokes or lessen damage: fruits, vegetables, fatty fish, tea
- Food rich in iron: red meat, liver, green vegetables, eggs, dried apricots, sardines, spinach, fortified breakfast cereals, wholemeal bread
- Vitamin B1: meat, poultry, fish, eggs, milk, cheese, fortified breakfast cereals
- Folic acid: wheatgerm, broccoli, green cabbage, pulses, nuts, yeast extract.
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