The immune system is a complex and dynamic network of cells, membranes and organs.

Cholesterol is a fat-like substance circulating in the blood. The body needs a certain amount to maintain cell membranes and perform other vital functions, but high levels lead to blocked arteries, which can cause a heart attack.

Bowel habits can vary widely from person to person, but most doctors agree that anyone who passes hard stools and does so less than three times per week is constipated.

Despite the appeal of supplements, we should not rely heavily on them to meet our needs.

Energy cannot be created or destroyed, it merely changes its state. This is what happens when we eat. The food we eat becomes glucose, which is used as fuel to make energy.