Lipids

There are six major classes of nutrients found in food: carbohydrates, proteins, lipids (fats and oils), minerals, vitamins (both fat-soluble and water-soluble) and water. Oils, fats, waxes, and sterols are collectively known as lipids. They play important and divers roles in health and nutrition.

Lipids contain hydrogen, carbon and oxygen but have far less oxygen proportionally than carbohydrates. They can be divided into 2 categories: saturated and unsaturated, based on the chemical structure of their longest, and therefore dominant, fatty acid.

- Lipids from plant sources are largely unsaturated, and therefore liquid at room temperature.- The ones that are derived from animals contain a higher amount of saturated fats, and they are therefore solid at room temperature.

Lipids were long considered to be passive passengers of carrier vesicles with the only role of sealing the transport container. Many lipids are essential for life; however, there is also considerable awareness that abnormal levels of certain lipids, particularly cholesterol (in hypercholesterolemia) and, more recently, trans fatty acids, are risk factors for heart disease and other diseases.

The energy contained in a gram of lipids is more than twice the amount in carbohydrates and protein, with an average of 9 kcal/gram. High levels of blood lipids can increase the risk of developing both heart disease and stroke, the greatest medical killers in modern world. A proper proportion of fat, sugar and proteins help assure normal blood lipids. Some forms of blood lipids, like triglycerides, are increased by drinking alcohol.