Lipids

Delicious, necessary and good for you - in moderation

Lipids are a group of substances which are insoluble in water and are known in a general sense as fats and oils.  They are a key part of the diet and a key part of our overall health having a number of uses in the body.  There are six major groups of nutrients we need in a balanced diet – put very simply -  minerals and vitamins, carbohydrates [sugars and starches], lipids[ fats and oils], proteins, fibre and water.

Lipids are a major part of cell membranes and we would soon become very very ill if we ate no lipids.  Some lipids have been erroneously associated with various diseases prompting campaigns involving very unwise medication.

Lipid groups

One group  of lipids are the fat-soluble vitamins (such as vitamins A, D, E, and K), but as these are described elsewhere on the site I have not covered them here.  The main groups of lipids essential to human and mammalian health are:

• Monoglycerides, Diglycerides and Triglycerides
• Phospholipids
• Waxes
• Steroids
• Cholesterol

Waxes – provide protection and waterproofing

Steroids – many animal hormones are steroids including oestrogen and testosterone.  Our reproductive system is controlled by these hormones, as such if we deny ourselves the nutrients needed to make these we may get difficult periods, become infertile, and suffer from an appalling menopause.

Cholesterol  - essential to health as is explained in the more detailed section.  It is either manufactured by the liver via an enzyme using Acetyl coA, which itself is made from Vitamin B5, or it comes from the diet. 

Animal fats are complex mixtures of triglycerides, with lesser amounts of phospholipids and cholesterol. As a consequence, all foods containing animal fat contain cholesterol to varying extents, in effect we can also get it from the diet.   Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry, fish, and shrimp.  Human breast milk also contains significant quantities of cholesterol.  Cholesterol is not found in significant amounts in plant sources.

Plant products such as flax seeds and peanuts contain cholesterol-like compounds called phytosterols, which are’ believed to’ [sic] compete with cholesterol for absorption in the intestines.  Thus if you have dire need of cholesterol, the last thing you should be eating is flax seed.  About 20–25% of total daily cholesterol production occurs in the liver; other sites of higher synthesis rates include the intestines, adrenal glands, and reproductive organs.  In effect, if you have any damage to these organs you may need more cholesterol not less.

lemon-butter-pavlova-with-fresh-berries-and-cream

Phospholipids – form a major part of cell membranes including the myelin sheath around nerve fibres that supports the rapid conduction of nerve impulses.  It should thus be clear how essential phospholipids are to our health and operation.  Phospholipids also give all cell membranes their fluid properties allowing lipid soluble substances to pass easily through them, thus they are key to all cell function.  Without them we die. 

Apart from animal fats, common sources of phospholipids are soya, sunflower seeds, chicken eggs, milk, and fish eggs - caviar!

Monoglycerides  - is the term for a glyceride in which each glycerol molecule has formed an ester bond with exactly one fatty acid molecule.  They are produced in the body from enzymes acting on triglycerides ‘by the action of lipoprotein lipase’. 

Di-glycerides [diacyl-glycerol] - is the term for a glyceride consisting of two fatty acid chains covalently bonded to a glycerol molecule through ester linkages. They are produced in the body from enzymes acting on triglycerides. 

Triglycerides  - are lipids made from glycerol and fatty acids and a saturated fat consists of triglycerides containing only saturated fatty acids.  Triglycerides are obtained in our diet.  The table below shows some saturated fatty acids