Guide to Fats 1: Introduction

Fat: a word that can be hard to hear at times, especially after a weekend of indulgence! 😉 But fats come in many forms and some are vital to good health. So, we boldly go to Fat Land to collect data on our oily pals. Which are friendly, and which are enemy aliens out to destroy our health? 

The fat family is big (no pun intended!), complex and controversial. We have tried to create a comprehensive guide to dietary fats but have also offered suggestions for further reading. For clarity, we have split the fat family up. Click on the 'Go to…' links to take you to subsequent sections. 

Fatty acids: a brief intro 
Fats (or lipids) are organic substances insoluble in water and greasy to the touch. Fatty acids are sub-units of fats. A fatty acid is a chain of carbon atoms with an omega (or methyl) end and a carboxyl end. Each carbon atom in the chain is chemically bonded to the next carbon atom, while hydrogen atoms are bonded to the side(s) of each carbon atom. Bonds between carbon atoms can be single (-) or double (=). Differences in bond-type, plus the number of carbon atoms on the chain, determine whether you have butter, olive oil or fish oil on your plate. 

Our bodies need fatty acids. They are incorporated into our cell membranes as phospholipids; circulate in our bloodstream as lipoproteins; aid digestion; have powerful anti-microbial and anti-viral properties; and provide building blocks for hormones, bile acids and prostaglandins – compounds that influence everything from hormone balance to inflammation to smooth muscle control. 

Fat food 
Although dietary fat has been damned, it is essential. Fats (animal and plant) provide a concentrated energy source, slow down food absorption and keep hunger at bay. They also serve as a carrier for vital fat-soluble vitamins (A, D, E and K); help convert plant-source carotene to vitamin A; and are key to mineral absorption. 

Cutting out fats is not a good idea. Being choosy is. Undamaged fats do the job properly. Whereas rancid, heat-distorted and chemically processed fats cannot, contributing instead to cardiovascular disease, cancer, mental health problems, skin issues, and a host of other ailments. 

Saturated, monounsaturated, polyunsaturated… 

Natural fatty acids fall into three main categories: saturated, monounsaturated (omega-9) and polyunsaturated (omega-3 and omega-6). Saturated fatty acids contain single bonds (-) linking carbon atoms along the chain. Monounsaturated fatty acids contain one double bond (=) linking two carbon atoms; the rest are single bonds. Polyunsaturated fatty acids contain two or more double bonds; the rest are single bonds. The more double bonds on the chain, the more unsaturated the fatty acid. At each double bond, only one side of the carbon atom is saturated with hydrogen atoms; the other is not, leaving room for oxygen to slither in and wreak havoc. 
Oxygen damage (aka lipid peroxidation, or plain ol' rancidity) creates free radicals: unstable molecular muggers that damage cells. Polyunsaturated fatty acids (e.g. ALA in flax oil) are especially prone to rancidity. Storing fresh oils away from heat, light and air can slow it down. 

Monounsaturated fats (e.g. oleic acid in olive oil) are less vulnerable. Saturated fatty acids (e.g. lauric acid in coconut oil) are least prone. Most natural edible fats contain a mixture of fatty acids (e.g. olive oil contains 75% oleic acid, 13% saturated fat, 10% omega-6 LA and 2% omega-3 ALA). 

Trans world 
Most trans fats are created by man. Man-made trans fats are unsaturated vegetable oils that have been industrially saturated with hydrogen to make them stable and spreadable at room temperature (e.g. margarine). In the process, naturally shaped 'cis' fatty acids are distorted, creating an artificial, detrimental 'trans' shape. Like a key that slides into a lock but won't turn, trans fats function badly and block the right key (or good fat), leading to myriad health problems. 

Chain-chain-chain 
Scientists also classify fatty acids by length. Short-chain: 4-6 carbon atoms: these are always saturated (e.g. butyric acid in cows' butter). Medium-chain: 8-12 carbon atoms: these are also saturated (e.g. lauric acid in coconut oil). Long-chain: 14-18 carbon atoms: these can be saturated (e.g. stearic acid in beef), monounsaturated (e.g. oleic acid in olive oil) or polyunsaturated (e.g. GLA in evening primrose oil). Very-long-chain: 20-24 carbon atoms: these tend to be highly unsaturated (e.g. EPA and DHA in fish oil), though there are some very-long-chain monounsaturated fatty acids too (e.g. erucic acid). 

Over the next few blogs we look at unsaturated, saturated and trans fats in more depth. Go to… Guide to Fats 2: Essential Fatty Acids: Overview Further reading Loren Cordain, The Paleo Diet (Revised Edition), New Jersey, 2011 http://thepaleodiet.com/nutritional-tools/fats-and-fatty-acids-a-primer Mary Enig and Sally Fallon, 'The truth about saturated fat', www.mercola.com, 2002 (from Sally Fallon and Mary Enig, Nourishing Traditions, NewTrends Publishing, 2000)