Essential fatty acids

The diet of a wild goril­la is essen­tial­ly a great huge sal­ad, with­out dress­ing. Yet those foods con­tain enough fat for the goril­las to absorb fat-sol­u­ble vit­a­mins from their food, and enough of the essen­tial fat­ty acids for the goril­las to have a nor­mal healthy ner­vous sys­tem and lots of glossy hair. So when peo­ple tell me that I need to take fat sup­ple­ments, I’m not buy­ing. A spoon­ful of ground flaxseed in my oat­meal in the mor­ing, okay. But I’m not buy­ing any sort of oth­er fat­ty acid sup­ple­ment until I see data that shows that they do more good than harm.

I’ve seen lots of evi­dence in the sci­en­tif­ic lit­er­a­ture that switch­ing to a low-fat (<10% of calo­ries), oil-free diet can make peo­ple heart-attack-proof, reduce their risk of can­cer, and even fight arthri­tis. I haven’t seen any­one get­ting results like that from swap­ping one fat for anoth­er in a high-fat diet, or by adding oil sup­ple­ments to an unhealthy diet. If you are sick and are think­ing of using some sort of fat sup­ple­ment as a drug, ask your doc­tor and a reg­is­tered dietit­ian about try­ing a low-fat, plant-based diet first.

Don’t wor­ry about suf­fer­ing from a defi­cien­cy of fat on a low-fat diet. Most of the actu­al cas­es of peo­ple who had trou­ble because they didn’t con­sume enough fat were get­ting fed noth­ing but sug­ar intra­venous­ly. In those cas­es, sim­ply rub­bing some veg­etable oil on the skin solved the defi­cien­cy. It’s also pos­si­ble to get into trou­ble if you can’t absorb fat from your food, usu­al­ly because of some dis­ease of the diges­tive sys­tem. But if that’s your prob­lem, you real­ly need to be under the care of a doc­tor and a reg­is­tered dietit­ian.

What’s the difference between fat and a fatty acid?

An oil is mere­ly a fat that stays liq­uid at room tem­per­a­ture. Most of the oils and oth­er fats in our food are main­ly in the form of triglyc­erides. Each mol­e­cule of triglyl­ceride con­tains three mol­e­cules of fat­ty acid, bound to one mol­e­cule of glyc­erol.


If you’ve ever got­ten soap in your eye, you’ll under­stand why the body prefers to store fat as triglyc­erides than as free fat­ty acids. Free fat­ty acids have a car­boxyl group (-COOH) on one end. The car­boxyl group is what gives vine­gar its bite, and it caus­es the free fat­ty acids in soap to be irri­tat­ing. Bind­ing that car­boxyl end to a glyc­erol mol­e­cule makes it much less reac­tive, and much less irri­tat­ing!

Structure of acetic acid

Why aren’t fats all alike?

At room tem­per­a­ture, olive oil is liq­uid but choco­late is sol­id. That’s because the fats in them con­tain a dif­fer­ent mix­ture of fat­ty acids. Olive oil con­tains a lot of ole­ic acid, while choco­late con­tains a lot of stearic acid. Although both of these fat­ty acids con­tain 18 car­bon atoms, the stearic acid con­tains as many hydro­gen atoms as it could pos­si­bly hold. Thus, we say that it is a “sat­u­rat­ed fat.” Ole­ic acid has one dou­ble bond between car­bon atoms, so it is a monoun­sat­u­rat­ed fat. The two essen­tial fat­ty acids also con­tain 18 car­bon atoms but have even more dou­ble bonds in them, so they are “polyun­sat­u­rat­ed.”

Accord­ing to the Food and Nutri­tion Board of the Nation­al Research Coun­cil, human beings can eas­i­ly make all the sat­u­rat­ed fat and monoun­sat­u­rat­ed fat that their bod­ies need. This means that there is no need to get any sat­u­rat­ed or monoun­sat­u­rat­ed fat what­so­ev­er from the diet. That means that you don’t need to eat but­ter or olive oil. The Food and Nutri­tion Board also says that you don’t need to get any trans fat from the diet. Trans fats are rarely found in nature, but they are com­mon in fats that have been hydro­genat­ed. For an expla­na­tion of hydro­gena­tion and trans fats, click here.

Accord­ing to the Food and Nutri­tion Board, only two fat­ty acids are con­sid­ered to be essen­tial in the human diet. One of these two essen­tial fat­ty acids is linole­ic acid, which is an omega-6 fat­ty acid. The oth­er is alpha-linolenic acid, which is an omega-3 fat­ty acid. They are essen­tial because we need them for var­i­ous pur­pos­es but can’t make our own sup­ply. That’s because we don’t make the enzymes that would be nec­es­sary to put a dou­ble-bond at the omega-3 or omega-6 posi­tion.


We can burn linole­ic acid and alpha-linolenic acid for ener­gy. We can also con­vert them into oth­er use­ful sub­stances, but first we have to length­en the car­bon chain. Linole­ic acid and alpha-linolenic acid both con­tain 18 car­bon atoms. The human body can con­vert linole­ic acid into arachi­don­ic acid (AA), which has 20 car­bon atoms. The body can con­vert alpha-linolenic acid into eicos­apen­taenoic acid (EPA), which also con­tains 20 car­bon atoms. The body uses AA and EPA to make eicosanoids, which are chem­i­cal sig­nals that play an impor­tant role in the process of inflam­ma­tion and in the ner­vous sys­tem. The body can also con­vert EPA into docosa­hexaenoic acid (DHA), which has 22 car­bons.

Unlike human beings, cats can’t make arachi­don­ic acid from linole­ic acid. As a result, they have to get arachi­don­ic acid from their food. Since arachi­don­ic acid is rarely found in plants, those ani­mals have to eat meat. In oth­er words, they are “oblig­ate car­ni­vores.” If you want to design a plant-based diet for cats, you’ll have to sup­ple­ment it with arachi­don­ic acid, among oth­er things.

How much of the essential fatty acids do we need?

Human require­ments for the essen­tial fat­ty acids are sur­pris­ing­ly low, only about 2% of our calo­rie require­ments. To find peo­ple who have a defi­cien­cy of linole­ic acid, you have to look at peo­ple who have been fed a lot of sug­ar intra­venous­ly. They end up with signs of fat­ty acid defi­cien­cy part­ly because they aren’t get­ting any linole­ic acid from food and part­ly because their high insulin lev­els keep them from releas­ing the omega-6 fat­ty acids from their fat stores. To find peo­ple with an out-and-out defi­cien­cy of omega-3 fat­ty acids, you have to look at hos­pi­tal or nurs­ing-home patients who had been tube-fed some­thing that was prac­ti­cal­ly devoid of alpha-linolenic acid for an extend­ed peri­od.

Absolute defi­cien­cy of the omega-6 or omega-3 fat­ty acids is extreme­ly rare; how­ev­er, there has been con­sid­er­able con­cern about the bal­ance between omega-6 and omega-3 fat­ty acids in the diet. If peo­ple eat too much omega-6 fat­ty acid, com­pared to their intake of omega-3 fat­ty acid, they could end up mak­ing more of the eicosanoids that come from arachi­don­ic acid and less of the ones that come from eicos­apen­taenoic acid. This could end up shift­ing the body toward a pro-inflam­ma­to­ry as opposed to anti-inflam­ma­to­ry state. The obvi­ous solu­tion to this prob­lem is to eat a low-fat diet with lots and lots of veg­eta­bles. Although veg­eta­bles don’t con­tain much fat, a lot of the fat they do con­tain is alpha-linolenic acid. To make sure that you get enough alpha-linolenic acid to bal­ance your linole­ic acid intake, you can eat a spoon­ful of ground flaxseed every day, or per­haps a few wal­nuts.

Can you get too much omega-6 or omega-3?

Amer­i­cans tend to think that you can’t get too much of a good thing. We tend to think that if more is bet­ter, then too much is just right. Yet it is pos­si­ble to get too much fat in the diet, even too much of the essen­tial fat­ty acids. Peo­ple should keep this in mind, espe­cial­ly if they are con­sid­er­ing using fat­ty acid sup­ple­ments as a drug.

Eat­ing too much fat makes you fat. If you eat more calo­ries than you burn up, your body will tend to burn the dietary car­bo­hy­drates first and store the excess fat you just ate. The fat goes straight to your fat cells, and where very lit­tle ener­gy is con­sumed in turn­ing it into body fat. In con­trast, you waste about 30% of the calo­ries from sug­ar when you turn sug­ar into body fat. That’s one of the rea­sons why high-fat diets are more fat­ten­ing than high-car­bo­hy­drate diets.

Eat­ing too much fat, even too much of the omega-3 fat­ty acids, can pro­mote ath­er­o­scle­ro­sis, which is the buildup of plaque on the insides of the arter­ies. A high-fat diet caus­es the body to pro­duce more cho­les­terol, which helps to digest fat. Peo­ple who eat ani­mal prod­ucts also get some cho­les­terol ready-made in their diet.

Ath­er­o­scle­ro­sis can lead to heart attack and stroke. The best way to pre­vent these prob­lems is to eat a low-fat (<10% of calo­ries), high-fiber, plant-based diet. Plant foods con­tain no cho­les­terol, and a low-fat diet reduces the amount of cho­les­terol that your body makes. Some kinds of dietary fiber bind to cho­les­terol in the intes­tine, to keep your body from recy­cling it. Togeth­er these effects help reduce cho­les­terol lev­els to the “heart-attack-proof” zone of <150 mg/dL.

Is omega-3 fatty acid a medicine?

Although the best way to pre­vent ath­er­o­scle­ro­sis is to switch to a low-fat, plant-based diet, some peo­ple argue that eat­ing fish will pre­vent heart dis­ease. The truth is a bit con­fus­ing. You might be able to reduce your risk of a fatal heart attack a lit­tle by eat­ing fish instead of oth­er fat­ty ani­mal prod­ucts. How­ev­er, you can make your­self heart-attack-proof by shift­ing to a diet that con­tains no ani­mal prod­ucts what­so­ev­er and gets less than 10% of its calo­ries from fat of any kind.

Besides pro­mot­ing ath­er­o­scle­ro­sis, eat­ing too much omega-3 fat­ty acid can cause oth­er prob­lems. Because it thins the blood, it can increase the risk of bleed­ing. Research also sug­gests that eat­ing too much polyun­sat­u­rat­ed fat, includ­ing omega-3 fat­ty acids, can pro­mote the growth of can­cer.

Many of the dis­eases that peo­ple hope to man­age by using omega-3 fat­ty acid sup­ple­ments are actu­al­ly a result of the stan­dard Amer­i­can diet. Heart dis­ease results from eat­ing too much fat and cho­les­terol. Arthri­tis is often the result of eat­ing ani­mal pro­tein instead of plant pro­tein. Even depres­sion could be relat­ed to the stan­dard Amer­i­can diet. It would make more sense to cor­rect the diet by shift­ing to a low-fat, plant-based diet, instead of trad­ing one fat for anoth­er or adding fat sup­ple­ments. If you have a dis­ease that you want to man­age by using omega-3 fat­ty acid sup­ple­ments, talk to a reg­is­tered dietit­ian as well as a med­ical doc­tor.