All About Dietary Fat:
Saturated, Monounsaturated, Polyunsaturated, Omega-3, Omega-6, and all the Other Confusing Terms:

Why Eat Fat?

If a person doesn't eat any fat, he will get quite sick and die prematurely. We need to eat fat for most of our bodily organs to function, especially in the hair, skin, brain cells, blood, digestion, and immune system. Critical nutrients like vitamins A and D are not water-soluble and could not be absorbed without fat. Most critical are two specific kinds of fat known as "essential" fats: omega-3 and omega-6. Even if you get enough fat in your diet, lack of either essential fat will cause sickness and ill health.

Unsaturated Fats: Omega-6, Omega-3, and Omega-9

The confusing terms "saturated, "mono-unsaturated", etc., are just chemical classifications. Saturated mean full. The "saturation" refers to hydrogen atoms; if a fat molecule has open spots where a hydrogen atom could fit, it is not saturated; if it has all the hydrogen that could fit, it is full of hydrogen, so it is saturated.

Unsaturated (and monosaturated) fats, like a half-full sandbag (which is "unsaturated" with sand), are squishy; at room temperature, they form the viscous liquids you call "oils". Saturated fat, like a loaded sandbag, are firm, and at room temperature are solid, like the fat on a raw steak. Since unsaturated fats are generally good for you, or at least not terribly harmful, this makes for an easy rule of thumb: oils are better for you than solid fats. The "best" fats will not even become completely solid in the refrigerator.

Although unsaturated fats are present in most fat, vegetable products tend to have much higher concentrations. Polyunsaturated fat can be found mostly in grain products, fish and sea food (herring, salmon, mackerel, halibut), soybeans, and fish oil. Foods like mayonnaise and soft margarine may also be good sources, but you should always check the nutritional label first. Monounsaturated fats are found in natural foods like nuts and avocados, and are the main component of olive oil and canola oil. They can also be found in grapeseed oil, ground nut oil, peanut oil, flaxseed oil, sesame oil and corn oil. 1 

Omega-6

Almost all polyunsaturated fats are either omega-3 or omega-6 oils. These are essential fats -- your body can't produce them and so you must eat them to live. The most prevalent Omega-6 fat is more technically called linoleic acid (LA)2  Luckily, it is abundant. Except in areas of starvation, people have no trouble getting enough omega-6, either from eating the source food (like corn or nuts), or by using oil pressed from the source food.

In fact, most fat contains at least some LA. In the Western world, the problem has become getting too much Omega-6 in the form of LA. Excess LA seems to be associated with inflammation of joints and possibly high cholesterol. This brings us to the other two major groups of unsaturated fats:

Omega-3

Omega-3 is the second essential group of fats; your body can't make it and needs it for many functions. In addition, however, it appears to have positive benefits above and beyond its "essential" benefits.

In the Western world, especially the United States, the population eats ten to forty times more omega-6 than omega-3, or a ratio somewhere between 10:1 to 40:1. A proportion of about 3:1 is very healthy or even ideal 3  Omega-6 and omega-3 fats will compete for absorption into human cells, so eating a proper proportion of them is important. Your body just takes whichever one comes along first, so you have to make sure that at least one out of four fat molecules is omega-3.

Long-chain and Short-chain Omega-3

We apologize for getting a bit technical, but understanding something about long- and short-chain Omega-3 oils is extremely important to your health. If you have a baby or small child, it is even more important to their health.

SUMMARY: Long-chain omega-3 oils ("DHA" and "EPA"), primarily found in fish, are extraordinarily good for your health. They can be a "miracle drug" for heart health and cholesterol levels, and also for early childhood development. See Research. Short-chain omega-3 ("ALA"), found in flaxseed, walnuts, etc., is good for your health but not nearly as good as the long-chain ones. In fact, for men, eating short-chain omega-3 may not provide very much potential improvement in cholesterol. See Research.

The most prevalent omega-3 oil is found in plants. This is a "short-chain" omega-3, ALA (linolenic acid). It is notably abundant in flaxseed and walnuts. ALA is better for your health than omega-6 fats, but it is not nearly as good for you as "long-chain" omega-3 oils, especially EPA and DHA. In fact, the best thing about short-chain omega-3 is that your body converts some of it into long-chain omega-3. The process of converting ALA into EPA and DHA is inefficient: current research indicates that your body will convert roughly 5% to 10% of ALA into EPA, and roughly 0% to 5% into DHA. You might get no DHA at all from consuming short-chain Omega-3. This is especially important for adult men who need to improve their cholesterol profile; solid research has indicated that ingesting ALA may not raise DHA levels for adult men significantly. 4 

The two primary "long-chain" Omega-3 oils are DHA and EPA. 5  The scientific research on the health benefits of DHA and EPA seems reliable enough, as of 2007, to state the following health benefits with considerable confidence:

1. In adults, DHA supplementation lowers levels of serum triglycerides and increases the size of LDL particles (that is, it has a beneficial effect on bad cholesterol). The improvement in individual serum cholesterol levels can be significant or even radical.
2. In adults, EPA supplementation decreases chronic inflammation.
3. In adults, EPA lowers triglyceride levels.
4. In infants, DHA is critical for development of the brain, nervous system, and vision. Breast milk contains DHA (estrogen improves the conversion of ALA to DHA6 ), and perhaps 75% of commercial infant formula marketed in the US has DHA added to it. DHA is "Generally Recognized as Safe" in the US, and the US FDA has approved DHA derived from algae as an additive to baby formula.

There is additional evidence, which needs more research, that DHA may lower the chances of developing dementia (including Alzheimer's Disease) and age-related macular degeneration, and that EPA may reduce blood-clot formation in blood vessels.

How to Get Adequate Omega-3 in Your Diet

So why don't Americans eat more omega-3? Primarily because it comes from fish. Some people don't like fish; it can be expensive and/or hard to get, especially inland; the oceans are being depleted of omega-3 fish; and people are justifiably worried about dangerous contaminants in ocean fish, especially mercury (in the form methylmercury), but also other heavy metals and PCBs.7  Even farm-raised fish can be contaminated.

Methylmercury and Omega-3

This makes for a dilemma. Unlike many health boogeymen touted in the media, the danger from mercury in fish is real. A toxic organic substance, methylmercury, does not break down and is not eliminated from animals' bodies. As fish at the top of the food chain continue to eat smaller contaminated fish, the amount of mercury in their flesh becomes continually greater. Real life people can and do get sick and die from eating mercury-contaminated fish. In the 1960's and 1970's, 1,800 Japanese died from eating heavily contaminated fish from areas near methylmercury dumps, and many more suffered permanent nerve damage, fetal damage, etc. But the benefits of long-chain omega-3 fats are also real; they provide a high level of protection against the US's number one killer, heart disease.

To set this in context, there is no fish sold commerically in the US which will even come close to giving a diner a harmful amount of mercury when eaten occasionally. The very highest species, such as tilefish and swordfish, can be eaten once a month without any danger of toxicity whatsoever to an adult. The problem is that, to get the beneficial effects of omega-3, fish must be eaten several times per week. Also, although most scientists believe that fetuses and infants are harmed by lower levels of mercury than adults, there is no research demonstrating what levels of mercury are potentially toxic to them.

Sadly, mercury is a problem in some of the best-tasting high omega-3 fish, notably tuna and swordfish. Swordfish is practically a lost cause.8  It's woefully high in mercury. Eating swordfish two or three times a week is like eating mushrooms you picked in the woods; unless you are an expert, there is a major risk, and the longer you do it, the higher the risk.

As for tuna, the better it tastes, the more mercury it probably contains. The best tuna -- fresh steaks and sushi -- contains some mercury and, due to the lack of solid evidence about fetal accumulation, pregnant women are well-advised to avoid it completely, and even non-pregnant women of childbearing age should be cautious.9 

The tuna with the lowest mercury content is cheap canned light tuna. Albacore, a superior tasting tuna, is three times higher in mercury.

Healthiest Sources of ALA, EPA, and DHA.

The best solution is salmon, very high in long-chain omega-3 oils and comparatively unlikely to contain contaminants. Good fresh salmon also lacks a strong fishy odor or taste; even most people who aren't fish-lovers enjoy it. Salmon oil, with concentrated EPA and DHA, is also available in capsule form; a good manufacturer of these capsules will test the oil and guarantee that it is free from contaminants.10  Shrimp, which has a small amount of omega-3, is very safe, and for those who enjoy stronger-flavored fish, sardines and herring are very good choices for frequent consumption.

Omega-3 can also be found in non-fish foods, such as walnuts and flax-seed. These are not as beneficial as the omega-3 in fish, however; fish contain EPA and DHA, long-chain fatty acids that provide the greatest benefit to health. Vegetable sources are almost entirely ALA, which provides less benefit (although the body will convert it into EPA and DHA to some degree). We would certainly not discourage anyone from eating flaxseed, walnuts, etc.

EPA and DHA are also commercially available as supplements grown from algae, most often added to baby food -- this is an expensive but extremely healthy and safe omega-3 source. Test after test has shown that babies who eat algae-grown omega-3 develop faster, healthier and smarter.

In addition to cardiovascular benefit, various other benefits have been ascribed to DHA and ELA, ranging from a remedy for depression to increased sexual vigor. Fish has long been informally called "brain food", implying a beneficial effect to cognition and memory. Until reliable and repeated scientific testing has established these benefits, you would be well-advised to remain skeptical.

Omega-9

Omega-9 oils are primarily monosaturated (some are polyunsaturated, but these aren't a major part of human diet). These have become increasingly popular due to the Mediterranean diet, which characterizes populations with a low incidence of cardiovascular disease. The best-known source of Omega-9 is olive oil and canola oil. Olive oil is particularly tasty, but has a low smoke point and so is difficult to use in frying or sauteeing; canola oil has a high smoke point and is excellent for frying. The taste is also more neutral than that of olive oil.

The health benefits of Omega-9 oil (actuallly, the absence of ill effects) have been sufficiently proven that it is advisable to use them in place of animal fats. Olive oil is particularly good in this regard, as it is good on bread, rice, asparagus, etc., in place of butter or margarine. The only downside is that it is liquid and so a bit more difficult to handle on bread.

Saturated Fat

Saturated fats are generally solid at room temperature. These are the fats that are responsible for so much heart disease. Common foods that contain a high proportion of saturated fat are butter, suet, tallow, lard, coconut oil, cottonseed oil, palm kernel oil, dairy products (especially cream and cheese), red meat, and some prepared foods. The advice on saturated fat is simple: eat as little as possible. If you love red meat, find the cut that is lowest in saturated fat and still satisfies you.

Saturated fats can be hidden. Two cuts of beef can look identical, even though one is four times higher in saturated fat. Fried food tastes little different when it is fried in lard than when it is fried in vegetable oil.

Trivia Break

Fats are actually acids. For example, the omega-3 fat ALA is alpha-linolenic acid. The reason they don't taste sour is that they don't dissolve in water, so your taste buds can't detect the acidity.

Soap would not exist otherwise. Making soap begins by combining fat -- a "fatty acid" -- with a powerful alkali, such as lye or caustic potash, which neutralizes the fatty acid. The neutralized fat molecule is then (loosely speaking) soluble in both oil and water. Even better, one end of it will attract a water molecule and the other end a fat molecule, with the result that the oil and water mix together.

Fat isn't the only acid that will work; most shampoo contains detergents made from sulfuric acid! Look at the ingrediants listed on your shampoo bottle; that sodium lauryl or sodium laureth sulfate is a euphemism for "sulfuric acid monododecyl ester sodium salt". You can see why they made up the euphemism: Imagine how many people would put "Sulfuric acid monododecyl ester sodium salt" in their hair :).