Know your fats
By Chris Kresser
If you put gasoline in a diesel engine, or vice versa, the engine may run but it won’t run well – or for very long. In a similar way, the human body can run on the entire range of fats, carbohydrates and proteins. But it runs much better on the ones it was designed to run on, and if you put too much of the others in, the body will eventually break down.
With this classification in mind, let’s look primarily at how the different types of fat and carbohydrate (our primary sources of energy) affect us, and which of them we should choose as our preferred “human fuel”.
LONG-CHAIN SATURATED FAT
We’ll begin with long-chain, saturated fats (LCSFA): myristic, palmitic and stearic acid. These fats are found mostly in the milk and meat of ruminant animals like cattle and sheep. They form the core structural fats in the body, comprising 75-80% of fatty acids in most cells, and they’re the primary storage form of energy for humans. In other words, when the body stores excess energy from food for later use, it stores it primarily as long-chain saturated fat.
Unlike polyunsaturated fats (PUFA) and carbohydrates like glucose and fructose, saturated fats have no known toxicity – even at very high doses – presuming insulin levels are in a normal range. Long-chain saturated fats are more easily burned as energy than PUFA. The process of converting saturated fat into energy the body can use leaves no toxic byproducts. In fact, it leaves nothing but carbon dioxide and water.
This means that, assuming you are metabolically healthy, you can eat as much saturated fat as you’d like without adverse consequences. I’m sure this will come as a surprise to many of you, since we’ve been collectively brainwashed for 50 years to believe that saturated fat makes us fat and causes heart disease. If you still believe this is true, watch these two videos and read all of the articles in my special report on cholesterol, fat and heart disease.
Verdict: eat as much as you’d like. The majority of the fats you consume should be LCSFA.
Medium-chain triglycerides (MCT) are another type of saturated fat. They’re found in coconut and in mother’s milk, and they have unusual properties. They’re metabolized differently than long-chain saturated fats; they don’t require bile acids for digestion and they pass directly to the liver via the portal vein. This makes MCTs a great source of easily digestible energy. They’re so easy to digest, in fact, that they’re used in the liquid hospital formulas fed to patients that have had sections of their intestine removed and aren’t able to digest solid food.
In addition to being a good energy source, MCTs have therapeutic properties. They’re high in lauric acid, a fat found in mother’s milk that has anti-bacterial, anti-viral and antioxidant properties.
Verdict: eat as much as you’d like. Coconut oil is an especially good cooking fat, because it is not vulnerable to the oxidative damage that occurs with high-heat cooking using other fats.
Monounsaturated fat (MFA), or oleic acid, is found primarily in beef, olive oil, avocados, lard and certain nuts like macadamias. Like saturated fats, MFA form the core structural fats of the body and are non-toxic even at high doses. Interestingly, monounsaturated fats seem to be the only fats that typically fat-phobic groups like the AHA and fat-friendly groups like Atkins and other low-carbers can agree are completely healthy.
Verdict: eat as much as you’d like. But be aware that certain foods that are high in monounsaturated fats, like nuts and avocados, can contain significant amounts of the dreaded omega-6 polyunsaturated fats, which we’ll discuss below. Exercise caution.
These three fats – long-chain saturated, medium chain triglycerides and monounsaturated – should form the bulk of your fat intake. In addition to their lack of toxicity, eating these fats will:
- Reduce your risk of heart disease by raising your HDL, lowering your triglycerides and reducing levels of small, dense LDL (a type of LDL associated with a higher risk of heart disease). If you don’t believe me, read this.
- Increase muscle mass. Muscle is composed of equal weights of fat and protein.
- Stabilize your energy and mood. Fat provides a steadier supply of energy throughout the day than carbohydrate, which can cause fluctuations in blood sugar.
Polyunsaturated fat (PUFA) can be subdivided into omega-6 and omega-3. PUFA are fragile and vulnerable to oxidative damage, a process that creates free radicals in the body and raises our risk for everything from heart disease to cancer. As I pointed out in Step #1: Don’t Eat Toxins, both anthropological and modern research suggest that for optimal health we should consume roughly the same amount of omega-6 and omega-3 fat (1:1 ratio), and that our total intake of PUFA should be no more than 4% of calories.
But Americans’ omega-6:omega-3 ratio today ranges from 10:1 to 20:1, with a ratio as high as 25:1 in some individuals! This means some people are eating as much as 25 times the recommended amount of omega-6 fat. And it is this excess consumption of omega-6 PUFA – not cholesterol and saturated fat – that is responsible for the modern epidemics of cardiovascular disease, type 2 diabetes, obesity, metabolic syndrome, autoimmune disease and more.
Omega-6 PUFA (linoleic acid, or LA) is found in small or moderate amounts of a wide variety of foods including fruits, vegetables, cereal grains and meat. But it is found in very large amounts in industrial processed and refined oils, like soybean, cottonseed, corn, safflower and sunflower. These oils are ubiquitous in the modern diet, present in everything from salad dressing to chips and crackers to restaurant food. LA is also relatively high in most nuts and in all poultry, especially in dark meat with skin.
Linoleic acid is an essential fatty acid. This means it is required for proper function but cannot be produced in the body, and thus must be obtained from the diet. However, the amount of omega-6 that is needed is exceedingly small:less than 0.5 percent of calories when supplied by most animal fats and less than 0.12 percent of calories when supplied by liver. When consumed in excess amounts – as is almost always the case in industrialized countries like the U.S. – omega-6 contributes to all of the diseases mentioned above.
Omega-3 PUFA can be further subdivided into short-chain (alpha-linolenic acid, or ALA) and long-chain (EPA & DHA). ALA is found in plant foods like walnut and flax, whereas EPA & DHA is found in seafood and to a lesser extent the meat and fat of ruminant animals.
While ALA is considered essential, the long-chain EPA & DHA are responsible for the benefits we get from eating omega-3 fats, and they form the denominator of the omega-6:omega-3 ratio. A common misconception is that we can meet our omega-3 needs by taking flax oil or eating plant foods containing ALA. It’s true that the body can convert some ALA to EPA & DHA. But that conversion is extremely inefficient in most people. On average, less than 0.5% of ALA gets converted into the long-chain EPA & DHA, and that number is even worse in people that are chronically ill or have nutrient deficiencies (common in vegans and vegetarians).
This means that it is probably EPA & DHA that are essential, in the sense that they are crucial for proper function but cannot be produced in adequate amounts in the body, and thus must be obtained from the diet. Of the two, evidence suggests that DHA plays the more important role.
Verdict: for optimal health, eat no more than 4% of calories (about 9g/d for a 2,000 calorie diet) of polyunsaturated fat, with an equal amount of omega-6 and omega-3. Make sure the omega-3 you eat is long-chain EPA & DHA (from seafood and animal sources) rather than short-chain ALA from plant sources like flax. It is very difficult to limit omega-6 to 4.5g/day. See this article for tips.
There are two types of trans-fats: natural (NTF), and artificial (ATF). The primary natural trans-fat, conjugated linoleic acid (CLA) is found in small amounts (about 2%) in the meat, fat and dairy fat of ruminant animals. CLA does not have the harmful effects of ATFs, and may have anti-cancer properties and other benefits.
Artificial trans-fats have been linked with a variety of diseases. I think most people are aware of this, so I’m not going to belabor the point. We’ve still got carbs to talk about.
Verdict: avoid artificial trans-fats like the plague. Natural trans-fats like CLA are harmless and probably even beneficial, but as long as you’re eating long-chain saturated fats, you’ll get CLA. You don’t have to go out of your way to find it.
SUMMARY OF FATS
Long-chain saturated fat, monounsaturated fat and medium chain triglycerides should form the bulk of your fat intake. Long-chain omega-3 fats (EPA & DHA) should be consumed regularly, while omega-6 LA should be dramatically reduced. Click on the fat pyramid below for a graphic representation.