by Chris Kresser (web)
In step #1, we talked about what not to eat. In this article, we’ll talk about what to eat.
Most of the calories we get from food come from protein, carbohydrates and fat. These are referred to as macronutrients. We also get other important nutrients from food, such as vitamins and minerals. These don’t constitute a significant source of calories, so they’re called micronutrients.
For the last 50 years we’ve been told to follow a diet low in this or that macronutrient. From the 1950s up until the present day the American Heart Association and other similarly misguided and pharmaceutically-financed “consumer organizations” have advocated a low-fat diet. More recently, low-carbohydrate diets are all the rage.
Not all macronutrients are created equal
The problem with these approaches is that they ignore the fact that not all macronutrients are created equal. There’s a tremendous variation in how different fats and carbohydrates affect the body, and thus in their suitability for human consumption. Grouping them all together in a single category is shortsighted – to say the least.
What many advocates of low-fat or low-carbohydrate diets conveniently ignore is that there are entire groups of people around the world, both past and present, that defy their ideas of what constitutes a healthy diet.
For example, the low-fat crowd will tell you that eating too much fat – especially of the saturated variety – will make you fat and give you a heart attack. Tell that to the traditional Inuit, who get about 90% of calories from fat, and were almost entirely free of obesity and modern degenerative disease. The same is true for the Masai tribe in Africa, who get about 60-70% of calories from fat (almost entirely from meat, milk or blood.) And then there’s the modern French, who have the lowest rate of heart disease of any industrialized country in the world – despite the highest intake of saturated fat.
The low-carb crowd is very much aware of these statistics, which are often used in defense of low-carb diets as the best choice. Tell that to the Kitavans in Melanesia, who get about 70% of calories from carbohydrate and, like the Inuit and Masai, are almost entirely free of obesity, heart disease and other chronic, degenerative diseases that are so common in industrialized societies. We see a similar absence of modern diseases in the Kuna indians in Panama and the Okinawans of Japan, two other healthy indigenous populations that get about 65% of calories from carbohydrate.
These rather inconvenient exceptions to the low-fat and low-carb dogma vigorously promoted by advocates of both approaches show us that humans can in fact thrive on a wide range of macronutrient ratios, ranging from extremely high fat (Inuit, Masai) to very high carb (Kitavans, Kuna & Okinawans). They also hint at the idea that perhaps not all carbohydrates are the same in terms of their effects on human health.
Human fuel: food that nourishes the body
We need to shift away from the idea of macronutrients – as Dr. Kurt Harris of PaleoNu recently suggested – and move towards the idea of nourishment or fuel. This means we classify foods not based on their macronutrient ratios, but on their ability to provide the energy and nutrition the body needs to function optimally.
Gasoline and diesel are both fuel that cars can run on. 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”.
Know your fats
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
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
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: OMEGA-6 & OMEGA-3
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.
TRANS-FATS
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.
Know your carbs
Carbohydrates are broken down into either indigestible fiber, glucose or fructose. Let’s discuss the suitability of each of these as human fuel.
Glucose
Glucose is a simple sugar (monosaccharide) found mostly in plant foods like fruits, vegetables, starchy tubers and grains. It has three main uses in the body:
- It forms structural molecules call glycoproteins;
- Like fat, it is a source of energy for cells (especially in the brain); and,
- it’s a precursor to compounds that play an important role in the immune system.
Glucose preceded fatty acids as a fuel source for living organisms by a very long time, and it is the building block of foods that have the longest evolutionary history of use by mammals like us. The fact that glucose can be produced in the body from protein is often used as an argument that we don’t need to eat it in the diet. But I agree with Dr. Harris’s interpretation that, rather than viewing this as evidence that that glucose isn’t important, we should view it as evidence that glucose is so metabolically essential that we evolved a mechanism to produce it even in its absence in the diet.
One of the few differences between our digestive tract and that of a true carnivore, like a lion, is that we produce an enzyme called amylase. Amylase allows us to digest starch – a long-chain polymer of glucose molecules we can’t absorb – into single molecules of glucose that easily pass through the gut wall into the bloodstream.
Presuming we are metabolically healthy, the glucose and starch we eat is digested and rapidly cleared by the liver and muscle cells. It is only when the metabolism is damaged – usually by years of eating toxins like refined cereal grains, industrial seed oils and fructose – that excess glucose is not properly cleared and leads to insulin resistance and diabetes.
Verdict: the range of glucose that is tolerated varies widely across populations and individuals. Assuming no metabolic problems and an active lifestyle, glucose may be consumed relatively freely. However, many people today do have some form of metabolic dysfunction, and live a sedentary lifestyle. If you fall into this category, glucose should probably be limited to 400 calories (about 100g) of glucose per day.
Fructose
Fructose is another simple sugar found primarily in fruits and vegetables. While it has the same chemical formula and caloric content as glucose, it has an entirely different effect on the body.
As I pointed out in Step #1: Don’t Eat Toxins, fructose is toxic at high doses. It damages proteins in a process called fructation, which disrupts metabolic function and causes inflammation and oxidative damage. To prevent this, fructose is shunted directly to the liver for conversion into glucose or innocuous fats. But this process damages the liver over time, leading to non-alcoholic fatty liver disease (which one in three Americans now suffer from) and metabolic syndrome.
Another issue is that excess fructose is not well absorbed in the gut, which in turn leads to its rapid fermentation by bacteria in the colon or abnormal overgrowth of bacteria in the small intestine. Small-bowel bacterial overgrowth, or SIBO, is now believed to be the major cause of irritable bowel syndrome (IBS), a common functional bowel disorder that is the second-leading cause of people missing work behind only the common cold.
Most people without metabolic dysfunction can handle small amounts of fructose (as found in a few servings of fruit per day) without problems. But on the scale that fructose is consumed in the U.S. – including 64 pounds of high-fructose corn syrup per person each year on average – fructose wreaks havoc on the body. It should therefore be limited as a source of carbohydrate.
Verdict: 3-4 servings a day of fruit is fine for people without metabolic problems. Those with fatty liver, insulin resistance or other issues should further limit fructose intake, and everyone should avoid high-fructose corn syrup and other concentrated sources like agave syrup.
Fiber
Fiber is plant matter that is indigestible to humans. But although we can’t digest it, some of the 100 trillion bacteria that live in our gut can. In fact, up to 10% of the body’s caloric needs can be met by the conversion of glucose into short-chain fats like butyrate, propionate and acetate by intestinal bacteria. These short-chain fats are the primary energy source for intestinal cells in the colon, and butyrate in particular has been associated with several benefits. These are outlined in The Perfect Health Diet, by Paul & Shou-Ching Jaminet. Butyrate:
- Prevents obesity.
- Heals the intestine.
- Improves gut barrier integrity.
- Relieves constipation.
- Improves cardiovascular markers.
- Reduces inflammation.
- Stabilizes blood sugar.
The evidence clearly suggests that vegetable fiber is beneficial. However, just as not all fats are created equal, not all fiber is created equal. Grain fiber – which the AHA and other so-called “heart healthy” organizations have been promoting for decades – is toxic for two reasons: it contains toxic proteins like gluten, and it is prone to injure the intestinal wall.
We’ve been bullied into believing that grain fiber prevents heart disease and provides numerous health benefits. But this claim has only been tested in a single clinical trial, and the results were less than spectacular. The Diet and Reinfarction Trial, published in 1989, included 2,033 British men who had suffered a heart attack, and compared a high-fiber group with a control group. The high-fiber group ate whole grains and doubled their grain fiber intake from 9 to 17 grams per day.
How did that work out for them? Not too well. Deaths in the high fiber group were 22% higher over the two year study. 9.9% of the control group died vs. 12.1% of the high fiber group.
There are other reasons to limit all types of fiber. Fiber isn’t essential. Human breast milk doesn’t have any, and traditional people like the Masai – who are free of modern, degenerative disease – eat almost no fiber at all (subsisting on a diet of meat, blood and milk). And while fiber can feed the good bacteria in our gut and increase the production of beneficial short-chain fats like butyrate, it can also feed pathogenic and opportunistic bacteria in the gut.
Verdict: vegetable (but not grain) fiber is beneficial in moderate amounts – about one-half pound of vegetables per day. But think about vegetables and fiber as accompaniments or flavorful condiments to fat and protein, which should form the bulk of calories consumed, rather than the other way around.
SUMMARY OF CARBOHYDRATES
Assuming a healthy metabolism (which isn’t necessarily a safe assumption these days), glucose and starch can be eaten relatively freely, which fructose should be limited to 2-3 servings of fruit per day. Vegetable fiber is beneficial but should also be limited, to about one-half pound of vegetables per day. See the carb pyramid below for a graphic representation.
Know your protein
What about protein? As it turns out, eating the right type of protein is easy if you simply follow Step #1 (don’t eat toxins) and base your diet on the healthy fats I listed above.
Protein is mostly found in animal products, seafood, nuts, legumes and grains. Legumes and grains have toxic compounds that can damage the gut. These toxins can be partially and in some cases completely neutralized by traditional preparation methods like soaking, sprouting and fermenting. But the vast majority of people in modern industrial societies don’t do this and aren’t willing to do it, so I generally recommend that people avoid them altogether.
As I explained above, nuts are often high in omega-6 LA, which we get far too much of as it is. So nuts should not constitute a significant source of protein. Walnuts are especially high. Just 100g of walnuts a day amounts to a whopping 266g of omega-6 per week. Keeping in mind that we want a 1:1 ratio of omega-6 to omega-3, you’d have to eat 34 pounds of salmon a week to achieve a balance. Good luck with that.
Poultry, especially dark meat with the skin on, can also be very high in omega-6 and should also be limited. For example, chicken skin has about 14 times more omega-6 than even grain-finished beef, and 10 times more than grain-finished pork.
That leaves the meat and milk (including butter, cream and cheese) of ruminant animals (beef & lamb), pork, and seafood as the most suitable sources of protein. Animal protein is easy to absorb, is not toxic and is rich in beneficial long-chain saturated fats and natural trans-fats like CLA. Seafood is similarly easy to absorb, and is the primary dietary source of long-chain omega-3 fats DHA & EPA, as well as micronutrients like vitamin D and selenium.
We don’t need a pyramid for protein; you can simply follow the fat pyramid and you’ll naturally get the right type and amount of protein.
In the first article of this series we talked about the 
Our health continues to deteriorate at an alarming pace, and the incidence of chronic, degenerative disease is skyrocketing each year. Consider the following:
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