by Mark Hyman
The quality of our diet matters most. Real, whole, fresh, unadulterated, unmodified foods: Those must be the starting point. There are other things that contribute to weight gain and obesity besides what we eat—such as our genetics, activity levels, stress levels, gut flora, and environmental toxins and obesogens (toxins that cause obesity)—and that modify our risk of disease and even our response to different foods. But it is still true that the biggest determinant of our weight and our health is the food we eat.
And a review of the research shows that for many traditional cultures across the globe, fat is coveted, special, and necessary. Tibetans put butter in their tea. In China, pork fat is sold as a delicacy and preferred to the meat. Traditional cultures always preferred the organs of animals, high in fat. The Plains Indians ate the liver and organs of the buffalo first. And most of us thrive on higher-fat diets, especially those with pre-diabetes and type 2 diabetes, or what I like to call diabesity.
Our diets are so different today than they were 12,000 to 14,000 years ago when we were hunter-gatherers. The agricultural revolution and the advent of animal husbandry led to the replacement of traditional foods with cereal grains and dairy. However, all food was still organic, grass-fed, whole. Because of the Industrial Revolution, our diet has been transformed more in the last 100 years than it was in the previous 10,000. The Industrial Revolution has led to the manipulation of crop genetics through increased hybridization and genetic modification, intensive animal husbandry in confined animal feeding operations, the refining of vegetable and seed oils as well as cereal grains, the development of trans fats and high-fructose corn syrup, the dramatic decrease in omega-3 fats we obtained from wild foods, the increase in refined omega-6 oils, the use of chemicals (pesticides, herbicides, fertilizers, antibiotics, and hormones), and the depletion of nutrients in the soil. The quality of our diet has dramatically declined. From the perspective of food as simply a source of energy and calories, none of this would matter, but the science has peeled back this simplistic view to reveal a powerful understanding of the role of food in all of our biological processes, from the regulation of which genes get turned on or off, to the regulation of hormones, the production of immune messengers and neurotransmitters, the balance of gut flora, and even the structure and composition of our cells and tissues and organs.
Let’s dig into the wide world of fats, so you can make sense of the different kinds and how they affect your biology.
A PRIMER ON FATS: THE GOOD, THE BAD, AND THE UGLY
So what is fat, anyway?
Fat can be thought of in two main ways. First, by its chemical structure, which is how we name and classify it (that’s the easy part). Second, in terms of its biology and how it affects our health. Here comes the geeky science part, but it’s super helpful to understand, so hang in there with me.
First, the chemistry. Fat, or as we call it in nutrition-speak, “fatty acids,” is a chain of carbon, oxygen, and hydrogen atoms with a carboxyl group (more carbon, hydrogen, and oxygen atoms) on one end. Fatty acids are classified according to how many carbon atoms are in the chain, as well as how many double bonds exist within the molecule. There are short-chain and long-chain fats. And there are fats with lots of double bonds (polyunsaturated) or none (saturated). Fatty acid molecules are usually joined together in groups of three, forming a molecule called a triglyceride. Triglycerides are predominately made in our liver from the carbohydrates we eat.
These different chemical structures give fats different properties. For example, saturated fats are found in coconuts and in mammals and other warm-blooded animals. They are soft when they exist in the body of live animals but hard at room temperature outside the body, like butter or lard. Omega-3 fats are found in cold-water and Arctic fish. They are liquid at room temperature and can stay fluid when fish swim in very cold waters.
Fatty acids play a starring role in many important functions in the body, including regulating inflammation, hormones, mood, nerve function, and more. Most of us think of them as a form of energy storage. If glucose isn’t available for energy, the body uses fatty acids to fuel your cells instead. Burning fat for energy is actually better and more sustainable for health; in fact, it’s what your muscles and heart prefer. The ketones that are produced when you eat fat (especially the fat from coconut oil or MCTs) are better for your brain and can even be used in the prevention and treatment of Alzheimer’s.1 We have long believed that the brain could run only on sugar, but we now know that that is not true and that the brain can burn fat or ketones (produced from fat breakdown).
There are four types of fatty acids:
1. Saturated (SFA)
2. Monounsaturated (MUFA)
3. Polyunsaturated (PUFA)—omega-3 and omega-6
4. Trans fats (TFA)
What defines them is their structure: A saturated fat has zero double bonds (thus it is “saturated” with hydrogen), a monounsaturated fatty acid has one double bond, and a polyunsaturated fatty acid has more than one double bond. Trans fats are funny-shaped fats, not normally found as part of human biology; the double bonds are on the opposite side of the fat chain (or “trans”) from where they are found in naturally occurring fats. Your body doesn’t like them at all. The chemical structure of the double bonds found in polyunsaturated fats are unstable when they come in contact with a number of elements such as light, heat, and oxygen, and this makes them more likely to become damaged and toxic to our health.
It gets more complicated because there are many different subtypes of saturated fats, polyunsaturated fats, and even trans fats. Some polyunsaturated fats may be harmful, others healthful, and the same is true of saturated fats.
Adding to the complexity is the fact that most foods contain combinations of different types of fat. We say something is “saturated” or “monounsaturated,” but the truth is that the fat content in foods is made up of many different types of fatty acids; we usually just focus on the most abundant type when referring to that food. For instance, coconut oil—which we call a saturated fat—is made of 90 percent saturated fat; the rest is polyunsaturated and monounsaturated fats. We also call butter a saturated fat, but butter has only 60 percent saturated fatty acids, and the rest is monounsaturated and polyunsaturated fat.
Complexities aside, let’s look more closely at each category of fat and how it affects our biology, our weight, and our health. (For an even more detailed review of fats, please see my free e-book called The Fat Bible: The Whole Story on Fats, which you can download at www.eatfatgetthin.com.)
A Brief Note on Cholesterol
Cholesterol is complex and confusing. We will go into it in detail in Chapter 5, but the important thing to know as you read this chapter is that what we thought of as “bad” cholesterol, or LDL, actually comes in two types, and only one of them is bad. There are big, light, fluffy, beach-ball LDL particles, and small, dense, hard, golf ball–like particles. The small, hard particles are the ones that cause heart disease. When you eat sugar and refined carbs, you get more of the small, bad LDL particles. When you eat saturated fat, you get more of the light, fluffy LDL particles, which are not associated with heart disease risk. The story is a little more complicated than that, but understanding it in this way is most useful and will help you make sense of the discussion about saturated fats that follows. New cholesterol tests can measure not just the total amount of cholesterol or LDL but the kind of particles you have—good or bad.
SATURATED FATS (SFA)
Since saturated fat has gotten such a bad rap, I want to get into the details so you understand it better. After all, it means the difference between a life with butter and a life without it!
Saturated fats are categorized based on their chemical structure. The key question is whether the carbons in the fatty acid chain add up to an even or odd number. This matters because odd-number-chain fats generally are good for you, while even-number-chain fats may carry some risk (although shorter even-number-chain fats like lauric acid from coconut are good)
. I know, it’s complicated. Sorry. Please don’t shoot the messenger!
The main types of saturated fats are laurate, myristate, palmitate, and stearate, which are even-chain fats (but there are more). Grain-fed meat and dairy are rich sources of palmitate. They also contain stearate, which is the saturated fat that has no negative effect on cholesterol levels. Palm oil is mostly palmitate. Cocoa butter is mostly stearate, and coconut and palm oil are mostly laurate and some myristate.
Each of these different saturated fats has different effects on the body. Lauric acid from coconut increases LDL the most (compared to other saturated fats), but it also increases HDL (good cholesterol) the most, which is a good thing. The net effect is to improve your cholesterol profile by lowering the total-to-HDL ratio (which is far more predictive of a heart attack than just your LDL level). It also increases the harmless light, fluffy LDL particles (whereas sugar and refined carbs increase the small, dangerous LDL particles, which are the real cause of heart disease). On the other hand, stearate has no effect on LDL (bad cholesterol) but raises HDL (good cholesterol), improving the overall cholesterol profile.
Where many people, including scientists, get confused is that we think that the saturated fats you eat become the saturated fats in your blood, but the shocking counterintuitive fact is that dietary saturated fats don’t raise blood saturated fats. It is carbs and sugar (and excess protein) that cause your liver to produce the saturated fats found in your blood. Higher levels in the blood of stearate and palmitate are associated with increased cardiac risk. But these are produced mostly from eating carbs or sugar, not fat. In fact, eating foods with these types of fat—like meat or palm oil—has very little impact on your blood level of saturated fat; as it turns out, they are not associated with increased risk of heart disease.
Saturated fats are key fats that provide stiffness and structure to our cell membranes and tissues; they kind of keep the contents of our cells together. If we eat a lot of the very fluid and unstable refined polyunsaturated omega-6 oils (from seeds, grains, or beans—like corn, soy, or sunflower oils), our cells become too floppy and don’t function as well. The worst fats for our cell membranes are trans fats, which are stiff and hard and literally embed themselves into our cell membranes, causing them to malfunction and creating disease. This affects the cell membrane’s permeability (which allows cells to communicate with other cells). Basically, it makes your cells hard of hearing and a little blind!
Saturated fats play many critical roles in your body:2
Saturated fats such as lauric acid (from coconut) and conjugated linoleic acid (from butter) strengthen the immune system and help your cells communicate better, thus protecting you against cancer.
They help your lungs work better. Saturated fats in your body produce something called surfactant, which helps air cross over the lung membranes. Children given butter and full-fat milk have much less asthma than children given reduced-fat milk and margarine.3
They are required for you to make hormones such as testosterone and estrogen.4
They are critical for your nerves and nervous system to work properly.
They help suppress inflammation, despite the common view about their causing inflammation. When eaten with a lot of sugar or refined carbs (think bread and butter, or cookies), saturated fats can cause inflammation. Or if you are deficient in omega-3 fats, they also can cause inflammation. The important thing to know here is that saturated fats cause inflammation only when eaten with refined carbs or sugar or when you don’t consume omega-3 fats.5
Saturated animal fats contain essential fat-soluble vitamins and nutrients that we need to be healthy,6 including vitamin A, vitamin D, and vitamin K2, the animal form of vitamin K. Compared to those eating the nutrient-poor standard American diet, hunter-gatherer societies, with very nutrient-dense diets, had levels of these nutrients that were ten times that of the average American.7
I could go on about the benefits of saturated fats…
Several important saturated fatty acids provide excellent energy sources for the body: lauric acid, found in coconut oil, myristic acid, found in coconut oil and dairy fats, and palmitic acid, found in palm oil, meat, and dairy fats.8 Palmitic acid plays a part in the regulation of hormones, and both palmitic and myristic acid assist in cell messaging and immune function.9
Good brain function depends on saturated fats. In fact, most of your brain is made up of saturated fats and omega-3 fats. One study showed that consumption of saturated fats had the potential to reduce the risk of dementia by 36 percent.10 Saturated fats also assist the brain in renewal and regeneration of nerve cells.
MONOUNSATURATED FATS (MUFA)
Here’s the bottom line: MUFAs are good for you. Populations that consume a lot of olive oil and nuts, such as the people of Greece and Italy, have the lowest rates of heart disease in the world (except Japan, which has low MUFA intake).
The main dietary sources of MUFAs are whole olives, olive oil, avocados, lard, tallow (beef or sheep fat), certain types of fish, and many nuts, including macadamias, almonds, pecans, and cashews, to name a few. Monounsaturated fats are also found in dairy and animal foods.
For our pre-agricultural ancestors, MUFAs accounted for about half the total fat intake and 16 to 25 percent of total calorie intake from wild meat, bone marrow, and nuts. One of the only hunter-gatherer societies left on the planet, the Hadza, break open the bones of animals they hunt and suck out the fatty marrow, which is more than 50 percent monounsaturated fats. Modern grain-fed meat doesn’t have much MUFA, but pasture-raised animals have as much as wild meats, which contain a lot of MUFA.11
Eating more monounsaturated fats greatly benefits your heart and cardiovascular system, which is why most cardiologists recommend the Mediterranean diet. Even the American Heart Association agrees. Higher intakes of MUFAs are associated with improved cholesterol numbers as well as lower levels of LDL oxidation (which is necessary for LDL to cause damage in the body) and less risk of blood clots and stroke.12
Monounsaturated fats are rich in vitamin E and other antioxidants. They improve insulin sensitivity and therefore reduce diabetes risk, reduce breast cancer risk, reduce pain in people with rheumatoid arthritis, promote weight loss, and reduce belly fat.13
However, some monounsaturated fats are produced in such a way that makes them unhealthy and even toxic to the body. For example, canola oil has been touted as a healthy oil for many years. The process of creating canola oil, and other vegetable oils, includes applying high heat and using harsh chemical solvents in the refining process. In an article titled “The Great Con-ola,” the Weston A. Price Foundation states, “Like all modern vegetable oils, canola oil goes through the process of caustic refining, bleaching, and degumming, all of which involve high temperatures or chemicals of questionable safety. And because canola oil is high in omega-3 fatty acids, which easily become rancid and foul-smelling when subjected to oxygen and high temperatures, it must be deodorized.”14 Avoid canola oil and stick to extra virgin (and ideally organic) olive oil, avocados, and almonds.
POLYUNSATURATED FATS (PUFA): OMEGA-6 AND OMEGA-3 FATTY ACIDS
There are two main types of PUFAs: omega-6 and omega-3 fats. These fats are considered “essential.” When scientists label a nutrient as “essential,” they’re not just saying that it’s very important or nice to have. In nutrition-speak we call something essential if you get sick or can’t live without it. It is essential because we can’t make it in our bodies; thus, we have to eat it or take it as a supplement.
Polyunsaturated fats (PUFAs) play a key role in cellular, immune, and hormonal function. They are potent regulators of health and disease. Omega-3 fats, one type of PUFA, make up much of your cell membranes and regulate insulin function, inflammation, and even your neurotransmitters, which is why they are critical for preventing and treating diabetes, depression, and arthritis and autoimmune disease.
Soybean oil, canola oil, safflower oil, sunflower oil, flax oil, and fish oil are all exam
ples of polyunsaturated oils, but not all of them are good. Other food sources high in PUFAs include walnuts; sunflower, sesame, pumpkin, and chia seeds; and fish.
But again, it’s important to understand that, as with monounsaturated fats, the processing or cooking of polyunsaturated oils affects their ability to create health or disease. For example, PUFAs develop harmful free radicals when subjected to heat, and these can damage your tissues and promote disease of all sorts, especially age-related diseases such as heart disease, diabetes, cancer, and dementia. In fact, your LDL is harmful only if it is oxidized and damaged by free radicals.
So, the two essential fatty acids found in food are:
LA—linoleic acid (omega-6): found in commercial seed and vegetable oils and certain nuts and seeds. We do need the LA omega-6 fats in moderation, but only from whole foods like nuts and seeds, or from cold- or expeller-pressed vegetable oils (and only in small amounts).
ALA—alpha linolenic acid (omega-3): found in organ meats, pastured egg yolks, macadamia nuts, walnuts, and flax oil.
There are other longer-chain omega-3 and omega-6 derivatives that can be synthesized in the body, considered “conditionally essential fatty acids.” But most people need to get them from dietary sources because their bodies are not effective at converting ALA into the active forms of the omega-3 fats called EPA and DHA. So I also consider these “essential”:
DHA—docosahexaenoic acid (omega-3 that can be made from ALA, but only about 5 to 10 percent of ALA can be converted to DHA): found in fish or algae or wild or pasture-raised animals.
EPA—eicosapentaenoic acid (omega-3 that can also be derived from ALA, and a good anti-inflammatory fat): found in fish or wild or pasture-raised animals.