The Skinny on Brain Fat

4: The Skinny on Brain Fat, Brain Food

WHAT IS BRAIN FAT?

Throughout the book so far, there have been hints about how important some nutrients are to the health of our brains. There have also been hints about how misrepresented some other nutrients are in relation to brain health. Fat is among the latter.

Most people are aware that the human brain is rich in fat, which accounts for about 11 percent of the brain’s weight. However, I bet you expected a much higher percentage of fat in the brain than 11 percent. If you did, it could be because you’ve heard somewhere that the brain is made up of fat, usually 60 percent or higher. If you haven’t heard that, just google “brain fat.” As of March 2017, there were 127,000,000 results that confirmed precisely that. There might be even more by the time you read these pages.

I was always puzzled by these statistics and had never been able to find any scientific study that confirmed such a high prevalence of fat in the brain relative to other nutrients. From a purely biological perspective, the mismatch is in part due to whether you include water in the calculations. Basically, there are two ways to evaluate the brain’s composition: you could estimate it including its water content or in terms of the brain’s “dry weight,” which excludes water. Including water lessens the fat content, while excluding it increases the fat content. If you include water in the calculation, fat makes up about 11 percent of the brain’s composition. If you take water out of the equation, fat accounts for less than half the brain’s weight. Incidentally, there isn’t much more fat than protein, which made the Internet posts even more puzzling to me. The problem is that many people, including several journalists and even a few doctors, believe that eating fat is good for the brain—the argument being that since the brain is “made of fat,” like cholesterol, eating that fat must be good for you. On the other hand, the vast majority of scientists will tell you exactly the opposite. Unfortunately, scientists rarely appear on the evening news and their voices remain confined to academic journals nobody has access to except other scientists, which further complicates an already complex picture. This lack of clarity has become problematic from a medical perspective, and brings us to a discussion of good versus bad fats, a discussion that features prominently in much research and seems to be making headlines of late.

While the prevailing wisdom of the past several decades suggested that low-fat, high-carb diets were the most beneficial for human health, society is now in full “fat redemption” mode. This trend is well exemplified by the June 2014 Time magazine’s thought-provoking cover story “Ending the War on Fat”—an attention-grabbing headline juxtaposed over an image of a generous dollop of butter.

It turns out that Americans are eating more full-fat foods than in previous decades, to the extent that experts expect the pro-fat trend to continue over the next fifteen years. Butter sales in the United States went up 20 percent in 2015. The number of people buying whole milk has gone up 11 percent, while skim milk sales plummeted 14 percent. In addition, everybody is ditching carbs for fats. Part of this dramatic shift in dietary habits is due to science’s change of heart in its position on fat and our health. Recent research has shown that high-carb diets can promote weight gain as much as high-fat diets, and that eating cholesterol has only a modest influence on the level of cholesterol in the blood and, therefore, a lower impact on the risk of heart disease than previously thought.

While dietary trends come and go, a common misconception seems to have remained unaltered regarding brain health. As I learned from my research participants, the public is persuaded that eating fat is necessary to make sure our brains work correctly. But when patients are asked what a high-fat diet should consist of, it turns out that many, if not all, are suggesting a sizzling slice of bacon, a nice piece of cheese, perhaps a scoop of sugar-free whipped cream. Are these foods really good for your brain?

The answer is no.

It’s time to bring some clarity to this controversial issue. The human brain contains fat—that much is true. But it might not be the kind of fat you’re thinking of. The truth is, fat isn’t just fat. There are many different types of fats (or lipids). Some fats have become household names, like cholesterol. Cholesterol is one of the fats we are all familiar with thanks to our doctors’ routinely measuring them in our blood work.

But there are many more and likely unfamiliar fats inside our brains, like phospholipids and sphingolipids. If you are thinking “What and what?” you are not alone. Most people have never heard of these terms. The truth is that these largely neglected fats, rather than the familiar ones, account for as much as 70 percent of all the fat found in the brain. There are many inconsistencies like this one in “popular neuroscience” that have generated much confusion about which nutrients are really important for neurological health. There will be many more to come—and to correct.

NOT ALL FAT MAKES YOU FAT

Another common misconception is that the brain needs fat for energy. That’s because we all intuitively know that our bodies will use the fat contained in fattening foods to give us energy. Instead, despite containing quite a bit of fat, the brain actually lacks the ability to burn that fat to produce energy for itself.

Reading this might lead to raised eyebrows and puzzled faces. Don’t we burn fat to make energy? Didn’t you say our ancestors really started to thrive once their bodies learned to store fat as an energy source? What does the brain do with all that fat if it can’t use it? This “brain-fat paradox” has been giving a headache to many nutritionists and dieters alike.

The reality is that when it comes to fuel, the brain doesn’t touch any of this fat. It simply can’t.

What most people don’t realize is that there are two types of fat in the human body: storage fat and structural fat.

When we talk about “fat,” we are usually talking about storage fat (also called adipose fat or white fat), the fat that our body uses to store energy. Storage fat is the soft, squishy, visible fat you can actually see on your body. What about that muffin top people talk about losing? That’s storage fat.

Storage fat is in large part derived from our diet. When we eat foods that contain fat, such as meats, cheeses, or candy bars, their fat is broken down into smaller units like saturated fat. This process itself generates heat and energy. These fats are then reassembled into triglycerides, the molecules that your doctor routinely checks in your blood work in tandem with cholesterol. Triglycerides are then stored away in adipose tissue for future fueling. This makes storage fat the largest energy reservoir we possess as human beings, acting as a convenient, portable battery pack.

A typical 160-pound (~70-kg) man has almost 27 pounds (12 kg) of adipose tissue fat, equaling roughly 100,000 calories’ worth of energy. If he were starving, this reserve would supply him with fuel for nearly two months’ time. So as far as your body is concerned, having some “meat on your bones” is a very good idea.

On the other hand, the brain does not contain that sort of fat at all. In fact, there is no storage fat in the brain.

Whatever fat is found in our brains is a totally different kind of fat called structural fat. The rest of our bodies also contain plenty of this fat. Structural fat is just as essential to life as storage fat is to fueling us, but the way our body uses these two fats couldn’t be more different. For starters, structural fat is not utilized as energy. Second, it isn’t the type that floats around in our bloodstream or clogs our arteries. Instead, as the name indicates, it is used to structure our cells and as a sort of “technical” support. For example, as far as the brain is concerned, brain cells are wrapped in a fatty sheath called myelin, which provides a clever insulation for electrical impulses traveling to and from the brain. Whatever cholesterol the brain contains is found mostly on this myelin sheath, acting as an insulator. Neurons are also enclosed by delicate fatty membranes that not only protect them from external insults but also allow signals and nutrients to flow in and out of the cell. These membranes are made of other kinds of fat, like the famous omega-3s and the largely overlooked phospholipids. There are many more examples of how brain fat is used exclusively for structure rather than for energy.

A likely explanation for this is that if the brain had been made of combustible or “burnable” fat, it might start eating itself in case of starvation—which would certainly put us at quite an evolutionary disadvantage.

In the end, the only fats we actually need to feed our brains are the building blocks that support its structural health. If you’re wondering which foods contain these fats, here’s another surprise. Just because these fats are present inside your brain doesn’t mean you have to eat them.

FATTY ACIDS: SOME ARE NEEDED, SOME ARE NOT

When we think about fat, we typically think of fatty acids. You might have heard of saturated and unsaturated fat. Those are fatty acids and they are the smallest fats you can find.

From a chemical point of view, fatty acids are molecules with a tail. These tails (or chains) are covered in hydrogens. The extent to which hydrogens cover the fat’s tail is called saturation. Saturated fats are completely covered by hydrogens, while unsaturated fats are only partially covered with hydrogens. Why is this important? Because depending on their level of saturation (e.g., how many hydrogens they carry), these fats serve very different roles in your brain—and have profoundly different effects. In other words, a pound of bacon is not nearly the same as a pound of tofu or a pound of olive oil.

Let’s begin with saturated fats. We are all familiar with the look and feel of saturated fat—whether we know it by the layer of cream that forms atop full-fat farm milk, the white ribbon that edges a slice of prosciutto, or the marbling on our favorite cut of beef. These fats are quite rigid, which is why butter is solid at room temperature.

On the other end of the spectrum are unsaturated fats. These fats are quite supple but also very delicate and easily damaged. For example, many vegetable oils rich in unsaturated fats, like olive oil, become rancid very quickly if exposed to light or heat, or when they’re not stored properly. Another important thing to know is that there are different types of unsaturated fats: mono-unsaturated (with one free hydrogen “spot” in its fat chain) and poly-unsaturated (with many free “spots”).

Monounsaturated fats are abundant in oils such as olive oil, in several nuts and seeds, and in high-fat fruits like avocados, as well as whole milk, wheat, and oats.

Polyunsaturated fats (or PUFAs) are found mostly in oils from plant and marine sources, especially in fatty fish like salmon, algae, and some nuts and seeds. You have probably heard of PUFAs and have seen them encapsulated in the light yellowish liquid of fish oil supplements, labeled as omega-3 fats, or advertised in your breakfast cereal fortified with omega-3s.

Saturated and unsaturated fats are an excellent example of how, even though the brain contains both, it doesn’t actually need all of them replenished.

Remember how selective the brain is relative to import/export? Saturated fat is not on the brain’s grocery list. Contrary to what many diet books preach, the brain is able to make as much saturated fat as it needs locally, and as such, doesn’t require restocking. When you eat a meal that is full of saturated fat (barbecue spareribs or a piece of cheese), the brain might take up a little bit, but for the most part, uptake is minimal after adolescence. The brain needs saturated fat only while it’s growing new brain cells, which corresponds to the period of time between infancy and adolescence. After our teenage years we pretty much have all the brain cells we will ever have, and so our brains no longer need saturated fat. It is at that point that the brain’s “saturated fat gates” shut down. Afterward, with a few exceptions, saturated fat can’t even get inside the brain.

Now for the exceptions. There are a few very specific types of saturated fats that can still enter the adult brain, when needed. Their tail has to be fairly short, like the butyric acid found in whole milk, or of medium length, like the myristic acid found in coconut oil. Otherwise, the vast majority of saturated fat found in the brain is actually produced inside the brain alone and is not absorbed from our diet. It looks like the same fat that we find in meat and cheese, but it doesn’t come from these foods. The same applies to monounsaturated fat, which is largely “homemade” on the brain’s premises.

Since the brain’s got these fats covered, they are referred to as non-essential fats. It’s as if, in a dialogue that’s been going on for millions of years, the brain is telling the body: “Don’t worry, I got this. Please bring me the other fats I need instead.”

So what are these other fats that the brain needs? PUFAs, of course. The rarest and most precious of brain-essential fats.

PUFAs are the only kinds of fat the brain cannot make on its own and, at the same time, determinedly craves. This is especially true for the omega-3s and omega-6s found in fish, eggs, nuts, and seeds. Does this remind you of our early ancestors’ diets before meat arrived on the menu? Indeed it does.

PUFAs are the most abundant fatty acids in cell membranes throughout the brain. The brain is specifically designed to collect these fats through dedicated gateways located within the blood-brain barrier. Therefore, a large number of PUFAs are constantly flowing inside the brain—or at least they would if we ate the right foods. These fatty acids are in such immediate demand that as soon as they arrive at the brain, they are consumed accordingly. In fact, the brain needs them to form larger and more complex fats—the phospholipids and sphingolipids mentioned earlier.

Since PUFAs are so crucial to brain health, let’s look into these brain-essential fats in more detail.

THE GOOD: THE OMEGA FAMILY

Among all possible types of PUFAs, two varieties, omega-3s and omega-6s, are the best known for promoting brain health. It is definitely worth a concerted effort to eat both of these PUFAs in our daily diets, as they serve very different functions.

Omega-6s are generally regarded as having pro-inflammatory properties. This is a big deal. In biology, inflammation is not a swollen thumb. Inflammation means how activated your immune system is, and therefore how well protected you are from danger. Omega-6s participate in this process by encouraging our bodies and brains alike to mount an inflammatory response in the case of a wound or an infection. The omega-3s are needed to turn down this response once the danger is no longer present. As such, they are regarded as being anti-inflammatory.

Countless scientific studies have demonstrated that the balance of these two PUFAs is essential for proper neuron communication as well as a means to maintain a healthy immune system. A disruption to this balance of pro- and anti-inflammatory agents could lead to either unnecessarily sustained inflammation, which can damage the brain in the long run, or a reduced capacity to fight off disease, an obvious liability.

This balance directly depends on our food choices.

Research has determined that a ratio of two-to-one (twice the amount of omega-6 to omega-3) is an ideal balance to shoot for. However, there are some estimates that Americans consume twenty or thirty times more omega-6s than omega-3s, making the typical American diet highly inflammatory in nature.

Worse still, current dietary recommendations for omega-3 and omega-6 PUFAs strongly favor the latter. The U.S. Food and Nutrition Board has established dietary reference intakes (DRIs) for many nutrients identified as essential to health, including PUFAs. DRIs tell you how much of a nutrient you should consume every day to avoid both deficiencies and excesses that can lead to toxicity. At present, the recommended dose for an adult man is 1.6 grams of omega-3s and between 14 and 17 grams of omega-6s per day, and that for an adult woman is 1.1 grams of omega-3s and 11 to 12 grams of omega-6s. This is ten times the amount of omega-6 to omega-3!

By eating too many omega-6-rich foods and too little omega-3s, we are putting ourselves at risk for many diseases that are associated with excess inflammation in our bodies. These diseases include atherosclerosis, arthritis and vascular disease, autoimmune processes and tumor proliferation, and last but not least, neurological disorders such as Alzheimer’s. We need to take this matter into our own hands and make sure our diets are supportive of the important and delicate two-to-one balance.

What are our options?

Starting with the omega-6s, foods that are naturally rich in these fats, and therefore need to be drastically reduced, are fatty animal foods such as bacon and chicken fat as well as vegetable oils from grape seeds, canola, corn, peanuts, and sunflower seeds (Table 2).

As for the omega-3s, there are three major types that come from different foods. These are alpha-linoleic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA comes from plant sources, especially flaxseeds, walnuts, chia seeds, and wheat germ, along with some sea vegetables such as spirulina. DHA and EPA are plentiful in fish oils instead of vegetable oils. The richest food sources are cold-water fish like salmon, mackerel, and cod. But the real star is caviar. Black caviar has a higher density of brain-building DHA than any other food. One ounce of caviar contains three times the amount of DHA found in the highest-quality salmon. Additionally, caviar is an excellent source of memory-boosting choline, which makes for a perfect brain combo. These are the foods we need to provide our brains with on a daily basis.

Omega-3 PUFA (g/100 g of product)
PLANT SOURCEALAANIMAL SOURCEDHA + EPA
Flaxseed oil 52.8Caviar, black6.8
Flaxseeds22.8Salmon roe6.7
Hemp seeds12.9Wild salmon2.2
Butternuts, dried 8.7Herring2.0
Chia seeds3.9Mackerel1.9
Black walnuts3.3Sardine1.7
Soybeans (raw)3.2Anchovy1.5
Oats, germ1.4Sardine, canned1.0
Spirulina0.8Trout0.9
Wheat, germ0.7 Shark0.8
Omega-6 PUFA (g/100 g of product)
PLANT SOURCEOMEGA-6ANIMAL SOURCEOMEGA-6
Grapeseed oil70Turkey fat21
Sunflower oil66Chicken fat19
Wheat germ oil55Duck fat12
Corn oil53Lard 10
Soybean oil51Pork belly5.2
Sesame oil41Bacon4.5
Walnuts38Egg yolk3.5
Mayonnaise37Chicken3.1
Peanut oil32Frankfurter (beef and pork)2.3

Table 2. Top ten food sources of omega-3 and omega-6 PUFAs, ranked by PUFAs’ density, which is a convenient way to compare the relative amounts of PUFAs available to the brain in each food.

A large body of epidemiological studies identified omega-3s as the number one nutrient to fight age-related cognitive decline and dementia. For example, a landmark study of six thousand participants ages sixty-five years or older showed that people who consumed low quantities of omega-3s had a 70 percent higher risk of developing Alzheimer’s than those who consumed more omega-3s. Specifically, people who consumed less than 1 gram of omega-3s per day had the highest risk, while those who ate more than 2 grams were unlikely to develop dementia at all. Moreover, even among people who did not develop dementia, a lower intake of omega-3s directly impacted their ability to remember details, switch focus, and manage time.

As several other studies replicated these findings, a consensus was reached: people who consume omega-3-rich foods on a regular basis remain mentally clearer and have a lower likelihood of developing cognitive deterioration than those who consume less of these healthy fats.

Perhaps even more fascinating is that the beneficial effects of omega-3 consumption are evident in brain scans as well. As we age, our brains naturally lose some volume. But studies of thousands of dementia-free elderly showed that those who didn’t consume enough omega-3s in their diets had accelerated brain shrinkage, as shown on MRIs. Their brains, and especially their hippocampus (the memory center of the brain), lost neurons at a rate equivalent to two extra years of aging. In other words, a diet poor in omega-3s, especially DHA, increases the speed at which the brain ages! Some specifics: people who ate less than 4 grams of DHA a day showed the highest rates of brain shrinkage, whereas those who consumed 6 grams or more had the youngest-appearing brains.

While all of this points to the protective effect of omega-3s on brain aging, randomized clinical trials have still failed to show significant changes in cognitive health as a result of fish oil supplementation. Why is this?

Rather than being disappointed by the negative results, there’s actually a lesson to be learned. First, clinical trials were based on supplements. But research shows that the protective effects of omega-3s are particularly strong in people who derived their fats from natural sources like fish rather than from supplements. Further, most clinical trials to date used fairly low doses of omega-3s, generally about 2 grams a day—less than half the minimum dose found to slow down brain shrinkage in the MRI studies mentioned earlier. This might be related to current dietary guidelines recommending even lower doses of omega-3s, especially for women.

In the end, the research studies offer a much better, brain-specific rule of thumb. The goal is to eat at least 4 grams of our brains’ coveted fat every day to keep our brains young and working to the fullest.

It really doesn’t take much to reach our brain-fat goals. Just 3 ounces of wild Alaskan salmon (that’s a small piece) provides almost 2 grams of omega-3s, most of which is DHA. Pair that with a handful of almonds (or perhaps a scoop of caviar) and you’re good to go.

As for omega-6s, you need very little: a few drops of grapeseed oil or a handful of peanuts is all your brain needs for the day.

Easier said than done. Unfortunately, the typical Western diet tends to include exactly the opposite proportions of these foods. There are several ways to reverse this balance to increase our consumption of omega-3s. A simple way to do that is to swap out some omega-6-rich foods, such as the peanuts in our peanut butter, for other nuts higher in omega-3s, like almonds and walnuts.

Another good idea would be to increase our consumption of cold-water fish by eating it in lieu of pork, beef, and other fatty meats. If we compare a portion of fish and beef possessing the same amount of protein, the fish is rich both in protein and omega-3s, while the meat provides more omega-6s than omega-3s.

When properly prepared, fish is a delicious and healthy alternative our brains need more than anything else. The Mediterranean diet, common in my home country of Italy and throughout much of Europe, features fish much more than is traditional here in the States. What most of us really appreciate is that fish tastes like the sea—with its briny flavor, the slight iodine tang to it, so reminiscent of the jeweled turquoise waters of the Mediterranean Sea. Red snapper, mussels, vongole (clams), orata (sea bream) . . . they all taste like a beach holiday to me.

Every sea has its own forte. A grilled fresh-caught branzino (sea bass) is a Mediterranean delicacy, as are oysters in France and wild salmon and herring in northern Europe. Japanese cuisine, particularly sushi, has now become popular throughout the world, and eating raw fish has replaced the traditional slice of pizza as the dinner of choice in many households, bringing an unprecedented amount of healthy omega-3s to American tables.

For you traditionalists who really love your steak, invest in grass-fed beef, which is far richer in omega-3s and void of the GMO and hormonal feeds present in lower-quality beef.

Another perhaps unexpected way to replenish our reserves of brain-essential fat is to eat foods rich in phospholipids. Even though you may not have heard about them until now, phospholipids are present in your entire body and much more so inside your brain. This particular type of fat is crucial to providing all brain cell membranes with shape, strength, and elasticity. As such, it is needed for all mental operations and thoughts to take place. Phospholipids are made up mostly of omega-3s. As a result, foods that contain phospholipids are at the same time excellent sources of omega-3s. What happens is that your body breaks down these bigger fats into smaller units, releasing their omega-3s first in the circulation and then inside the brain. Phospholipids-rich foods include all fish, crustaceans like crab and krill, and eggs. The egg yolk in particular packs the biggest punch, with over 10,000 mg of phospholipids per 100 grams of product—and also 230 mg of omega-3s. Think about it next time you’re about to order an egg white–only omelette—you’re throwing the baby out with the bathwater. Of all animal foods available to us, eggs are hard to beat for brain nutrition. In a way, eggs are to animals what berries are to plants—over the course of thousands, if not millions, of years, eggs have been optimized to produce and sustain life by providing the offspring with nutrition, structure, and protection, all in each egg. That’s because eggs contain all sorts of nutrients that are needed not only for bones and muscles to grow but also for the neural tube to develop into the brain and spinal cord. Memory-forming choline, omega-3 fatty acids, complete protein, a wide range of vitamins and minerals, and even disease-fighting antioxidants like lutein and zeaxanthin—the egg has it all because the developing organism needs it all.

When we talk about eggs, we typically refer to chicken eggs. But the same principle applies to all egg-laying birds, from quail to ostrich. I recommend that you explore all available options, as diversity is key in neuro-nutrition. And let’s not forget about fish. Fish eggs, aka caviar or roe, are the best treat for our big, hungry brains. Even Picasso expressed his gratitude to benefactors by presenting them with caviar, and did them a greater favor than he knew. Caviar is the most potent phospholipid source available, not to mention that one tablespoon alone contains more than 1 gram of high-quality omega-3s.

Additionally, the vegetable kingdom is also rich in phospholipids. Sweet peas, cucumbers, and tapioca (a staple of South American cuisine) are unexpected yet plentiful sources. Grains like oats, whole wheat, and barley, as well as soybeans and sunflower seeds, are also good sources. By eating these foods, you’ll help your brain obtain all the “brain fat” it needs. This is especially helpful if you have medical reasons or allergies requiring that you steer clear of fish, or if you are vegan/vegetarian. There are also other ways to increase your omega-3s. For example, you can eat more foods that contain ALA. ALA is found in considerable amounts in plant sources, especially oils from flax, chia, hemp, and sunflower seeds (Table 2), making them an attractive option for vegetarians. The catch is that our brains must convert ALA to DHA to meet its needs, and 75 percent of ALA is lost in the process.

High-quality fish oils containing DHA are a suitable alternative, easily available in the form of supplements or as ingredients in a wide variety of fortified foods, from DHA-fortified milk to enriched eggs and bread. Many people who take fish oil supplements remark on the pill’s lingering, fishy aftertaste. If that bothers you, try a vegan source of omega-3s derived from marine plants, such as high-purity algae, instead. Another advantage of these vegan supplements is that they are free from the contaminants and environmental pollutants that might be present in some fish oils.

Finally, although results are not always consistent, some studies have shown that a higher consumption of monounsaturated fats such as those found in olive oil and avocados correlates with better cognitive functioning and a lower risk of dementia in the elderly. In those studies, people who consumed at least 24 grams of these fats a day had an 80 percent reduced risk of Alzheimer’s as compared to those who consumed 15 grams or less. Monounsaturated fats are renowned for their beneficial effects on heart health, and in this case, what’s good for the heart is good for the brain. The good news is that it takes only 2 to 3 tablespoons of olive oil to reach the desired brain-protective daily dose.

To sum it all up, omega-3s, omega-6s, phospholipids, and, to some extent, monounsaturated fats are the good guys the human brain has chosen as its allies—not to mention suppliers—over the course of millions of years. At the same time, your brain has also made a few enemies.

THE BAD: SATURATED FAT

Even though this seems to be relatively unclear to the public, saturated fat tops the list as public enemy number one. While some doctors support and even encourage unlimited consumption of foods rich in saturated fat, it is well established in the scientific community that high levels of these fats have a negative impact on our mental capacities, increasing our risk of dementia.

As described earlier, the brain doesn’t consume much saturated fat after adolescence. However, a high intake of saturated fat from the diet can cause inflammation throughout your entire body and reduce oxygen flow specifically to the brain. The brain is a glutton for oxygen, so it’s possible that even a slight lack of circulation could affect its performance. Additionally, too much saturated fat can increase the risk of heart disease and type 2 diabetes—which in turn raises one’s risk of dementia.

One example among many. A study of over eight hundred elderly participants showed that those who consistently ate the most saturated fat had up to four times the risk of developing cognitive deterioration as they aged as compared to those who ate the lowest amount. Specifically, people who consumed more than 25 grams of saturated fat per day were much more likely to develop dementia in the years to come than those who ate half that amount (13 grams per day).

In practical terms, six slices of bacon contain 25 grams of saturated fat. So cutting down your bacon from six slices to three can cut your risk of dementia in four.

Subsequent studies have shown that even though 13 grams a day are less bad for you than 25, they are too many anyway. For instance, a study of six thousand elderly showed that those who ate 13 grams of saturated fat (or more) daily were almost twice as likely to develop cognitive impairment as those who ate less than 7 grams per day. Now we’re down to one and a half slices of bacon.

A number of well-controlled studies have confirmed these findings: high saturated fat increases the rate of decline in cognitive abilities as we age. So while the body certainly needs some saturated fat to stay healthy, scientists agree that as far as the brain is concerned, the less saturated fat, the better.

Currently, most nutritionists recommend aiming for a diet that includes no more than 5 percent to 6 percent of calories from saturated fat a day. For example, if you are on a 2,000-calorie-a-day diet, no more than 120 of these calories should come from saturated fats. That’s about 13 grams a day, or three slices of bacon, which is consistent with the studies mentioned earlier. As you can imagine, most people eat much more saturated fat than a few slices of bacon a day. So if you want to maximize your brain’s performance, while at the same time minimizing your risk of dementia and heart disease, I would recommend eating less than 13 grams a day, or even better, half of that—while also focusing on healthier, high-quality sources.

If you’re wondering which meat and dairy products are safe, here’s my rule of thumb. Fresh, organic fatty foods are much better for you than processed foods of any kind. When you’re eating animal foods, make sure you eat organic free-range eggs, chicken, and turkey and lean grass-fed cuts of beef instead of commercially raised meat, pork, and bacon. Ditto for all processed meats, whether processed cold cuts of ham or mixed meats like pastrami. These foods are not good for you, especially for your brain. We’ll talk a whole lot more about this in Step 2: Eating for Cognitive Power.

With respect to dairy products, fermented, organic whole milk products like yogurt and kefir are definitely our best bet. Besides providing a better ratio of unsaturated to saturated fats, they have the added benefit of containing live active bacteria that support the digestive and immune systems alike. Instead, processed foods like American cheese, string cheese, sweetened yogurt, commercial ice cream, pudding, and most milk beverages are downright bad for you and should be restricted, if not completely eliminated from your diet. Not only are these foods high in the kind of saturated fat the brain has no use for, but they are also high in multiple harmful ingredients, not the least of which are trans fats.

THE UGLY: TRANS FAT

We all have heard about trans-saturated fats (aka trans fats) and how terrible they are for the body. Most doctors consider trans fats the worst type of fat you can possibly ingest. This kind of fat has been making headlines of late for its dangerous effects on health, and it is increasingly recognized as a brain enemy as well.

A large body of literature indicates an association between consumption of trans fats and increased risk of cognitive decline and dementia in old age. In fact, it takes very little trans fat in the diet to develop cognitive impairments. Across several studies, people who consumed 2 or more grams of trans fats a day had twice the risk of those who ate less than 2 grams. Fairly disheartening is the realization that most people in those studies ate at least 2 grams a day, with the majority of participants eating more than double that on a regular basis.

But what exactly are trans fats, and where are they hiding?

Trans fats are created via an industrial process called hydrogenation, by which hydrogen is added to otherwise healthy unsaturated vegetable oils, thereby chemically “saturating” them. Manufacturers do this to create a specific consistency in products, one that is nearly solid at room temperature but melts upon baking or heating. For example, canola and safflower oils are artificially hydrogenated to create margarines and soft spreads. These so-called partially hydrogenated oils are less likely to spoil and less prone to rancidity, granting foods a longer shelf life. Some restaurants use these oils in their deep fryers because they don’t have to be changed as often as do other, healthier oils. Clearly, trans fats are convenient, not to mention cheap.

Unfortunately, trans fats have many adverse health effects, from raising cholesterol and triglyceride levels in the bloodstream, to globally promoting inflammation throughout our bodies. This increases our risk of cardiovascular disease and stroke, and in turn, our risk of dementia. As of today, partially hydrogenated oils are no longer “Generally Recognized as Safe” (GRAS) in human food. Several countries, like Denmark, Switzerland, and Canada, have reduced and even restricted the use of these fats in food service establishments. There is hope that continued research will soon lead to a final and complete ban of all trans fats from the American diet. In the meantime, we need to protect ourselves and safeguard our brains from any food products that include trans fats.

They are relatively easy to spot. First of all, they are almost always found in processed foods. The definition of what constitutes a processed food can vary, but generally speaking, it’s a food packaged in boxes, cans, or bags. Also, these foods have a very long shelf life. Some canned soups can last up to four years. That can’t be natural, can it?

It appears easier than ever to determine the amount of trans fats in any packaged food by checking its nutritional label. A typical Nutrition Facts panel will list not only the serving size and calories per container but right underneath that you will find Total Fats. The Total Fats listing is then broken down into saturated fats, cholesterol, and trans fats. You want anything you put in your cart to read trans fats: zero/“0” grams.

But there’s a catch. Due to some latitude in current regulations, even foods appearing to be trans fat–free might instead contain up to 0.5 grams of trans fats per serving. In other words, if a food contains 0.49 grams of trans fat per serving, the company is allowed to list it at “0” grams.

But how many people only eat just one serving of anything? Let’s say you eat two servings of such a food (such as a “butter spread,” where two servings could equal as little as 2 teaspoons). Doing so, you’ll actually be eating almost 1 full gram of trans fat—all the while thinking you didn’t have any at all. One example among many is the product Land O’Lakes Fresh Buttery Taste Spread. The Nutrition Facts panel proudly states “0” trans fats. But the ingredients list tells a whole different story. Several trans fats feature in the smoothness of the spread, such as partially hydrogenated soybean oil, hydrogenated soybean oil, and hydrogenated cottonseed oil. If you can’t believe it, google it.

The bottom line is this: the more packaged and processed foods you consume on a regular basis, the more hidden trans fats you are probably consuming, and the higher your risk of getting sick. My recommendation is to take a careful look at the ingredients list on the food packages you pick up. Watch out for any of the following: hydrogenated fats (like the ones mentioned above), partially hydrogenated fats and oils (also known as PHO), and vegetable shortening (or just shortening). The most common PHO include partially hydrogenated soybean oil, cottonseed oil, palm kernel oil, and vegetable oil. If the list includes any of these substances, you are better off putting the package down.

Typical processed foods that are high in trans fats are baked goods like commercial doughnuts, cakes, pie crusts, biscuits, and frozen pizza, as well as many snack foods such as cookies and crackers. Then there are all the margarines (stick or spread), along with many other spreadable or “creamy” products, which are by definition made of hydrogenated or partially hydrogenated oils. Trans fats are even added to most coffee creamers. A special note to moms: you might be inadvertently serving your children a considerable amount of toxicity atop their birthday cakes, since ready-to-use frostings are plied with trans fats. So take a close look at your shopping cart. Many of the foods you stock in your pantry are probably laden with a substance that we must now begin to avoid at all costs.

CHOLESTEROL: FRIEND OR FOE?

Cholesterol has become such a hot topic that we even find ourselves talking about our cholesterol levels at parties. Is cholesterol a good thing or a bad thing?

What might come as a surprise is that brain cholesterol is very different from the cholesterol we generally talk about. When your doctor tells you that your cholesterol is too high, they are referring to the cholesterol in your blood. Your levels of blood cholesterol are at least in part determined by how many cholesterol-rich foods you eat, like meat, eggs, and some dairy products.

However, that cholesterol has nothing to do with the cholesterol inside your brain.

Unlike any other organ in the body, the brain makes its own cholesterol. All of it. Perhaps even more surprisingly the majority of brain cholesterol is produced during our very first weeks of life, when our neurons are growing at light speed and need the extra structural support. The brain continues to make cholesterol at a lower rate throughout adolescence, but once that process is complete, it slows down to make very little during adulthood.

By the time we are past our teenage years, we have all the brain cholesterol we will ever have. In order to preserve its own cholesterol, the brain completely seals it away from the rest of the body. As an additional safety measure, dietary cholesterol (from the foods we eat) is not on the list of nutrients that are allowed to cross the blood-brain barrier. There are simply no passageways to let it in.

Consequently, there is no connection between the amount of cholesterol you eat and your brain’s function. No matter how many eggs you put in your omelette or how much bacon you’ve had on the side, the cholesterol from those foods will not benefit your mental capacities—although it might eventually clog your arteries.

That way, cholesterol from the diet can affect the brain in as much as it affects heart health. When our hearts are not running at their optimal levels, our brains suffer as well. Here’s the story.

The cholesterol in your body needs help to move about. Help is provided in the form of lipoproteins, the private drivers of your body’s fat-transport system. You might recognize them from your most recent blood work. They are split into two groups: low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs). When doctors talk about “bad cholesterol” and “good cholesterol,” they are referring to these molecules.

LDLs carry cholesterol to specific organs. Sometimes this process doesn’t run as smoothly as it should. Because of genetic inheritance or other medical conditions, LDLs can end up dropping their passenger at the wrong destination—inside your artery walls, for instance. As this process continues, a buildup of cholesterol can occur, beginning to cause a thickening along the artery. This thickening is called a plaque, or atherosclerotic plaque formation. As these plaques increase, they can eventually clog the arteries, causing heart attacks, strokes, and other serious medical problems. Instead, HDLs pick up cholesterol and shuttle it to the liver, where it is either eliminated or converted into hormones for other uses. This is why, even though LDL and HDL are not actually cholesterol, they got labeled “bad LDL cholesterol,” becoming the villain we need to get rid of, and “good HDL cholesterol,” the superhero we seek.

Regardless of medical terminology, in order to protect your heart and brain alike, it is crucial to keep your total cholesterol low, particularly in conjunction with high HDL and low LDL.

A large number of studies agree that if you have high blood cholesterol (hypercholesterolemia) in midlife, you are at increased risk for developing dementia later in life. For reference purposes, the term “high cholesterol” indicates a blood cholesterol level higher than 240 mg/dL. Several studies with up to ten thousand elderly participants found that those with high cholesterol in midlife had almost three times the risk of cognitive issues and dementia later in life as compared with those who had normal cholesterol levels. But when researchers looked at the risk of Alzheimer’s in particular, the healthy limit was even lower. A cholesterol level of 220 mg/dL, which is considered borderline high by current standards, was high enough to nearly double the risk.

What are we to do to keep our cholesterol in check?

Traditionally, if you had high cholesterol, your doctor would advise you to reduce consumption of cholesterol-rich foods such as eggs and cheese. However, it is becoming increasingly accepted that cholesterol from our food doesn’t increase blood cholesterol levels as much as once thought. The truth is, up to 75 percent of cholesterol in your body is produced by the body itself, and only 25 percent or so is derived from the diet. This is because the body tightly regulates the amount of cholesterol in your blood via its strict internal controls to make sure that you do not absorb too much cholesterol from the foods you eat. In other words, eating cholesterol isn’t necessarily going to give you a heart attack.

However, other nutrients can push your cholesterol levels up to the sky. As puzzling as this might sound, it is consuming saturated and trans fats that seems to affect cholesterol levels more than consuming cholesterol itself. So if you need to lower your cholesterol, you are better off reducing consumption of those other fats we talked about earlier. We have already clarified that trans fats should be eliminated altogether from your kitchen. Foods high in saturated fat should also be limited. The tricky part is that the majority of cholesterol comes from foods that also contain a good amount of saturated fat, like fatty meats, pork, poultry, and dairies, which makes it hard to eat one but not the other.

Fish, shellfish, and eggs are exceptions to this rule, as they are high in cholesterol but lower in saturated fat, and therefore not as harmful as previously thought. For instance, clinical trials reported no association between eating eggs and the risk of heart disease. One more good reason to ditch the egg-white omelettes and start eating yolks again. However, if this news inspires you to pay a visit to your local diner for a ten-egg scramble, you are taking this encouragement too far. Healthy egg consumption means no more than a couple of eggs a week. Again, mind the old adage: “Everything in moderation.”

Also keep in mind that not everyone responds to dietary cholesterol or saturated fat in the same manner. If we took a group of people, fed them a diet high in those fats, and measured how much cholesterol they produce, we’d see a wide range of responses. Some will make more, some will make less. If you have high cholesterol, or a family history of heart disease, you might want to talk to your doctor about testing your own individual response to eating fatty foods. If consuming saturated fat does increase your total or LDL cholesterol, you have plenty of good reasons to change your diet.

BRAIN AND BODY—ARE THEY ON THE SAME PAGE?

Now that we’ve reviewed the major types of fats and whether or not they belong in a brain-healthy diet, let’s sum it all up. Certain dietary fats such as PUFAs are an excellent example of how what’s good for the brain is good for the body. The brain needs PUFAs (especially PUFAs from fish and eggs) for proper structure and function. The rest of the body needs PUFAs as well, and can even burn these fats to make energy. For instance, fatty acids like PUFAs are the heart’s main source of fuel. So you want to make sure you eat enough of the PUFA-rich foods listed in this chapter to keep both your brain and your heart happy.

However, it doesn’t necessarily work in the reverse, and not all fats that are good for the body are good for the brain. There are some who recommend eating foods rich in saturated fat and cholesterol to keep your brain healthy. I disagree. In the case of saturated fat, the body alone has the ability to burn this fat to make energy. Likewise, the body alone can use dietary cholesterol to carry out a number of functions—everything from supporting organ membranes to producing several hormones. The brain, on the other hand, has no particular need or use for these fats after adolescence.

That said, the subject of saturated fat is a complicated one and it is important to keep in mind that some saturated fats are better for you than others. As mentioned earlier, occasionally the brain might do well to take up some saturated fats like the ones found in whole milk and coconut oil. Even though your brain doesn’t require these fats on a regular basis, it won’t hurt to consume them sparingly or on occasion—especially in preference to other, more harmful sources of fat like trans fat. We’ll talk more about which fatty foods are best to support both your brain and the rest of your body in the next chapters.

Meanwhile, a note of caution for all new parents out there. Don’t assume that what’s good for you is good for your two-year-old. A developing brain (which means anywhere between birth to adolescence) needs more saturated fat than an adult brain. In Italy, pediatricians recommend that children eat at least two servings of high-quality meat a week, along with plenty of (organic, fresh) milk and dairy and, of course, fish. I follow this rule with my two-year-old, who adores wild salmon and Parmesan cheese, and also enjoys coconut oil as much as organic grass-fed sweet cream butter. As we’ll discuss later in the book, and especially if you have children, of all the criteria to hold for food, the quality of the ingredients might well be the most important part.