How We Became Deficient in the Most Abundant Fat on the Planet
Have you ever wondered why Americans—who, like all humans, evolved on the savannas of Africa—are now being advised to consume fish twice a week?
This would boost our consumption of omega-3s, of course—essential fats that are important for the health of our hearts and brains and every other tissue in the body. But how did we come to be deficient in these fast-acting fats? And where did early humans on the savannas get their daily dose of omega-3s?
Now, some would argue that fish has always been a mainstay of the human diet and that this ancient food choice is in fact responsible for the evolution of our large brains.
But there’s a simpler explanation—one that doesn’t require any revisions to the archeological record. It begins with the fact that omega-3s don’t originate in fish, but rather in the chloroplasts of green leaves, including plankton, the green leaves of the oceans.
The parent omega-3, alpha-linolenic acid, is found in highest concentrations in the membranes of the chloroplasts of green leaves. And because green leaves are about the most abundant thing on the planet, it follows that omega-3s are the most abundant fat. They’re not the rare nutrient we’ve been led to believe. They’re all around us and in most of our foods.
Alpha-linolenic acid helps plants photosynthesize—capture light molecules and turn them into sugars—which is the basis, need I say it, of all life on earth. Photosynthesis is a plant’s speediest and most metabolically demanding activity, requiring the coordination of about 75 different enzymes. Alpha-linolenic acid, a fat with three kinks (or double bonds) in its structure, enables all those enzymes to run quickly and smoothly.
Animals that eat green leaves accumulate lots of this speedy omega-3 fat in their tissues. But because animals are faster—that is, more mobile—than plants, they make this fat even speedier (kinkier) by adding length and double bonds to its structure. Animals then concentrate those elongated fats (known as DHA and EPA) in their most metabolically active tissue: their brains, hearts, eyes, and muscles, including the muscle of the heart.
For most of human history, humans never had a problem consuming enough omega-3s. There was no such thing as an omega-3 deficiency. Our ancestors would have obtained this essential nutrient from the many plants and greens they ate—or via the eggs they foraged and the animals they hunted, animals that themselves had consumed plants and greens. For most of human history, heart disease and all the other ailments linked to a deficiency of omega-3s were rare phenomena. Fish wouldn’t have added much in the way of omega-3s to most diets.
But all that changed at the beginning of the 20th century when Americans began to consume more and more seeds, and especially seed oils, a trend that began in the early 1900s with the first commercial presses for extracting oil from seeds. (Before then, butter and lard were the most common added fats.) And this trend was compounded when farmers began feeding the animals they raised on seeds instead of grass, a method of husbandry that was fueled by the corn surpluses of the post–World War II era.
Seeds, such as corn and soybeans, are much richer in a second family of essential fats: omega-6s, which we now know compete with omega-3s for positions in our cell membranes and have very different effects on membranes and health. Omega-6s promote blood clotting, inflammation, tumor growth, and weight gain, while omega-3s protect against all these effects. We need both—omega-3s and omega-6s—in our diets and our tissues, but because they compete with each other for limited positions in cell membranes, too many omega-6s causes a deficiency of omega-3s. It’s like a game of musical chairs. There are only so many chairs in the game, and if they are occupied by omega-6s, they can’t be occupied by omega-3s.
Let’s look at a few foods to see just how omega-6s out-compete omega-3s. Say you decide to eat the greenest, healthiest lunch possible—a big bowl of steamed spinach. It doesn’t have much fat in it but the fat it contains is mostly omega-3s (which is true of any bowl of greens)—until you dress it with a modest tablespoon or so of peanut, or grapeseed, or sesame oil dressing. Now, suddenly, that once-healthful bowl of spinach has at least 10 times the amount of omega-6s as omega-3s. Only a concentrated source of omega-3s, such as a piece of fish, could offset this imbalance.
Because fish live under pressure in cold, dim environments, they require more omega-3s in their diet and tissues than terrestrial animals—and are indeed a great source of these vital, flexible fats. But there aren’t enough fish in the ocean to fix America’s omega-6 habit in this way. Americans would have to eat about 10 times as much fish as they currently do in order to meet current recommendations. And most of our fisheries are already overstressed.
If, on the other hand, Americans simply consumed smaller amounts of omega-6s, by choosing oils and fats that have a better balance to begin with—canola, for example, a seed oil that has a very healthy balance of omega-3s and omega-6s (and, yes, there are non-GMO canola oils!), or a mixture of canola and olive oils—and by greatly reducing their consumption of corn- and soy-fed meats, eggs, and dairy, there would be no need for the fish solution. Other oils that have a healthy balance are flax and hemp seed oils, which shouldn’t be used for cooking but can be added to dressings.
This is not the first time that populations have created a nutritional deficiency with their agricultural techniques. Think of the epidemics of beriberi in the 19th century, when Asian populations relied on polished white rice—stripped of its vitamin B1-bearing husk—as a staple food. And it probably won’t be the last. But how we solve our omega-3 deficiency matters greatly, not just for our individual health, but for the health of our oceans—and the fish that swim in them.