One person’s response to a high omega-6 diet

By Susan Allport

In This Section

November 2010

Editor's note: In a departure from the norm, inform presents a single-subject study from Queen of Fats author Susan Allport. In this first-person account, Allport writes about how a month-long experiment in radically altering her diet had almost immediate effects.

Research has shown associations between diets high in omega-6 fatty acids and weight gain, diabetes, heart disease, and depression. I decided to find out first-hand how such a diet could affect my personal well-being. For a month, I was planning to eat a diet with a gross imbalance of the two essential fats: omega-3s and omega-6s, fats that are called leaf fats and seed fats because omega-3s originate in the green leaves of plants and omega-6s are much more abundant in seeds. These two fats, both of which are polyunsaturates, are currently grouped together in most health recommendations, including the US Dietary Guidelines for Americans. But evidence is mounting that a balance between them is critical for good health.

The leaf fats, omega-3s, are the more dynamic of these fats. They speed up the activity of cells and are concentrated, not surprisingly, in all our most active tissues: brains, eyes, hearts, sperm. They originate in green leaves-including phytoplankton, the microscopic green leaves of the ocean-and accumulate in animals that eat green leaves: fish, of course, as well as grass-fed cows and other animals. Omega-6s, the seed fats, are slightly less dynamic and much more inflammatory. They help animals fight infections and store fat for the winter. In excess-as in the North American diet and the diet I was planning to go on-they've been implicated in everything from obesity to heart disease; cancer to Alzheimer's and other mental disorders.

To the casual observer, the foods in my experimental diet would look just like my normal fare: lots of whole grains, nut butters, vegetables, fruits, lean meats, fish, and salads (see sidebar below). But they would differ in a small way that I, and a growing number of scientists, know to be very important: the fats I would cook with; the oils I would dress my salads with would be vegetable (or seed) oils that are very rich in omega-6s, oils such as safflower, sunflower, corn, and soybean oil, oils that constitute most of the added fats in the North American food supply.

Omega-3s and omega-6s compete for positions in our cells, as scientists have known since the 1950s, such that anyone consuming a diet too rich in omega-6s would have fewer omega-3s in all of her tissues-no matter whether she continued to eat fish. US consumers eat 10 times as many omega-6s as they do omega-3s, according to the Agricultural Research Service of the US Department of Agriculture. And it is that imbalance-not the amount of fish we eat-that is causing us to be deficient in omega-3s. Some experiments show a healthy balance is on the order of 4:1.

So why was I doing this? Because no one, as far as I know, had ever done it before-and the results might just convince a few skeptics that the balance of omega-6s to omega-3s is really important. No one has ever taken an individual with healthy amounts of omega-3s in her tissues, and then switched her to a diet high in omega-6s-while monitoring the results.

This is very different from putting people with large amounts of omega-6s in their tissues on a high-omega-3 diet-something researchers do all the time by giving fish oil to average subjects. Because we store large amounts of omega-6s (but not omega-3s) in our fat tissue, it can take years to see the benefits of those omega-3s. So the results of many of those studies have been equivocal or confusing.

But going in the opposite direction might be very quick, I hypothesized. If animals, as I have suggested in my book The Queen of Fats, use the differences between omega-3s and omega-6s to prepare for the changing seasons-for periods of activity and reproduction when the faster fats of green leaves are available and periods of hunkering down and survival when the slower fats of seeds are more abundant, then the response to a high-omega-6 diet would have to be pretty quick if it were going to be useful.

The scientists I told about this project were enthusiastic (it was my body, after all, not theirs!). Doug Bibus, an AOCS member at the University of Minnesota, agreed to test my blood on a daily basis with his home omega-3 kit  and monitor how the omega-3s and omega-6s changed over the course the month. Bibus also put me in touch with Jeff Volek, an associate professor in the Human Performance Laboratory at the University of Connecticut, who offered to measure my resting metabolic rate (RMR), the amount of energy my body expended at rest, before and after the diet.

I drove to the University of Connecticut, where preliminary medical tests were carried out before I began the diet. The first thing was to determine my RMR. Next, five vials of blood were drawn, which would be divided at the end of the month between Volek and Bibus. And then a body composition scan was carried out using a state-of-the-art dual-energy X-ray machine to determine the amount, and distribution, of fat and lean tissue throughout my entire body.

The scan was followed by an ultrasound of the artery in my arm (the brachial artery) and an assessment of how well this artery responded to an increase in flow-what scientists call shear stress. This test, called Flow-Mediated Vasodilation, was developed in the 1990s and is a good measure of overall vascular health and a good predictor of the risk of developing atherosclerosis, hypertension, and heart failure.

Omega-6s have been implicated in all these conditions (because of their inflammatory nature and because they also increase blood pressure and promote blood clotting and constriction of the blood vessels), and Volek thought it would be interesting to see if my month-long diet would produce a change in my arteries. I doubted it, but was impressed by how quickly I was taken through this, and all the tests.

The morning ended with breakfast at the inn where I had stayed. I ordered scrambled eggs and whole wheat toast, something my omega-3 self would rarely ask for in a restaurant. Eggs are high in omega-3s when they are laid by chickens that forage for greens and insects-or chickens that have been fed a high omega-3 diet, such as flax and fish meal. But commercial eggs, of the kind that would be served in a restaurant, are sure to be high in omega-6s. The chickens that laid them are sure to have been fed on corn and soy.

And thus this month of omega-6 eating began. I won't bore you with the details of every meal, but the sidebar summarizes the kinds of changes I made. It wasn't an unhealthful diet-by most people's standards. What would happen if I kept the quantity, and the kind, of food the same, but just changed the essential oils?

Most medical organizations, as I've said, wouldn't see anything harmful in this change, but a large number of scientists believe that our reliance on cheap, high omega-6 vegetable oils is the underlying cause of many of our health problems. Both omega-3s and omega-6s are essential: We can't make them ourselves and must consume them in our diet. But a balance between them creates tissues with just the right amount of speed and activity, inflammation, and blood flow. Ever since vegetable oil consumption began to skyrocket in the 1950s (replacing butter and lard) so has the incidence of inflammatory diseases, such as heart disease, and metabolic diseases, such as obesity and diabetes. 

My temporary shift to a high omega-6 diet didn't result in any of these diseases (I hope), but I did experience an almost immediate thickening in my belly area. I know from the literature that omega-6s promote the development of fat tissue; still I was amazed it was happening to me. I didn't weigh myself during the diet since I feared that any weight gain might send me on a secret, subversive diet, but I felt sure that I was putting on pounds. Any other symptoms were more fleeting and hard to attribute to diet alone. My stomach felt on fire after several meals, and I flushed more and longer after drinking alcohol. My husband thought my body smell was different; and I was short of breath on several of my daily walks.

Flash forward 30 days, and I was thrilled to be at the end of my diet. By the time I returned to the University of Connecticut, I had a large, unpleasant wad of belly fat that I could grab in one hand. I was certain I had gained at least five pounds. I was shocked, therefore, when I found that my weight was exactly as it had been a month before-56 kilograms or 124 pounds.

Later that morning-after all the tests were completed-I learned from Volek just how profound the changes to my body had been. Yes, my weight was almost the same, but what weight I had gained-5.6 ounces or just under half a pound-was almost entirely fat and in my abdominal area, as the follow-up body scan showed-exactly as I had experienced it. Just as interesting, and the cause, perhaps, of this gain, was that my RMR had fallen by 5%. This drop was within the day-to-day variation for this test (6.2%), but it was in the direction predicted by the diet and the magnitude to explain my small gain in weight.

In just one month, it seems, I had reduced the number of calories I needed to maintain my body at rest by 5%, the equivalent of 76 calories. This may not sound like a lot, but over time, those calories-the amount in a one-ounce piece of mozzarella, for example, or eleven whole almonds-would add up. If I didn't reduce my food intake in order to compensate for this decrease (go on a diet, in other words), I would put on a pound in about 46 days; eight pounds in a year. And this 5% drop in metabolic rate was after just one month. What if I kept to this high-omega-6 diet for six months? Or a year? Or a lifetime, as many people do?

The change in RMR wasn't all. At the same time my RMR was falling, my arteries were becoming stiffer, or less able to expand and contract, as revealed by the follow-up ultrasound. In just 30 days, the amount of dilation my brachial artery was capable of had dropped by 22%, a change much larger than the day-to-day variation of this test. The direction of this change was also predicted by what is known about omega-6s, but the amplitude surprised everyone involved in this project.

In the coming weeks, these findings from Volek's lab were backed up by the results of the blood tests, analyzed by Bibus in Minnesota. At the same time that my metabolic rate was decreasing and my arteries were becoming stiffer, the omega-6s in my red blood cells (and therefore the rest of my body) were increasing and the amount of omega-3s was falling-dramatically and precipitously.

In the first 10 days, the total amount of omega-3s in my red blood cells dropped from 10% to 6%. The amount of omega-6s rose from 21% to 29%. The substitutions continued during the last 20 days of my diet, but the biggest change was almost immediate, as I thought it might be. The omega-3s in my cells were quickly being replaced by seed fats, as I find it helpful to think of them, fats that change with the seasons for most animals, but that Americans eat, and overeat, all year long.

It would be easy to poke holes in this experiment, I realize. I am only one subject and anything but random. It would be easy to wait until this experiment was repeated on a larger scale. Nevertheless, I'm glad to be back on my normal diet and hope that my month-long experiment in high-omega-6 living helps others to better understand these fats.                 

Susan Allport is a science writer and author of The Queen of Fats: Why Omega-3s were removed from the Western diet and what we can do to replace them (University of California Press, 1996). Contact her at

SIDEBAR: Typical menu before and during experiment

Breakfast • Instead of my usual cereal-whole grain flakes with flax seed-I had either oatmeal or a whole grain cereal without flax seed. Instead of the 1% milk I usually bought, from grass-fed cows, I now bought 1% milk from grain-fed cows. On those days when I didn't eat cereal, I had either eggs (commercial ones, of course) with whole grain toast or toast with peanut butter. My omega-3 self would always have spread a peanut butter made with flax oil and peanuts on this toast. For this diet, though, I bought freshly ground peanut butter, which is high in omega-6s, from the health food store. The other foods I always had at breakfast-bananas, grapefruit juice, and tea-remained the same.

Lunch • I often had a sandwich and a bowl of soup-or a salad of arugula from my garden. When it was a peanut butter and banana sandwich, I made it with the whole peanut butter. When it was tuna fish, I made it with a mayonnaise made with soybean oil, instead of my usual canola-oil based mayonnaise. Canola, flax and walnuts are three seeds that happen to be rich in alpha-linolenic acid, the omega-3 fatty acid found in plants, and all play a big part in my normal diet. My usual salad dressing is made of lemon juice, mustard, and a mixture of canola and extra virgin olive oils. For this diet, though, I dressed my salads with a mixture of safflower, sunflower, corn, and soybean oils.

Dinner • Dinner was usually lots of vegetables or salad, accompanied by chicken, fish, pasta, or a baked potato. When I ate at home, I always used my mixture of high omega-6 oils as the cooking fat. When I ate out, I made the assumption that the restaurant also used one or more of these oils-because they tend to be less expensive and more shelf-stable than oils that are high in omega-3s. I also assumed that the meats and fish they served were from grain-fed rather than wild- or grass-fed animals. These assumptions probably overestimated the amount of omega-6s in my experimental diet because many restaurants do, in fact, use canola oil for cooking, but it allowed me to eat out during this month. Fish was on my menu, at least twice a week, as recommended by the American Heart Association, and I usually had wine or beer with dinner. Dessert was often fruit, though sometimes ice cream or a piece of chocolate. I snacked throughout most days on fruit, raisins, and almonds instead of my usual omega-3-rich walnuts.