Twenty years ago this year, former Massachusetts Institute of Technology researcher Dr. Barry Sears published Enter the Zone: A Dietary Road Map, a book that helped change the discussion about diet and health. Against the established nutritional powers--still clutching the "high carb, low-fat" mantra--Sears championed what he called an "anti-inflammatory" dietary approach to undermining obesity and a host of chronic diseases, including diabetes, cardiovascular disease and brain-based diseases. At the time, little was being said about the connection between diet and diseases like Alzheimer's and Parkinson's, but Sears pointed to trends in the modern American diet that were fueling the expansion of these and other conditions.
Considering that cases of diabetes have risen nearly 180% in the last 30 years, and both the incidence and severity of new Alzheimer's cases have skyrocketed in the same period, Sears's points are well worth revisiting. I corresponded with him recently about his latest book, The Mediterranean Zone, and his evidence-based position on what our diet is doing to our bodies and brains.
DiSalvo: In your past work and your latest book you say that there is a direct link between a series of dire health conditions, two of which are already epidemics—obesity and diabetes--and a third that is an epidemic in the making: Alzheimer's. What’s the line connecting the three?
Sears: The linkage between all three chronic conditions is increased inflammation in the adipose tissue, pancreas or the brain. What you see is the movement of cellular inflammation initially from the adipose tissue to the pancreas and then to the brain, respectively. This is similar to the metastatic spread of a cancer. Virtually all chronic disease involves increased inflammation.
Most of us are familiar with "inflammation" as it relates to injuries, but here you’re talking about a particular sort of inflammation that you argue plays a major role (albeit unseen) in the health of our bodies and brains.
There are two types of inflammation. The first type is classical inflammation, the kind that hurts. That’s typically why you go to a doctor. The other type is below the perception of pain. This is cellular inflammation. Initially it causes disruption of hormonal signaling in the cells. However, since there is no indication of its presence, it will continue causing increased cellular damage until there is enough accumulated damage that you can call it chronic disease. It could be obesity, diabetes, heart disease, cancer, or Alzheimer’s, but they are all ultimately caused by cellular inflammation.
Is this type of inflammation reversible?
The best approach to increased inflammation is to follow an anti-inflammatory diet. This is one that maintains a balance of low-fat protein, low-glycemic carbohydrates (i.e. fruits and vegetables), and moderate amounts of fat that are low in both omega-6 and saturated fats (both of which can increase cellular inflammation) at every meal. This is because the hormonal responses of any meal will last only five hours. Such an anti-inflammatory diet can be supplemented with anti-inflammatory supplements rich in either omega-3 fatty acids and polyphenols (the chemicals that give fruits and vegetables their color) and ideally both. Clinical data suggests that cellular inflammation can be rapidly reduced with such a dietary approach. The secret is to follow it for a lifetime.
In your latest book you talk quite a bit about the distinction between omega-6 and omega-3 fatty acids, and the problems associated with an imbalance between the two. What is the main issue here?
Omega-6 fatty acids are the building blocks to make pro-inflammatory hormones, whereas omega-3 fatty acids are the building blocks to make anti-inflammatory hormones. You need a balance of both to maintain a healthy immune response. However, an excess of omega-6 fatty acids or a deficiency of omega-3 fatty acids causes an increase in cellular inflammation. This increase in cellular inflammation is accelerated in the presence of elevated insulin levels which comes from a high-carbohydrate diet.
Give us a sense of the imbalance in terms of how much omega-6 we’re consuming.
The average American now consumes 7-8% of their total calories as omega-6 fatty acids. This is nearly a 400% increase in the past century. A hundred years ago the average omega-6 to omega-3 fatty acid content of the American diet was about 2:1. Today, it is closer to 20:1.
And you say in your recent book that fast food is a major source of the imbalance.
The typical fast food meal has an even higher level of omega-6 fatty acids than grocery-store bought foods. That’s because they are the cheapest source of calories known and make any food taste better (especially fried chicken or French fries). Industrialized beef, chicken, and pork products are also rich in omega-6 fatty acids as they also drive the fattening process.
I've read research suggesting that a super saturation of omega-6 fatty acids in our diets may be linked to psychological-emotional issues, even higher rates of violence. Do you think there's credible evidence for this?
The answer is yes from both epidemiological studies and intervention studies using high-dose omega-3 fatty acids (especially in the treatment of depression, ADHD, and anxiety). I believe the increase in the cellular inflammation in the brain is causing disruption of neurotransmitter signaling patterns, thus preventing the transmission of the appropriate signals to the interior of the nerve cell.
Many people think that eating more fish, like salmon, will boost omega-3 levels, but you’ve said that there are problems with this approach.
First, fish are being hunted to extinction. Second, all fish are contaminated by pollutants we have put into the environment over the past two generations. These include mercury from burning coal to industrial toxins such as PCBs, dioxins, and flame retardants. All of these toxins are known neurotoxins and carcinogens. Third, most people like lean fish, which means they are low in omega-3 fatty acids. Salmon is the only popular fish that is rich in omega-3 fatty acids. Finally, only the Japanese eat enough fish to maintain an appropriate balance of omega-6 to omega-3 fatty acids in their blood.
The solution is to use highly purified, omega-3 concentrates derived from anchovies and sardines to reduce cellular inflammation. The first reported use of fish oil to reduce inflammation was reported in 1989 by Harvard Medical School investigators in The New England Journal of Medicine. Fortunately, omega-3 fatty acid concentrates today have a much higher purity and potency than those used in 1989.
What about farmed fish, particularly the restaurant standbys – farmed salmon and tilapia?
Farmed tilapia has very high levels of omega-6 fatty acids and very low levels of omega-3 fatty acids. This is because the tilapia can grow on cheap vegetable oils instead of more expensive crude omega-3 fatty acids needed for farmed salmon growth. This was discussed in a 2008 article in the Journal of the American Dietetic Association. In fact, the levels of omega-6 fatty acids in farmed tilapia were similar to eating the same amount as found in a hamburger that you might find in a fast food restaurant.
Farmed salmon have higher levels of omega-3 fatty acids because they require omega-3 fatty acids for growth. However, the crude fish oil used in the farming is rich in PCB so that the PCB levels of farmed salmon are about five times that of wild salmon. However, with the increasing price of crude fish oil, the levels of omega-3 fatty acids in farmed-raised salmon are dropping as cheaper alternatives are being used. These include vegetable oil (2/3 of oil used in Norwegian farmed-raised salmon is now vegetable oil rich in omega-6 fatty acids) as well as algae, insects, barley protein and trimmings from seafood processing plants.
If someone wants to tackle inflammation and turn things around, where do they begin?
Try to remember what you grandmother told your parents. Eat small, but balanced meals (at least in terms of calories) throughout the day, never consume any more low-fat protein at a meal than you can fit in the palm of your hand, and never leave the table without eating all your vegetables. Her final advice was to take a tablespoon of cod liver oil (rich in omega-3 fatty acids) before you left the house. Who knew she was at the cutting-edge of 21st century anti-inflammation nutrition? If a person wants more detail on modern anti-inflammatory diets, then I would recommend going to www.zonediet.com.