Chapter 27
The Dietary Inflammatory Index
Since 2014, we have known that dietary cholesterol promotes the swelling of fat cells and inflammation of belly fat in monkeys, but there were no studies in humans until researchers in 2019 compared biopsies from vegetarians with those from meat-eaters. Vegetarians generally consume considerably less cholesterol than omnivores. Although eggs are the single largest source of cholesterol in Americans’ diets, more than any one type of meat by itself, the number one source of cholesterol is meat overall (with twice as much cholesterol coming from white meat as from red). The researchers therefore expected to find less inflammation in the vegetarians than in the meat-eaters, and that is what they found. The vegetarians had not even half as many pro-inflammatory macrophages in thigh fat as the omnivores, and, in addition, the meat-eaters had an 80 percent higher expression of tumor necrosis factor, a powerful inflammatory marker, in belly fat.
Mark Hegsted, the brilliant Harvard professor of nutrition science, once wrote that if cholesterol were to be introduced as a new food additive, the conclusion would almost certainly be that it cannot be considered safe in any amount, if only because any amount greater than zero increases the risk of heart disease, our number one killer.
As we get older, our visceral fat grows—the deep belly fat that wraps around the internal organs, infiltrates them, and makes a thick belly. The increased fat mass alone could contribute to inflammaging, but to the extent that they age, even individual fat cells spew more inflammatory mediators like IL-6 than younger fat cells. Thus, the reduction of body fat through sustained calorie restriction could play a role independent of the triggering of autophagy, with this kind of weight loss working disproportionately better at reducing inflammation than obesity (bariatric) surgery over the same period of time. With bariatric surgery, body fat is reduced by about 60 percent and CRP by about the same amount, whereas in the calorie-restriction group without surgery, a weight loss of only 10 percent was associated with a drop in CRP of 40 percent.
Visceral fat is not the only place in the abdomen that can secrete pro-inflammatory factors. As we get older, our microbiome changes. We pick up opportunistic, pro-inflammatory bacteria, and at the same time the gut becomes more permeable, causing bacterial components to enter the blood. We will see that, fortunately, we can calm all these factors that contribute to inflammaging with diet.
The Dietary Inflammatory Index
The pervasive meta-inflammation that we carry around with us our whole lives appears in part to be our immune system’s response to many unhealthy aspects of daily life—from environmental factors like exhaust pollution and toxic chemicals to our everyday lifestyle choices, which include cigarettes, sleep, chronic stress, and the extent of physical activity. But perhaps we deliver to our bodies the primary driver of metainflammatory chronic disease multiple times a day—each time we eat.
How do you know whether a food is pro- or anti-inflammatory? Very simply. You just have to observe what happens to levels of C-reactive protein and other inflammatory markers after someone eats the food. This can also be used to assess the effects of individual nutrients, whole foods, meals, or complete dietary patterns.
Scientists sifted through thousands of such experiments and developed a scoring system called the Dietary Inflammatory Index (Dietary Inflammatory Index). It is very straightforward: The more pro-inflammatory foods we eat each day, the higher the score, and the more anti-inflammatory foods we consume, the fewer points. The goal is a negative value, which we achieve when we eat more anti-inflammatory foods than pro-inflammatory ones. In other words, through an anti-inflammatory diet.
Generally speaking, components of animal products and industrial foods such as saturated fats, trans fats, and cholesterol are pro-inflammatory, and those of whole plant foods such as fiber and phytonutrients are strongly anti-inflammatory. That is why it is not surprising that the Standard American Diet (Standard American Diet, SAD) is pro-inflammatory. This peaked during the Atkins craze in the early 2000s, but we are still not cured, and we can prove it by high disease rates.
Higher scores on the Dietary Inflammatory Index are linked to impaired kidney, lung, and liver function and a higher risk of heart and vascular disease. Those who eat a more pro-inflammatory diet also seem to age faster at the cellular level. Pro-inflammatory diet, the development of frailty, and increased risk of falls in older people go hand in hand.
Pro-inflammatory dietary patterns do not show up only in physical condition. A recent review also concludes that every study that examined the relationship between the Dietary Inflammatory Index and cognitive performance found that diets with higher inflammatory potential are associated with memory deficits and cognitive impairment. In addition, there is a connection between this diet and poorer mental health, including higher rates of depression, panic disorders, and diminished well-being, as well as lower sleep quality.
What about cancer? Eating pro-inflammatory foods is associated with a higher risk of prostate, breast, uterine, and ovarian cancer. Higher scores on the inflammatory index are also associated with increased risk of esophageal, stomach, liver, pancreatic, colorectal, kidney, and bladder cancer, as well as non-Hodgkin lymphoma.
Overall, pro-inflammatory eating results in a 75 percent increased cancer risk and a 67 percent increased risk of dying from cancer. It therefore stands to reason that those who eat a more anti-inflammatory diet live longer and suffer less from functional limitations. A meta-analysis of a dozen cohort studies that followed populations found that participants at the higher end of the Dietary Inflammatory Index had a 23 percent increased risk of dying prematurely compared with those at the lower end.
Use it or lose it
In mice, lifelong voluntary running on a wheel slows inflammaging, but what about men and women? There have been more than 20 controlled intervention studies on the effect of exercise on older adults, and all consistently showed its positive, anti-inflammatory effect. IL-6 levels in active older adults are up to 30 percent lower than in inactive peers. Unfortunately, eight tenths of American adults fall below the national physical activity recommendations.
Pro-inflammatory Foods
The dietary components rated as most strongly pro-inflammatory are saturated and trans fats. In the United States, the five largest sources of saturated fats are cheese (including pizza), desserts like cake and ice cream, chicken dishes, pork, and hamburgers. Since the ban on added trans fats, the only remaining sources in the diet are the small natural amounts in meat and dairy products and those that arise during the refining of plant oils.
Reducing Endotoxin Exposure
The inflammatory effect of saturated fats can be seen after just one meal. We have known for almost 20 years that just hours after a high-fat meal (Sausage & Egg McMuffins were used in the original study), arteries can stiffen and their ability to relax normally can be cut in half. Unhealthy meals do not cause harm only decades later, but here and now, within hours after you’ve wolfed them down. How do we know it was the fat and not the junky refined carbohydrates in the yeast roll? Because you can also provoke a spike in inflammation levels by drinking pure cream, which has zero carbohydrates and consists mostly of saturated butterfat. And just as this inflammatory state begins to settle down five or six hours later, it is time for lunch, when perhaps a new load of saturated fats crashes into your arteries. Through this cycle, many Americans are stuck in a dangerous trap of chronic, silent inflammation. No wonder saturated fats in the diet have been called an “accelerator for the aging process.”
After just one meal high in saturated fats, IL-6 levels can double in six hours and approach those that imply a doubled risk of premature death. Why does saturated fat promote inflammation so vehemently?