Inflammation has recently emerged as an important player in the development of age-related disability and many of our major chronic diseases including heart disease, cancer, diabetes, and Alzheimer's disease. Now that laboratory tests such as C-reactive protein have been developed, we can measure the effects different foods and diets have on inflammatory markers.
Most plant-based foods decrease inflammation. Processing destroys the anti-inflammatory effects of some (garlic decreases inflammation but garlic powder does not), but improves these effects in others (tomato juice decreases inflammation but whole tomatoes do not). For a review of which plants have been found to be most anti-inflammatory, check out my 3-min. video Anti-inflammatory Effects of Purple Potatoes.
Do these anti-inflammatory plant foods actually have an impact on inflammatory disease mortality though? In my 2-min. video Fighting Inflammation in a Nut Shell I profile a new study out of Australia, which followed about 2,500 older adults and their diets for 15 years. In that time, about 200 participants died of inflammatory diseases, allowing the scientists to calculate the specific aspect of the survivors' diets that seemed to help the most. It was nuts! The equivalent of half a walnut a day appeared to cut the risk of dying from inflammatory disease in nearly half. Fish consumption, to their surprise, didn't seem to help, which may be due to pro-inflammatory industrial pollutants that build up the food chain. This may help explain why most studies done to date on those eating vegetarian or vegan have found lower levels of inflammatory biomarkers in their bodies.
However, just because plant-based diets decrease markers of inflammation doesn't necessarily mean that plant-based diets can successfully be used to fight inflammatory disease. To find that out, you've got to put it to the test. The gold standard for evidence in nutritional science is an interventional trial. You split people into two groups and ask half to go on one diet, half to go on another, and then stand back and see what happens. That's just what researchers recently did for the inflammatory bowel condition known as Crohn's disease, profiled in my 4-min. video Dietary Treatment of Crohn's Disease.
Crohn's disease is an autoimmune condition where your immune system attacks your own intestines. There is no cure; all you can do is try to keep it in remission as long as possible between attacks. Sufferers are often put in anti-inflammatory and immunosuppressive drugs and may find themselves in and out of the hospital getting segments of their intestines surgically removed. Since it's the intestine itself that's inflamed, it would seem a good condition to test out the anti-inflammatory power of plant-based diets. We've known that meat, cheese, fish, and animal protein in general has been found to increase risk of developing inflammatory bowel disease but what about plants to to not just prevent, but treat it?
Japanese researchers took a group of Crohn's patients in remission, either because they just came out of surgery or because they were able to beat it back with steroids. And for two years asked half of them to eat a semi-vegetarian diet, meaning in this case vegetarian except for half a serving of fish a week, and half a serving of other meat once every two weeks, so less than one serving of meat per week. Now this wasn't a prison study or anything, these were free-living adults, so the results are not what necessarily happens when Crohn's sufferers actually go on a plant-based diet, but what happens when people they are just told to eat a more plant based diet and how much they comply is up to them, which makes the results even more astounding.
You can see the graph in the video, but basically 200 days into the study all of the patients told to eat more of a plant-based diet were still in remission, but about 20% of the group not told to eat anything different relapsed. After a year 100% of the semi-veg group still symptom free, but the disease re-emerged in half of the standard diet group. And at the end of two years, 92% of the patients told to eat a more plant-based diet remained without disease, whereas the majority of those not given that advise relapsed back in the cycles of drugs, hospitalizations and surgery.
And that horrible relapse rate is typical on typical diets. Most Crohn's sufferers relapse within a a year or two--unless, it seems, they start eating healthier. Remission rate, meaning disease-free status, with the semi-vegetarian diet was 100% at 1 year and 92% at 2 years. To the best of the researcher's knowledge this is the best result in relapse prevention ever reported.
Inflammatory bowel disease risk has been tied to arachidonic acid, which may partially explain the animal protein connection given the levels in chicken and eggs. The anti-inflammatory nature of plant foods may also explain why those eating plant-based diets have less diabetes (Preventing Macular Degeneration With Diet), fewer allergies (Preventing Allergies in Adulthood), less heart disease (China Study on Sudden Cardiac Death), better moods (Improving Mood Through Diet), and fewer chronic diseases in general (Say No to Drugs by Saying Yes to More Plants).
-Michael Greger, M.D.
Image credit: Dylan Luder / Flickr