One of the buzzwords thrown around in nutrition circles lately is the term "inflammation." It seems like every food we eat or activity we do can be labeled pro or anti-inflammatory. But what does the science say?
First of all, not all inflammation is created equal. First of all we have acute inflammation, which is usually caused by an injury such as getting punched in the face, cutting your leg while cleaning up your adopt-a-highway section (ask me how I know!), or getting exposed to a virus. What follows is a fascinating (to me) process that combines both a repair cycle and a "do not use" order. First, something called pattern recognition receptors (PRR) located at sight of the injury/virus exposure call up various inflammatory mediators which then start a process called vasodilation (widening of the blood vessels). More blood flows to the injury site, which causes it to feel warm and turn red. The blood vessels become more permeable (think of little doors opening up in your blood vessels), which allows plasma and leukocytes (white blood cells--five different types that target different pathogens!) to flow through the vessel walls and into the
injured tissue to do their work. This increase in plasma causes the swelling you see. While that's going on, your body releases an inflammatory mediator called bradykinin which causes you to feel more pain at the sight of injury. So, not only is the swelling, redness, heat, and pain a sign that something is going on, but you are less likely to use the affected area (or do anything if you've got a really bad cold) and allow the "repair people" and "cleanup crew" to do their jobs. (Would you interrupt a skilled technician doing delicate electrical work in your home? Or a janitor cleaning up a, um, body fluid spill? I don't think so!)
Now, if said process continues longer than the acute period, it is said to be chronic inflammation, and sometimes the products of inflammation can cause disease itself. For example, when a person who has dermatitis herpitiformis ingests something with gluten there is going to be a nasty rash that results. If someone with asthma is exposed to tobacco smoke or paint fumes they better have an inhaler handy. And there is also evidence that inflammation plays a role in heart disease (Link), and cancer (Link).
For those of you who are trying to avoid pain and inflammation from an injury or virus exposure, you are probably going to try to avoid the causes. You might wear long pants to keep from getting cut on your adopt-a-highway cleanup (but it was hot outside, ok!) and you will hopefully was your hands frequently during cold and flu season. If you are having a life-threatening reaction, you might even have to (gasp!) take some kind of (gasp again!) medicine to help you well, live. When it comes to avoiding chronic inflammation, however, here is where we have to dig deeper. And since this is a nutrition blog we will look at diet and inflammation.
So what causes the ACUTE inflammatory response? Well, everything apparently. Food, in general is going to have something the body perceived as a foreign object in it, and we have an acute response until the body takes care of assimilating the nutrients. Plenty of studies have measured post-meal reponses. (1, 2, ), and it appears after 250,000 years we have adapted pretty well to that. And of course it's the long term inflammation associated with the C-words that we are probably more worried about. It appears that there are some other studies pointing to either a high processed carbohydrate diet as problematic for inflammation, other studies point towards specific types of carbohydrate foods like those who contain gluten as promoting inflammation markers, and some studies point toward saturated fats causing inflammation, but a lot of these studies involve a very small group of people (larger double blind studies are more expensive) or rely on the notoriously unreliable food questionnaires, so they are there for us to say "huh, that's interesting" but hardly pivotal. (1, 2, 3) So, in other words, as badly as some of us want to point the finger at one particular food or group of food, it looks like, in the words of Dr. Ben Goldacre at Bad Science, it's more complicated than that.
And those complications involved some other physiological issues like insulin resistance, obesity, fatty-liver disease, how much and what type of exercise we do, etc. (1, 2, 3) But wait a minute here, can't some of these other problems be corrected by diet as well? Well, yes, it looks like we have circled around again. If you are a person who is insulin resistant, in other words you have the marker's for metabolic syndrome, or have been diagnosed with pre-diabetes or Type 2 diabetes, or have been told your triglycerides are high, you can improve your insulin sensitivity and see improvement in your clinical marker's by restricting your carbohydrate intake. (And please, go to your physician and get your lab work done, no internet diagnosing!) (Link). And if you restrict your carbohydrates (in other words, you stop drinking a ton of soda and eating platefuls of pasta, you know who you are!) then your calorie intake has a pretty good chance of decreasing so you can lose weight (and people find when they are producing less insulin, they may not be as hungry either). And by the way, if you have fatty deposits in the liver, restricting the carbohydrates might help you there to. So does eliminating or restricting one food group cure your inflammation? Apparently not. Could it lead to some improvements in other health markers and therefore lower your risk of heart disease and cancer? Possibly, but for now the improvement in other health conditions might have to be our main staying point. (Link)
But what about the omega-3 fats? Aren't they the cure all for inflammation? A lot of my patients think so, and they feel like as long as they take those fish oil capsules faithfully they don't have to make any other changes in their diet. Remember, there are no magic cures! And it also appears that if people are taking their fish oil capsules faithfully but still consuming a lot of omega-6 fats, it's not going to produce a favorable response. Both of those fats are essential, meaning our body doesn't make them, but apparently if we tip the balance toward omega-3 and away from as much omega-6 our inflammation markers decrease. One of the better postings I have found on this topic is over at Caveman Doctor. His blog persona is a bit goofy (hello pot, meet kettle) but he does some pretty solid research.
Speaking of, he also has an interesting post on exercise and inflammation. If you are distance/endurance athlete and are having joint problems, you might want to take a look at your routine and see if it's time for a change. Now, using the small data set of Friends of SkepticRD Who Enjoy Cheating Death by Triathlon and Other Scary Things, I know that there are people who love being endurance athletes for a host of reasons. As I stated in a previous post you can't expect to have a poor diet and compete well anyway; but we'll need to do some more studies to show if the diet also helps reduce inflammatory markers in that particular subset of the population.
Now what about other issues attributed to inflammation such as lupus, rheumatoid arthritis, etc? Can diet "cure" those problems as well? There are some people who think so. First of all, as stated above, not all inflammation is the same. For example, if I have an infected cut on my leg, changing what I eat will not directly heal that infection. Second, you can always point at a particular food and group of foods and say "this will stop it," but you might have other underlying health problems that may be helped by a change in diet. For example, if you have uncontrolled diabetes and have an infected cut on your leg, changing your diet can lower your blood glucose levels and promote wound healing that way, but there was no one food that will do so. Third, a lot of the diets that people follow for rheumatoid arthritis, etc have a large placebo effect, and as they say in this WebMD article "some people find relief and some people don't." I usually tell people to think about the ramifications of what they are giving up in a "first do no harm" kind of way. For example, if you think gluten is aggravating your rheumatoid arthritis, giving it up for 2-4 weeks may result in you being very, very cranky because you won't be drinking beer and eating pizza, etc for that time, but as long as you are eating protein/good fats/vegetables you won't wind up with a nutrition deficiency. If you give up gluten and animal protein, however, then you might find yourself cranky and having to work hard to get quality protein. Some people are willing to take that chance for pain relief, others that follow the evidence will not.
Take home message--consuming more omega-3 fats and less omega-6 shows the most promise for reducing inflammatory markers. If you are obese and/or have a condition that involves insulin resistance you will likely benefit from restricting your carbohydrate intake to improve health marker's associated with those conditions. If you think that other foods are aggravating a particular condition that you have; think about the ramifications about eliminating that food before you try it.