Quick note: I am not a healthcare-provider, mental or otherwise. My discussion of inflammation and mental health is based on research that I have read and linked to so you can check it out for yourself. However, it should not be a substitute for legitimate medical advice. If you think you or a loved one is suffering from depression, please seek help from a medical professional or the counsel of a trusted friend or family member.
As promised, today we’re going to talk about how diet and gut permeability can cause the inflammatory
response linked to depression.
I’ll be explaining how inflammatory diets correlate with risk for depression, how gut permeability is involved, and what types of foods are inflammatory vs. anti-inflammatory.
(Psst–if you’re wondering what inflammation has to do with depression, you might want to go back and read the first post in this series.)
Inflammatory Diets and Depression
A cohort study conducted in Spain demonstrated an association between a strongly pro-inflammatory diet and an increased incidence of depression diagnoses (Sanchez-Villegas et al, 2015). Interestingly, this association was stronger in older adults (>55 years old) and people with cardiovascular diseases. The researchers used the Dietary Inflammatory Index (DII) to measure the inflammatory quality of the participants’ diets; we will discuss what makes a food “inflammatory” shortly.
Numerous other studies since 2009 have found inverse relationships between diet quality and common mental disorders–primarily depression and anxiety. Furthermore, obesity itself is an inflammatory state, so diet that promote obesity also promote inflammation, even if indirectly. A 2011 meta-analysis (Faith et al) found that obesity was a predictor of depression and/or depressive symptoms in 80% of the studies that the authors analyzed. Meanwhile, only 53% of the studies analyzed for depression-to-obesity associations showed depression to be a predictor of obesity.
“Leaky gut syndrome” is a condition likely caused by increased intestinal permeability, and it is usually accompanied by bloating, gas, cramping, and other unpleasant gastrointestinal symptoms. Leaky gut is created when space develops at the junctions between intestinal cells, which are supposed to be nice and tight to prevent substances from leaking through. After all, the gut is actually the largest immune organ in the body. But in people with leaky gut, substances such as pro-inflammatory cytokines and lipopolysaccharides (LPS) can get out of the gut and wreak havoc on the rest of the body. People with major depressive disorder (MDD) have been shown to have elevated serum levels of the immunoglobulins that target a number of gram negative bacteria that normally live in the gut and produce LPS. This implies that more LPS is escaping from the gut to the bloodstream in depressed people than in non-depressed controls. In other words, leaky gut seems to play a role in driving the inflammatory pathology of depression.
But what causes leaky gut, you ask? Well, the seemingly cyclical answer is that inflammation causes leaky gut. A leaky gut cannot create inflammation where there isn’t any, but it can take underlying low-level inflammation and exacerbate it dramatically. A pro-inflammatory diet, chronic stress, obesity, bacteria overgrowth (possibly due to an imbalanced microbiome), infection, and smoking can all create inflammation that will lead to a loosening of the intestinal cell junctions–a.k.a. leaky gut–which will in turn increase the body’s inflammation.
Inflammation is the gentle push needed to get the ball rolling, but a leaky gut is steep hill that allows it to pick up speed.
Pro- and Anti-Inflammatory Foods
Ok, so now that we’ve established the importance of diet in creating or preventing an inflammatory state (with possible leaky gut syndrome), what are the actual good and bad foods?
Studies have shown correlation between the “Mediterranean diet” and reduced inflammatory markers in blood plasma, along with the opposite effects from diets high in processed foods, refined carbohydrates, and red meats. (Although the inflammatory affects of red meat are not without controversy. Plenty of evidence suggests that red meat will not promote inflammation for the average person.) Furthermore, individual components of diet may also impact inflammation, in addition to overall diet quality. Fiber packaged in whole-grain foods seems to modulate inflammation as a result of their high beta-glucan content–and the same goes for fungi! Phytochemicals in whole-grain foods may also protect against the oxidative stress that results from inflammation and is a feature of depression.
- Refined carbohydrates
- White bread, white pasta, white rice, many cereals–anything with white flour
- Processed meat
- Sausage, hot dogs, lunch meat
- Trans fats
- Foods that contain margarine, shortening, or partially hydrogenated vegetable oils
- Most fried fast foods
- Alcohol, in excess (2+ drinks a day)
- Tomatoes (thanks to the lycopene content)
- Olive oil
- Leafy green vegetables
- Kale, spinach, collards, etc.
- Most other (non-starchy) vegetables
- Whole grains, in moderation
- Whole wheat bread and pasta, old-fashioned oatmeal
- Good sources of omega-3 fatty acids–which the modern Western diet does not contain nearly enough of!
- Fatty fish
- Salmon, mackerel, tuna, sardines
- More good sources of omega-3 fatty acids!
- Strawberries, blueberries, oranges, cherries
- The trick is to get it without too much sugar or fat, which is why a small amount of dark chocolate is your best bet.
- Some herbs and spices
- Turmeric, ginger, garlic, basil, and others
- Alcohol, in moderation (1 drink per day, preferably red wine)
Next up in the Inflammation and Mental Health series, we’ll be talking about ways other than diet to reduce inflammation in your body.