Recent studies have emphasized the important, but perhaps counter-intuitive, role of gut microbes in lung health. These new insights suggest that managing gut microbes could be effective for helping to manage lung problems. One way of doing that is through diet.
This article reviews the role of gut microbes in lung conditions, and advocates for nutritional approaches to support a healthy relationship between the gut and lungs.
Some highlights include:
- Diets rich in fiber affect the composition of both gut and lung microbes.
- A high-fiber diet protects against inflammation associated with allergy, highlighting the therapeutic potential for fiber in the diet of Chronic Obstructive Pulmonary Disease (COPD) and asthma.
- A key mechanism by which fiber-eating gut microbes influence lung inflammation is by production of short-chain fatty acids (SCA): butyrate, acetate, and propionate. These substances are now well-established to exert anti-inflammatory effects on immune cells.
- SCA effects are believed to be indirect, as levels of these substances in the lungs seem to be very low. Rather, it is believed SCA work mostly by programming immune cells in the gut or bone marrow, which then migrate to the lungs to control inflammation.
- Asthma is the most common non-communicable condition in childhood, and is a good example of the importance of early-life microbes in disease prevention. For example, breastmilk favors the growth of bifidobacteria and lactobacillus (two important types of immune-regulating microbes), and direct breast-feeding has been reported to be the most important factor in prevention of asthma.
- A prospective study of infants in Europe showed that babies with higher levels of SCA in their poo were less likely to develop asthma or atopy (rashes, hives) than children with lower levels, suggesting that these early-life microbe products can program a child's immune system to be more tolerant and less inflammatory.
- Among 3-year-olds, intestinal polyunsaturated fatty acids (PUFA) were inversely related to asthma, whereas conversely, a diet high in fried foods and processed meats was linked to asthma.
- A similar pattern is seen in adults with COPD. A study from the UK reported that a "prudent" dietary pattern (I like it!) of high consumption of fruit and veg, oily fish and wholemeal grains was associated with protection of lung function and COPD, "especially among male smokers." It was interpreted that the antioxidants in a prudent diet can protect against tissue damage. It is worth reiterating, though, that the "prudent" diet will also feed microbes that regulate inflammation and immune function. So there are two important ways that a prudent diet can benefit COPD and other diseases associated with lung damage.
- The gut-lung axis may also be disturbed in cystic fibrosis (CF), a genetic disease caused by dysfunctional chloride receptors that leads to thick mucus that obstructs airways. A pattern emerges whereby dysbiosis in CF is characterized by fewer microbes that make SCA, suggesting that the lower SCA levels contribute to the lung inflammation in CF.