Diet and Asthma: The Inflammation Connection

Whale meat. Wild berries. Seaweed. Lots (and lots, and lots) of fat.

The traditional Inuit diet is the prototypical high-fat, low-carb traditional diet. Even with All That Saturated Fat and Cholesterol, Inuit eating their traditional foods rarely suffer from heart disease or related problems. And so their diet has been Exhibit A for the low-carb Paleo crowd since the beginning.

But putting obesity and heart disease aside, guess what else the Inuit diet is protective against? Asthma. When Inuit populations move out of Greenland and start eating a Western diet, weight predictably goes up – but so does asthma.

One study found that about 3.6% of Inuit living in Greenland have asthma. But about 9% of Inuit living in Denmark have it, and the Denmark-dwellers have higher levels of inflammatory markers to match. The researchers thought that the “more westernized diet” of Denmark actually caused the increased inflammation, causing the higher rates of asthma.

(As an interesting side note, that was true even though the Inuit living in Denmark actually ate more fruits and vegetables than the Inuit living in Greenland. So the modern diet/lifestyle in Denmark was so inflammatory that even adding more fruits and vegetables couldn’t make up for it.)

Here’s a look at the ways diet can affect asthma symptoms by causing (or resolving!) inflammation.

None of this is an argument that diet is the only cause of asthma. Obviously, there are other causes. Genetic factors are big. Environmental pollution and air quality is huge.

Asthma can be life-threatening, especially if it’s left untreated. If you have asthma, go see a doctor first – no nutrition advice can substitute for medical treatment.

Asthma is an Inflammatory Disease

The fundamental reason why diet affects asthma is that asthma is an inflammatory disease. Inflammation in the airways causes muscles to constrict, which causes wheezing, coughing, and shortness of breath, along with changes in immune and inflammatory markers. Diet can increase or decrease inflammation, depending on what you eat (if you don’t know what inflammation really is, here’s an explanation). Diet-induced inflammation can strongly affect asthma risk.

One big piece of evidence for this is the asthma-obesity connection. Obesity is associated with an increased risk of asthma (and to a lesser extent, other allergic diseases). As this review explains, the connection could be the way fat tissue regulates overall inflammation:

“Chronic low grade systemic inflammation is considered as a hallmark of obesity and may possibly explain the link between obesity and chronic disease, in particular the increased incidence, prevalence and severity of asthma in obese individuals.”

This “chronic low grade systemic inflammation” is strongly affected by diet. For example, if a person gained weight eating a lot of junk food rich in industrial oils like “vegetable oil” and soybean oil, their fat tissue probably has a high concentration of Omega-6 fat. This can work like a built-in inflammation dispenser that keeps up a low-grade state of inflammation all the time. (for more on that, see here).

So in other words: yes, there is evidence that a diet-induced inflammatory state can actually modify symptoms of asthma specifically.

Diet and Asthma: The Details

This review in Nature Reviews Immunology goes over several different aspects of asthma and dietary fat.

Dietary Fat and Cholesterol

Saturated fats, might help asthma by suppressing certain parts of the allergic response called PPARs. The naturally occurring trans fat Conjugated Linoleic Acid, found in grass-fed meat and dairy, might be particularly helpful. For example, in mice, CLA from milk fat reduces airway inflammation.

Cholesterol may also be helpful, because it’s broken down into metabolites that combine with other receptors to reduce inflammation.

Interestingly, Medium-Chain Triglycerides, a type of fat found mostly in coconut oil, might actually increase allergic sensitization (although the study authors made it very clear that this was a theory and not proven). So if you have an allergic disease and you’re taking an MCT supplement or cooking with a lot of coconut oil, it might be worth testing out an elimination to see if it works.

Polyunsaturated Fat

Polyunsaturated fat comes in two types: Omega-3 (from fish and seafood), and Omega-6 (from nuts, seeds, soy, and industrial oils). Both types are important for regulating inflammation. This review covers PUFA and asthma. The long story is incredibly complicated, but the short story is…

• Omega-3 PUFA is probably anti-inflammatory and may be helpful for asthma.
• But supplements are underwhelming. The best approach seems to be a whole-diet, holistic pattern of reducing Omega-6 (avoid seed oils, “vegetable oil,” soy, and huge amounts of nuts) while increasing Omega-3 (eat more fish).

Dietary Fiber and Fat Produced in your Gut

On top of dietary fat, there’s also the fat you make yourself. Short-chain fatty acids (like butyrate) are produced by your gut flora – you eat fiber, and your gut bacteria turn it into short-chain fatty acids. These fats may also be protective against allergic inflammation. For example, feeding mice a high-fiber diet increases the production of short-chain fatty acids and suppresses asthma-like inflammation.

To get more of these fats, you wouldn’t eat more fat; you’d eat more fiber from fruits and vegetables.

Vitamins and Antioxidants

Vitamin D is anti-inflammatory and reduces allergic inflammation. This review found that, of all the vitamins studied, Vitamin D had some of the strongest evidence connecting it to asthma symptoms. This is really interesting given that asthma is so strongly associated with diet-induced obesity, and people with obesity often have low levels of Vitamin D as well.

Dietary antioxidants are also associated with a lower risk of asthma, but, a lot of the evidence for this is unclear. This review explains that there’s not much evidence for isolated nutrient supplements in otherwise healthy adults. Just like Omega-3 fats, the real key is probably to change dietary patterns overall to be anti-inflammatory, not to rely on some particular wonder nutrient as a supplement.

(As a side note: the mother’s diet during pregnancy also affects the baby’s risk of asthma and allergies, but that’s not discussed here because it’s just too much stuff.)

Gut Health and Inflammation

Asthma is associated with changes in the gut flora, and this review argues that the changes might be causal. The gut flora help regulate the immune/inflammatory response, so this isn’t surprising at all.

This is especially obvious in babies – the review argues for a “window of opportunity” to start a baby’s gut biome off right and avoid the development of allergic/inflammatory diseases like asthma down the line.

It’s not clear which probiotics would be best for adults trying to improve their gut biome, but focusing on overall gut health – prebiotics and probiotics if they play nicely with your gut, avoiding gut irritants, getting enough sleep, managing stress – probably can’t hurt.

Summing it Up

So far, here’s what we have:

• Asthma is an inflammatory disease. Inflammation is at the heart of the problem.
• The inflammatory modern Western diet and lifestyle are associated with asthma.
• Traditional diets are associated with a much lower rate of asthma.
• BUT it’s hard to pin down particular individual nutrients that are helpful as supplements. Diet quality overall seems to matter more.

There’s evidence that a Paleo-style diet might be really great for asthma specifically, especially considering the beneficial effects of saturated fat and cholesterol on airway inflammation, and the importance of gut health. But supplement recommendations are really premature at this point; the important thing seems to be diet overall.

We’re not all Inuit, and not everyone likes or needs a high-fat, low-carb diet. But almost everyone can eat nutrient-dense foods, reduce industrial seed oils, eat fish regularly, and take care of their gut.