Asthma, Allergies and Nutrition

July 17, 2023

Asthma, Allergies and Nutrition - The Story

Part II

THE NUTRITIONAL STUDIES

We know that the foods that we consume affect our intestinal microbiome, our immune system, our metabolism and therefore have a significant effect on inflammation.

Is this knowledge translatable to asthma? Let us look specifically at nutrition as it relates to Asthma. Are there specific diet studies available that lead us toward a unified diet for better asthma health? Can we make good recommendations for our patients on a macronutrient basis with fats, carbohydrates and protein ratios and types. Do we have data to support certain micronutrient needs in asthma and how a diet could provide these nutrients? How much can we trust the data?

There are true and legitimate reasons why nutritional studies are difficult to use.

A single macronutrient or micronutrient study doesn't reflect normal life as we consume food stuffs synergistically
It is hard to adequately power a nutritional study to show statistical significance
Animal studies are unlikely to reflect human reactions exactly making generalizability difficult
GWAS, genome wide association studies, data is showing how genetically and metabalome-ically unique humans are, making it difficult to draw conclusions
Patient compliance with diet interventions is notoriously poor begging the question that if compliance is good in a study was the patient already on a different path than the average American
Knowing that the above statements are likely true, we will press on with the data as it is because we have no better options. Some imperfect data is better than no data.

Let us start by defining the large macro type diets. The three main dietary types that have been reasonably well studied in human disease are: DASH (dietary approaches to stop hypertension), Mediterranean and Western or otherwise known as SAD, the standard American diet.

Many people are looking at the Keto diet and the Paleo diet for help these days, however, they have some data in relation to neurological disease and cancer, but no data that I can translate to asthma and allergy.

The three main diets:

The DASH diet is based on eating lots of vegetables, fruits and whole grains. Fish, poultry, legumes, nuts, seeds and vegetable oils are a large part of the diet. It is very limited in refined and processed carbohydrate foods. It is low in saturated fats. It is well studied and has shown significant benefit in reducing hypertension and cardiovascular disease. (Siervo et. al. 2015)(Saneei et. al. 2014)

The Mediterranean diet is based on the foods eaten in the Mediterranean region. It is filled with vegetables, fruits, legumes, whole grains, olive oil, fish and full fat dairy products. It is lower in non-fish meats and processed foods of all types. Its prominent benefit, which is highly touted by Integrative Medicine Physicians, is the beneficial load of antioxidant vegetables and fruits along with a healthy balanced fat profile and limited refined pro-inflammatory carbohydrates. It is also loaded with fiber feeding the intestinal microbiome and reducing inflammation systemically.

The Western "SAD" diet is popular in the United States and is composed of large volumes of highly processed flour and sugar-based foods, red and processed meats, sugar laden beverages, dairy, eggs and poultry. It is largely a convenience and taste-based diet that our American population thoroughly enjoys. Unfortunately, it is highly associated with inflammation and chronic disease in humans.

Now that we have defined them, we can begin to dissect the studies and see if we can come to a conclusion for asthma sufferers on what or what not to eat.

Looking at the studies, there is a paucity of evidence that the DASH diet has any effect on asthma prevalence or morbidity because it has not been studied other than a pilot study in poorly controlled asthma that showed a non-statistically significant reduction in symptom scores.(Ma et. al. 2013) The known benefits to cardiovascular disease are not immediately translatable to asthma.

The Mediterranean diet is the most studied of all of the "positive", i.e. thought to be beneficial diets. When it comes to the onset and prevalence of asthma, the Mediterranean diet has mixed results. It has positive results in relation to asthma morbidity.(Barros et. al. 2008)(Sexton et. al. 2013)(Garcia-Marcos et. al. 2013)(Papamichael M. 2017) Other studies that looked just at vegetable and fruit intake noted improved asthma symptoms with increased intake. (Garcia-Larsen et. al. 2016)(Wood et. al. 2012)(Guilleminault et. al. 2017)(Appel et. al. 2008) The mechanism biochemically for this effect would be that vegetables and fruits have a high volume of antioxidants that protect the cells from oxidative damage, especially the mitochondria. Finally, the infamous Western diet is believed to be associated with worsening asthma, but this is weakly associated with the studies. (Brigham et. al. 2015) (Nkosi et. al. 2020)(Reyes-Angel et. al. 2021)

The best summary of the available data as it relates to macro diets and asthma is that increasing intake of vegetables and fruits in the diet has strong evidence for benefit. The diversity of the whole foods taken in is the key to the best possible outcome. (Venter C. 2019)

When it comes to preventing asthma in children through pregnancy, the data is a little better and improving with studies like the Grow baby project and others. The key here remains a diverse, minimally processed diet with lots of vegetables and fruits and limited sugars. (Reyes-angel et. al. 2021)(Nuzzi et. al. 2022)

Hypothetically, but not proven, it is most likely that the Western diet is not beneficial and the DASH and Mediterranean diets are beneficial. The lack of data on the western diet and asthma does not take away from the known mechanistic pathways of this diet inducing inflammation and immune dysregulation that could affect an asthmatic patient especially as it relates to fructose/uric acid/inflammasomes as well as excessive saturated fatty acids and inflammation.
Knowing that the nutritional studies are incomplete as they relate to asthma specifically, let's attack this issue of diet and asthma from another angle, inflammation. The available best quality nutritional data is that what decreases total body inflammation and excess weight gain will decrease the disease burden whether it is cardiac, pulmonary or gastroenterological disease.(David et. al. 2014)(Sharon et. al. 2014)(Pollan 2013)(Manco et. al. 2010) Interestingly, obese individuals have a 92% increased risk of asthma. (Kull et. al. 2006) Therefore, one would presume that what drives obesity may also drive asthma morbidity. Is there a surrogate population that has a rapid change in weight and also asthma disease?
The obese population that undergoes bariatric surgery is this group. They undergo a rapid metabolic change that is a perfect surrogate for a dietary change. Post bariatric surgery patient outcomes note that asthma steroid medicine needs drop post-surgery by 40%. (Reddy et. al. 2011) The reason at first blush was thought to be related to decrease caloric intake and straight weight loss. However, a deeper dive at the pathophysiology of gastric bypass has proven that the surgically induced shift in the microbiome's bacterial makeup and subsequent inflammatory response is at the root of disease improvement. (Rubino F 2017)(Celiker H 2017) This microbiome shift can also be achieved by dramatically changing the diet. (Conlon et. al. 2015)(Carmody et. al. 2015)(Kau et. al. 2011)(Sonnenburg et. al. 2016)(Turnbaugh et. al. 2009)(Cani P 2008)

What remains fascinating and actually logical is that those individuals with severe excess weight and asthma but no severe metabolic syndrome will benefit from bariatric surgery significantly because they are removing the voluminous food inputs of disease . For those that have developed full metabolic syndrome and likely continue liquid fructose and sucrose based calories, the effects are negated post surgery. (Forno E. et. al. 2021) Anything that leads to metabolic derangements and immune dysregulation will improve post correction if the inputs can me modified. Bariatric surgery is one such method. For me, this is the key to why diet and asthma are intimately tied. I firmly believe that the processed foods and liquid sugars are driving metabolic derangements that are worsening most disease, including asthma.

This may be the key to understanding how diet and asthma are linked since the epidemiological data is moderate to weak. The emerging strong evidence that the microbiome drives inflammation and disease morbidity is critical in making decisions where they are related to nutrition. Now we must continue to follow the data as it evolves in regards to what dietary influences have the most profound positive effect on the intestinal microbiome and thus inflammation, endotoxemia and asthma.

The story continues next week,

Dr. M