July 24, 2023

Asthma, Allergies and Nutrition - The Story Part III



There is good quality data on specific parts of a diet or

nutritional plan as it relates to asthma. This section will detail these micronutrient and macronutrient benefits and how to implement them in an overall asthma plan. We will start by looking at a list of high quality nutritional interventions and then follow with an expanded view of a few critical players.

The best review to date on the topic of global nutrition and asthma was authored by Dr. Valerie Julia in the Journal Nature Reviews Immunology.( Julia et. al. 2015) She gives a thorough review of the available literature. The highlights are as follows:

  • Maternal food antigen and allergen avoidance during pregnancy or breastfeeding is not recommended.
  • An increased diversity of food antigen exposure during the first 12 months of a child's life reduces asthma risk.
  • Probiotics can reduce the risk of asthma and allergy
  • Obesity is a direct risk factor for asthmatic disease and worsened morbidity.
  • High fat meals increase airway inflammation.
  • Supplementation of a diet with omega three fatty acids as fish oil can be beneficial in reducing disease morbidity.
  • A diet high in whole food fiber from 6 months of age and on is associated with a healthier microbiome and reduced asthma risk. Fiber is consumed by the healthy gut microbes producing short chain fatty acids that modulate innate immunity. 
  • Low micronutrient status is associated with worse asthma risk and disease. Vitamins A, D, and C are necessary for functional T regulatory cells and immune dampening and tolerance. 

 The Key Players


Fiber is likely the most important ingredient of a wholesome diet and behind the reductions of inflammation and asthma burden in the DASH and Mediterranean diets. We know that historically humans consumed considerably more fiber in past generations compared to current times owing to the flood of low fiber refined carbohydrate foods in society today. Fiber plays a critical role in bowel health as a stool bulking agent, food source for intestinal bacteria, immune modulator and maintaining a healthier metabolism. The data on fiber and disease burden reduction is strong and covers diseases from colon cancer to cardiovascular disease and asthma.(Rimm et.al 1996)(Fuchs et. al. 1999)(Aldoori et. al. 1998)(Trompette et. al. 2014)

There are two major forms of fiber, soluble and insoluble based on their ability to dissolve in water. Soluble fiber dissolves in water while insoluble fiber does not. Both forms of fiber are beneficial and should be a large part of a daily diet. Fiber is found primarily in whole fruits, vegetables, legumes, whole grains, seeds and nuts. The soluble fiber type is the form found in the SAD type processed foods that claim to be higher in fiber. The bacteria promoting insoluble fiber type is found in whole vegetables and fruits. Increasing the volume of these whole foods and removing low fiber refined carbohydrates from the diet will pay dividends for asthmatics.(Guilleminault et. al. 2017)

The Mediterranean diet is loaded with fiber and this diet pattern reduces asthma symptoms in children.(Papamichael et. al. 2017) Blue zones diets are also fiber dense and are correlated with longevity and reduced disease.(Appel L. 2008) 

The hard science asthma dampening effect appears to be based on the fact that fiber feeds the intestinal gut microbiota which in turn produces short chain fatty acids that are immune modulating towards a tolerant and calm state of activity. They specifically alter the function of the immune cells called dendritic cells to a less inflammatory phenotype. (Fomalhault et. al. 2014)(Huffnagle G. 2014)

Grab some apples, beans, broccoli, avocado and berries and feed your gut bacteria while dampening the inflammatory and irritated immune system's reactions. 

Antioxidants and Asthma

Antioxidants are a class of chemicals found primarily in high volumes in stressed plants as a defense mechanism against their predation. When we consume these foods, we presume that we garner the benefits of their function in our body. For our purposes, the definition of an antioxidant is a chemical that inhibits the damage to our cells from natural oxidation events that occur in the body during cellular metabolism, inflammation or infectious killing events*(see below). Essentially, they cool down inflammation post infectious or disease activity at the cellular level. The scholarly research data to date on this effect as it relates to asthma amelioration are very mixed and not inspiring. (Allen et. al. 2009)(Casino et. al. 2009)(Han et. al. 2014)

Vitamins A, C and E are the principle antioxidants and chemicals involved in immune function and many other pathways. According to one large meta-analysis, their insufficiency is associated with worse asthma lung function and wheezing in asthmatic populations.(Allen et. al. 2009) The mechanism of action is plausible for vitamin A acting as a cofactor for correct innate immune function and immune dampening via T regulator cell function.(Raverdeau et. al. 2014) Vitamin C has a mechanism of action as a reducing agent to clear oxygen radicals and reduce oxidative damage to tissues. It has also been associated with reduced exercise induced bronchospasm. (Hemilia et. al. 2012) Vitamin E has the ability to bind up overloaded oxidative chemicals that are triggered by air pollution which in turn is known to worsen asthma. (Han et. al. 2014)

The balance point for antioxidants is important as they are critical for cellular induced pathogen killing when an infection is taking root in our lung tissue or other location. Taking too many supplemental antioxidants can paradoxically worsen asthma as infections are a major exacerbant of reactive airway issues. Mechanistically, this would occur when pathogen killing is weakened by too many vitamins blunting the oxygen radical killing mechanisms of of immune system. 

Food sources of vitamin A are dairy, fish, liver, red/orange/green vegetables like carrots, sweet potatoes and green leafy spinach. Vitamin C is found primarily in citrus foods like oranges and grapefruits. Other good sources include brassica vegetables broccoli, cauliflower and brussel sprouts as well as leafy greens and peppers. Vitamin E food sources are nuts, nut butters, seeds, certain fish, avocados and fortified foods like cereals. 

There are no good quality studies to warrant the use of high dose supplemental antioxidant vitamins in order to ameliorate asthma.  

However, I think that it is prudent to consume antioxidant foods based on the mechanistic pathways of immune function even in the absence of quality data to support their consumption. In my mind, the only potential downside to antioxidant consumption would be to megadose vitamins where infection killing is needed via the reactive oxygen species pathways discussed above. In all of my reading, I cannot find a downside to the consumption of whole foods with antioxidants as part of high quality diet. 

The story continues next week,

Dr. M

Allen Thorax Article

Cassano Thorax Article

Raverdeau Journal of Immunology Article

Hemilia British Medical Journal Open Article

Han Lancet Respiratory Medicine Article

Linus Pauling Micronutrient Center 

Julia Nature Reviews Immunology Article

Rimm JAMA Network Article 

Fuchs NEJM Article

Aldoori Journal of Nutrition Article

Trompette Nature Medicine Article

Guilleminault Nutrients Article

Papamichael Public Health Nutrition Article

Appel Circulation Article

Fomalhault Nature Article

Huffnagle Nature Medicine Article

*The antioxidant plays a role in cleaning up reactive oxygen species that are DNA damaging in high volume. Many things promote excessive amounts of reactive oxygen species (ROS) formation including exogenously ingested chemicals like smoke, toxins, drugs, as well as inflammatory food. We naturally make ROS during day to day cellular metabolism, intense exercise or to kill microbes.

ROS are chemically reactive molecules that have an unpaired electron. In the normal state, most electrons are paired off to keep them stable in the oxygen molecule. When they are unpaired they are unstable, dangerous and looking for an electron to steal. Imagine an amoral single guy being invited to a couple's party. He meanders around the crowd and doesn't care with whom he hooks up with as long as he does. In the cellular world the unpaired electron will attack any cell stealing its electron causing stress and damage. Cells suffer DNA and protein dysfunction, which in turn causes the cell to not perform properly or flat out die.

Antioxidants in this situation are your best friend watching your amoral guest meander around the party eyeing your wife or your friend's wife. Once he sees his true intent is damage, he grabs him by the arm and goes Bruce Lee on him taking him out of circulation.

Vitamin C is necessary to regenerate the cleaning capacity of vitamin E via a chemical called glutathione. Maintaining adequate volumes of vitamin C is critical.