March 18, 2019
THE NUTRITIONAL STUDIES
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. 2105) 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. 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.
The story continues next week,
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