Harvard study links vitamin D lack to kids’ food allergies
Last month, researchers from Harvard Medical School linked a well-documented rise in rates of food allergies among American children to a parallel rise in vitamin D deficiency (Vassallo MF et al. 2010).
As they wrote, “Concurrent with the increase in food allergies is an epidemic of vitamin D deficiency (VDD) caused by several factors, especially decreased sunlight exposure.”
Food allergies stem from maladaptive immune responses to common and otherwise innocuous food factors, especially certain kinds of proteins.
The Harvard team proposed that vitamin D deficiency during developmentally critical periods increases the chances that a child’s gastrointestinal system will be colonized by abnormal microbial flora and suffer infections.
These adverse events would contribute to abnormal permeability of the child’s intestinal barrier, resulting in excessive exposure of the immune system to normally benign food factors, causing the undesirable immune responses commonly called “food allergies.”
And the Harvard group noted that a vitamin D deficiency would also increase the chances of developing a food allergy, because of the hormone-like vitamin’s role in regulating immunity.
They made the obvious point: “We propose that early correction of vitamin D deficiency might promote mucosal [intestinal] immunity, healthy [intestinal] microbial ecology, and allergen tolerance and thereby blunt the food allergy epidemic in children” (Vassallo MF et al. 2010).
Population studies link asthma to vitamin D deficiency
During the 1960s, rates of asthma and allergic diseases began to rise worldwide, with more than 300 million people now affected.
Three years ago, researchers from Boston’s Brigham and Women's Hospital took note of growing epidemiological evidence that associates low vitamin D levels to higher risk of asthma (Litonjua AA et al. 2007).
Accordingly, they proposed that lack of sunlight may be a chief cause of both vitamin D deficiency and asthma.
As they wrote, “We hypothesize that as populations grow more prosperous, more time is spent indoors, and there is less exposure to sunlight, leading to decreased cutaneous vitamin D production” (Litonjua AA et al. 2007).
(“Cutaneous” means “relating to the skin”, and “cutaneous vitamin D production” simply refers to the fact that vitamin D is produced in human skin upon exposure to the sun’s UVB rays.)
The Boston team noted that—coupled with inadequate vitamin D intake from foods and supplements—lack of sunlight leads to vitamin D deficiency, “…particularly in pregnant women, resulting in more asthma and allergy in their offspring”.
In fact, vitamin D has been linked to the development of fetuses’ immune systems and lungs.
And population studies suggest that higher vitamin D intake by pregnant mothers can reduce asthma risk by as much as 40 percent in children three to five years old.
As the Boston group wrote, “Providing adequate vitamin D supplementation in pregnancy may lead to significant decreases in asthma incidence in young children” (Litonjua AA et al. 2007).
Providing more evidence of this previously overlooked link, vitamin D deficiency and asthma are both more common in obese individuals, African Americans, and darker-skinned immigrants to western countries who come from sunnier climes.
Dark skin blocks the sunrays that create vitamin D, and D deficiencies are more common among urban African Americans, who presumably get less sun than their rural peers (Yanoff LB et al. 2006).
The higher rates of deficiency seen in obese people stem from the fact that vitamin D tends to concentrate in body fat, where it is less “bio-available” for essential needs (Wortsman J et al. 2000; Alemzadeh R et al. 2008).
Vitamin D could reduce mold allergies
Two recent studies linked lack of vitamin D to increased rates of mold allergies among asthmatics and people with cystic fibrosis (CF).
Allergies—especially to a common mold called Aspergillus fumigates—can cause often severe complications for asthma sufferers, and commonly affect CF patients.
This particular mold is one of the most commonly inhaled by humans, but does not cause any problems in the vast majority of people.
Up to 15 percent of CF patients have severe allergic responses—called Allergic Bronchopulmonary Aspergillosis (ABPA)— triggered by inhaling this unremarkable mold.
Researchers from universities across the U.S.—led by a team at Louisiana State University (LSU)—conducted a cell study that revealed a connection between vitamin D levels and the activity of certain allergy-associated immune cells (Nguyen et al. 2010).
They found that adding vitamin D to human cells substantially reduced the production of a protein that promotes an allergic response to otherwise normal, innocuous food factors, and also increased production of compounds that promote tolerance of those food factors.
Immune cells from patients without ABPA were found to have higher levels of certain proteins that are essential in the development of allergen tolerance.
And the study revealed that high allergen reactivity in ABPA patients was associated with lower blood levels of vitamin D.
As lead researcher Dr. Jay Kolls of LSU said, “We found that adding vitamin D not only substantially reduced the production of the protein driving an allergic response, but it also increased production of the proteins that promote tolerance.”
The authors also concluded that the study’s outcome “…strongly implicates vitamin D deficiency as a risk factor for ABPA” (Nguyen et al. 2010).
Clinical study in mold sufferers confirms lab findings
The LSU-led team also conducted a small clinical trial in people with ABPA (Kreindler JL et al. 2010).
They compared groups of CF patients who carried Aspergillus fumigates, some of whom showed symptoms of ABPA, and some who did not.
The LSU scientists detected “heightened reactivity” of an allergy-related immune system protein among those in the ABPA group with the lowest vitamin D blood levels.
And when they exposed immune cells from those patients to vitamin D, the treatment beneficially altered expression of two key allergy-related immune system proteins.
As they wrote, “These data provide rationale for a therapeutic trial of vitamin D to prevent or treat ABPA in patients with cystic fibrosis” (Kreindler JL et al. 2010).
Unsurprisingly, the LSU team suggested that vitamin D supplements could help treat and possibly prevent allergic reactions to common molds in people suffering from respiratory conditions.
Dr. Kolls also noted that studies in mice suggest that vitamin D might reduce the risk that people will develop other allergies.
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