The number of small children affected by asthma and allergy is a growing worldwide problem. Vitamin D deficiency is also an increasing problem among pregnant women and newborn babies. Vitamin D is important for a well-functioning immune defense and for that reason, a team of Dutch scientists have looked closer at the relation in a review article. They conclude that having sufficient vitamin D in the blood during pregnancy and the first years of life can lower the risk of developing asthma and allergies. The scientists also observed that vitamin D supplements can lessen the burden of these widespread diseases. Their study is published in Nutrients.
The rate of asthma and allergies has skyrocketed over the last decades, especially in the Western world, including Europe, USA, and Australia. The allergy rate among small children has doubled. In Europe alone, the diagnosis and treatment of allergies are estimated to cost more than 25 billion Euros annually.
Allergies have tremendous health and socio-economic costs because they are linked to a number of symptoms such as asthma, hay fever, itchy eyes, diarrhea, and anaphylactic shock in worst case. According to the “State of the World Allergy” report, around 25 percent of people in western countries are believed to have one type of allergy or another, including food allergy. It is important that science focuses on trying to identify the underlying causes of this explosive growth. Treating the symptoms simply isn’t enough.
The purpose of the new study
Over the last 20 years or so, vitamin D deficiencies have become increasingly common, especially in places such as Europe, the United States, and Australia. It has something to do with things like spending too much time indoors, getting too little sun exposure, changing our eating habits, and being overweight. Blood levels of vitamin D are measured as 25-hydroxyvitamin D3 and vitamin D status is generally divided into three categories: Deficiency (less than 20 ng/ml), insufficiency (20-30 ng/ml), and sufficiency (over 30 ng/ml). These values are based on vitamin D’s role in calcium metabolism and the prevention of rickets. They do not, however, take into account that all the body’s cells need vitamin D for a number of metabolic processes, including the development, activation, and regulation of the immune system. Therefore, many scientists now recommend levels that are above 60 ng/ml to make sure that there is plenty of vitamin D for all these processes.
The Dutch scientists behind the new study found that 54 percent of pregnant women and 75 percent of newborn babies had blood levels of vitamin D that were below 30 ng/ml. They also observed a strong correlation between low blood levels in the mother and in her newborn baby. It is therefore essential for an expecting mother to have adequate levels of vitamin D in the blood so the baby is able to develop a strong, well-functioning, and balanced immune defense. The purpose of the new study was to look closer at how maternal vitamin D deficiency during pregnancy affects the development of the baby’s immune defense and how this may increase the risk of allergies early in life
The development of the baby’s immune defense
The fetus lives in an almost sterile environment. However, at birth the baby is exposed to a host of different vaginal microorganisms. Once the baby has been born, it is exposed to an array of microorganisms from the surrounding environment, which is only natural.
The baby’s innate immune defense consists of physical barriers (epithelial cells in the digestive tract and in the airways), chemical barriers such as antibiotic substances and different proteins. The baby also has various immune cells such as macrophages, dendrite cells, natural killer cells, and mast cells that work together as a team.
Once the baby has been born, it must develop its adaptive immune system and form its own immunity after the initial contact with microorganisms from the surrounding environment. It is also important for the baby to be confronted with virus and bacteria to help activate all parts of the immune defense. The special troops of the immune defense consist of various T cells that work in a highly effective and targeted manner by forming memory cells and a type of immunity. It is important to have the right balance between the different T cells.
T helper cells (Th cells) are the officers of the immune defense and work by doling out different commands and forming signaling compounds called cytokines. Th1 cells stimulate the T killer cells that launch chemical attacks. T killer cells are especially targeted at virus-infected cells. Th 2 cells stimulate the B cells to form various antibodies. Th 2 cells and B cells aim specifically for bacteria and toxins.
Regulatory T cells make sure to curb the immune reaction once the enemy has been defeated. It is therefore the number of and balance between the different T cells that determine the impact of the different immune reactions. If there are too many Th 2 cells and too few Th 1 cells, the risk of allergic reactions increases.
In the case of infections, it is also important to have the right balance between pro-inflammatory cytokines (IL-6, IL-12) and anti-inflammatory cytokines (IL-10, TGF-β) to prevent the immune reactions from going haywire and causing aggressive inflammation and tissue damage.
As mentioned before, the newborn baby is confronted with a host of different microorganisms during and after birth, which is good and completely natural. It is therefore especially important for the baby’s immune defense to be properly prepared the next four months to help it react in a desirable way without uncontrollable reactions such as allergies or chronic inflammation. The immune system is met with many challenges from the time of birth and is not considered to be fully developed before the baby is two years of age.
The bacterial flora and intestinal immune defense
Right after birth, the baby’s gastrointestinal mucosa is colonized by a huge number of microorganisms. Most of them are beneficial and produce enzymes, vitamins, and lactic acid that help maintain a normal pH value and displace other microorganisms that are harmful. The gut’s microorganisms must be controlled in a delicate balance. Some microorganisms may be harmful if there are too many of them or if they spread to certain areas where they do not belong. Everything we eat and drink passes through the digestive tract that harbors around 80 percent of our immune cells and many other vital defense compounds.
The lining of the intestine is called the intestinal epithelium and is the functional barrier of our intestine. This is where our immune cells are found.
The lower part of the small intestine has a particularly large production of antibodies (IgA) that line the mucosa in our digestive tract and airways.
There is a very close teamwork between the gut flora, the immune cells, and other defense compounds. Gut flora disturbances and reduced function of the intestinal immune defense can result in poor digestion, infections, allergies, and chronic inflammation.
Vitamin D and its importance for the immune defense and allergies
Most of the body’s cells have vitamin D receptors (VDR) that affect around 10 percent of our genes by means of different on-off switches. Vitamin D activates both the innate immune defense and the acquired immune defense that has the ability to specialize and form immunity. Vitamin D also helps control the immune defense so it doesn’t overreact.
According to the Dutch study, vitamin D blocks the maturation of dendrite cells which results in lowered production of Th cells. The scientists also observed that the development of regulatory T cells and interleukin-10 had increased, which helps counteract unwanted inflammation and allergic reactions to foreign bodies (allergens).
They saw how vitamin D binds to the epithelial cells and strengthens their barrier function. Vitamin D also contributes to the production of antibiotic peptides that prevent harmful microorganisms from invading the body. Because vitamin D deficiencies are so widespread, the scientists suggest vitamin D supplementation as a way of reducing the disease burden of asthma and allergies. Their study is published in Nutrients.
The Danish Veterinary and Food Administration’s guidelines for vitamin D supplementation of children and pregnant women
Women planning to become pregnant or who are pregnant already should make sure to get enough vitamin D. It is also important that children get extra vitamin D after birth. The Danish Veterinary and Food Administration recommends the following:
Pregnant women: 10 micrograms daily all year round
Babies under 4 years of age: 10 micrograms daily all year round, from the age of 2 weeks until 4 years.
Children and adults with dark skin who avoid sun exposure or wear clothes that completely cover the body: 10 micrograms daily all year round
EU’s Scientific Committee on Food has established the following daily safe upper intake levels for vitamin D: 25 micrograms for babies aged 0-6 months, 50 micrograms for children aged 6 months to 10 years, and 100 micrograms for children older than 11 years and adults, including pregnant and breastfeeding women.
Common reasons why children and fertile women lack vitamin D:
Daniela Briceno Noriega and Huub F.J. Savelkoul. Vitamin D and Allergy Susceptibility during Gestation and Early Life. Nutrients 2021.
University of Copenhagen. Vitamin D crucial to activating immune Defences. 2010
Margherita T. Cantona et al. Vitamin D and 1,25 (OH)2D Regulation of T-cells. Nutrients 2015
Urashima M, et al. Randomized trial of Vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr 2010
Pernille Lund. Immunforsvarets nye ABC. Hovedland 2012
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