The world is currently, understandably, focused on boosting immunity. If you have food sensitivities though, it is worth thinking about your immune system even when you’re not concerned about viruses.

We want our immune system to be able to respond rapidly to viral and bacterial infections, as well as remain vigilant and deal with abnormal cells, which have the propensity to develop into cancers. However, the default state should be that your immune system does not respond unless there is a threat about (1). Food antigens, pollen, and perfumed toiletries to our mind don’t constitute threats – but for those of us with allergies or food or chemical sensitivities, our immune system doesn’t seem to have got that memo.

80% of our immune system resides in the gut. If you have incomplete protein digestion, because you are not chewing your food or you lack digestive capacity, for example, and larger protein fragments can make it through a gut lining that for some reason is more permeable than is ideal, these fragments can activate the immune system leading to inflammatory reactions throughout the body. Working to support digestion and gut barrier function is critical in reducing reactivity to foods, but calming down the immune system is equally important.

Dendritic cells

A key player in the gut immune system is the dendritic cell. Dendritic cells are like bouncers. They sit just underneath the gut wall, but can wiggle tentacle-like projections in between the gut lining cells to sneak a peek at what is going on inside the digestive tract. They engulf samples of bacterial or food proteins, break these down, and then stick them like flags on their surface to display to other immune cells. If they decide that what they have captured could be harmful, they can call upon other immune cells to come and deal with the problem (2). However, if they think that the body is not under threat they activate other types of immune cells (regulatory T-cells) to calm down any immune reactivity and so generate tolerance to a food or harmless bacteria.

In certain circumstances dendritic cells can become ‘jumpy’ and launch an immune response more readily. One reason can be exposure to too many undigested food antigens – which brings us back to the importance of digestion and gut lining integrity. Think of that bouncer. If a particular troublemaker started a fight in the past, the bouncer would justifiably get his colleagues to chuck him out of the party if he sees him again. But what if twelve different people all rush the doors at the same time – maybe just one of them might disrupt the party, but as the bouncer is overwhelmed, he might ask his mates to get rid of them all just to be on the safe side…

Having a diverse range, and the appropriate amount, of resident bacteria in your digestive tract can also support immunity. These bacteria can help stimulate the secretion of IgA antibodies, which can bind to food antigens and reduce the amount of them that pass through the gut wall. Also, the short chain fatty acids these bacteria produce when you eat fibrous food and the mucus they stimulate both make dendritic cells more likely to activate regulatory T-cells (1,3)

What else helps?

Having adequate amounts of vitamin A and vitamin D.

Vitamin A is required for the development of regulatory T cells (1). Liver and eggs are good food source of vitamin A, and orange and green vegetables contain beta-carotene which can be converted into vitamin A (though there are genetic variants which mean that some people are less good at this conversion (4)).

Vitamin D may affect how dendritic cells develop – making them more tolerogenic (or less jumpy) (5). The best source of vitamin D is getting your skin exposed to the sun, though fatty fish, liver and egg yolks, and mushrooms that have been in the sun can provide a little. Though it’s been a little sunnier today, supplementing if you live in the UK is often necessary – though I’d advise getting your levels checked to make sure you’re taking the right amount (you can have too much vitamin D).

Lifestyle factors also play a key role in immune system regulation. Exercise and sleep both affect regulatory T-cell function (6,7), and the importance of reducing your stress for supporting reduced food reactivity cannot be overemphasized, as stress negatively affects digestion, gut motility, immune function and sIgA secretion. More on that another time…

If you are experiencing reactions to foods and would like help understanding what is going on, or with supporting your body through diet and lifestyle changes, contact me by email at gemma@intunenutrition.co.uk to arrange a free 15 minute discovery call today.

References

  1. Tordesillas and Berin, 2018 ‘Mechanisms of oral tolerance’ Clin Rev Allergy Immunol. 55(2) pp.107-117 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110983/.
  2. Stagg, 2018 Front Immunol 9: 2883 ‘Intestinal dendritic cells in health and gut inflammation’ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6291504/.
  3. Dain et al., 2017 ‘Detrimental impact of microbiota-accessible carbohydrate-deprived diet on gut and immune homeostasis: an overview’ Front Immunol 8 :548. https://www.frontiersin.org/articles/10.3389/fimmu.2017.00548/full
  4. Leung et al., 2008 ‘Two common single nucleotide polymorphisms in the gene encoding β‐carotene 15,15′‐monoxygenase alter β‐carotene metabolism in female volunteers’. The FASEB Journal, 23: 1041-1053 https://doi.org/10.1096/fj.08-121962
  5. Dankers et al., 2017 ‘Vitamin D in autoimmunity: Molecular mechanisms and therapeutic potential’ Front Immunol https://www.frontiersin.org/articles/10.3389/fimmu.2016.00697/full
  6. Clifford et al., 2017 ‘T-regulatory cells exhibit a biphasic response to prolonged endurance exercise in humans, Eur J Appl Physiol 117(8) 1727-1737 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5506211/
  7. Bollinger et al.., 2009 ‘Sleep-dependent activity of T cells and regulatory T cells’, Clin Exp Immunol 155(2) 231:238 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2675254/

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