Vitamin A, foods and immunity

Vitamin A is needed for immunity and is cheap

Vitamin A (which is retinol) and immunity

WHO report

Vitamin A has several important functions

helping natural defence against illness and infection (immune system) work properly

helping vision in dim light

keeping skin and the lining of some parts of the body, such as the nose, healthy

Good sources of vitamin A

Good sources of vitamin A (retinol) include:

cheese

eggs

oily fish

fortified low-fat spreads

milk and yoghurt

liver and liver pâté

If you're pregnant you should avoid eating liver or liver products, (NHS, 2023)

Excess vitamin A is toxic.

Vitamin A deficiency

What are the consequences and implications?

Night blindness is one of the first signs of vitamin A deficiency.

In its more severe forms, vitamin A deficiency contributes to blindness by making the cornea very dry, thus damaging the retina and cornea.

An estimated 250 000–500 000 children who are vitamin A-deficient become blind every year,

and half of them die within 12 months of losing their sight.

World’s leading preventable cause of childhood blindness.

Deficiency of vitamin A is associated with significant morbidity and mortality from common childhood infections,

Vitamin A deficiency also contributes to maternal mortality and other poor outcomes of pregnancy and lactation.

It also diminishes the ability to fight infections.

Even mild, subclinical deficiency can be a problem, because it may increase children's risk for respiratory and diarrhoeal infections,

decrease growth rates,

slow bone development and decrease the likelihood of survival from serious illness.

Beta carotene

Red-orange pigment, in plants and fruits,

especially carrots and colourful vegetables.

The body converts beta carotene into vitamin A

The advantage of dietary beta carotene is that the body only converts as much as it needs.

Healthy antioxidant

May prevent cognitive decline

May help lung function

Both may be due to preventing oxidative stress

Foods rich in beta carotene:

Apricots, Asparagus, Broccoli, Carrots, Chives, Dandelion leaves, Grapefruit, (Chilli powder, oregano, paprika, parsley), Kale,

Onions, Peas, Peppers, Plums, Pumpkin, Spinach, Squash, Sweet potatoes.

Role of Vitamin A in the Immune System

Needed for mucous membrane innate immunity (respiratory and GI)

Essential for the normal function of many immune cells such as T lymphocytes

Vitamin A deficiency is associated with severe Mycoplasma pneumoniae pneumonia in children

Beijing, Feb, 2020

N = 122 children, (0 – 15)

52 sMPP

Severe Mycoplasma pneumoniae pneumonia

70 nsMPP

Non-severe Mycoplasma pneumoniae pneumonia

Serum levels of vitamins A, D, and E were measured and compared, and correlated with nsMPP and sMPP.

Results

The age was older in the sMPP samples than that in the nsMPP samples.

(7.12 vs. 4.01)

So older children suffered more severe infections.

Vitamin A deficiency was present in both the nsMPP and sMPP samples.

Vitamin A levels were significantly lower in the sMPP serum than that in the nsMPP serum.

(0.15 vs. 0.19)

Vitamin A deficiency was defined

Deficiency, less than 0.2 mg/L,

Subclinical vitamin A deficiency, 0.2–0.3 mg/L

Normal vitamin A level by 0.3–0.7 mg/L.

So, children with lower vitamin A levels suffered more severe infections.

Vitamins E and D levels were also lower in sMPP children

Vitamin E (7.4 vs. 8.22)

Vitamin D (23.08 vs. 32.07)

Both sMPP and nsMPP did not show a deficiency of vitamins E and D.