When our immune systems let us down, we often reach for the vitamins we should have been taking in the first place.
The phrase ‘closing the stable door after the horse has bolted’ springs to mind. While vitamins can help us boost, tune and enhance our immune response, endeavouring to avoid easily-rectified nutritional deficiencies is the best policy.
Eating a diet rich in these immune-boosting vitamins is key if you wish to not only avoid seasonal colds, but maintain a good state of health year-round.
Also known as retinol or retinolic acid, vitamin A has a crucial effect on immunity – particularly by nourishing the gut mucosal immune system.
This matters a great deal, since 70 to 80% of our immune tissue is actually located in the digestive tract.
What’s more, the multitudinous mucosal surfaces of the body are continually exposed to foods, microbes and toxins, each of which has the potential to trigger an immune response.
Vitamin A helps to maintain mucosal tolerance, helping the gut identify friend from foe. Specific genes responsible for immune responses are also regulated by vitamin A.
Although vitamin A plays a key role, a study published in 2015 suggests that supplementation should only be used to correct a deficiency; and that supplementation over and above typical levels may actually negatively impact the immune system.
Nevertheless, you should be able to get all the vitamin A you need from your diet. Dietary sources include an array of plant and animal-derived foods such as carrots, kale, berries, eggs, sweet potato and organ meats.
Known as a catalyst for multiple biochemicals reactions that take place in the immune system, vitamin B6 is one of the most essential dietary immune-boosters.
While vitamin B12 receives more press, B6 is every bit as vital and helps to improve immune markers such as T lymphocytes and neutrophils. It also manufactures antibodies to combat harmful bacteria and viruses.
In a Taiwanese study from 2006, a two-week course of high-dose vitamin B6 (50-100mg/day) boosted the immunity of critically ill patients.
Foods rich in vitamin B6 include chicken, fatty fish like salmon and tuna, organ meat, whole grains and leafy green vegetables.
Although you should be able to obtain enough B6 from your diet, certain drugs are known to deplete one’s stores. If you feel you need a supplement, consult with your healthcare advisor.
Vitamin B12 is the second immune-enhancing B vitamin, though don't forget that B vitamins work in tandem: it is therefore advised to ensure a plentiful supply of all of them.
Our comprehensive guide to vitamin B is a good resource, and lists both the functions of each nutrient and the best dietary sources.
The problem with vitamin B12, at least in the eyes of vegetarians, is that it can only be found in animal products: eggs, meat, shellfish and dairy. A vitamin B12 supplement is therefore advised.
Our sublingual Vitamin B12 from Frunutta is a good option, as it provides a generous dose of 1,000mcg per micro tablet.
Insufficient B12 impacts numerous processes, but as far as immunity is concerned it reduces your white blood cell count, increasing your vulnerability to infections.
Does vitamin C boost the immune system? Absolutely. In fact, it is one of the most important anti-stress, detoxifying and antioxidant agents in existence.
What a great shame, therefore, that humans are one of few species of animal unable to naturally synthesise the nutrient – since we lack the key fourth enzyme crucial to the process.
Vitamin C bolsters immune defence by facilitating cellular functions of the innate and adaptive immune systems; supplementation also appears to prevent and treat respiratory and systemic infections.
Furthermore, vitamin C protects essential biomolecules from damage caused by oxidants created by toxins and pollutants.
Dietary sources of vitamin C comprise oranges, red and green peppers, broccoli, Brussels sprouts, strawberries and blackcurrants. Though the RDA for adults is just 40mg, many believe that a much higher dose is required for optimal immune function.
Indeed, clinical studies have used anywhere between 200mg and 1,000mg.
If you wish to top up your vitamin C, you can do so sublingually with Frunutta’s ultra pure Vitamin C; each micro tablet supplies 500mg, and there are no chemicals, coatings or fillers whatsoever.
Lastly, we come to vitamin D – probably the best-known immune system ingredient.
So effective is vitamin D that analysis published in the British Medical Journal last year suggests it could spare more than three million Brits from colds or flu each year.
Supplements are actually recommended for all of us during autumn and winter, when sunlight is scarce.
Our immune systems rely on vitamin D to fashion antimicrobial weapons which target bacteria and viruses. Just like vitamin C, it is particularly effective at preventing respiratory tract infections (sniffles, flu, pneumonia etc).
Because food sources are limited, you are best to take a daily supplement. In our own store, you can choose between organic vitamin D3 tablets from Vibrant Health or sublingual vitamin D3 from Frunutta. While the former delivers a 4,000 i.u. dose, the latter is available in two strengths: 1,000 i.u. and 5,000 i.u.
Again, there is some debate over the optimal intake. We tend to err on the side of the Vitamin D Council, who recommend 5,000 i.u per day. This is an amount they say will get most people to achieve a healthy blood level, defined as 40 ng/ml.
One thing which should be remembered is that obese individuals require a higher dosage, just as underweight individuals also require less to achieve sufficient levels.
The Vitamin D Council determined that obese individuals would actually need 8,000 i.u. per day.
Minerals for the Immune System
Of course, vitamins are not the only nutrients which enhance the immune system; minerals help too.
The key immune minerals are zinc, selenium, magnesium, copper, folate and iron. Opinion varies on whether it is possible to obtain enough of each nutrient from the diet, particularly for optimising immunity, with soil erosion usually mentioned.
In any case, a combination of the key vitamins and minerals will keep your immune system firing on all cylinders; and if you can avoid a deficiency of any one of them, so much the better.
Incidentally, you can read more about minerals in our blog “The Function of Minerals”, which gives examples, sources and functions of all key dietary minerals.
Which Other Factors Affect Our Immunity?
While diet is hugely influential on both our immune and inherent health status, we should not overlook the other factors at play.
It is well-known that those born via natural birth and breastfed enjoy higher levels of immunity than their Caesarian, bottle-fed counterparts. This is because our microbial immunity matures and strengthens from bacteria picked up in the birth canal and also from colostrum ("the first milk").
Other factors which influence immunity include exercise levels, sleep, sugar intake, alcohol intake, smoking status, exposure to chemicals, heavy metals and toxins and stress.
Our age, sex, infection history and genetics can also affect our immune system and make us more or less susceptible to illness. Identifying how much bearing to give each factor is an ongoing process in the field of medicine.
The take-home? Eat nutritious food – 10 portions of fruit and veg every day should be the target – and use supplements where necessary. Get plenty of sleep, plenty of rest and maintain a consistent exercise regime without overdoing it: overtraining is actually bad for your immune system.
You would also do well to nourish the beneficial bacteria in your gut: this will help to rebalance your immune system in times of stress or disruption; it’ll also keep the amount of pathogenic bacteria in your gut in check. Eat probiotic foods like sauerkraut, kimchi, kefir and miso.
You can also benefit from taking a high-strength probiotic like Progurt, whose bacteria is derived from healthy humans. One sachet provides a megadose of 1 trillion friendly bacteria, more than any other supplement.