Winter is nearly upon us, bringing with it one (or even two) of the 200 colds we’re estimated to catch in our lifetimes. But while many of us can’t leave home without tissues during flu season, we all know people who seem to sail through the winter months completely unscathed. Is the secret to their good health a diet rich in immune-boosting vitamins?
An improved ability to fight off a virus could be the sign of a healthy lifestyle. Everything from managing stress to improving sleep and taking moderate exercise have been shown to improve our resistance to bugs. But our diets are known to play a key role in supporting the immune system, too.
Scientists have long been aware that people who are malnourished are more prone to infectious diseases. In fact a whole alphabet of micronutrient deficiencies, from vitamin A to zinc, have been shown to weaken our immune responses,  while having low levels of vitamin D has also been seen in those suffering from autoimmune diseases.
But with so many immune system booster vitamins and cold-fighting supplements available at this time of year, which ones should really be on your Winter shopping list? Read on to find out.
Immune system booster vitamins
The immune system is exactly that – a system. Rather than one single entity, it’s actually a network made up of physical barriers (like the skin and mucous membranes in the nose), organs (like the tonsils and the spleen), bodily processes (such as the lymphatic system) and tiny proteins known as antibodies.
Hundreds of different immune system cells each have their own role to play, too. Some identify invaders, others carry messages to mobilise other parts of the system into action. Some cells even remember how to fight off old enemies if they come back for a return visit.
With a system so mind-bogglingly complex, can something as simple as ensuring you’re eating enough vitamins for immunity really help? Several studies suggest it can. One found that micronutrients are crucial for the development, maintenance and expression of the immune response, regardless of your age or stage of life.
The best vitamins for immune system function were found to be A, B6 and B9, C, D and E. Let’s take a closer look at each one to find out exactly how they support your body’s defences.
Vitamin A and immune system function
How it works: Some vitamins, such as the classic cold remedy vitamin C, boost the immune system in powerful but relatively nonspecific ways. But vitamin A is different. This immune support vitamin has hormone-like properties that can target certain parts of the immune system directly. It’s so effective that scientists once dubbed vitamin A the ‘anti-inflammation vitamin’.
Vitamin A stimulates the production and activity of a kind of white blood cell called a lymphocyte. Lymphocytes attack invaders and help produce proteins called antibodies, which also help us to fight off infections.
But what’s really intriguing is the role vitamin A plays in the mucous lining of your gut. Because the gut lining is in constant contact with allergens, toxins and bacteria from the food we eat, it’s an important physical barrier against infection. Vitamin A helps the gut lining to function optimally, ideally not overreacting when it encounters harmless substances, but still having the ability to kill off the bad guys.
In fact, new research has found that having moderate levels of vitamin A in the intestine can stop the immune system from overreacting to perceived (but harmless) threats, something that’s implicated in autoimmune disorders such as Crohn’s disease.
Where to find it: You’ll find vitamin A in high amounts in cod liver oil (not to be mistaken with fish body oil) and chicken liver, but they’re not to everyone’s taste and should be avoided if you’re pregnant. Luckily, you’ll also find this vitamin for immune system support in sweet potato, butter, kale, spinach, cheese and milk.
Vitamin B complex and immune system function
How it works: From better wound-healing to improving some cases of depression and anxiety, this complex of nine different micronutrients has some well-known health benefits. But two of the B vitamins in particular (B6 and B9) can help our immune systems stay balanced.
Vitamin B6 is used by the body to make immune system cells and can help increase your number of infection-fighting antibodies. It also acts as a messenger between cytokines and chemokines, two signalling proteins used by the immune system whenever it encounters a foreign invader. So useful is B6 when it comes to our health that critically ill patients given supplements of the immune boosting vitamin were all found to show increased immune responses.
Vitamin B9 is also known as folic acid, and it’s particularly useful when it comes to supporting the immune system as we age. T-cells are immune system helpers that can recognise foreign invaders and clone themselves to kill them off. Whenever a virus enters our bodies, T-cells jump into action, proliferating rapidly. As we get older, we naturally produce less and less T-cells as time goes on. Luckily, folate helps T-cells proliferate again, and that’s good news when it comes to your ability to fight off the germs.
Where to find it: You’ll find vitamin B6 in bananas, chickpeas, milk and potatoes while vitamin B9 is found in fortified cereals, leafy vegetables, peas and broccoli.
However, as much as 50% of these essential nutrients can be lost when such foods are heated, canned, frozen or processed. A daily supplement (or high quality multivitamin) can be helpful to ensure you’re eating enough.
Vitamin C and immune system function
Vitamin C is well-known when it comes to helping us fight back against winter colds, and with good reason. Without vitamin C your body can’t manufacture the collagen it needs to make the lining in your nose, gut and lungs – your first line of defence when it comes to warding off germs.
But the advice to load up on hot lemon at the first sign of a sniffle actually stack up? Sadly there’s no evidence that vitamin C can stop a cold once it’s started, no matter how much you take. But a Cochrane review on all the evidence of vitamin C and immune system function found that supplementing could reduce a cold’s severity and duration, meaning at least you won’t feel quite as terrible.
Vitamin C helps our immune response to viruses by increasing the production of white blood cells, enzymes and antibodies. But while immune boosting vitamin C is found in high concentrations in all the cells of the immune system, it’s also easily depleted when you’re fighting an infection, smoking, drinking too much alcohol or training intensively.
Where to find it: You’ll find vitamin C for immunity in blackcurrant, strawberries, red and yellow peppers, kale and citrus fruits. Our bodies aren’t able to store much vitamin C, so we need foods rich in this vitamin daily.
Vitamin D and immune system function
Although widely known for its role in maintaining strong, healthy bones, vitamin D and immunity seem to go hand in hand, too. Several observational studies have shown a strong link between vitamin D deficiency and respiratory tract infections, such as colds, bronchitis and pneumonia.
But deficiencies have also been linked to various autoimmune disorders, where the body starts attacking healthy cells. In fact, 67% of lupus sufferers were found to be deficient in vitamin D, and the more vitamin D they had, the less severe their symptoms.
Vitamin D seems to keep the immune system in check, activating T-cells when they’re needed to fight off an infection, but not allowing them to overreact, making them a good autoimmune vitamin.
But while vitamin D is a true immune system saviour, many of us aren’t getting enough, with pregnant women, people with darker skin, those over 65, children and teenagers found to be particularly at risk.
Where to find vitamin D: Strictly speaking, vitamin D is a hormone rather than a vitamin. It’s made in the skin during exposure to sunlight and found in certain foods such as fatty fish, cheese and egg yolks.
But it’s impossible to get the amount of vitamin D we need from food alone and most of us aren’t getting enough sunshine, either. According to government surveys one in five people in the UK are now thought to be deficient.
The new advice is that everyone over the age of five (including pregnant and breastfeeding women) should consider taking a daily supplement of the immune system boosting vitamin, at least during the winter months.
Based on current research, it’s believed that consuming 1,000 to 4,000iu of vitamin D daily is the only way for most people to achieve healthy blood levels. Taking the best multivitamin for immune system support you can find will help. For example, taking just one Inessa Multivitamin each day will provide you with a clinical 50mcg dose of immune-boosting vitamin D, which equates to 2,000iu.
Vitamin E and immune system function
How it works: More well known as a free-radical-fighting antioxidant, vitamin E is often overlooked when it comes to the immune system. But the body also uses vitamin E to fight off infections and it’s especially useful if we’re not looking after ourselves quite as well as we should.
It’s all to do with our T-cells, the white blood cells that are like the soldiers of our immune systems. Once a T-cell has identified a pathogen, it divides and divides, making clones of itself in an attempt to overwhelm the invader. But this immune response does not work efficiently if a lot of oxidative stress is present, for example if you’ve been smoking, eating a poor diet or burning the candle at both ends. Vitamin E protects the T-cells’ membranes from this kind of damage, so they can successfully fend off the virus.
Several studies have highlighted vitamin E’s effects on this immune response, but the best results were found in a study of elderly male smokers. Those who smoked 5 to 19 cigarettes a day experienced a 69% lower incidence of pneumonia when given vitamin E supplements.
Where to find it: You’ll find this immune system booster vitamin in seeds, nuts and leafy greens along with vegetable oils such as sunflower.
Other immune system supplements
Ingesting vitamins to help immune system functioning is a great way to keep you at your desk while your colleagues are shivering in bed. But they aren’t the only micronutrients your body needs to stay well. Here’s why zinc and probiotics deserve their rightful place among your cold remedies this year.
Zinc for immune system function
How it works: Zinc is one of the most important virus-fighting minerals we can take. Cells in the immune system use zinc to communicate with each other and the important micronutrient also has anti-inflammatory properties that promote wound healing. Some studies suggest that zinc might attach itself to receptor sites in the nose, too, stopping viruses from entering the body.
But zinc is especially important when it comes to warding off infections as we age due to the role it plays in the thymus gland. One of the most important organs of the immune system, the thymus gland produces infection-killing T-cells. But after we reach 40, the thymus gland begins to shrink and it stops making as many T-cells as it did before. By age 65, it barely produces any T-cells at all.
Luckily, when researchers gave zinc supplements to the elderly they found that the thymus gland got bigger and that T-cell counts returned to their youthful levels.
Where to find it: Foods highest in zinc include shellfish, seeds, nuts legumes, meats, whole grains and egg yolks.
Probiotics for immune system function
How it works: A large part of the immune system is housed in the gut, so it’s important to keep it healthy. Although it’s not known precisely how it works, our gut microbiome (the range and quantity of microbes in our gut) directly impacts our immune system.
Probiotics benefit immunity because they help to add more healthy bacteria to our gut microbiome. These live microorganisms, of which lactobacillus, bifidobacterium, and saccharomyces are the most extensively studied, work in several ways. These include blocking bacteria from entering, competing with pathogens for space on the lining of the intestinal tract and enhancing the lining of the gut wall itself.
Probiotics can strengthen immunity in children, too. In one study, children who consumed a probiotic milk had fewer days’ absence from nursery due to respiratory and gastrointestinal illnesses.
Where to find it: You’ll find probiotics in fermented products such as yoghurt, kefir and kombucha, but taking a well-researched probiotic supplement may also be helpful.
The best food for the immune system
Incorporating certain foods and eating habits into your daily diet could give your immune system a helping hand. Put the following on the menu to strengthen your body’s defences.
Eat more fruit and vegetables
Eating a wide variety of fruits and vegetables will ensure you’re getting the best range of vitamins for immunity possible. Citrus fruits, broccoli and colourful peppers may be the obvious choice, but there’s more to ‘eating a rainbow’ than just vitamin C. Spinach and sweet potatoes both contain immune-boosting vitamin E. Peas and beetroot contain zinc. And blueberries are full of flavonoids which have been shown to play a role in the respiratory tract’s defense system.
A sweet treat may give you a boost when you’re feeling under the weather, but it actually does the opposite when it comes to your immune system. Large quantities of sugar can interfere with the ability of white blood cells to destroy the illness-causing bacteria.
Enjoy dark chocolate Brazil nuts
Satisfy your sweet cravings with dark chocolate Brazil nuts (in moderation!) instead. Dark chocolate contains an antioxidant called theobromine which can protect cells from harmful free radicals, while the selenium in the nuts is an immune-boosting antioxidant.
Add some spice
Head for the spice rack at the first sign of a cold. Cinnamon not only smells great, it’s full of antioxidants and can reduce bacteria’s ability to multiply. Ginger has anti-inflammatory effects while turmeric can help regulate your T-cells, activating them when they’re needed, but signalling them to step down when they’re not.
Have some chicken soup
Grandma was right all along. Full of vitamin-packed vegetables, the chicken is high in protein and contains the amino acids you need to make antibodies and T-cells. The warm broth can help dilute nasal secretions while the garlic is particularly medicinal, containing compounds known to improve your body’s ability to fight off viruses.
Drinking water can do wonders for your immune system, helping your kidneys flush toxins from the body. It can also keep your respiratory and nasal passages well lubricated and less prone to infection. Or switch the water to green tea, as this contains flavonoids shown to improve respiratory tract infections.
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