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Eating for Immunity- Can Diet Prevent Infection?
By Elaine Guinan on January 30, 2017
By Elaine Guinan on January 30, 2017
Flu season is upon us once again, and for many of us it can see like it’s impossible to avoid catching a bug. No one likes to feel ill, and there is a whole industry built around supplements and foods which claim to super-charge your immune system. While the thoughts of being able to take something to make you invincible to bugs sound appealing, does the science back it up? Let’s look at the facts.
Every day, we are exposed to numerous germs; however a number of factors determine whether you actually get sick from this exposure. One is pre-existing immunity, either from being previously exposed to a similar strain of the disease before, or through a vaccine. Another factor is the ability of the body to mount an immune response which prevents the infection from taking hold. Good nutrition is essential to allow this response to occur.
When the body mounts an immune response, it creates antibodies which defend against the bug trying to cause infection. Adequate macronutrients (i.e. carbohydrates, proteins and fats) are needed for the body to produce these antibodies, hence having a poor intake of macronutrients severely reduces the immune system’s ability to respond to infection. This is why malnourished patients are at increased risk of infection.
Micronutrients also play a vital role in many aspects of immunity. The most well-known micronutrient when it comes to colds and infections is vitamin C. Vitamin C plays a role in immunity by stimulating the formation of antibodies. Contrary to popular belief, studies have shown that taking vitamin C does not prevent you from catching a cold. Taking vitamin C regularly may shorten the length of time one suffers from a cold, but only by a small amount. Brightly coloured fruits and vegetables are full of vitamin C. These include oranges, lemons, bell peppers, strawberries and tomatoes. White potatoes are also a great source of vitamin C.
Vitamin A plays a role in maintaining skin and gut barriers, and in immune cell function. It is found in sweet potatoes, red bell peppers, carrots and leafy green vegetables among others.
Vitamin D helps to regulate the immune system, and stimulate the production of antimicrobial proteins. Dietary sources of vitamin D include eggs, oily fish (such as salmon) and fortified products such as milks and spreads.
Vitamin E is an antioxidant found in vegetable oils, nuts, seeds and green leafy vegetables. Studies have shown supplementing vitamin E may increase immunity in older generations, but this must be confirmed by further studies.
Zinc plays an important role in immune cell formation, and can be found in meat, dairy foods, wholegrains, nuts and pulses.
Should I take dietary supplements?
There are many other supplements available which claim to boost immunity, such as echinacea or ginseng. To date, there is no scientific evidence proving that any of these supplements are effective. Furthermore, taking supplements if you are a cancer patient can be dangerous, as they can interact with treatment medications and cause issues.
Nutrition has a huge role to play in immunity, however there are no specific nutrients or supplements you can take which can prevent infection. The best method of ensuring your immune system is up to scratch is by eating a wide variety of foods which will provide your body with the nutrients needed to mount a good defence. If you feel your diet is lacking, speak to your doctor or dietitian about whether a supplement may be needed.
Gandy, Joan. The Manual of Dietetic Practice, Fifth Edition.