Nutrients, foods and the common cold
It is that time of year again when there are a lot of coughs and colds going around! A question I get asked quite frequently is ‘what foods or supplements boost the immune system’ or ‘what should I feed my kids to stop them getting so many colds?’. From a scientific perspective, foods, ingredients and nutrients can’t ‘boost’ the immune system but good nutrition can help to make sure it is working as it should. However, even with a tip top immune system, it is sometimes impossible to avoid everything – it can be down to bad luck (e.g. walking into a sneeze mist, yuck). The immune system is uber complex and so many different factors can affect how well it functions. Sleep has a big impact on immune function – adult short sleepers have been shown to have an increased risk of developing a cold. Stress, smoking and general fitness may also help determine whether you do or don’t get a cold and how your body copes with it if you succumb to one. Good hand hygiene is something which can really help reduce your chances of getting a cold, but this is often hard to enforce with kids, especially younger ones who want to put everything in their mouths – germs are one thing they are very good at sharing! Young children, under the age of 2 years, typically have around 6 colds a year, mainly due to their immature immune system and exposure to viruses which cause the common cold. The older you get, the less colds you generally get – adults get around 2-3 colds a year and older adults suffer from an average of 1 cold a year.
If you or your children seem to be getting more than your fair share of colds, it is well worth looking at your diet and lifestyle. A healthy, balanced diet, containing all the main food groups will help to provide a wide range of nutrients, which in turn will help your immune system to function as it should.
Micronutrients and the immune system
The micronutrients which are important for the normal functioning of the immune system include;
- Vitamin A
- Vitamin B6
- Vitamin B12
- Vitamin C
- Vitamin D
Let’s have a look at the research findings for some of these nutrients and the common cold;
This is my top nutrient when it comes to colds. For children at least, zinc may reduce the likelihood of getting a cold. Research also shows zinc may be able to reduce the length of a cold in adults. Zinc can stop viruses from replicating and zinc supplementation within 24 hours of onset of symptoms has been found to reduce the duration of the common cold in healthy adults. Zinc lozenges in particular, have been widely studied in adults, and there is a significant reduction in the duration of cold when using these from the start of a cold. However, zinc lozenges and supplements can have quite a bitter taste and can make some people feel nauseous. The following foods are a good source of zinc;
- Some shellfish (including crab, cockles and mussels)
- Nuts and seeds
- Wholegrain breakfast cereals and
- Wholegrain and seeded breads
Vitamin C is well-known for its role in the immune system. Vitamin C deficiency can make you more susceptible to infections. However, it’s role in preventing or reducing the duration of the common cold is not clear cut. For the general population there appears to be no significant benefit to taking vitamin C supplements on a regular basis to prevent the common cold. However, under certain conditions, vitamin C supplementation may be of benefit. For example, vitamin C supplementation helps to reduce the number of colds people who are more physically active suffer. This is likely to be because exercise increases oxidative stress and the vitamin C in the body is used to reduce this oxidative stress, making the vitamin C less available to fight off infections. Individuals who are marginally deficient in vitamin C have also been shown to have a reduced incidence of colds when supplemented with vitamin C. However, vitamin C intakes are generally quite good in the UK. Good food sources of vitamin C include;
- Citrus fruits
- Green vegetables
Vitamin D plays an important role in immune function. There aren’t many good food sources of vitamin D and we get most of our vitamin D in the Summer months from the sun’s rays. However, in the Winter months, the sun’s rays in the UK are the incorrect wavelength to produce vitamin D in our skin and it is very difficult to get all the vitamin D we need from food alone. Therefore, we should all consider taking a vitamin D supplement (10 micrograms per day) from Oct to March (for young children – daily supplement throughout the year is recommended – see previous blog). Some studies show vitamin D supplementation can help to reduce the likelihood of developing a cold, whilst others show no effect, which may relate to whether or not individuals who took part in the studies were deficient in vitamin D. Around 20% of adults in the UK have a low vitamin D status.
What about probiotics?
Probiotics may be helpful in preventing upper respiratory tract infections and the need for antibiotics, but the evidence is inconsistent. This is probably because the probiotics tested in clinical trials varied in types of bacteria, combinations of bacteria, formulations (e.g., tablets, liquids) and quantity (colony-forming units). Probiotics is such an exciting area of research, but currently there is insufficient evidence to recommend probiotics for the common cold.
A variety of other foods and herbals have been studied for the prevention of the common cold. Studies of garlic, ginseng and homeopathy showed unclear evidence of benefit, whereas randomised, controlled studies of echinacea showed no evidence of benefit.
Hard to know who to trust when it comes to nutrition advice? As a Registered Nutritionist (RNutr) with experience in leading clinical research in nutrition and health, I’m able to bring you the facts and dispel the fiction. For nutrition advice you can trust, get in touch. I offer 1-2-1 consultations and workshops on a variety of topics to help you understand how you can improve your diet and health.
Healthy Eating Advice for Adults & Children
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