What foods are bad for the immune system?

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Qualified Nutritionist (BSc, MSc, RNutr)
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14 May 2021

What foods are bad for the immune system?

Foods combining sources of refined sugars and processed ingredients could risk compromising your immune system and its functions, therefore putting us at greater risk of infections. Some high-risk foods can include: sugary foods including sources of refined carbs, salty foods, bad fats heavy in omega-6, plus, copious processed or red meats.

Throughout this blog I explain why these foods could be harming your immune system, and offer some suitable alternatives instead.

1. Sugary foods

Just like fried or fatty foods as we'll go on to discuss, refined sugar is an obvious health risk, but it may be even more prevalent in our society than we first realised.

Sugar isn't just found in chocolate bars and boiled sweets – it can lurk in yoghurts, fruit juices and sources of processed carbohydrates such as white bread, pasta and rice too. Although most guidelines recommend around 30g of sugar a day, you can find almost half of this in some fruit juices and nearly double in specialised lattes and hot chocolates!

While this intake of sugar can exacerbate skin problems, upset your sleep patterns and interfere with your digestion, it could also affect your immune system by promoting unnecessary inflammation, and may even more directly inhibit some of the immune cells that we rely on for attacking pathogens. (1)

What should I have instead?

A little good quality sweetness is fine now again; such as some good quality dark chocolate or a homemade, whole-fruit based dessert.

Then, why not work on reducing some of the load of hidden sugars in your diet elsewhere, such as by reducing some of the sources of refined carbs you are eating; try opting for brown varieties of rice or pasta instead or why not go fort some homemade breads from the bakery section in supermarkets rather than the sliced, pre-packaged options which tend to be higher in lower-quality carbs.

Also, if you're worried about the effects of excess sugars, adding some extra vitamin C into your diet can be a useful way to help counter some of the more negative side effects; seeing as sugar and vitamin C can end up competing for receptor sites that can influence the functions of your immune cells. (2)

Finally, for some extra, added protection, why not opt for a supplement such as Immune Support which not only has some vitamin C in, but also some additional nutrients for optimal immune support including vitamin D and zinc.

Boost your Vitamin C intake with Immune Support

• Rich in naturally occurring vitamin C
• Made with acerola cherries, which contain up to 100 times more vitamin C than oranges (1)
• Nasturtium extract is also a very rich source of vitamin C (2)
• A great source of zinc & also contains vitamin D
• Zinc, vitamin C and vitamin D help support the immune system
• Vitamin C reduces tiredness and fatigue
• Convenient one-a-day tablet

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2. Salty foods

Much like sugar, whilst many of us might assume that we don't add copious amounts of extra salt to our diets; unfortunately the high presence of processed foods in the typical Western style diet is where we fall down. It is these foods which are thought to contribute to the vast majority of out total salt intake.

Read my blog: 'Too much salt weakens the immune system' for some more details on how exactly excess salt could be having a negative effect.

What should I have instead?

Once again, my thoughts are that cutting down on the amount of processed items that we include in our diet, can go a long way in terms of tackling our excess salt consumption.

See, adding a little salt in the form of something like Herbamare when cooking fresh foods is fine, and we are then very unlikely to go anywhere near the recommend 6g of salt per day by just using salt for seasoning in this way.

3. Bad fats

Once again, unhelpful fats tend to be hidden in lots of processed foods, as well as some of the more obvious options like fried foods. It's been hypothesised by researchers that these fats which are omega-6 heavy, may be capable of weakening your immune system by contributing to underlying inflammation.

One study, in particular, backed this idea by showing that by reducing your intake of fatty, fried foods, it could help to restore some of your body's natural defence mechanisms, which had otherwise been unknowingly depleted. (3)

What should I have instead?

It's a common theme, but cutting down on processed items as well as more obviously fried foods, can help to limit your intake of unhelpful, potentially immune-compromising fats.

Then, if you're wondering where to start when it comes to cooking oils, refer to my blog: 'Our guide to the healthiest cooking oils' for my more in-depth guide.

4. Processed meats

Red meat can be considered as a good source of iron and other nutrients, so most experts don't see a problem with including a little red meat in your diet, when in moderation of course.

However, moderation is key and unfortunately, many of us simply eat far too much red meat which can then risk having some unhappy consequences for our health, as elaborated in one recent study by the University of California. This research found that red meats such as beef, lamb and pork, contain a unique sugar, Neu5Gc which is naturally produced by carnivores but not omnivores such as humans. (4) Therefore, when large amounts of red meat are consumed, your immune system may potentially recognise this sugar as a pathogen and inspire a low-grade inflammatory immune response.

Arguably, some of these ill-effects may be even more apparent when processed meats come into the equation. Whilst nutrition studies can often struggle to arrive at conclusive cause and effect conclusions, for me, the quality of the meat you eat is likely to have a big bearing on the overall effects on health.

Processed meat options such as sausages, bacon, burgers or cured meats often contain some of the more worrying ingredients we've already mentioned throughout the blog including hidden sugars, salt and poor-quality oils; therefore there could be a number of underyling factors at play.

What should I have instead?

In my expert opinion, a little good quality meat is fine; but for those who admit they could perhaps work on reducing their intake a little, why not work on having a couple more meat-free days per week, or even try to include more fish instead?

Remember, not only can we often benefit from reducing certain things from our diet, but we can also benefit from what we put in instead; such as some anti-inflammatory omega-3 in the case of some lovely oily fish options including tuna, salmon, kippers, herring or trout.


Originally published on 25/04/18, updated on 13/05/21

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