26/04/2020
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The foods that can hinder your immune system
Plus, the best foods to include in your diet to boost it.
by JENNIFER SAVIN APR 24, 2020
ingredients for healthy breakfast, shown on a pink background, including cereals, grains, dairy products, seeds, nuts to illustrate a story on how to keep your immune system healthy
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We all know how important diet is when it comes to, well, pretty much everything. It affects how well we sleep, our mental health, and our energy levels. But it can also play a big part in keeping your immune system healthy, says Alex Ruani, UCL Doctoral Researcher and Chief Science Educator at The Health Sciences Academy.
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"A nutritious diet that supports the immune system might help fight viruses more efficiently and faster," she explains. "But it's important to be aware that it cannot lower your risk of contracting an infection in the first place (nothing can prevent that other than a vaccine)."
While research on the impact of diet and coronavirus in particular is still very recent, Alex explains that essential nutrient deficiencies can result in a weakened immune system in general (and therefore a reduced ability to fight off an infectious disease). Here, she advises which foods to eat more of (and what to avoid) to keep your immune system in tip top shape.
What foods can hinder your immune system?
Similar to the way that there isn't strictly one food that can work wonders for your immune system alone, there's no one food that can mess it right up. However, there are certain dietary traits that can have a negative impact, explains Alex. They include the following:
Too much salt
Currently, it's recommended to eat less than 5 grams (1 teaspoon) of salt a day (but it's estimated more than half of that intake comes from food we eat (hello, soy sauce), rather than sprinkling extra on your chips). Avoid adding any to meals where possible.
a pile of salt and a salt shaker on a pale blue background, to illustrate too much salt can impact on your immune system's ability to function
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Too many calories
"There’s a misconception that malnourishment is exclusive to people who are underweight – more calories doesn’t always mean more essential micronutrients and good immunity." Many of us are ‘overfed’ yet malnourished (lacking the essential nutrients needed to keep your immune system functioning well), Alex says. "What’s more, excess body weight results in a poorer initial response to a pathogen, plus impaired immune cell proliferation, diversity, and functioning," she also notes. "For example, we know that during the 2009 influenza pandemic, obese individuals had higher infection and mortality rates, compared to those of a healthy weight."
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Alcohol
"The general evidence shows that alcohol intake weakens the immune system and undermines the body's ability to cope with infectious disease," says Alex. "It may also decrease the production and function of cytokines in the body, which are necessary to respond to pathogenic viruses and bacteria." Check out Cosmopolitan's tips on how to cut down on booze for help.
glass of red wine alcohol and your immune system
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What foods are good for boosting your immune system?
"There’s no single food that has a miraculous effect on our immunity," says Alex, explaining that we need a variety of foods to provide a range of nutrients. She recommends a diet made up of the following:
Fibre
"If your gut bacteria isn’t getting enough fibre to produce short-chain fatty acids, the immune cells won't function at their best," explains Alex. Whole grains (oats, rye, quinoa, brown rice), root vegetables (carrots, sweet potatoes, squash), fruits (apples, pears, banana), cruciferous vegetables (broccoli, Brussels sprouts) and legumes (red beans, lentils) are all good sources.
a photo of eggs and cottage cheese, which provide all eight amino acids needed as part of a diet that contributes to a well functioning immune system
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Amino acids (protein)
"Protein is made up of amino acids, which are required for proper functioning of the immune system," says Alex. "Deficiency of essential amino acids may lower immune function capabilities and immune cell replication." Foods such as fish, chicken, eggs, yogurt, and cottage cheese provide all eight essential amino acids, making them well worth stocking up on.
Plant-based foods alone may not give you all eight essential amino acids needed for good immune function, meaning vegans need to ensure they're combining a variety of plant foods (including leafy greens, root vegetables, seeds, beans, lentils, and grains like quinoa, oats, and rice) to get a decent hit.
Omega 3 Fatty Acids
"A deficiency lessens immune response, as they have antioxidant and anti-inflammatory roles," says Alex. Get a good hit by eating fish, namely mackerel, swordfish, marlin, fresh tuna (not canned), salmon or sardines. If you're not a fish fan, egg yolks and algae will do the job nicely.
"Equally, the body can make its own EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) found in these foods," she adds. "Do this by eating flaxseeds, walnuts, chia seeds, shelled h**p seeds, and sunflower seeds."
foods to help immune system demonstrated by a bowl of walnuts which are an excellent source of omega 3 acids
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Vitamin A
"A deficiency increases our susceptibility to infections," notes Alex. "Vitamin A helps with the functioning of innate immune cells such as macrophages, as well as T-cells (lymphocytes) and the generation of an antibody response." Key food sources include beef liver, veal liver, milk, cheese and yogurt, or beta-carotene heavy choices, such as carrots, cabbage, butternut squash, sweet potatoes or melons. Pumpkin, mangoes, tomatoes, broccoli, apricots, papayas or tangerines will also earn you top marks.
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Vitamin B6
A deficiency in Vitamin B6 lowers immunity and increases risk of infection - so you want to make sure you're getting enough. It's also essential for protein digestion and making new immune cells. "Get a hit by eating salmon, turkey, red kidney beans, cauliflower or peppers." Bananas, squash, broccoli, asparagus, Brussels sprouts, lentils and eggs are all excellent go-tos too.
foods that can help boost or hinder your immune system demonstrated by a picture of bell peppers and cauliflower which are great sources of vitamin b6
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Vitamin C
A deficiency in vitamin C can increase the severity and duration of symptoms resulting from an infection (not ideal tbh). "Vitamin C also plays a role in anti-microbial and natural killer (NK) cells function," adds Alex. "Plus, it can increase blood levels of antibodies." Get a dose from greens including cabbage, broccoli, spinach, peas and cauliflower, or fruit such as strawberries, lemons, kiwis, melons, oranges, grapefruit, limes or tomatoes. With plenty of choice there's no excuses.
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Vitamin D
"A deficiency both increases susceptibility to infection and worsens the severity of symptoms," says Alex. Avoid this by including fortified cereals and fortified vegan milks in your diet, or some of the other foods on his handy list.
Iron
Looking for the science behind why iron is so important? "Iron aids a rapid response of the immune system to a pathogen (a nasty virus)," says Alex. "It's also necessary for the health of immune cells and is involved in antioxidant responses." Nuts and seeds are a great source of iron, in particular pumpkin seeds, almonds, cashew nuts, Brazil nuts, pecans, sesame seeds and walnuts. If you're not into seeds and nuts, dry pork, dates or raisins.
close up of raisins in bowl on cutting board
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Zinc
"A deficiency may prolong the duration of an infection, such as a cold," notes Alex. "Zinc aids immune cell proliferation and is necessary for the production of proteins needed to fight pathogens too." Find it in ginger root, lamb, pecan nuts, dried split peas, haddock, green peas and shrimps, turnips. Brazil nuts, egg yolks, whole wheat grain, rye, oats, peanuts and almonds contain zinc too.
Flavonoids
This family of phytochemicals are heavy in antioxidants, which limit free-radical damage. "They also exhibit some antibacterial activity and support enzyme function, which is important for immune cells." Green and black teas, citrus fruits, berries, spinach, apples, cacao and soy-based products are all good flavonoid sources.
Probiotics
Probiotics are live organisms (usually bacteria) in a food or supplement. "They beneficially interact with cells of the immune system, like dendritic cells, and improve T-cell function," advises Alex. "Yogurt, soft cheese, tempeh, kefir, sauerkraut, miso, and kimchi usually contain probiotics."
miso soup with tofu and leeks, miso is a good probiotic source which is needed as part of a varied diet to aid your immune system
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JENNIFER SAVIN features writer
Jennifer Savin is Cosmopolitan UK’s Features Writer, specialising in investigative reports, health and relationships, alongside writing the odd entertainment or lifestyle story.
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