Well and good: eating for immunity
A healthy diet can help to support a healthy immune system, but eating too much of the wrong things can make you more susceptible to getting sick this cold and flu season.
So, what should you be eating, and what should you try to cut down on? We had a look at what science had to say, and then checked in with Amazonia in-house dietitian Tara Kaff to ask her about the best ways to keep our immune system firing on all cylinders.
WHAT TO EAT
Go high fibre
A diet that’s high in soluble fibre – the kind found in foods like apples, oats and nuts – can strengthen your immune system, according to research from the University of Illinois, US. The researchers found that soluble fibre changes the “personality” of immune cells, changing them from being pro-inflammatory “angry” cells to anti-inflammatory healing cells that can help your body recover more quickly from infection.
There’s another type of fibre that’s even more important – resistant starch. This is needed for a healthy gut microbiome, and a healthy gut means a healthy immune system.
“Resistant starch is a prebiotic,” Kaff explains. “That’s basically food for the good bacteria in our gut – it’s their fuel source. You’ll find it in things like green banana flour and cooked and cooled potatoes and pasta.”
Cooking potatoes and pasta and then cooling them changes the chemical formation of these foods and allows the resistant starch to be more available to your body.
“A lot of people are scared of carbs, and don’t eat enough,” Kaff says. “I think that’s where people are going wrong, because that’s where we get those prebiotics. It’s all good and well to have all lots of vitamins and minerals from whole foods, but those prebiotics you can only really find in wholegrain, starchy foods.”
Be a herbivore
Eating more plants and less red meat can also keep you healthy. Several studies have found that vegetarians tend to have more stronger immune systems. This is believed to be due to a number of factors, including the fact that vegetarians tend to eat a wider variety of fruits and vegetables, as well as the beneficial effect that a vegetarian diet has on gut bacteria.
“Fruits and veg have all your vitamins and all your minerals, but especially iron and zinc,” Kaff says. “Iron is a co-factor for enzymes that fight unwanted substances in our bodies.”
You can get iron from red meat, but there are plenty of other ways to get iron in your diet.
“Lots of wholegrains contain iron, as do spinach and other green leafy vegetables, as well as red kidney beans and lentils,” Kaff explains.
Leafy greens – as well as carrots, sweet potatoes, pumpkin, red and yellow capsicum, peas and broccoli – are also high in beta-carotene, a powerful antioxidant that’s been shown to increase immune cell numbers and the activity of “natural killer cells” – white blood cells in our bodies that kill any cells infected with a virus.
Zinc is a key mineral when it comes to immunity. It helps your body to fight off any nasty bacteria or viruses that try to invade your body, and even aids in wound healing. One study from Ohio State University, US, found that zinc helps to control infections by “tapping the brakes” on the immune response in a way that stops it from spiralling out of control. You can find zinc in foods like shellfish, nuts and seeds, legumes, eggs and dairy foods.
“Zinc is also a co-factor for the enzymes that help to fight unwanted substances in our body,” Kaff says. “People are very focused on their macronutrients [protein, carbs and fats], but it’s the micronutrients – vitamins and minerals – that do all the background work for those macronutrients. They’re like the driving force for all the chemical reactions in your body that are needed for the body to function at its peak, including the immune system. They help the cells that pick up all these nasty substances floating around in our bodies that can dampen our immune system or make us ill.”
WHAT TO AVOID
Cut back on fast food
Too much salt isn’t just bad for your blood pressure. Research from the University Hospital Bonn, Germany, revealed that mice fed a high-salt diet were found to suffer from much more severe bacterial infections. Human volunteers in the study who consumed an additional six grams of salt per day also showed pronounced immune deficiencies. As a reference, six grams is about the amount of salt you’ll find in two fast food meals.
“The majority of the time, when you have a high-salt diet, it’s from foods that are also highly processed and high in saturated fat,” Kaff says. “Foods that are highly processed and have high amounts of saturated fats or sugar feed the ‘bad’ bacteria in our gut, and that’s what can dampen our immune system. Basically, you’re giving the bad guys what they want.”
Researchers at the University College Cork in Ireland found that a high-fat diet reduces the efficiency of the immune system, making it harder for your body to fight illness. Too much fat in your diet has also been found to impair the function of white blood cells – these are the cells in your body that fight infection.
Cut back on booze
This is a no-brainer when it comes to health, but right now alcohol consumption has increased dramatically as we’re all bored and stuck at home in lockdown.
“Alcohol is not good for our gut,” says Kaff. “And it’s not good for overall health. Our liver, for example, is one of the most important organs in our body. It helps to regulate the immune system. Having too much alcohol – enzymes in the liver break down alcohol, which is a toxic substance – puts a lot of stress on the liver as it works to get rid of it, and this works to dampen our immunity. When the body is stressed it can’t fight infection as well. “
Instead of slugging back a few wines after dinner, switch to water. “Staying hydrated is so important,” Kaff stresses. “Our body is 70% water, and every single chemical reaction in our body uses water, including the reactions needed to fight infection or any sort of virus.”