Dietitian Katrina Pace cuts through the sometimes puzzling language of gut bacteria — and explains the best foods to boost your immunity during the cold and flu season.
As winter takes hold and we find ourselves exposed to others with ills and chills, we often start to think about what we can do to fight off germs and bugs.'
While you may already know you need to load up on vitamin C and chicken soup, your gut health is relatively unreported territory — and it has far more control over your immune system than you realise.
The inside story
The word immune means ‘free’ or ‘untouched’. And that’s exactly the role your immune system plays to keep you free from those things that may harm you.
A healthy immune system works tirelessly to help you counter a cold, fight off chickenpox or bat away a host of other unwelcome infections.
Your immune system is a network of cells, tissues and organs that work together to keep out a host of pathogens. Pathogens are anything foreign to your body that may harm it. The list is a long one — they might be dust, pollen, a splinter, a virus, bacteria or a range of other harmful substances.
Your body has layers of defences to protect it from pathogens. Your skin is one layer of your immune system — a physical barrier keeping out pathogens. If you cut your skin, bacteria may get through and cause an infection. There’s also the mucous layer that coats the inside of your nose to keep out irritants like dust and pollen.
Listen to your gut
The lion’s share of your immune system, however, is located deep in your digestive system. A whopping 80 per cent of your immune system resides in your gut, making it the largest single immune organ in your body. Think about it — your gut is one of the key places where your immune system encounters lots of foreign objects. Whatever you put into your body has to pass through this system, whether it’s food and nutrients, bacteria, viruses, fungi or parasites.
Many cells in your gut work to release immune agents that affect your whole body, while others only function to protect the lining of the gut. This gut lining allows nutrients to be absorbed into the bloodstream, but acts as a barrier to prevent germs passing from inside the bowel into the bloodstream.
Getting the balance right
Trillions of live bacteria, viruses and microbes live inside your digestive tract as an ecosystem, just like the plants and animals found in a rainforest. Collectively, this system is known as the gut microbiome. We now know that these gut bacteria are essential to help make sure your immune system is working properly.
In a healthy gut, the ‘good’ bacteria tightly control the balance of ‘good’ and ‘bad’ bacteria, so that your immune system works in harmony to fight infection and keep you healthy.
When you eat fibre-rich foods, like grains, fruit and vegetables, your friendly bacteria break the fibre down and produce substances called short-chain fatty acids (SCFA).
One of the roles SCFAs play is to reduce inflammation, which helps to protect the lining of your gut from various pathogens thatcan make you sick.
However, when the balance is out of whack and the amount of ‘bad’ bacteria increase, you become more susceptible to certain illnesses.
Ways to boost your immune system
Try these tips to keep your immune system in peak condition this winter.
1 Choose healthy fermented foods
Kombucha, kefir, sauerkraut, kimchi and probiotic-rich yoghurt contain bacteria and yeasts to help reduce inflammation and boost gut bacteria growth.
Start with 1–2 tablespoons daily and gradually increase.
2 Drink coffee wisely
Coffee contains caffeine, which changes the balance of bacteria in your gut. Coffee contains naturally occurring soluble fibre and phenolic compounds that are food for gut bacteria. But don’t overdo it, and drink plenty of water and herbal teas.
3 Manage stress
Stress influences your gut bacteria, and the growth of certain types of bacteria has been linked to a higher risk of anxiety and depression. Managing your stress can be one step towards improving your gut health and immunity.
Although no studies have yet looked at the impact of stress management on changes in gut bacteria growth, yoga has been found to be as effective as a low-FODMAP diet in managing the symptoms of irritable bowel syndrome (IBS).
4 Mind the fat
A high-fat, Western-style diet of takeaway, fried food and pastries reduces a bacterium which plays a big part in lowering inflammation by making changes to immune cells. So choose healthier fats, like avocado, nuts, extra-virgin olive oil and oily fish.
5 Go for oily fish
Regular omega-3 fats from oily fish, like salmon, are great for your gut bacteria. Omega-3 from fish oils act as an anti-inflammatory to help prevent heart disease and ease the pain of arthritis.
It now appears that omega-3s also work tor educe inflammation in the gut by encouraging or discouraging the growth of certain bacteria.
6 Avoid artificial sweeteners
Many ‘diet’ and ‘sugar-free’ products have artificial sweeteners, such as mannitol and sorbitol, which are known to change gut bacteria.
In fact, if you have IBS and are also following a low-FODMAP diet, these sweeteners can cause bloating and other gut symptoms.
7. Cut back on alcohol
Alcohol can increase the growth of certain bacteria that may cause increases in bacterial toxins inside your gut. Alcohol can also increase inflammation. Spirits may do more gut damage than wine or beer, and the amount and frequency of alcohol intake definitely plays a part in the level of gut damage. You should aim for no more than two standard drinks a day.
8 Eat more fibre
Fibre is your gut’s favourite food, so try to increase your intake of fruit, vegies, nuts and whole grains. Much of the fibre is found in the skin of fruit and vegetables, so leave the skin on wherever possible. Legumes, such as beans, chickpeas and lentils, are another good source of fibre for your gut.
The bacteria in your gut digest fibres to produce short-chain fatty acids, which can help to reduce inflammation and protect against colon cancer.
9 subtract some additives
Emulsifiers are additives mainly mixed with liquids that would not bond naturally — such as salad dressings or mayonnaise — to stabilise them. Sometimes chemicals are used as emulsifiers, and there is some evidence that these types of emulsifiers can cause gaps in the gut lining.
Choose whole foods and try to avoid packet foods as much as possible to help to reduce your intake of emulsifiers.
Your flu-fighting menu
Start the day with a bowl of porridge, topped with kiwifruit, apple and seeds, mixed with probiotic-rich yoghurt. Or try poached eggs on wholegrain toast with sautéed spinach, mushrooms and tomatoes.
Enjoy salad made with leafy greens, cucumber, tomato, red onion, olives and red capsicum, with canned salmon and 1 tablespoon of kimchi or sauerkraut, plus 1 slice of seeded sourdough toast.
Whip up some Chicken tikka with chickpeas and spinach rice.
Round off the day with a handful of unsalted cashews, dip some vegetable sticks in hoummos, and enjoy two refreshing mandarins.
The best foods to cold-proof your body
Eat foods rich in the following components to boost your immunity and help stave off colds and flu.
Zinc may just be the ultimate winter mineral. Scientists have found it can help with ailments from the common cold and diarrhoea to pneumonia and acute respiratory tract infections.
What to eat
Oysters are one of the greatest sources of zinc, but if they don’t tempt you, try a steaming pot of mussels with tomato and garlic.
Consuming probiotics can significantly lower your riskof fever and influenza, two Japanese studies reveal.
What to eat:
Try a probiotic-rich, low-fat plain yoghurt, and top it off with some stewed fruit for a healthy vitamin boost. Ormake a tasty miso soup.
All spices have health benefits, but research has shown ground cumin is particularly good for boosting your immunity.
What to eat:
Add some ground cumin seeds to a wholesome curry, soup, sauce or stew.
Vitamin A helps keep the lining of your digestive tract healthy. This helps to prevent infection because your digestive tract isan important physical barrier to infection and illness.
What to eat:
Choose carrots, butternut pumpkin and sweet potato, which go well in soups, roastsor just simply steamed. Put eggs on your gut-health menu too — just one egg will provide almost half your recommended daily intake of vitamin A.