Nutrition and immunity: the facts

Kate Freeman

The internet is full of rubbish information about health. True story. Here are some facts about colds, flus, immunity and nutrition that are actually true!

The difference between a cold and the flu

Cold

Lasts anywhere from three days up to two weeks.

Symptoms: cough, sore throat, watery to whitish nasal fluid/discharge and may also cause low fever, body aches and a little fatigue.

Progression of symptoms: sore throat, nasal discharge or blockage, headache, fever and body aches, cough.

Flu

The severe and initial symptoms last about two to five days, but coughing and tiredness can last for two to three weeks longer.

Symptoms: fever over 39 degrees (key symptom), chills, sweats, headache, extreme body aches and tiredness, may also cause a cough and sore throat.

The key difference is the presence of a high fever and the rapid and widespread onset of the flu. No more over exaggerating when you call in sick to work – it’s not likely that you have the flu. Colds are much more common. Both are caused by viruses.

Natural remedies/prevention

Is it true?

Remember the teaspoon of honey that mum gave you in the middle of the night for a bad cough? Is that an actual thing?

A large, outpatient study found that honey was rated superior by parents for their kids’ night time coughing and sleep issues. These finding are preliminary, however, and more research is needed for stronger conclusions.

Is it true? 

Good gut bacteria boosts your immune system.

Some studies suggest that a probiotic supplement with particular strains of good bacteria can reduce the duration and severity of a cold or flu.

Is it true? 

Drinking lots of fluids is important when you have a cold or flu.

Interestingly, there is actually no evidence for this in the literature, but there’s also no evidence that it causes harm either. So drink more if you want to, but just drinking the same as you would normally to stay hydrated is totally fine.

Is it true? 

Gargling and saline nasal irrigation is good for you.

Gargling with water and nasal irrigation with saline solution multiple times a day can flush microbes from the oral and nasal cavity and help prevent you from getting sick.

Is it true? 

Starve a fever?

Hippocrates used starvation to treat fever, a method which persisted until the early nineteenth century when Dr Robert Graves revolutionised common practice from ‘starve a fever’ to ‘feed a fever’. The main reasons you don’t want to starve a fever is because starvation boosts immunity towards bacteria infections, but reduces immunity to viruses and most fevers are viral in origin. Feeding is usually the best way to go, as well as common sense. Always see your doctor if you’re not sure!

Is it true? 

Garlic will boost your immune system. Suck on a raw clove. Take supplements.

There’s actually some great research around garlic and its health promoting properties. Not only does it aid your immune system, but as a rich source of sulphur compounds it may have antimicrobial and anti-cancer activity as well.  It’s also a good source of fermentable carbohydrates and can feed your gut bacteria.

You don’t need to suck on a raw clove or pop supplements to reap the benefits. Include it regularly in your cooking and don’t be afraid to add lots!

Vitamins and Minerals

Research has identified certain vitamins and minerals that play a specific role in assisting or boosting the ability of the immune system to ward off disease. These are:

  • Vitamin C
  • Beta-carotene (vitamin A)
  • Vitamin D

It’s all well and good to know this information, but we don’t eat individual nutrients, we eat whole foods which are a combination of thousands of different nutrients and chemicals. Because of this, it’s very difficult to study the effects of individual nutrients on the human immune system and I would argue that even though there is evidence to support the involvement of these nutrients, it’s most likely the combination of naturally occurring ‘chemicals’ in food that work together to get our body fighting fit.

Vitamin C

Is it true?

Downing lots of vitamin C tablets when you feel a throat tickle will ward off your cold.

Vitamin C plays an important role in cell mediated immune response including macrophage and lymphocyte function as well as phagocytosis. How cool are those words? So sciencey!

Before you go all gangbusters chewing on a bottle of orange tablets, be mindful. Vitamin C only helps you if you’re consuming adequate amounts each and every day. If your vitamin C intake has been poor prior to your throat tickle, it’s too late for vitamin C to do its work. If your vitamin C intake is good day to day, it won’t stop you from getting a cold but it’ll reduce the length and severity of it.

How can I increase my vitamin C intake? 

Fruits and vegetables are your best source of vitamin C! Very high amounts are found in red capsicum, oranges, kiwi fruit, grapefruit, broccoli and moderate amounts in most other fruits and vegetables.

Try these recipes:

Vitamin A

Is it true?

Carrots, rich in beta-carotene, help you see in the dark. This is a super power which I’m sure is related to immunity boosting (joke).

When you eat beta-carotene it gets converted into vitamin A by your liver. Vitamin A is important for healthy eyesight, however, it doesn’t actually give you night vision. Research does show, however, that adequate intake of vitamin A can actually help prevent colds and flus from taking hold. This is because vitamin A protects our mucous membranes.

Sound a bit technical? Mucous membranes line our mouth, nose, throat and breathing passages and thus strong mucous membranes are more resistant to virus and bacteria that can cause infection. It is also involved in the production of tears, saliva and sweat which also contain antiviral and antibacterial properties.

This is possibly one nutrient where it’s worth upping the intake of once you’re feeling that little throat tickle. Again, no rushing off for supplements – vitamin A is stored by the body and as such it can build up to levels that start to become toxic.

Vitamin A toxicity can occur when intake from supplements are 5-10 times the RDI level. A safety Upper Level (UL) limit was set at 3000ug/day. Acute toxicity can be in the form of a stomach upset, headache, blurred vision and poor muscle coordination, but these symptoms disappear if the dose is stopped. Chronic toxicity shows a range of symptoms and can result in coma or even death. You’re better off getting your vitamin A from beta-carotene found in food.

How can I increase my vitamin A intake? 

One of the highest food sources of pre-formed vitamin A is pan-fried beef liver. If this doesn’t float your boat or you’re vegetarian, beta-carotene is generally found in yellow or orange vegetables. It’s so abundant in these vegetables that you’ll have no problems meeting your body’s vitamin A requirements. The RDI for adults is 900ug of vitamin A per day for men and 700ug of vitamin A per day for women. One large carrot has approximately 1200ug, so one carrot a day will also help keep the doctor away! Choose sweet potato, pumpkin, yellow capsicum, spinach, carrots, rock melon and red capsicum.

Try these recipes and food ideas:

  • Cumin & Sweet Potato Soup
  • Carrot & capsicum sticks with hummus
  • Roast sweet potato, carrot, capsicum & zucchini salad with spinach leaves, cashews, avocado and feta or haloumi (ummm yum!)

Vitamin D

Is it true? 

You’ve got a cold. Your mum (or significant other) says: Go sit out in the sun, it will do you good.

Vitamin D is not technically a nutrient.  Nutrients, by definition, are essential for the body, but must be consumed through the diet. The body actually makes its own vitamin D when the skin is exposed to the sunlight. So you don’t need to eat it, but you do need the right conditions in order for your body to make enough. It’s also not abundant in the food supply, so it’s hard to meet our daily needs with even the healthiest of diets.

Vitamin D has been linked with a good immune system, however, you need to have an adequate vitamin D status for a minimum of three months or so before it will benefit you. So although sitting out in the sun and fresh air might make you feel better – because chilling in the sun is lovely – it’s probably not going to make that cold or flu go away quicker.

How can I increase my vitamin D intake? 

There are two ways humans can source vitamin D:

From sunlight

It is almost impossible for the human body to source enough vitamin D from food so adequate sunlight exposure is the best way. Canberra is known for its deceptive winter days: it looks nice and warm and sunny through the windows even though it’s actually freezing. Take advantage of this, rug up and take a walk in the sunshine – the skin on your face will absorb as much vitamin D as it can while you are out!

From food

The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils have some vitamin D. Some juices and yoghurts are also be fortified with vitamin D which is a good option for vegetarians. For vegans the best food source of vitamin D is cereals that have been fortified with vitamin D. If you leave mushrooms out in the sun for an hour or so before you eat them, they will make vitamin D too!

Recipe to try:

Salmon, Crispy Potatoes, Garlic & Almond Vegetables

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Kate Freeman

Kate Freeman is a Registered Nutritionist and the founder and managing director of The Healthy Eating Hub. Kate’s healthy eating philosophy is all about whole, fresh foods, being realistic about life and creating long term healthy eating habits. She doesn’t believe in detoxes, fad diets or quick fixes. Once you’ve finished working with Kate, you’ll be empowered to feed yourself well for the rest of you life! More about the Author

  • I love this article! Very useful information, thanks.