There are a lot of theories on how to boost the immune system to ward off diseases, particularly in reference to cold and flu season, when people are most concerned with avoiding illness when everyone around them seems to be sick.

But is there any truth in these theories? Let’s look at a few of the most common myths about your immune system, and the facts you need to stay healthy all year round. Are they true or false?

Myth 1: Eating more fruits and vegetables can keep your immune system strong

Fact. It is not simply an old wive’s tale that eating your fruits and veggies will keep you strong. Studies have shown that people who eat them regularly tend to be healthier than those who do not. They offer a range of nutrients that can help your immune system fight viruses and bacteria.

Try to eat fruit and vegetables of all the colors of the rainbow every day so you can ensure you’re consuming a variety of antioxidants and phytochemicals, or plant-based nutrients, to fight off disease.

Myth 2: Vitamins and supplements can help ward off illness and make you feel better faster

This is partly true. A good daily multivitamin can help fill in any gaps in an otherwise healthy diet, but it is no substitute for high-quality nutrition from a range of all-natural foods.

Then there are those who take high doses of Vitamin C to ward off colds. This can be of great benefit. Vitamin A is also important to the immune system, though it’s important not to take too much because it can be stored by the body, leading to Vitamin A toxicity in larger doses.

Many companies are now selling cold prevention remedies with zinc in them, which promise to ward off colds, or relieve symptoms more rapidly. Many of them are used in the nostrils.

While some of these products have been shown to have some benefit in warding off colds, they have also been shown to cause potentially permanent loss of smell. Plus, not all colds and flu enter the body through the nose.

Myth 3: Getting enough sleep can boost your immune system

True. There’s a strong link between sleep and a healthy immune system. The main point to remember is that it should be high-quality sleep—that is, deep sleep that offers the body and mind refreshment and healing.

Most studies agree that the average adult needs 8 hours a night. However, recent studies have also shown that sleeping too much can have a negative effect on your health.

Occasional insomnia should not be an issue, but if it becomes chronic, you should take steps to improve the quality and duration of your sleep. Otherwise, sleep deprivation can lead to you feeling run down, leaving your immune system weakened and you vulnerable to disease.

Get into a good sleep routine of regular bedtimes and rising times, and see what a difference it can make to your health.

Myth 4: Covering your mouth when you cough can keep germs at bay

False. This can help you stop the spread of illness, but do little to help you ward off illness unless everyone in your household and immediate environment does the same.

Don’t forget that viruses like cold and flu germs can also survive on a range of surfaces such as doorknobs, phones, countertops and more. Wash your hands often and avoid touching your face, especially nose, mouth, and eyes while sick and when around sick people.

Myth 5: A positive mindset can boost your immune system

True. A good outlook may be good for your health. One study of law students showed that their immune system was directly affected by their thoughts about their studies.

If they felt things were going well, they had a better immune system. When they were worried, their immune system slowed. Therefore, looking on the bright side is not just good for you mental health, but your physical health as well.

Now that you’ve separated myth from fact in relation to your immune system, you can use what you’ve learned to help strengthen your immune system and ward off disease.