16/02/2016 10:25 AM AEDT | Updated 15/07/2016 12:51 PM AEST

The 6 Most Common Nutrition Myths

Adam and Eve are going to eat an apple
Mallivan via Getty Images
Adam and Eve are going to eat an apple

When it comes to nutrition, it seems the truth just doesn't sell.

As a dietitian, I spend a lot of time debunking nutrition myths, which range from the partly true to the completely ridiculous.

While some of these can admittedly be entertaining, it's also frustrating that so many people are given inaccurate nutrition information that they believe, and even follow, for years to come. I hate to think how much time, effort and money is wasted because of some of these myths.

So I'm busting a few of my favourites:

1. A glass of water with lemon in the morning aids digestion and detoxes the liver

A glass of water first thing in the morning is great, and adding some lemon or other fruit can certainly make it easier to drink. However, it doesn't produce any magical effect.

Lemon is an excellent source of vitamin C, which does have plenty of health benefits, but you would get the same, if not more, benefits from having a handful of strawberries on your cereal, some tomato with your eggs or even just an orange.

Lemon juice can also damage tooth enamel when it's in direct contact with teeth, so if you do love your lemon water first thing in the morning, make sure you have a plain glass of water afterwards.

2. Eating six meals a day boosts your metabolism

Eating regular meals can be a great way to keep energy levels high. It can also stop you from getting so hungry you inhale the first thing you see as you walk in the door at night. But unfortunately it doesn't speed up your metabolism.

If eating five to six small meals per day works for you, go for it. If not, stick to three and rest assured you're not doing your metabolism any damage. There are enough items on your to-do list without having to constantly be planning and prepping your next meal.

3. Skim milk has more sugar than full-fat milk

People often tell me that they don't drink skim milk because of the added sugar, but plain skim milk does not have sugar added to it.

It can be slightly higher in natural sugar (lactose) because the fat has been removed, and it may also taste a bit sweeter because the fat isn't there to round out the flavor, but no sugar is added (unless it's a flavoured milk, which is a different story altogether).

Go for full-fat milk if you prefer, but don't do it under the assumption that you're consuming less sugar that way.

4. You need to drink 2.5 litres of water per day to stay hydrated

We do need around 2.5 litres of fluid per day to stay hydrated. However, this includes all of the fluid we consume, including tea, coffee and the fluid in the food we eat (of which there is a surprising amount -- for example, cooked rice is at least 50 percent water).

Good old water is, of course, the best source of fluid and is preferable to other drinks, but we don't need to be chugging down litres of it each day to stay hydrated.

5. Spinach is a good source of iron

This one is partly true -- spinach is high in iron compared to most other vegetables. But it's also high in oxalic acid, which binds to the iron so our bodies end up absorbing much less of it.

If you're relying on vegetarian sources of iron such as spinach, there is a way around this problem. Vitamin C helps our bodies to absorb iron from plant sources, so have your spinach with a food that is high in vitamin C, such as tomato, capsicum, broccoli, lemon juice or chilli, or drink a small glass of fresh orange juice with your meal.

6. Eating late at night causes weight gain

Food does not become magically 'fattening' once the sun sets, nor are carbs more likely to make you pack on the kilos if you eat them at night.

Many myths are based on a grain of truth, and in this case that grain may simply be that many people overeat at night.

A lot of us are in the habit of having our largest meal at night, and we tend to be really hungry by the time dinner rolls around so it's easy to overeat. Plus, after a long day at work, getting stuck into a block of chocolate while sitting on the couch watching TV can be very tempting.

If you do tend to overeat at night, make sure you're having regular meals throughout the day so that you're not starving by nighttime. Also, think about why you want to eat -- is it real hunger or are you just feeling bored, stressed or wanting to avoid doing something?

Learning to check in with your appetite and listen to your body is one of the best things you can do for your long term health.