The easiest work lunch option known to mankind? Last night’s leftovers in a microwavable container. Done. Easy. Or is it?

Turns out not all foods are made to be reheated. In fact, doing so can can actually cause you to be very, very sick.

These are the six foods experts recommend you think carefully about before packing them into your lunch bag.

1. Rice

Oh, leftover Chinese takeaway, how we will miss you so.

The problem here? The variation in temperature encourages bacteria growth.

“Uncooked rice can contain spores of bacteria that can cause food poisoning. When the rice is cooked, the spores can survive… Then, if the rice is left standing at room temperature, the spores will multiply and may produce poisons that cause vomiting or diarrhoea. Reheating the rice won’t get rid of these poisons,” advises Food Standards Australia ( FSA).

If you must, the FSA recommends reheating all food rapidly to at least 70 degrees and holding it at that temperature or hotter for at least two minutes to minimise the risk.

2. Chicken

It’s common knowledge that poultry, in particular chicken, carries a high risk of salmonella if not prepared or cooked properly.

When reheating in the microwave, not all sections of the food are penetrated equally meaning varying temperatures can encourage bacteria growth.

Watch: Dani Venn shares her delicious hoisin pork rib recipe – too good to have leftovers! Post continues after video

As a protein-dense food, the proteins also break down differently when reheated which can upset the stomach.

We'll be rethinking our chicken lunches. Image: iStock

3. Mushrooms.

It's a similar story for mushrooms, sadly. The proteins deteriorate as soon as they're cut up and reheating 'em will exacerbate this and potentially cause some painful stomach issues.

According to the European Food Council, there's a way round it if you can't bear to think of missing out on that leftover mushroom risotto.

"If they are stored in a fridge and for not more 24 hours, it is in general no problem to reheat mushrooms again at recommended temperatures of 70 C," their guide states. Thanks guys, we'll take it. (Post continues after gallery.)

10 foods you never knew were healthy

Bread

KATIE THOMSITT, Dieticians Australia spokesperson says: "Lots of people shy away from bread to achieve weight loss. But bread is such an important source of fibre, and plays such a helpful role in weight loss and preventing bowel cancer. A couple of slices of a dark, seedy bread per day is absolutely fine."

Cheese

KATIE SAYS: "Cheese is definitely a higher fat source of dairy, but still a good dairy fat. Choose low-fat options if you have it regularly, otherwise consume it in moderation. One serve of dairy is 30g, so a couple of slices is absolutely fine."

Chocolate

KARA LANDAU, The Travelling Dietician says: "Studies have been able to show that dark chocolate can improve insulin sensitivity, reduce blood pressure in healthy individuals, protect against heart disease, and improve HDL good cholesterol (not a bad start for such a tasty food!). Dark chocolate also contains polyphenols, whilst white chocolate does not. These polyphenolic compounds are able to relax blood vessels allowing for better blood circulation, and thereby assisting with the maintenance of healthy blood pressure levels."

Coffee

KATIE SAYS: "Coffee is a really good snack, in particular if its milk-based to get the dairy in - for example, a skim latte. As long as its in moderation - daily guidelines say a maximum of three per day! And you want lots of water on top of that."

Eggs

KARA SAYS: "Yes, even the yolks are good for you! Healthy fat soluble vitamins, as well as half the protein found in an egg, are all found in the yolk!"

Avocado

KATIE SAYS: "Avocado is a healthy fat. Lots of people think its high-fat and not good for you, but its rich in mono unsaturated fats, which give you protection against heart disease. It also helps with controlling lower cholesterol levels."

nuts

KATIE SAYS: "Nuts fall into the same category as avocado - they have lots of healthy oils and fibre."

dairy

KARA SAYS: "Often milk and yoghurts are fortified with Vitamin D (a fat soluble vitamin) which requires a small amount of fat to be present in order for the body to absorb it, therefore having the full fat variety can be of value to enhance the nutritional benefits from the products' consumption. The fat in the dairy also aids with satiety, which could prevent unhealthy snacking at a later point in the day."

Potato

KATIE SAYS: "Potato always gets a bad rap as a starchy vegetable, but it's an excellent source of fibre. Sweet potato in particular is great for weight management and sugar level control. Potatoes are also really rich in potassium."

Red meat

KARA SAYS: People tend to restrict red meat unnecessarily, thinking that its high in saturated fat. "But lean red meat is high in protein, CLA (which has been found to be associated with lower body fat percentages), B12, iron and zinc. These are all nutrients we want to get into our body!"

4. Spinach.

Popeye may have eaten it everyday for breakfast, lunch and dinner, but unless it's fresh you shouldn't be.

Along with other leafy veggies, spinach can often contain high concentrations of nitrates. When heated multiple times, these nitrates become toxic and release carcinogenic properties. The European Food Information Council advises avoiding reheating this food entirely.

5. Eggs.

Eggs can contain traces of salmonella, which when consumed can seriously harm or even kill. The US Food and Drug Administration estimates that salmonella poison is responsible for 79,000 cases of food poisioning and 30 deaths - so it's not to be taken lightly.

Whether they're boiled, scrambled or fried, if you can, avoid reheating. If you must, ensure cooked eggs or egg dishes are immediately refrigerated after serving and heated to over 70 degrees Celsius before being served a second time.

Image: iStock

6. Potatoes.

The issue with potatoes is largely to do with how they are stored after they are cooked.

Leaving them at room temperature and out of the fridge may encourage conditions in which the bacteria Clostridium Botulinum thrives. The situation is worsened if they're kept in foil, which prevents any oxygen from getting in.

The temperature we reheat potatoes at is not always enough to ensure the bacteria is killed off, so it's really important to take care how you store them when they're cooling. Not sure? Don't reheat and eat.

Any foods you didn't realise you weren't meant to reheat?