Is it bad to fry with olive oil? What does extra virgin mean? And how bad is butter?
The benefits or risks of fats and oils remain a vexed question for many of us.
So Jesse Mulligan consulted Laurence Eyres to bring some science to the table.
Eyres is a food industry consultant and a member of the Oils & Fats Specialist Group of the New Zealand Institute of Chemistry.
A fat, chemically, is a compound of glycerol and fatty acids. Fats and oils are exactly the same, but oils are the liquid version of fats, he says.
And the body needs fat. Fats carry vitamins and solubilises food to make it edible.
"You try eating a dry salad, compared to drizzling olive oil on it.
"The olive oil will liberate the vitamins from the tomatoes and the lettuce."
Fat works with some foods to make them better for us, he says.
He says the general recommendation is that no more than 30 percent of our total food intake should be fats.
"If you equate that to the number of grams per day, that's approximately 70 to 80 grams for a normal sized person.
"I think on average we eat 100 to 110 grams."
Of the 70 to 80 grams of fat we have a day, no more than 20 to 25 grams of that should be saturated, he says.
Examples of a saturated fat include butter, coconut oil, dripping, chocolate, cocoa butter and palm oil.
Fats tend to be defined as those that are solid at room temperature and oils, those that are liquid at room temperature.
Mono-unsaturated fats, of which olive oil, avocado oil, macadamia oil and nut oils are all examples.
Poly-unsaturated fats, divide into two types - one omega 6 (soy bean oil, sun flower oil, rice bran oil.
And omega 3, mainly found in fish oils.
Then he says there are the trans fats, which we should avoid.
"They were almost artificial fats, produced by the edible oil industry about 100 years ago.
"Trans fats affect the lipids in our bodies and have been linked to long term cancers."
Doughnuts, biscuits, crackers, muffins, pies and cakes are examples of foods that may contain trans fats.
If you have a history of heart disease, or your GP says your lipid levels are very high, you may want to cut down on your butter or cheese.
But if you're active and healthy, go for it, he says. But you do need some liquid oils to balance that.
"If you decide to have butter in your fridge, because you like the taste… then fine. But make sure, perhaps, you've got a nice bottle of New Zealand olive oil, to counter that."
Laurence Eyres also answered a number of listener questions on fats and oils:
Can I fry with extra virgin olive oil?
Yes, if you have a boutique oil, or an oil that's not further refined.
"New Zealand olive oils that are made from fresh olives under stringent conditions have very low acidity and satisfactory smoke points for frying.
"A lot of imported virgin olive oils perhaps are not made to the same quality standards as New Zealand, and they have higher acidities and lower smoke point."
Is coconut oil a saturated fat?
Coconut oil is 92 percent saturates.
"The claims made for it are based on nice marketing.
"There is no basis to the claims that they make that this is the healthiest oil going."
Are fish and chips bad for me?
"There's no need to give up fish and chips, but it pays to take note of what oil the fish and chip shop is using.
"Perhaps just have a quick look in the vats. If it's dark brown and it's starting to smoke, that's not a good look.
"If you buy good quality fish that's got a good sensible batter on it, it won't pick up a lot of the oil.
"Soggy fish and chips are probably pretty nasty for you."
How long can I keep olive oil for?
Once olive oil is opened, Eyres recommends using it within four weeks and recommends buying small bottles regularly.
He says not to buy oils in a clear bottle, as light damages the oil and will make it go off.