Top nutritionists name the surprising foods they wouldn't go near

Superfoods are worshipped one minute and shot down in flames the next, so it's hard to know what we should be putting in or bodies. Lists of "what you should and shouldn't eat" are constantly contradicting each other, and how can everyone's diet be the same? Well, it's not, but in case you're wondering what the experts have banned from their shopping lists, here are the interesting answers.

Cans of tomatoes

WHY?: "Tomatoes have high levels of acidity and I'm personally concerned that this could cause corrosion of the metal of the can, increasing the possible risk of metal poisoning," says model turned nutritionist Rosemary Ferguson.

"Some cans are lined with plastic, but this may not be any better. If the lining of the can is plastic it may leach into the tomatoes, and so possibly interfering with the endocrine system.  I suggest using passata if you can't get hold of fresh tomatoes as it is usually sold in glass bottles, which don't carry the above risks."

Microwave popcorn

WHY?: Although popcorn is widely seen as a healthy, low-fat snack the microwaveable version should be avoided, according to Jackie McCusker.

"It comes in bags lined with toxic perfluorinated compounds (PFCs) - a large group of chemicals including perfluorooctanoic acid (PFOA), which has been linked to cancer," she says.

"PFCs have been used for more than 60 years in non-stick pans and food packaging, yet research in Denmark shows they are a likely human carcinogen and can cause cardiovascular and thyroid problems (a possible EU ban is being discussed). The first thing you're likely to do when opening the hot popcorn bag is put your nose in for a good sniff, but just inhaling enough of this PFOA can make you feel sick," says Jackie.

"Instead, make your own popcorn using organic kernels, coconut oil, butter and a little salt."

Gluten-free foods

WHY?: Gluten-free products are the latest food obsession, yet nutritionist Patrick Holford is wary of gluten-free foods in general. He believes that modern wheat is the main problem rather than gluten itself.

"Wheat does cause some people digestive problems, whereas kamut, which is an ancient form of wheat, does not. Every person in a study of irritable bowel syndrome got better on kamut, but worse when eating modern wheat," he says.

"I don't think it's gluten that is the enemy, but rather how we've changed the composition of modern wheat."

Soya milk

WHY?: The new milk darling for your latte is not the health food that it is commonly hailed to be, according to Henrietta Norton.

"Not only is it often highly processed before reaching us in milk or yoghurt form, but soya contains trypsin, which may inhibit protein digestion and pancreatic function," she says.

"Furthermore, soya milk contains phytic acid, which can inhibit the absorption of key minerals such as zinc, iron, calcium and magnesium. The latter two of these minerals are especially important post-menopausally when, ironically, soya consumption is often recommended."

"Instead, I eat unhomogenised and unpasteurised dairy products. These are not ideal for everyone as their 'raw' nature makes them more likely to contain the bacterium listeria, - and so they are not recommended during pregnancy, for example."

Rice - particularly brown!

WHY?: "There are health risks associated with rice and rice products, especially for those who regularly eat a large amount. Although low levels of arsenic are found in many crops, rice - organic and inorganic - has ten to 20 times more than other cereal crops as it is grown in flooded conditions which allow for easier absorption of arsenic into the rice," says nutrition therapist, Gabriela Peacock.

"Basmati rice has lower levels, brown rice usually contains more arsenic than white because of the husk, while rice cakes and crackers can contain higher levels than cooked rice. Rice milk is no better: arsenic levels far exceed those allowed in drinking water. When using rice, always rinse it thoroughly before cooking and use plenty of water when cooking."

Raw kale

WHY?: Kale is everywhere, from salads to juices, yet Dr Glenville says she would never eat kale or other cruciferous vegetables (the family that includes broccoli, Brussels sprouts, cabbage, cauliflower, collards and kale) raw on a regular basis.

"They are often added in handfuls to smoothies or juices, yet these vegetables are classed as goitrogens [substances that can affect thyroid function]. And as an underactive thyroid can mean weight gain, raw kale could actually be contributing to your weight problem" says nutritionist and author Dr Marilyn Glenville.

"But I would definitely eat them cooked as they carry many health benefits." 

Probiotic yoghurt

WHY?: "This trendy supplement is often packed full of sugar, which defeats the object of taking it in the first place," Shona Wilkinson warns.

"Probiotics are also known as 'live cultures' or 'good/friendly bacteria' and are excellent to take for the digestive system. The majority of your immune system cells come from the digestive tract so it's important to have good gut health for the immune system. The problem is that probiotics are very delicate and are destroyed and die quite easily. They are attacked by the stomach acid so will only survive in certain forms. Capsules are the best way as they are designed to withstand the stomach acid. There is one liquid probiotic which is excellent called Symprove. This 'tricks' the stomach acid so that it passes through untouched."

Pasteurised cheese

WHY?: "I only eat unpasteurised cheese for its amazing probiotic benefits that can be found in just one simple slice," Eve Kalinik says.

"The pasteurised versions are heat treated - meaning you don't get the natural microbial benefits that are so important for the health of the gut. I tend to opt for ewe's or goat's cheese such as manchego, pecorino or halloumi, but parmesan is excellent, too, and you can get the unpasteurised versions of these in many supermarkets now."

Vegetable oils

WHY?: "People talk about trans fats sometimes. We talk about saturated fat a lot of the time. However, one thing very, very rarely discussed are fatty acids. Vegetable oils like sunflower oil, rapeseed oil, soy/canola oil etc are packed with omega 6 fatty acids. These are important to our health in tiny amounts, but as soon as we go past the small amount we need, they are converted into substances that trigger and worsen inflammation" Dale Pinnock explains.

"This is inflammation at a micro level that, over time, may cause damage in tissues and has been linked with cardiovascular disease and other degenerative conditions. By avoiding such oils, we keep our intake of these potentially harmful substances very low. Instead, opt for olive oil or butter. And forget anything you've been told about olive oil being bad if you heat it. It's perfectly stable at the sort of temperatures reached during normal stove-top cooking."

Decaffeinated products 

WHY?: Two of the main "decaffeination" processes use chemical solvents (methylene chloride and ethyl acetate).

"Although both are deemed safe as food processing agents in liquid form, they are highly toxic as vapours and in contact with skin, and we can't yet know the effect of long-term use. So why take the risk?" says Caroline Skirrow.

"Any solvent residue is likely to be very small, but we are bombarded with chemically manipulated foods and products and our ever increasing 'toxic load' is impacting our health. My rule of thumb is to avoid synthetic additives of any sort and go less processed where possible."

Looks like everything we thought we knew was a lie.

This article was first published on nzherald.co.nz and is republished here with permission.