8 superfoods that can actually be bad for you

Zoe Bingley-pullin

Step away from the kale!

That saying about consuming everything in moderation? It applies to a whole lot more than just chocolate, alcohol and carb-loaded bread. In actual fact, it’s relevant for virtually every food. Because whether you’re consuming leafy greens, wholegrains, nuts or any other variety of ‘healthy foods’, there’s always going to be a breaking point where you can have too much of a good thing. Here, we – along with three of Australia’s top nutrition experts – explain how eight of the most commonly consumed superfoods can actually cause you harm when consumed in large doses.

#1 / Avocado

If you’ve been out to breakfast or brunch anytime in recent memory, there’s a very good chance avocado has graced the menu. Avocado is super popular not just because they’re positively delicious, but also because “they’re rich in healthy monounsaturated fats, which are good for our heart; and they contain important nutrients such as folate, vitamin E, vitamin C, vitamin B6 and magnesium, which are all beneficial for mood, skin health and overall wellbeing,” says nutritional medicine practitioner Fiona Tuck.

However, “due to avocado’s high fat content, they are high in kilojoules, so if you’re watching your weight be mindful of portions. In addition, avocadoes contain polyols, which can be poorly absorbed in the small intestine, which anyone on the Low FODMAP Diet would familiar with. If you suffer from irritable bowel syndrome (IBS) and have found out you are sensitive to polyols, eating over one eighth of an avocado may cause an exacerbation of IBS symptoms. For those not sensitive to FODMAPS, as a general rule, stick to one-quarter to half an avocado day per as a maximum serve,” explains nutritionist Zoe Bingley Pullin. 

#2 / Legumes

While the benefits of consuming legumes are numerous (they’re low in fat and high in fibre, and a good source of plant-based iron, potassium, minerals, folate and many B vitamins), they can “interfere with the absorption of nutrients and may produce food intolerance-type reactions in sensitive individuals if eaten all the time,” says Tuck.

Additionally, Tuck explains, “legumes can contain potentially harmful substances such as phytic acid, which can inhibit the absorption of iron, zinc and calcium.” To avoid this, it’s important to soak and cook legumes well, as this “makes them easier to digest and helps to deactivate the potentially harmful compounds,” Tuck adds. 

#3 / Goji berries

According to Bingley Pullin, the main active component of goji berries – polysaccharides – “are believed to have antioxidant and anti-ageing properties as well as being a rich source of vitamin C.” The problem with goji berries however, is that they’re very high in sugar, which means “when they’re eaten in excess, they have the potential to negatively impact blood sugar levels and cause digestive upset in sensitive individuals,” adds Bingley Pullin. As a general rule, she recommends limiting intake to a quarter-cup daily.

#4 / Kale

Kale is touted as one of the best leafy greens to incorporate into your diet because it’s “high in iron, vitamin C and phytochemicals, all of which help to boost your immune system,” explains accredited practicing dietitian and spokesperson for the Dietitians Association of Australia, Gabrielle Maston, adding that, “It’s also high in fibre and relatively low in energy, which helps you feel fuller for longer as well as promoting positive bowel health”.

But when consumed in large doses, “Cruciferous vegetables, or green leafy vegetables, such as kale, have been suggested to be associated with lowering thyroid function,” explains Maston. “However, research has shown that this only occurs with extreme over-consumption of these vegetables coupled with iodine deficiency.” So you can continue eating your favourite kale salad, just make sure you’re incorporating other colourful vegetables into the mix as well.

#5 / Chia seeds

“Chia seeds are a great plant-base source of essential fats, protein and fibre, however due to its high fibre content, when eaten in excess there is potential for chia to cause gastrointestinal symptoms such as bloating, abdominal pain and/or constipation and diarrhoea,” says Bingley Pullin. 

#6 / Protein powder

Protein is essential in every diet as it assists in “muscle repair, satiety, neurotransmitter synthesis and immune function,” explains Bingley Pullin. For athletes or those with high nutritional requirements, protein powders can be a convenient option for consuming large doses of protein. However, Bingley Pullin says that excessive protein intake can cause “dehydration, kidney damage and bone damage. In addition to this, excess consumption may cause digestive upset. A typical serve of protein powder is 25-30g and limiting to one or two serves daily depending on individual tolerance is best.”

#7 / Brazil nuts

“Brazil nuts are a source of protein, unsaturated fats, fibre, magnesium, copper and zinc,” says Bingley Pullin. However, “they are most well-known for their high selenium content. Selenium is a trace mineral with antioxidant properties, which is also necessary for optimal thyroid function. Despite its benefits, selenium is toxic in high doses and just two nuts per day are necessary to meet the RDI [recommended daily intake] of selenium. This means it’s important to not sit down to a bag of Brazil nuts and eat mindlessly,” adds Bingley Pullin.

#8 / Coconut oil

While many of us made the switch years ago from cooking with oil and butter to coconut oil, we may have done so too soon and without enough information. According to both Maston and Bingley Pullin, coconut oil is high in saturated fat, which can raise our unhealthy LDL [low-density lipoprotein] cholesterol, which then raises the risk of heart disease. Additionally, “the high fat content in coconut oil can lead to digestive upset including diarrhoea if eaten in excess,” says Bingley Pullin.

Diet in need of an overhaul? Then discover the six foods you should be eating for better skin, and find out why you should also add fermented foods to your diet, stat.

Let us know which superfoods are your favourites, and how you add them to your daily meals in the comments below.

Main image credit: @zoebingleypullin

Inset image credit: @zoebingleypullin; @thehealthyania; @fionatucknutrition

Kate has worked for BEAUTYcrew since early 2016, first as a contributor, before being named Beauty Writer in 2017. She loves picking the brains of the industry's top experts to get to the bottom of beauty's toughest questions. Bronze eyeshadow palettes are her weakness and she's forever on the hunt for the perfect nude nail polish to suit her fair skin. Her words can also be found in Men's Health magazine.