Hard to swallow: The eight biggest nutrition myths
There's no shortage of confusing food advice online. But which popular health claims really stack up? Dietitians Rosie Saunt and Helen West take a closer look
With so much advice available about food and diet, it's hard to know what to believe.
We all know that what we choose to eat can have an impact on our health - and right now, there's no shortage of advice, from cookbooks, apps and Insta health gurus.
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But most of us are still wondering things like: should I be cutting carbs? Or eating them? Should I be vegan? The act of eating has become a minefield of paradoxical 'facts'.
Not everybody talking about nutrition on the internet is doing a bad job - and many of the people out there have good intentions. But as dietitians, and founders of The Rooted Project - offering up nutrition information based on facts, not fads - we believe that people with influence and followings have an ethical responsibility to get it right.
Here, we expose eight of the most popular myths we hear peddled in the world of wellness.
1 Coconut oil is better than olive oil
Along with being a cure for diseases from diabetes to Alzheimer's, this 'miracle' ingredient is claimed to promote weight loss by affecting our metabolism and appetite. It contains lauric acid, a fat belonging to a group called medium chain triglycerides (MCTs), which have been found to have these effects. However, scientists now dispute whether lauric acid behaves like an MCT in the body.
Like all oils, coconut oil is a high-calorie food. One tablespoon contains about 120 calories, roughly the same as half a jam doughnut, so adding a lot to your diet could cause weight gain. Coconut oil increases cholesterol more than vegetable oils; it also contains 82pc saturated fat, whereas butter contains 63pc and olive oil 14pc.
Coconut oil is promoted as being a good oil to cook with as it remains stable when heated, however this is only the case with the refined variety. Refined olive oil, rapeseed oil and avocado oil are better choices for high-temperature cooking.
2 Low carb diets are best for weight loss
How many times have you heard that to lose weight you should 'cut the carbs'? The theory is that carbohydrates are uniquely fattening because when we eat them our insulin levels go up, meaning we break down less fat and move more of it into storage.
However, we know from 'metabolic ward studies' - where the participants live in a controlled environment, with food intake measured and recorded - that the percentage of dietary fat or carbohydrate in a diet makes little difference to the amount of weight lost. Real world studies have found the same thing.
Often, people who prefer low-carb diets state that they make them feel less hungry - which may be due to them eating more protein - and that they find they lose weight quickly in the initial stages, which is less to do with fat-burning efficiency and more to do with a loss of water weight. After about 12 months, however, on average there is no difference between low-carb and low-fat diets for weight loss.
3 Sugar feeds cancer
Recently, amid claims that cancer cells ferment sugar, it has been suggested that cutting it out of our diet (and following a high-fat, ketogenic diet) could help to slow or even cure cancer. The picture is complicated. Although there are animal studies that suggest reducing carbohydrates in the diet might be beneficial for some cancers, human evidence is extremely limited, and scientists are still (rightly) sceptical.
It might be that, in the future, we learn that a diet lower in carbohydrates could work alongside chemotherapy for some types of cancer. However, as of yet, we just don't know. Undertaking a diet like this with a cancer diagnosis (or not) is not without risks and has the potential to make things much worse.
4 Dairy leaches calcium from your bones
The rise of veganism has seen a rise in conspiracy soundbites like this. People who promote this myth state that milk is 'acidic', and causes calcium to leak out from your bones to neutralise the threat, making them weaker. Some observational studies have seen that the countries with the highest intake of dairy products also have the highest incidence of osteoporosis.
However, this theory falls down in a number of places. Firstly, dairy foods are rich in calcium, protein and minerals, all essential for good bone health. Secondly, it does not acknowledge the role your kidneys play in maintaining blood pH; they filter out any 'acidic' compounds and you pass them out in your urine - your bones aren't involved in this process.
5 An alkaline diet is healthier
This diet removes 'acid-forming foods' and replaces them with 'alkaline-forming foods'. When you metabolise foods they produce waste, which can be either acidic or alkaline and is often referred to as 'ash'. The alkaline diet is based around the idea that acidic ash can cause diseases such as depression, cancer and osteoporosis.
The trouble is that your body's inbuilt regulatory systems (lungs and kidneys) keep your blood pH tightly controlled, and it isn't possible to change your body's pH with diet. You can, however, change the pH of your urine, which is what often draws people into the diet.
Most of the foods suggested on the alkaline diet are fresh fruits and vegetables, and many on the 'avoid' list are things like sweets, cakes and biscuits, etc, so followers may see an improvement to the quality of their diet. But this is nothing to do with acidity, and avoiding 'acid-forming' foods like meat and lentils could mean you miss out on beneficial nutrients.
6 Grains are toxic for the gut
Many claim grains are toxic and can cause damage to our gut lining, in turn causing 'leaky gut'. This has been blamed on lectins, an indigestible protein found in grains.
However, we don't eat lectins in isolation or in large enough amounts for them to be a problem. Uncooked grains and legumes have high amounts, but as long as you're cooking and preparing your food properly, they're nothing to worry about. Grains also contain gut-loving fibre and antioxidants, so the benefits far outweigh the risks.
7 Meat causes cancer
Although scientists are fairly certain that people who eat larger amounts of red meat, particularly processed meats, have a higher risk of colorectal cancer, the level of risk is fairly small. Cancer is a complex disease that doesn't have one single cause.
It's also likely from a dietary perspective that your actual risk of cancer also depends on your diet as a whole. This was reflected in the Oxford EPIC study, which found a small reduction in risk of all cancers in vegetarians, but a higher risk of colorectal cancer.
Scientists may believe the link between red meat and colorectal cancer is pretty certain, but the level of risk is fairly small.
8 Turmeric is anti-ageing
It's claimed that turmeric's anti-inflammatory effects promote healthy brain ageing and decrease your risk of chronic health conditions like diabetes and even cancer.
The part of turmeric thought to possess these beneficial properties is curcumin. Turmeric only contains teeny amounts (maximum 5pc, but often as low as 2-3pc).
Studies in test tubes have shown that turmeric has some potential as an anti-inflammatory/anti-cancer agent, but so far we have very few human experiments.
Regularly using it in curries or having a turmeric latte may have a beneficial effect over the long term - who knows? - but it certainly shouldn't replace modern medical therapies.
Is Butter a Carb? by Rosie Saunt, Helen West is published by Little, Brown Book Group