Myth-busting and uncovering the truth about food is part of a day's work for a dietitian. From the latest celebrity diet, to the supposed miracle approaches of the latest nutritional 'guru'; some myths are easily explained, others more insidious and seem to return like a nasty bout of flu circulating.
Here are some of the latest myths that I have recently discussed with patients.
'I think I'm lactose intolerant'
Lactose intolerance itself is not a myth - it is a medical condition where low activity of the enzyme lactase results in lactose, the sugar naturally found in dairy, building up in the gut and causing symptoms such as bloating, wind, abdominal pain and diarrhoea.
However, the prevalence of this condition is wildly overstated and for many, it may even be completely misdiagnosed. Self-reported statistics suggest up to 20% of the UK believe they are lactose intolerant, yet less than 5% of Brits are actually affected.
So are people simply making these symptoms up? Well no, as there is more to milk than lactose. Cows' milk also contains proteins that can be potentially allergenic in some people or cause intolerance in others. For instance, recent research suggests that the A1 beta-casein sub-type found in most European cows' milk may produce the same symptoms of lactose intolerance and that switching to milk containing only the A2 protein, found in specific breeds of cows, resolves symptoms.
Is it possible that milk doesn't agree with you? Absolutely. Is it always the lactose? Absolutely not.
'What about negative-calorie foods?'
Firstly, calories are simply a unit of energy, and as Isaac Newton first advised, energy can't be created or destroyed - therefore you can't have 'negative calories'.
Digestion expends energy in order to obtain nutrients; this is called the 'thermic effect of feeding' and our metabolism elevates slightly through this process, which makes people think certain foods 'burn fat' at a higher rate than others.
The truth is that foods that need more 'expense' through digestion tend to be raw, fibrous foods which I'd advocate patients to eat more of anyway, such as vegetables, fruits and whole-grain sources of carbohydrate, as well as lean, protein-rich foods such as meats and pulses.
Calories do count, hence why balanced nutrition and staying active is necessary.
'Is fresh always best?'
Many patients are convinced that fresh produce is the only kind worth eating. However, frozen or tinned meat, fish and poultry are close to nutritionally identical to their fresh counterparts. Milk and dairy products can also be heat treated and remain fresh for much longer.
When it comes to plant-based foods, their vitamin content begins to fall the moment the vegetable or fruit is picked. This is particularly true for fruits and vegetables with a high water soluble vitamin content, such as berries, cherries, apples, oranges, broccoli and tomatoes or other 'above the ground' vegetables - so in these cases, frozen could be more beneficial.
My aim is to get patients closer to eating more home-cooked foods that help alleviate their medical problems, but often cost is a major barrier. Ultimately a mixture of fresh and preserved is the best course - don't abscond from the odd tinned or frozen food, it might even help you reach your '10 a day'.
'Should you feed a cold and starve a fever?'
Perhaps this should be retitled, 'feed a virus and starve a bacterium', but it's not as crazy as it first sounds. This traditional verse was put to the test by scientists from Yale University in a series of animal experiments last year. Mice were infected with either Listeria monocytogenes - a common food-borne bacterium that causes food poisoning - or the influenza virus. The mice with Listeria monocytogenes who were given little amounts of food survived longer than those given plentiful food, with the exact opposite seen in those with influenza.
So perhaps for this myth, there is some truth. Making sure you eat well during a course of the flu might just get you through it faster; on the other hand, going a bit lighter when suffering from food poisoning may help.
'I'm gluten intolerant'
It's very easy these days to blame bread as soon as bloating occurs, but non-coeliac gluten sensitivity - commonly termed as gluten intolerance - does exist.
Gluten is a grain-derived protein found in wheat, barley, rye, oats and triticale. Apart from causing a severe autoimmune response in those with coeliac disease, gluten also seems to have an inflammatory effect on the gut in some without coeliac disease. The extent to which this causes symptoms seems to depend on overall gut health, which we now know is affected by the billions of microbes that make up the microbiome and protect our gut from gradual degeneration. A more diverse gut microbiome, perhaps less chance gluten is a problem.
So is this a case of gluten-o-phobia? Perhaps the research, much like milk protein intolerances, just hasn't caught up yet. In any case, if you feel better going gluten free then perhaps you should do so, but let's not assume it is always healthier.
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