Cancer, diabetes, heart disease, dandruff…can these things really be cured or at least prevented, by what we eat?
“Whether it’s coconut oil, chia seeds or apple cider vinegar,” says Duane Mellor, an assistant professor in dietetics at the University of Nottingham and a spokesperson for the British Dietetic Association, “There is no scientific evidence to suggest that if you top up your diet with any ‘miracle’ or special food that you’ll get any of the promised effects. The idea is almost entirely a marketing vehicle, but when people read claims online, they start to think differently and can start believing it.”
Even when used as supplements, antioxidants don’t seem to provide any benefit. A large study ─ Vitamin E Supplementation and Cardiovascular Events in High-Risk Patients ─ published in the New England Journal of Medicine that followed nearly 10,000 people over an average of four-and-a-half years showed no benefit of Vitamin E supplements in the prevention of heart disease. Studies for antioxidant supplements have been equally discouraging.
Part of this confusion is because diet is complex. It’s tough to tease apart the contribution of individual components because the nutrients in many foods become available to us only when eaten as part of a wider diet: studies have shown that only when we cook carrots can their beta-carotene become more available and; the lycopene in tomatoes is most readily available when they are eaten with oil.
But what about all the other vague claims about foods that can help you lose weight, or support a healthy immune function, or lead to a healthy heart? They all sound good and sort of make sense, don’t they? According to Ali Khavandi, a cardiologist at the Royal United Hospital in Bath, these claims are vague for a reason – they are based on experiments carried out on animals or on human cells in a lab. They have not been shown to have any effect on people, and until such effectiveness is shown, he says, we should stay open-minded but cautious about exaggerated claims.
“There is certainly no such thing as an anti-cancer diet,” says Justin Stebbing
“There is certainly no such thing as an anti-cancer diet,” says Justin Stebbing, a consultant oncologist and professor of cancer medicine and oncology at Imperial College London. “But I have patients asking me things about these foods all the time.” He puts a finger on why cancer-busting food is such an appealing concept. “As a patient, disease makes you lose control. People immediately want to regain that control and a very easy way for them to do that is by diet, and they can get all sorts of things off the internet. We should understand that the internet is a double-edged sword and if we’re looking for information we should go to reputable sites.”
Mythbuster: the facts about 5 ‘miracle foods’
1. Coconut Oil
The claim: Coconut oil is a saturated fat. While not the heart-clogging evil they were once thought to be, it would take a leap of faith to proclaim that they are good for you. A recent review of studies suggested that saturated fats raise levels of both good and bad cholesterol. The oil is predominantly a medium-chain triglyceride that, proponents state, might carry benefits for weight loss, but this claim has not been shown in human studies. Other suggestions for the benefits of coconut oil include helping blood glucose regulation and preventing strokes and Alzheimer’s – again, none of these benefits have been shown in people.
Dietetics professor Duane Mellor’s verdict: Probably best to enjoy a little coconut oil in a Thai dish occasionally rather than using it daily!
2. Apple Cider Vinegar
The claim: Doubtless a tasty condiment, but has been anecdotally linked with an eye-wateringly long list of potential health benefits in areas including: digestive disorders, sore throats, high cholesterol, indigestion, preventing cancer, dandruff, acne, energy boosting, cramps, and helping with blood sugar control. The EFSA, however, hasn’t approved any of these claims. Many of the studies have been on animals or in laboratories using human cells.
Mellor’s verdict: Vinegar is probably best kept as a condiment. Use it on salads instead of high calorie oils and mayonnaise and to add flavour to sauces to help reduce salt intake – it might help, not because of anything it contains, but because it would be replacing less-healthy foods.
3. Manuka Honey
The claim: A medical-grade version of this honey is used in sterile wrappings. As with most honeys it has hydrogen peroxide, which gives it its antibiotic qualities. It also has methylglyoxal, an antibacterial component, in much higher quantities than found in other honeys. Studies have suggested that manuka honey might help to ease symptoms of infections such as coughs, but it’s not clear whether the honey is having an antimicrobial effect or whether it is just soothing like all syrups.
Mellor’s verdict: Any of the claims for eating manuka honey, all of which have been rejected by regulators, are vague. Any health benefits must be balanced against the very high quantities of sugar compared with the very small amounts of these proposed active compounds.
The claim: This is another proposed miracle food for which regulatory agencies, this time the US National Institutes for Health say there is not enough scientific evidence to support any health claims. Rejected claims include those relating to metabolic and heart disorders (eg blood pressure control and diabetes), and also mental health disorders such as anxiety, depression and ADHD. It does have useful nutrients – calcium, niacin, potassium, magnesium, B vitamins, iron, and essential amino acids – but the jury is out on whether your body can use these nutrients in plant form.
Mellor’s verdict: Spirulina shouldn’t be relied on as a source of nutrients. Rather than taking such supplements, it would be better to spend your money on vegetables and fruit – this will help to make your whole diet better rather than adding a supplement and not thinking about the food you actually eat.
5. Chia seeds
The claim:Packed with antioxidants, but many of these are of plant origin so less likely to be available to us. They have high omega-3 content, too, but our bodies are not great at using omega-3 oils from plants – it’s best to get these oils from oily fish such as salmon. But for people who don’t eat fish, chia and other seeds can be a good substitute. Other potential pluses are linked to their high protein and fibre content, which have led some to suggest they might help you lose weight by reducing hunger. However, two trials to date have shown no evidence of any benefit in terms of weight loss or reduced risk of heart disease.
Mellor’s verdict: Chia seeds can add an interesting texture to bread. Linseed and hemp seed are also rich in omega-3 fatty acids, so chia is not unique and should be enjoyed more for its effect on texture rather than any particular health effects.
This story is excerpted from the guardian.com