Do 'Superfoods' Really Work?
Are kale, coconut water and chia seeds as good as their billing, and are there less expensive alternatives?
Building immunity, extending life and preventing cancer are among the purported superpowers of so-called superfoods. And while last week research found that a compound in pomegranates could increase longevity, one complaint about many of these foods is that they have a price tag to match their celebrity status. A Which? report found shoppers could save as much as $815 a year by replacing superfoods with everyday items containing the same nutrients.
Experts also urge caution, especially if you are compensating for a bad diet by eating one or two “superfoods”. Dr Sue Reeves, principal nutrition lecturer at the University of Roehampton, says: “If you’re focusing on a superfood, you might not get enough variety into your diet, and the sum of what you eat is more important than any individual food.”
What exactly is a superfood?
The term suggests a food that contains antioxidants and flavonoids to help specific conditions, but there is no agreed definition and in 2011 the EU banned the term from food labels unless supported by scientific evidence.
“It’s a marketing term that is leaving consumers confused because these foods are touted as having magical abilities, but often claims aren’t supported by evidence,” says Anna Daniels, a registered dietitian and spokesman for the British Dietetic Association.
However, another term, “functional foods”, describes a food that is said to improve your health and can carry that claim on a label because there is enough compelling evidence to justify using it. “These have to provide a certain amount of a nutrient per 100g to make their claims,” says Daniels. “Examples include oats that contain beta-glucans, a substance proven to lower cholesterol, while garlic contains allicin, which can help immunity.”
Where does the hype come from?
Scientists might look at a specific food and isolate the chemicals and molecules present, says Prof Tim Spector, professor of genetic epidemiology at King’s College London and author of The Diet Myth: The Real Science Behind What We Eat. “They isolate the nutrients and then show links in studies, usually in animals, showing it prevents something such as osteoporosis or cancer.”
But often the evidence fails to tell the whole story. “They might drop large amounts of these chemicals on cancer cells in a Petri dish and if they slow the rate of cancer growing, they may say it could slow the rate of tumour growth, but you would have to eat huge amounts to get the same effects,” he says.
Indeed, for the pomegranate study, researchers at Ecole Polytechnique Federale de Lausanne fed a molecule found in the fruit, urolithin A, to nematode worms and found it increased their average 10-day lifespan by up to 45 per cent. But research like that is far from proving a similar benefit in humans.
So here’s the low-down on six of the most common “superfoods”.
What’s so special? “Kale is one example of a superfood that adds up nutritionally,” says Prof Spector. A 100g uncooked portion contains only 33 calories, but huge amounts of vitamins A and K as well as - gram for gram - 17 times the vitamin C of carrots.
“Kale is so nutrient dense, it’s almost like a medication,” says Jennifer Sygo, a registered dietitian and author of Unmasking Superfoods: The Truth and Hype about Acai, Quinoa, Chia, Blueberries and More.
Cheaper alternatives: “There are at least a dozen varieties of kale that pack a good nutritional punch,” says Prof Spector. “Broccoli, spinach, good old cabbage and old-fashioned spring greens.”
Brussels sprouts are also similar nutritionally to kale, says Dr Reeves. While 11g of kale provides an impressive 5.9mg per 100g of beta-carotene, the same amount of sweet potato with the skin will give you 8.5mg.
What’s so special? Blueberries are famed for their antioxidant content, but Jennifer Sygo says: “They are an excellent source of only a handful of vitamins and minerals, vitamin C, vitamin K and manganese, and we don’t have as much hard data on their ability to ward off disease in humans as we might have assumed.”
Cheaper alternatives: The Which? research found swapping a handful of blueberries costing $1.20 - blueberry prices doubled between 2004 and 2013 - for a portion of two kiwi fruit costing 63 cents could result in an annual saving of $67 while providing similar nutrients.
“Blueberries are a source of polyphenols [plant chemicals in foods with antioxidant properties] that our gut flora love,” says Prof Spector. “But you can get the same compounds from any seasonal berries, which are often cheaper.”
Even a cheap dark red apple would have polyphenolic compounds in the skin, says Dr Reeves.
What’s so special? A 200g portion of cooked quinoa contains a good amount of protein (eight grams) along with B vitamins, iron and zinc, says Sygo. “But there is little evidence to support the claims that it can help prevent or manage medical conditions such as diabetes, heart disease or coeliac disease.”
Anna Daniels says that much of the research is based on the make-up of raw quinoa and cooking it would lead to a loss of some nutrients. The price of quinoa trebled between 2006 and 2011 and in countries such as Bolivia, where it is a staple crop, there have been reports of land disputes between farmers and ecological damage because of intensive farming.
Cheaper alternatives: Bulgar wheat and buckwheat are great protein sources, too, says Daniels. Cooked bulgar wheat contains almost six grams of protein per 200g.
What’s so special? The South American seeds are rich in alpha-linolenic acid, the plant form of omega-3 fats, says Sygo. “But this seems to have limited impact on the body’s ability to produce DHA, the omega-3 fatty acid thought to have the biggest impact on health.”In animal studies, feeding chia to rats has resulted in reduced levels of LDL (bad cholesterol) and triglycerides, a type of fat associated with heart disease. “You would probably only have about three grams of chia seeds, which would provide 0.6g of omega-3, much less than the four grams you would get from a 200g portion of salmon,” says Dr Reeves.
Cheaper alternatives: Sardines or mackerel - a 200g serving of sardines provides almost three grams of omega-3s, while the same amount of mackerel will give you two grams. For vegetarians, three grams of flaxseeds will provide a similar amount of omega-3s (and they’re cheaper).
What’s so special? Some claim coconut water is more hydrating than tap or bottled water after exercise because it is high in natural sugars and electrolytes. But a 2012 study published in the Journal of the International Society of Sports Nutrition and performed on 12 men, who drank bottled water, pure coconut water, distilled coconut water and an electrolyte-based sports drink after 60-minute bouts on the treadmill, found they were adequately rehydrated by all four drinks - but the ones drinking coconut water reported more bloating. That suggests coconut water may be as good as, but not better than, water at rehydration.
“There is some evidence to support coconut water as a sports drink, but for those not doing sport, it’s little more than a sugar drink with extra calories,” says Sygo.
Cheaper alternatives: Water. “We have evolved to exercise our bodies and then drink water,” says Prof Spector. “The idea that non-athletes need extra electrolytes after exercise is rubbish.” If you really want to get the electrolyte potassium, eat a banana.
What’s so special? According to Sygo, these are the “real deal” when it comes to superfoods. Avocados contain large amounts of fibre, vitamin C and monounsaturated good fats helpful in controlling cholesterol and diabetes.
Cheaper alternatives: Few foods can match the texture and taste of an avocado, but if it’s nutrients you’re after, other sources include olives, olive oil and raw nuts, says Dr Reeves.
— The Daily Telegraph