DO "SUPERFOODS" HAVE MIRACULOUS HEALTH-GIVING PROPERTIES?

Are any of them actually worth eating?

You don’t have to shop at Whole Foods or hang on Gwyneth Paltrow’s every nutritional word to have heard the buzz – about exotic-sounding seeds that replenish your energy and make you glow, or obscure berries from afar that disease-proof your organs. Such are the promises of so-called superfoods, an ever-expanding category of nutrient-rich foods credited with allmanner of miraculous health-giving properties – and often priced to match.

We are certainly swallowing the hype. In a recent survey of more than 1000 UK adults, 61 per cent admitted to buying a food because they considered it a superfood. Thirty per cent agreed that “superfoods are scientifically proven to have health benefits” and 14 per cent said they were willing to pay more as a result. Are we being ripped off?

On the following four pages, we consider the claims of individual superfoods, from goji berries to beetroot juice and powdered baobab. But before we do, some context. The first thing is that the term “superfood” has no scientifically agreed meaning. The Oxford English Dictionary defines one as “a nutrient-rich food considered to be especially beneficial for health and well-being”, but the term was invented to sell products.“Superfoods are marketing gimmicks,” says Duane Mellor, a nutrition scientist at the University of Canberra in Australia.

In 2007, the European Union banned the word on packaging unless it refers to a specific claim based on convincing research from an approved list. There are no such regulations in the US, but the Food and Drug Administration can take action if they find any claims to be false or misleading.

Even where claims are not directly misleading, scratch the surface of the scientific jargon designed to attract health conscious consumers and things quickly get murky. Sure, studies often show that concentrated extracts or isolated compounds found in abundance in certain foods have particular effects in a Petri dish or a mouse. But that does not mean they work in the same way when people eat them. Reliable, long-term studies to support most claims are thin on the ground.

For the average punter doing the weekly shop, it can all get a bit confusing. So what’s the real story? Are the things we call superfoods any better for us than ordinary, every day fruit and veg? Read on to find out.

GOJI BERRIES

Long revered in Chinese medicine, goji berries (Lycium barbarum and Lycium chinense) are said to pep your immunity, boost libido and protect against heart disease and cancer. But Chinese medicine also prizes ground-up rhino horn – and there is precious little research identifying the supposedly unique active ingredients in goji berries, never mind measuring their health benefits.

What research there is tends to focus on a group of chemicals called “Lycium barbarum polysaccharides”, or LBPs. According to a recent review of in vitro and mouse research, they can stop tumour growth, regulate blood sugar, protect eye and liver cells from free-radical damage and improve sperm motility.

There are reasons to be sceptical. First, few studies definewhat LBPs are.Polysaccharides are long-chain carbohydrate molecules, but in the goji berry literature, LBPs appear to include carbohydrate chains linked to proteins – collections that are not typically considered polysaccharides. What’s more, there are no rigorous human trials measuring which components get into the blood stream and what they do. So even if the studies of LBP extracts turn out to be reliable, their relevance to you is far from clear.

The other big claim is that goji berries contain high levels of zeaxanthin, a compoundlinked to the prevention of age-related degeneration in eye cells. Catherine Collins, a dietician at St George’s Hospital in London, is not convinced. “Other foods that will have exactly the same effects are far cheaper,” she says. If it’s zeaxanthin you’re after, you can get your fill from leafy veg such as spinach and cabbage or from yellow peppers. And although goji berries do contain more vitamin C than blueberries, you get roughly the same amount from strawberries or lemons.

VERDICT: Just a berry.


KALE

Blended in smoothies, baked into crisps, blanched or raw in salads: once dowdy kale has become fashionable. Its main selling point is a family of sulphur-containing plant chemicals called glucosinolates that give all dark-green vegetables their characteristic bitter taste.

Glucosinolates are broken downin the gut to release glucose and isothiocyanates, which have been shown to stimulate enzymeswhosejob it is to eliminate cancer-causing chemicals. This much has been shown in animal research and it is supported by studies linking higher consumption of glucosinolate-rich brassicas to a lowered risk of cancer in humans, particularly that of the gut and lungs. Given that all brassicas contain similar stuff in similar amounts, however, kale is no better than white cabbage or Brussels sprouts.One analysis revealed that several varieties of cabbage contain as many glucosinolates as kale.

What’s more, there are more than 100 different glucosinolates, and each gets broken down into a different isothiocyanate, so it is probably best to munch all kinds of brassicas. Be warned, though: boiling reduces glucosinolate content, so the crunchier the better.

VERDICT: Super, but no more than other types of cabbage.


QUINOA

A handful of human studies have shown that replacing cereals with quinoa, a seed that is cooked like a grain, can reduce blood cholesterol and help people lose weight. But the sample sizes are so small that it is difficult to draw firm conclusions.

According to one recent review, such benefits are typically attributed to chemicals called saponins, thought to work by altering the permeability of the gut. It may also be because they produce a bitter taste that puts people off eating too much. Either way, washing your quinoa before eating it, as many people do, removes the saponins and thus the benefits they might bestow.

Thomas Simnadis, a nutrition scientist at Wollongong University in Australia, says we don’t know much for definite. So although quinoa is a good addition to your diet, there is no compelling health reason to favour it over staples like rice or wheat.

VERDICT: Eat if you like it, not for health benefits.


BLUEBERRIES

The blueberry is prized primarily for its ability to lower the risk of cardiovascular diseases. A2012 study of 93,000 women, for instance, showed that participants who ate three or more portions of blueberries and strawberries a week had a 32 per cent lower risk of a heart attack than those who chomped berries once a month or less. The berries can’t take all the credit, but the evidence is promising.

Such benefits are typically attributed to a compound called anthocyanin, part of a family of plant chemicals called flavonoids, found in particularly high levels in blueberries and red berries such as strawberries and raspberries. Alas, there’s a catch: hardly any of the anthocyanins in berries get into the bloodstream, says Gordon McDougall of the James Hutton Institute in Dundee, UK.

So the idea that blueberries flood your body with righteous compounds that roamaround mopping up cell slaughtering free radicals doesn’t quite stack up. It’s possible that it is not the anthocyanins that protect your heart, but the chemicals they are broken down into. These get into the bloodstreamin far higher quantities than the original compounds, says McDougall.

There could be other explanations. Maybe some other component stimulates your own free-radical defences. Or perhaps anthocyanins act as benevolent gardeners for your colon microbiome, nudging it towards a healthier mix.

VERDICT: Super, though no better than many other berries.


CHOCOLATE

Everyone wants chocolate to be virtuous, but the evidence is flaky. The most commonly heard health claims centre on chemicals called flavanols, found in cocoa beans. Studies with cell cultures and rats have shown that cocoa flavanols increase production of nitric acid, a precursor to nitric oxides, which are known to relax blood vessels and regulate blood pressure. Human studies, on the other hand, have produced conflicting results.

A solid-looking 2012 review concluded that flavanol-rich chocolate, meaning the dark and bitter stuff, may slightly reduce blood pressure – at least in the short term. But long-term trials are needed to see if the effects last. Duane Mellor, a nutrition scientist at the University of Canberra in Australia, who has spent years researching the health benefits of cocoa flavanols, is cautious. “We’ve got some statistical significance,” he says. “Whether it is actual clinical significance, I’m not convinced.”

What’s more, the promise of cardiovascular benefits from chocolate has to be weighed against the fact that to make it, manufacturers tend to combine cocoa with large portions of sugar and fat. That’s not to say that chocolate, especially the cocoa-rich stuff, is something you should avoid or feel guilty about – just don’t think you can gorge on it as shortcut to keeping your blood pressure down.

VERDICT: Fine occasionally, but no health reason to gorge.


BAOBAB

The fruit of the baobab tree, found only in sub-Saharan Africa and Madagascar, contains a powdery white pulp. Its particular mix of calcium, magnesium, potassium and vitamin C is supposed to make it a potent elixir for energy release and immune function. Hence you can now buy baobab powder to add to your drinks.

The trouble is, there is no indication as to why this particular blend would be so beneficial. The amount of each nutrient per 10-gram serving of powder, according to one manufacturer’s label, is relatively small: there is roughly three times more vitamin C in an orange, and there is twice as much potassium in a banana. What’s more, no one has presented any evidence to suggest that they somehow work wonders when put together.

If there are any particular benefits to be had from powdered baobab, they might lie in its ability to slow down the release of sugars from other foods. A recent human study showed that adding baobab powder to white bread significantly reduced sugar release for up to an hour after eating it as part of a meal.

Researchers speculate that polyphenols or tannins in the fruit might bind to starch molecules to prevent breakdown in the gut or inhibit sugar-releasing enzymes. Then again, it might be that including baobab raises the fibre content of your meal.

Whatever the reason, if you’re looking to slow down sugar release, there are plenty of other options. As long as you’re eating a variety and fruit and vegetables, which will give you a decent amount of fibre and polyphenols, there is no need to splash out on baobab powder.

VERDICT:Nothing you can’t get elsewhere.


CHIA SEED

The ancient Maya used chia seeds for thousands of years to make everything from flour for tortillas to tea. Now they are one of the trendiest superfoods, often said to be a great source of omega3s – fatty acids thought to reduce the risk of cardiovascular disease and depression.

Chia seeds contain roughly 17 grams of omega3s per 100-gram serving. At first glance, compared with oily fish, that looks impressive: a 100-gram portion of farmed Atlantic salmon gives you 2.2 grams of omega3s. Unlike salmon, however, the fatty acids in chia seeds come as alpha linolenic acid (ALA), which the body has to convert to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to get the cardiovascular health benefits.

We don’t do this conversion very well. It varies, but the median efficiency is 10 per cent, so the amount of EPA and DHA you get from 100 grams of chia seeds drops to 1.7 grams, fewer than from salmon.You also have to consider that to convert ALA, your body has to digest the seeds to extract the fats – and we all know that some seeds pass straight through.

For omega3s, then, it might be better to smash up your chia seeds in as moothie. Then again, if you’re after soluble fibre to mop up bad cholesterol, whole seeds are the way to go. Two tablespoons provides around 30 per cent of your daily intake. So with chia seeds you can have your fibre and eat your omega 3s – just not necessarily in the same serving.

VERDICT: Good, but oily fish packs more omega3s.


KIMCHI AND KEFIR

Kimchi is a Korean side dish made of fermented cabbage; kefir is a fermented milk drink from the Caucasus mountains in eastern Europe. These and other fermented foods have been around for centuries, only to suddenly receive acclaim as microbiome-balancing paragons of dietary virtue.

Some of their powers are put down to the fermentation process, in which bacteria partially digest the food, releasing a greater hit of nutrients. Indeed it seems to improve the availability of iron, essential for making red blood cells: one recent study in humans showed greater absorption of iron from fermented mixed vegetables than fresh ones.

The biggest health claim, however, is the supposed effects on your gut microbiome – the billions of bacteria that reside in your intestines, quietly regulating all kinds of bodily functions. The idea is that the fermentation process increases the numbers of beneficial bacteria naturally present in the food and,when you eat it, in your body.

Animal studies suggest that fermented foods might encourage a healthy mix of microbes in the gut. Adding kefir to the diets of mice, for instance, increased the population of beneficial bacteria like Lactobacillus and Bifidobacterium in their intestines and reduced potentially harmful ones.

However, John Cryan of University College Cork in Ireland,whostudies the gut microbiome, urges caution when it comes to the benefits for humans. Fermented foods do look as if they could benefit gut flora, he says, butwhat this does for your health is not clear. “It’s early days,” he says.

VERDICT:May be good for gut bacteria.



COCONUT WATER

When it comes to hydration, what could be better than water? The clear liquid tapped from young, green coconuts has been dubbed “nature’s sports drink”. But two recent studies comparing it with isotonic sports drinks and ordinary water found no difference in terms of how well they hydrated volunteers after vigorous exercise.

The claims for coconut water appear to rest on the idea that its higher potassium levels enhance water absorption. That doesn’t stand up: according to another recent study, neither coconut water nor a potassium-rich sports drink scored higher on fluid retention than water. Besides, you shouldn’t have any problem absorbing water so long as your diet contains adequate amounts of salt.

VERDICT: No better than water.


WHEATGRASS

Fans of the wheatgrass shot, the dark-green juice squeezed from the young shoots of wheat, insist that it will flood your tissues with oxygen. The story goes that chlorophyll, the compound that plants use to make sugars via photosynthesis, is structurally similar to haemoglobin, the protein in red blood cells that carries oxygen around the body. So as there is more chlorophyll in wheatgrass shoots than in other edible plants, you get more oxygen.

It’s nonsense. Chlorophyll is found in similar concentrations in many green vegetables. More to the point, there is no evidence to support the idea that chlorophyll functions anything like haemoglobin. Even if it did, it wouldn’t get into the bloodstream because chlorophyll gets broken down in the gut.

VERDICT: Whole shot of nonsense.


BEETROOT JUICE

No longer just soaked in vinegar and served from a jar, beetroot is now lauded as a blood-pressure lowering, metabolism-revving superfood. The main do-gooders are said to be nitrates. These are converted into nitrites by saliva and then pass through the stomach, where they are converted into nitric oxides – compounds that relax blood vessels.

Indeed, studies have shown that dietary nitrate brings down blood pressure and improves circulation. It might even jump-start your gym routine: one study found that a 500-millilitre glug of beetroot juice per day, containing 400 milligrams of nitrate, improves exercise performance, buying people an extra 90 seconds of intense exercise before exhaustion.

Maybe don’t overdo it, though. The European Food Safety Authority (EFSA) puts the safe limit for dietary nitrate intake at around 260 mg per day for an average adult – that’s equivalent to two whole beets or one 300 ml glass of beetroot juice. The main concern is that if nitrites combine with protein in the stomach, they could potentially form nitrosamines, which may contribute to gastric cancers. The link is not proven, and adding vitamin C may prevent the formation of nitrosamines. Even so, Collins says it might be possible to have too much of a good thing.

On balance, nitrates are a good addition to your diet and beetroot is a great source. As ever, though, there are plenty of alternatives out there: lettuce, rocket and other leafy vegetables are perfectly good sources too.

VERDICT: Good stuff, just don’t overdo it.


BREAKING IT DOWN

The most eye-catching health claims for superfoods tend to be associated with particular groups of compounds: the glucosinolates in kale and broccoli, for instance, or the anthocyanins in blueberries.

Trouble is, although we can study how isolated compounds act on cells in a dish or in mice, it’s much trickier to get a grip on what foods containing these ingredients do inside the human body.

“The way we do experiments is almost like a drug trial, testing one nutrient against something that doesn’t contain that nutrient, says Duane Mellor, a nutrition scientist at the University of Canberra in Australia. “Randomised controlled trials are good for drugs, but we don’t eat foods in isolation.”

Nor do we have a great understanding of how the foods we eat are broken down into their molecular building blocks, how these interact with each other and what happens to them when, or if, they reach different tissues. There is also variation from person to person in the gut bacteria that influence all of these processes. And in some cases, cooking can reduce the levels of active ingredients before they pass your lips.

“You put something in one end and it goes into this black box and we measure an effect,” says Mellor. “Is that a true effect? Unless you do very, very meticulous studies to measure the peaks of all the compounds from every bodily fluid you can get, including stools, you’re not going to know what’s going on.”

The upshot is that even when scientists do put superfoods to the test in human studies, it’s hard to figure out how they perform. Hence most claims you hear refer to cell or mouse studies, and should be taken with a hefty pinch of salt.

By Caroline Williams in "New Scientist", vol. 231, n.3085. week 6-12 August 2016, USA, excerpts pp.26-31. Adapted and illustrated to be posted by Leopoldo Costa.