EAT YOUR GREENS? How We’Re Turning Fruit and Vegetables Into Junk Food

UNDELETABLE Your online life can never be erased WEEKLY August 1 - 7, 2015 EAT YOUR GREENS? How we’re turning fruit and vegetables into junk food Science and technology news www.newscientist.com ONE DEGREE US jobs in science OF PERSPIRATION No3032 US$5.95 CAN$5.95 The ﬁrst big climate threshold is upon us FURRY ADOPTERS EXOMOONS TIME IS RIGHT Why do animals care The next frontier in our When to start for others’ offspring? search for alien life having kids COVER STORY Bitter truth Fruit and veg are getting tastier… at the expense of our health. Marta Zaraska reports 26 | NewScientist | 1 August 2015 HERE have all the white grapefruit identified so far, giving the bitter tang gone? When I was a kid, they were to familiar foodstuffs such as Brussels Walmost the only kind around, but sprouts and coffee. today white grapefruit are hard to find in my But despite phytonutrients being toxic local shops, often replaced by sweeter pink in large doses, a growing body of evidence or red varieties. suggests that small doses can confer a host I’m not imagining it. Thirty years ago, of health benefits. The elusive white grapefruit Florida, the grapefruit capital of North is a prime example. Its most prominent America, produced 27 million boxes of white phytonutrient is ultra-bitter naringin, and 23 million boxes of the coloured varieties. which turns out to have anti-ulcer and anti- Today, they ship more than twice as many red inflammatory properties. Naringin can also and pink grapefruit as they do whites ones. inhibit the growth of breast cancer cells, and And it turns out grapefruit is a bellwether of induces cervical cancer cells to commit a more insidious trend. It affects much of the suicide. The sweeter pink and red varieties fresh produce aisle, from cauliflower to have substantially less of the stuff. potatoes, tomatoes and juices. Our fruit and The mechanism at work is known as vegetables are becoming less bitter. hormesis – simply put, it’s the idea that On the face of it, reducing bitterness in what doesn’t kill you makes you stronger. foods sounds like a great idea. Wouldn’t it be “The reason bitter phytonutrients are nice if broccoli were always mild and sweet? cancer preventing is that they can destroy Supermarkets are already advertising milder cells. They are healthy because they are toxic,” Brussels sprouts as “kid friendly”. But there is says Adam Drewnowski, an epidemiologist a catch. The same chemicals that make fruit who studies nutrition at the University of and veg bitter also imbue them with many Washington in Seattle. One study, for example, of their health benefits. When scientists talk found that eating a diet rich in quercetin, about the healthiness of green tea, dark found in green tea, broccoli and red wine, chocolate, red wine or broccoli, much of might help protect against lung cancer, what they are talking about is due to bitter especially in heavy smokers. chemicals called phytonutrients. To satisfy our love of sweetness, food manufacturers are now removing many Sweet tooth of these substances, causing some people to And the list of phytonutrients thought to worry that we are turning bitter fruit and veg have anticancer properties is growing. It now into the junk foods of the fresh produce aisle. includes sinigrin – one of a group called “Eating fruits and vegetables without glucosinolates, which give the bitter edge to phytochemicals would in many ways be Brussels sprouts, cauliflower, cabbage and analogous to drinking the empty calories of kale. There’s also genistein in soya beans, a can of soda,” says Jed Fahey a molecular sulforaphane in broccoli, plus potatoes have scientist at Johns Hopkins School of Medicine solanine and tomatoes have tomatine. in Baltimore, Maryland. “Yes, you could Further explanation of the health benefits survive on de-bittered fruits and vegetables, of phytonutrients may be their antioxidant and they would help maintain life, but not properties. Antioxidant supplements have good health.” So if our preference for sweet come under some scrutiny in recent years. But over bitter is prompting the food industry to the thinking is that when eaten as whole foods, strip some foods of the very chemicals that rather than supplements, the phytonutrients make them good for us, what’s to be done? in bitter fruit and veg trigger our internal And how can we train our taste buds to better antioxidant system to kick in. “These enjoy bitter? compounds can activate the expression of It makes sense that as consumers we favour antioxidant genes that do have the ability to sweet ingredients – we have evolved to do so. remove oxidants and other potentially toxic Sweet foods hold the promise of a ready compounds,” says Henry Jay Forman of the supply of energy. Salty food contains sodium, University of Southern California. necessary for our bodies to function properly. A dose of the bitter stuff seems to have Bitter, on the other hand, suggests toxicity, benefits for heart health, too. Phytonutrients which is why our natural reaction is to want to in cocoa, coffee or berries can reduce the risk spit it out. Bitter phytonutrients act as a of cardiovascular disease – and not only due to natural pesticide, protecting plants against all their antioxidant and anti-inflammatory kinds of enemies, from bacteria to insects and properties. They also help to prevent the ALEXANDER KENT ALEXANDER cows. Thousands of these nutrients have been build-up of plaque in the arteries. > 1 August 2015 | NewScientist | 27 BOILING AWAY Even so, we evolved to recoil at the taste THE GOODNESS of substances that might poison us, rather Many vegetables contain glucosinolates, which may than favour them for any benefits relating to have anticancer beneits. Cooking diminishes the amount cancer or heart disease, which usually affect us after we have reproduced. This aversion to bitterness is especially strong in around a RAW BOILED third of us (see box, “Are you a supertaster?”). “Because they are bitter, for years we have been removing phytonutrients from the food White 5 supply,” says Drewnowski. cabbage As a result, what we eat today is noticeably less bitter than the food our parents and grandparents ate even a few decades ago, says Peter van der Toorn, who leads the vegetable 108.9 mg/100g 78.6 mg/100g breeding division of Syngenta in the Netherlands. Brussels sprouts are a good example. “We still have bitter sprouts on the market, but the majority of what’s introduced these days is milder.” Brussels 9 sprouts Downgraded drinks One way growers do it is to breed the offending compounds out. In fact, humans have been 226.2 mg/100g 123.7 mg/100g doing this since the dawn of agriculture. Take tomatoes, a fruit many of us wouldn’t even think of as bitter today. One wild species indigenous to Peru can contain 166 times as much bitter tomatine as the mild varieties we normally find on supermarket shelves. Cauliflower 10 When breeding and growing conditions are not enough, manufacturers can also sometimes remove bitter compounds later on, instead. They call this process de-bittering. Citrus juices, for example, naturally contain 62 mg/100g 42 mg/100g high amounts of phytonutrients such as limonin, naringin or naringenin. “Most juice manufacturers make a concerted effort to limit bitterness,” says Russell Rouseff, a food chemist at the University of Florida. One Turnip/ method involves passing the juice through 15 a bead-like resin that filters out bitter swede molecules. This can reduce the amount of naringin in grapefruit juice by as much as 64.5 per cent. Surprisingly, home-made freshly 56 mg/100g 29.1 mg/100g SOURCE: BRITISH JOURNAL OF NUTRITION, DOI:10.1079/BJN2003917 squeezed orange juice contains on average fewer healthy phytonutrients than do on bitter could have unwanted effects on commercial freshly squeezed juices. That’s our waistlines. “Bitter receptors, which are Cooking, on because these producers scrape out more amazingly spread along the gastrointestinal average, decreases phytonutrient-rich peel oils into the drink. tract and not only on the tongue, are now The more we learn about the role of bitter in known to play a pivotal role in many glucosinolates by our diets, the further the effects seem to reach. gastrointestinal mechanisms, such as appetite Drinking cocoa high in flavanols over a period regulation,” says Daniele Del Rio at the of four weeks has been shown to significantly University of Parma in Italy. “Therefore, % increase the presence of bacteria in the gut getting rid of bitter compounds, besides that boost digestion and immune function. depriving our body of potentially protective 30 These benefits weren’t seen with “dutched” phytonutrients, is also impairing our capacity cocoa, which has had the flavanols removed. to regulate food intake.” Some de-bittering processes are stripping Many scientists working in the field believe our food not only of the health benefits that the food industry has a responsibility to bestowed by phytonutrients, but also make sure that phytonutrients are preserved essential vitamins. What’s more, skimping in our food supply. It would be better for our 28 | NewScientist | 1 August 2015 NUTRIENT-RICH COOK BITTER VARIETIES BETTER Broccoli White grapefruit (Atlantic variety) contains contains % Using bitter food will make x3 50 you a better cook, says the more chef Jennifer McLagan beta-carotene flavanones (26.96 mg/100g) Understanding the role of bitter is an (1.47 mg/100g) essential skill for a cook. Bitter is vital for the harmony of a recipe and crucial to the composition of a meal. It enhances of Packman variety than red and pink grapefruit the flavours in a dish, subtly adding (0.49 mg/100g) (17.9 mg/100g) complexity and depth, often without any marked bitter taste.

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