‘Sugar is the most dangerous drug of the times and can still be easily acquired everywhere … Just like alcohol and tobacco, sugar is actually a drug. There is an important role for government. The use of sugar should be discouraged and users should be made aware of the dangers.’ So wrote the head of Amsterdam’s Health Service in 2013 at the peak of anti-sugar hysteria.1 At the same time, several bestselling books were released, such as Robert Lustig’s that described sugar as toxic.
This addictive poison is a particular carbohydrate combination of a fifty-fifty mixture of glucose and fructose – sucrose, in fact, and what we all commonly call ‘sugar’. The fructose component, in particular, is the villain that is attracting all the attention. A persuasive group of doctors and journalists have assembled an impressive case for the prosecution, alleging that this sweet substance above all others is responsible for our current obesity and diabetes epidemic. Most of us are still confused by the fat and cholesterol debate. Should we now be worrying about sugar too?
Glucose, one of sugar’s chemical components, is only slightly sweet and we don’t eat or drink it on its own. Glucose is the natural fuel of our bodies: it travels around the blood supplying vital energy to our muscles, brains and organs, where it is used up by our cells to power all our processes and functions. The other part of sugar, fructose, provides the sweetness and is a natural component of all fruits.
About five years ago, as I mentioned, like many others in middle age I started paying more attention to my diet and general health. Based on what I had heard, I wanted to reduce my intake of saturated fats and my risk of heart disease, as well as lose a bit of weight. I started by changing my breakfast: no more coffee, toast, butter and marmalade with eggs and bacon on Sundays. My ritual was now a healthy helping of soy milk added to my combo of healthy low-fat, high-fibre muesli and All-Bran, washed down with a cup of black tea and a glass of natural fat-free, concentrate-free orange juice from Florida. I would also have low- or zero-fat fruit yoghurt a few times a week.
What could be healthier? After all, sugar is just empty calories and, weight for weight, has half the calories of fat. Should I really be worried? Well, probably yes.
Everyone now knows that a normal 330 ml can of Coke or Pepsi contains 140 calories and over eight spoonfuls of sugar and a Mars bar contains seven, and if you are crazy enough to eat a bag of toffee popcorn you will get over thirty spoons of the white stuff. Eating or drinking any of these treats may feel naughty, but you know what you are doing. I was carefully avoiding these obvious sugary villains, yet like many people I was being conned by the food industry. Food labels present sugar content in grams, so to convert it to something meaningful you divide the stated grams by four to get the equivalent in teaspoons, so 8 grams of sugar is equivalent to two teaspoons.
My ‘healthy’ low-fat breakfast cereal was giving me plenty of fibre from the oats, whole grains and nuts but was actually equivalent to eating 20 grams of sugar, or more obviously five teaspoonfuls of the stuff. On top of that, my small serving of low-fat non-dairy soy milk gave me an extra teaspoonful, and there were another 4 teaspoons in my small glass of expensive (labelled not from concentrate) 100 per cent pure Florida orange juice. In fact, it’s not as pure as it sounds, as most of it is made by pasteurising the oranges, storing them in sterile vats without oxygen (or, by that time, much taste either) for months, then re-adding the taste as flavour packs. Incidentally, other, cheaper, orange juices made from frozen reconstituted concentrates are not very different in sugar content. They don’t need any extra – there’s plenty of natural sugar in the oranges. Anyway, that’s ten teaspoons of sugar before I had included my twice-weekly fat-free yoghurt, which adds another five. But I couldn’t taste anything like this much sugar because I was being fooled by the skilful chemistry, processing, texturing and added salt of the food manufacturers. I was also easily misled by the ‘No added sugar’ labels.
Everyone likes sugar. Even babies who have never been exposed to it are programmed to seek out the flavour, and the sweetness will uniquely soothe them if they cry or are in pain. The average Briton ingests around fifteen spoons of it daily, and many considerably more. It is a natural human response to seek out sweet non-poisonous fruits that we can use as a rapid energy and Vitamin C source. Another probable reason why we have this reflex is so that we could gorge on fruit at harvest time, thereby stocking up on vital nutrients to last over the winter. Our ancestors would never have been able to even dream about having access to an unlimited supply of liquid fruit or honey all year round.
So is eating fifteen spoonfuls of sugar a day either natural or, more importantly, harmful for us?
In the old days, sugar was the stuff in a sugar bowl on the table that people used to add to their tea, coffee and desserts and it came in a rectangular paper bag. Those days are largely gone. We now actually add less sugar to our food because so much is already pre-added for our convenience. An estimated 65 to 75 per cent of all processed foods on sale now in the US and the UK have some added sugar.
Pure energy or pure con?
Fructose is the sweetest naturally occurring substance and considerably sweeter than glucose. It is present in nature only in fruit, but thanks to modern food wizardry is present everywhere. Until recently we were so concerned with fat being the bogeyman that sugar got an easy ride, under the clever marketing guise of it being loaded with energy. In processed foods, sugar was slowly but inexorably filling the gap left by fat.
Sugars, whether sucrose, glucose or fructose, have been called ‘empty calories’ because there is no additional nutritional value in them. The food industry has skilfully used the word ‘empty’ to imply that sugar is just pure energy rather than a major source of body fat. The marketing teams were conveniently forgetting the fructose component and focusing on the glucose half of sugar, reminding us that athletes all use high-energy glucose sports drinks. Confectionery like Marathon (now Snickers) and Mars – ‘helps you work, rest and play’– were aimed, they said, at giving us the energy to get through the day, or even run a marathon.
Sugar could even fight illness. High-sugar-content drinks like Lucozade were heavily promoted (despite there being no proof) as aiding recovery from illness (and more recently from sports injuries), each bottle containing over 12 spoonfuls of therapeutic sugar. Breakfast cereals consisting nearly entirely of sugar (more sugar than puff, in fact) were also promoted as a great way for kids to kick-start the day. Apart from the minor irritation of causing tooth decay, it looked like cheap sugar was a great source of natural energy with no real downsides, if you were healthy, that is.
So my new ‘healthy’ breakfast got me off to a flying start with 10 to 15 spoonfuls of totally fat-free sugar, equivalent to two cans of Coke or Pepsi. My fibre intake was quite good, which might limit some of the damage by reducing the speed of absorption of the fructose and glucose; but the extra calories, empty or not, definitely were not helpful. I felt cheated.
Since the day I realised my errors, my trips to the shops have become educational. The ‘Zero Per Cent Fat’, ‘High Fibre’, ‘No Added Sugar’ or ‘Five a Day’ messages on products are often super-size and obscure the sugar content, which is hard to interpret without a magnifying-glass and a maths degree. The labelling around sugar is intentionally confusing – mixing amounts of carbs, natural and artificial sugars, agave syrup, corn syrup, fructose, and sugar from fruit (as if it were super-healthy) in different and obscure serving sizes and names and euphemisms.
Fruit juices alone now supply a daily average of 100 calories per person in Western countries, and most people believe these are healthy and an easy way to get your fruit portions and vitamin C. However, 98 per cent of them contain fruit juice concentrate with massive amounts of sugar, more than you would find in a Coke or Pepsi of the same size.
Twice as bad are pink and ‘old-style’ lemonades and ginger ales and many other fruit-flavoured drinks or fruit cocktails, to which even more extra sugar has been added. These contain up to ten spoonfuls per serving, and there are equally large amounts in foods such as organic yoghurts, where the manufacturers can cunningly call sugar ‘organic fruit-based’ or refer to ‘organic invert sugar syrup’. Agave syrup is often added as an alternative and you may find that the packaging suggests it’s healthier than sugar as it is made from tequila cactus (and pollinated by bats) and 15 per cent sweeter. However, sadly, despite its exotic origins, this is not an advantage because it is in fact its 70 per cent fructose content that gives it its ‘magical’ extra sweetness.
A stroll down the supermarket aisles tells you there’s sugar in Hovis bread and other healthy-looking wholemeal brands. The average burger bun has so much sugar that it would be classified as a dessert if we didn’t have a tiny gherkin on top to balance it. Each small serving of ketchup has a spoonful of sugar. There is sugar in steak pies, soups, tinned beans, lasagne, pasta sauces, sausages, smoked salmon and seafood sticks, healthy-looking salads, diet salads, muesli bars, bran cereals and ready-made curries. A bowl of canned tomato soup actually has more sugar (12 grams) than a bowl of Frosties cereal.
Basically, it’s hard to find anything in a packet or tin that doesn’t have serious amounts of sugar – again, if you can read the microscopic print on the label. If the sugar comes from fruit or another ‘better’ source, no matter, because if there is little or no fibre your body treats it just the same.
Why is there sugar in all these things? Partly, it’s because we like it. Our tastes have apparently changed. We no longer want to add our own sugar from the bowl on the kitchen table. These days we want everything to be sweeter; we wouldn’t like to go back to the good old days when fish tasted salty and dried fruits were a bit tart. As the food we eat becomes sweeter and more sugar is added to processed foods and juices, our thresholds increase and we need more sweetness to satisfy us. We also don’t like the taste of low- or zero-fat foods, and because salt contents have slightly dropped recently those helpful food companies have added something to compensate our deprived taste-buds. Sugar.
Our liking for sweetness is partly cultural and partly genetic. Although all humans like sugar to some extent, there is considerable variation due to differences in the sweet-taste receptor genes that we discussed earlier. The propensity for obesity is strongly genetically related to our preference for sugar, and in 2015 we identified via huge international collaborations an ever-increasing list of nearly a hundred obesity genes, each with a tiny influence.2 For some people just having the susceptibility genes is not a problem until they encounter certain types of food.
One study looked at over 30,000 Americans and at the variants they had in the top 32 obesity genes. People with the bad luck to have inherited over ten obesity-risk genes were particularly susceptible to the effects of sugary drinks. They effectively doubled their risk of becoming obese over the next five years if they drank just one sugary can each day.3 We don’t know yet why sugar seems to interact so strongly with our obesity genes but it does suggest that our bodies have a hard-wired need to seek out sugar, perhaps as a way of detecting edible carbohydrates. Interestingly, most of the genes interacting with sugar turned out to be those acting on the brain.
In our twin study with colleagues in Finland we found that nearly 50 per cent of the differences between sweet-tooth preferences was due to their genes, and the rest a mix of the dietary or sugar culture around them.4 We also found a clear positive correlation between how pleasant people rated a 20 per cent sugar solution and how often they ate other sugary foods.5 While genes in early life seemed to partly determine our sugar-related behaviour, subsequent exposure to high levels of the substance later in life also appears to have increased our sweetness thresholds and in the last few years to make us want yet more.
Individual governments have shied away from putting limits on sugar in food and drink, even more than they did for trans fats, preferring what they call ‘voluntary discussions’ with the food industry. When in 2002 the World Health Organisation first proposed to limit the percentage of total calories coming from sugar (for example, carbohydrates: of which sugar) declared on the label to 10 per cent, the industry reacted furiously. In the US the corn-sugar lobby petitioned Congress and managed to threaten the WHO with a withdrawal of funds. Not bowing to pressure, an updated 2014 WHO draft report has recommended that the original 10 per cent level proposed is still reasonable and that governments should aim at reducing this further to just 5 per cent, equivalent to a single can of cola.6
Without legislation these recommendations are of little use, as the average UK and US citizen is consuming over double this, and many teenagers much more. The industry has reacted predictably, attacking the evidence as weak and claiming that you can’t lump all sugars together as unhealthy. In response to similar industry lobbying, the UK government, despite pressure from doctors, from its Chief Medical Officer and from health groups, is also resisting any real change such as imposing limits or a sugar tax. In contrast, in 2013 Denmark, having scrapped its previous saturated-fat tax, increased its small tax on sugary foods to levels that have started to reduce consumption.
The rapid and recent rise of sugar in the Western diet came about mainly for economic and political reasons. During the Cuban missile crisis of the early 1960s Cuban sugarcane supplies dried up and prices rose, and the US wanted to be self-sufficient. Burger-loving Richard Nixon believed that keeping food costs low was a government priority, to keep the public happy and stop the poor rioting. The government was prepared to subsidise cheap food and the food giants were happy to oblige. In response to a surfeit of cheap corn being converted to starch, combined with generous US government subsidies, high-fructose corn syrup (HFCS) started to be used on a large scale in the early 1970s. This is a mixture of slightly higher-fructose-content sugar (a 55/45 ratio of fructose to glucose) that tasted much the same as conventional sugar made from cane or beet. Because the US government wanted to protect the corn business at all costs, they added extra taxes to imported sugar and ensured that US corn-made sugar was cheaper. This meant that it could be added cheaply to soft drinks and processed foods, thereby improving sales at little cost.
In Europe, the EU didn’t want to use corn-sugar as it subsidises the local (mainly French) sugar beet industry (beet is a root vegetable). It does this in two ways: both via its infamous Common Agricultural Policy, so as to keep beet prices for the farmers stable and costing taxpayers over 1.5 billion euros a year, and by putting a 300 euro per tonne tax on any imported sugar cane, thus doubling its cost. The UK, thanks to its old empire, used to be able to rely on cane sugar, and even a company as synonymous with sugar as Tate & Lyle has sold its cane sugar business, mainly thanks to EU policy. The net result is that sugar across the world is cheap and, ironically, heavily subsidised by taxpayers. This has contributed to the boom over the last thirty years in sales of sugar-enhanced drinks. Liquid calories for the first time in our history now make up a major part of the Western diet.
The question over whether it’s sugar or fat that is the cause of our modern obesity problems was debated fiercely in the 1970s. A British physiologist and nutritionist, John Yudkin, who was the most vocal critic of the Ancel Keys theory of high-fat diets causing disease, in 1972 wrote a prescient book called Pure, White and Deadly in which he presented his case that sugar, not fat, was the main enemy.7 At the time neither Keys or Yudkin, who became sworn adversaries, had access to decent clinical trials, and both relied on potentially flawed observational epidemiological studies for their arguments. In the end Keys was a much better politician than Yudkin and ‘won’ the debate, at least as far as governments were concerned. Any sugar concerns were pushed under the carpet for the sake of a clear anti-fat message that suited the major players.
Yudkin’s point was that refined sugar was a relatively new addition to our diets and that unlike in the case of fat we were now eating twenty times more sugar than ever in our history. Before the advent of early farming we could get sugar only from eating ripe fruit or wild honey, so for most people this was a rare event. As agriculture developed, sugar cane started to be grown, but it remained costly to produce and like honey was a luxury item. In the sixteenth century it was equivalent to buying caviar today. Plantations in the Caribbean, helped by the slave trade, started to increase the production and quality of sugar cane and slowly and progressively brought prices down.
The recent changes to sugar consumption per head are hard to estimate accurately because of so much now being added to food, but it has increased around twentyfold since the end of the nineteenth century. Since 1990, total sugar consumption in Britain has increased by 10 per cent per decade, mainly at the expense of total fat.
The question remains: Are these empty calories which, gram for gram, we eat more of than fat or protein, better or worse for us?
Busy tooth fairies and deadly mouthwash
‘I thought giving him juice in a bottle was good for him.’ Billy’s parents believed fruit drinks full of nutrients and Vitamin C would be healthy, but they inadvertently triggered a spiral of decay in their infant. Despite brushing twice a day with fluoride toothpaste, the five-year-old’s teeth have completely rotted. Billy had ten teeth removed under general anaesthetic at Manchester Dental Hospital, the maximum allowed under current guidelines. Surgeons wanted to take out fifteen, but that would have meant nine months on a waiting list and an overnight hospital stay. Billy now has just ten teeth left – four at the top, six at the bottom. The rest of his milk teeth, which were decaying before they even came through the gums, will fall out in the next six months to make way for his adult teeth. Meanwhile, he is no longer allowed to take fruit juice to bed.
Billy first had problems when he was two and a half. His mother, a twenty-five-year-old computer engineer, said: ‘I had never received any advice on how to look after Billy’s teeth. I know it’s probably my fault but my actions were innocent. I think Billy has a balanced diet and although he doesn’t drink that many juices or fizzy drinks or eat that much chocolate, I’m told now it’s the time of the day he had them that was bad. Bedtime was the worst, so the sugar had all night to work on his teeth.’
Five hundred kids in the UK need hospital admission every week to remove rotten teeth. Tooth decay is affecting over one in ten five-year-olds, and the current juicing craze is increasingly causing problems in adults. The first group of professionals to complain about sugar’s side effects were dental researchers, who after a dip during the Second World War noticed a surge in dental caries (the polite Latin word for ‘rot’) when sugar rationing ended.8 Mothers were still adding sugar to formula feeds and to dummies and soothers, but many dentists were happy with the extra work and rewards that filling cavities brought. They didn’t try too hard to alter their patients’ dietary habits but would sometimes tell them off for not brushing enough. Dentists’ families, in contrast, didn’t have sugary drinks at night, not even milky ones, and seemed magically never to suffer the same problems, showing that the decay was entirely preventable.
The epidemic that peaked in children in the 1960s dramatically ended as decay rates plunged 5 per cent a year, when countries introduced fluoride in water and toothpaste to combat the sugar. Some dental researchers like Aubrey Sheiham, whose lively lectures I remembered at medical school, were vocal over the lack of action by both the profession and the government against the increasing sugar consumption. By the mid-1980s, because of sugar, tooth decay in developing countries had now overtaken the West, where rates had halved, so Sheiham suggested our dentists should either ‘change countries or start playing more golf’.9 So by the 1960s we already had clear warning that not only were our bodies not adapted to this novel diet, but it was causing us harm.
In the West, while tooth decay was declining dramatically, some dentists were noticing the same in regions without fluoride or major changes in tooth brushing, and thought this could be due to the increasing use of antibiotics in children.10 It transpired that cavities were actually caused not directly by the extra sugar, but by microbes.
Our normal microbes were just not used to the abundance of sugar, but one particular species, called Strep mutans, loved the new food and fed hungrily off the sugar around our teeth and gums and quickly multiplied. Unfortunately, unlike the other harmless microbes, they used the sugar to produce lactic acid which made little holes in our tooth enamel. The Strep mutans stuck to our teeth by attaching themselves to dental plaque. This substance so familiar to us is in fact a colony of six hundred species of harmless bacteria stuck together to form a sticky mucous commune (called a biofilm). Ingeniously they produce a glue-like substance from the sugar they metabolise, which allows them to keep feeding safely while they hang on. Ironically, people who use a daily mouthwash may be killing off their healthy microbes and allowing the harmful ones to take over, leading to even more gum and tooth disease.11 One small study suggested this habit also increases blood pressure and risk of heart disease.12
Even at the height of the cavity epidemic, around 15 to 20 per cent of children would be relatively untouched. They are strangely protected, even if they have sugary cereal and a cola for breakfast and hardly ever brush their teeth. This is because they are lucky enough to have genes that make special saliva proteins which inhibit Strep mutans’s eating habits.13 My brother and I lacked these genes (by which I mean the good variants), and as young kids experienced the tooth decay epidemic at first hand. We regularly competed with each other to eat the most bowls of breakfast cereals we could manage so as to get a brief sugar rush and feed our microbes before starting to feel very sick indeed.
You may remember eating Sugar Smacks, Honey Smacks, Sugar Puffs, Coco-Pops, All Stars, Frosties etc., but what you probably didn’t realise was that they contained over 35 per cent pure sugar. In the US the same brands contained another 10 per cent sugar. We spent many happy hours at our local dentist, who was quite content for us to keep eating the cereal while building a large swimming pool at our expense. What is worrying is that forty years later these same cereals (some brands have dropped sugar from the name) are still being sold with healthy-looking nutrient packaging and no warnings. After decades without any tooth problems other than those caused by my over-zealous Australian dentist, I now have a couple of small cavities. This could be just bad luck, or may be caused by my extra sugar intake from my super-healthy low-fat breakfasts?
Recent research shows that probiotics, the friendly bacteria like lactobacillus, offer some protective effects against the acid-producing Strep mutans. A German company has developed a probiotic (sugar-free) sweet which when sucked five times a day reduces the numbers of the microbe.14 The probiotic is a lactobacillus similar to those found in cheese, but preheated so as to kill it. It still binds onto the mouth microbes, cramping their style, and prevents them sticking to the plaque around our teeth. They then get flushed away by the saliva. Longer trials of similar probiotics show they continue to survive in the mouth, providing benefit, for several weeks.15 Trials show that giving kids more natural microbial cheese or sugar-free yoghurt could do the same.16
Tooth decay, despite fluoride, is making a comeback. Rates are again increasing in most countries and about a third of the planet has untreated tooth decay.17 18 The only people without problems are rare tribes who live off meat or fish, as our hunter-gatherer ancestors did. Even our early Neolithic farming ancestors on their starch diets we now know suffered from tooth decay. In the UK dental extraction is now the commonest cause of admission for kids, and costs the country over £45 million. Increased sugar in the form of fizzy drinks and juices is the main culprit, and now together with our tooth microbes is overwhelming the protective effects of fluoride.
We know a lot about the effects of sugar on the bacteria in the mouth, but much less about the effects on the gut. This is because most studies have either focused on high-fat diets or on mixtures of high fat and high sugar. Given that our ancestors only rarely had access to honey and didn’t do smoothies, our system and our gut microbes are less well adapted to high doses of sugar, particularly as a liquid.
Chewing or sipping your carbs?
Our whole digestive system is set up as a planned sequence of events that trigger, then manage, the digestive process. It starts with the brain just thinking about food so as to get the gastric juices and the hormones flowing, as well as producing the amylase enzyme in saliva. Then comes chewing. The body expects us to chew and swallow our food slowly. Up to forty chews is believed to be optimal to break down tough meats and vegetables and to prepare the whole digestive system. Compared to our ancestors, nowadays we rarely use our chewing powers and jaw muscles to the full, as shown by the lack of growth of our jaws and the subsequent modern epidemic of impacted wisdom teeth resulting from a mismatch of jaw sizes.
Normally the well-chewed and broken-down food passes downwards, releasing hormones in the gut lining, the liver, the pancreas and the gall bladder that aided its breakdown. At the same time signals of fullness are sent back to the brain. The pancreas releases insulin so that any glucose released into the bloodstream can be quickly dealt with. The gall bladder releases bile salts which in turn send signals to the microbes further down the gut, in the colon, to get ready to digest the expected food.
So when you drink a large sugary drink with, say, a bowl of refined-carbohydrate pasta that requires minimal chewing, your body has no time to send the right signals. As the high-sugar load hits the stomach it passes rapidly into the small intestine, where most of the sugar is absorbed. This produces an abnormal and mistimed insulin response, altering the breakdown of glucose; the released bile salts now have the wrong mix for the unexpected sugars, and the normal gut microbes are replaced by unhealthy species that feed off the sugar scraps. These unusual microbes send out new messages to alter the hormonal signals and the bile salts. The result is a very disturbed system. The microbes expecting nutrients from the empty-calorie food send out signals to the brain to keep sending more sugar their way, while the glucose is being stored away as fat, often of the internal (visceral) kind.
Can our microbes defend us against fructose?
The reason for fructose being the latest hate item of the diet world despite its natural ‘found in fruit’ credentials is complex. Forty years ago Yudkin pointed out in his book that fructose was the likely villain, and that the glucose released from starch in plants was very different. He was largely ignored. However, the high-sugar content of soft drinks did eventually grab people’s attention.
George Bray, a distinguished obesity researcher, reignited the sugar debate in 2004 when he pointed out the clear observational correlation between rising sugar ingestion and rising obesity in the US.19 In most countries, the consumption of sugary drinks had increased three- to fivefold since 1950, and by 2009 around 20 per cent of total calorie intake in the UK came from high-fructose soft drinks (more than that, in some teenagers).20 Across the world, these changes mirrored increases in the incidence of obesity and diabetes.21 Confirmatory epidemiological evidence from the meta-analysis of other large observational studies showed that the consumption of soft drinks was associated with a later risk of obesity and diabetes.22
When fructose is compared to glucose it shows a number of major and worrying differences in how it is metabolised. Most of it is absorbed in the gut and goes straight to the liver, where it is converted to glucose, energy or fat. But unlike glucose it produces only a very modest insulin signal in the blood. At first, cocky doctors recommended fructose sweets for diabetics, which was a really dumb idea. Fructose does work differently, but it interferes with normal appetite signals to the brain. We know little about how fructose and glucose remnants in the gut interact with our gut microbes, but many sports drinks contain fructose and this triggers in a growing number of people microbial fermentation, bloating and discomfort.23 This fructose intolerance has a genetic basis; these individuals can’t process the fructose, which builds up to high levels in the blood, something that is hard to achieve in nature.
The important differences between fructose and glucose metabolism triggered a number of rodent studies that were tricky to do in humans. Fructose in rats causes the same toxic change in microbes that we saw with junk foods and high-fat diets – in particular, causing a fatty liver. But this side effect can actually be reversed by antibiotics.24 When rodents are fed high doses of fructose, it increases their visceral fat dramatically.25 Randomised trials of fructose in humans have been less clear-cut, but often show metabolic and visceral-fat changes after a few months.26 This internal fat effect of fructose and soft drinks is likely underestimated, and could be responsible for the diabetes epidemic in places like the Middle East where huge numbers of people consume soft drinks, often without looking externally fat. These people are called TOFIs (thin-outside, fat inside) and are metabolically very unwell.
Fruit contains high levels of fructose, so should we be worried about overeating fruits? There is a lack of good data on this subject, but it appears that eating the whole fruit is much less harmful. A study of 425 Japanese living in Brazil at high risk of diabetes found that the fruit eaters had normal insulin increases, in contrast to the doubling of insulin peaks in those that had acquired the same amount of fructose by consuming sugary drinks.27 Other smaller, detailed, studies showed similar results, and that there is something else in whole fruit that is protective. This is probably the increased fibre, which we discuss later.
Eating or drinking too much sugar in any form is harmful, and liquid calories appear particularly bad, even if dressed up as ‘healthy juice’. However, despite the hype, the evidence that fructose is the principal demon to be exorcised is not proven. Its metabolism and the way the body handles it is certainly different from glucose, and although theoretically it could be much worse for us we should remember that glucose overdose also leads to fat deposition.28
The critics of the fructose witch-hunt argue that the data is flawed, and for several reasons. These include, if total calories are controlled for, that fructose is no worse than other sugar sources; that the rodents studied are fed abnormally high fructose diets (60 per cent of calories); that rodent livers are not the same as humans’; and that the human studies are generally small, of poor quality and inconsistent.29 This renders inconsistent even the academics’ interpretation of the same trials by meta-analyses.30 31 32
Healthy lean people seem to be able to deal with occasional fructose drinks with no problems. Because humans in most cases are not rats, not enough money has been spent on careful trials. As a consequence, we still can’t prove that the excess calories from fructose are actually worse than the excess calories from glucose. Until we know more, then, we need to avoid the same mistakes of reductionism and avoid, too, singling out scapegoats like fructose, which takes our eyes and minds off the bigger picture. While I am now convinced that too much sugar is not good for us, particularly if it comes in liquid or unnatural form, the data is not yet clear that fructose is much worse than the equivalent amount of glucose or other sugars.
Looking back on my past ideal breakfast, it would seem that my high-sugar feast of muesli, fruit yoghurt and fruit juice should be replaced with a strong black coffee and some natural yoghurt. In fact, I’m beginning to wonder if I should go all the way back to my porridge, eggs and bacon.