For years we were told that salt was the villain. Now they tell us we can take that health guidance with a pinch of . . . well, you guessed it . . . and, instead, we should be worrying about the sugar in our diet. But even that's not quite right, a new study suggests, as within the world of sugars, there are bad guys and even worse ones.
The real sugar supervillain is HFCS, or high-fructose corn syrup-or just glucose corn syrup, as it's known in the UK-the sweetener now found in almost every processed and convenience food and soft drink.
HFCS is more lethal than sucrose or table sugar, a new study suggests. "This is the most robust study showing there is a difference between high-fructose corn syrup and table sugar," says lead researcher Wayne Potts, from the University of Utah.
Essentially, the more HFCS you consume, the more likely you are to die prematurely-and it's all to do with the molecules in this sugar. On the face of it, there's not much difference between the amounts of fructose and glucose found in HFCS and table sugar. But corn syrup has separate molecules called 'monosaccharides', which are combined (in 'disaccharides') in table sugar-and this one difference appears to have an enormous impact on our health.
Because they are separate, the fructose molecules in HFCS are quickly taken up and used by the body, whereas those in sucrose-the natural sugar from cane or beets-must go through an extra metabolic stage before the body can absorb them. Potts and his team fed two groups of mice a generally healthy diet, but added a mix of fructose/glucose monosaccharides-like those found in HFCS-to one diet, and sucrose to the other. Nearly twice as many mice in the monosaccharide group died, and they also produced 26 per cent fewer offspring, suggesting that the sugars interfered with their reproductive system.
The same team came to a similar conclusion in another mouse study carried out in 2013. In that one, the female mice fed HFCS monosaccharides died at twice the normal rate, while the male mice were less likely to hold on to their territory and to reproduce.
A weighty issue
Then there's the smoking gun. Potts points out that the diabetes and obesity epidemics started in the mid-1970s, which is just about when HFCS started to replace sucrose as the major added sugar in the West, especially the US.
And there's evidence to support his suspicions. Researchers at Princeton University have established that we put on far more weight after consuming HFCS than any other sugar. "Some people have claimed that HFCS is no different than other sweeteners when it comes to weight gain and obesity, but our results make it clear that this just isn't true," says lead researcher Bart Hoebel.
In an experiment using lab rats, Hoebel and his team found that the animals fed HFCS gained 48 per cent more weight than those fed a non-HFCS diet. But the rats didn't just get fat; they showed all the signs of becoming obese, with most of the fat gain around the abdomen and rising levels of blood fats (triglycerides) too.
Piecing it together
Another piece of the obesity jigsaw was provided by a different rat study. Obesity is linked to the body's ability to produce insulin, the hormone that uses and stores sugar (glucose) from carbohydrates, and this study found that HFCS interferes with that process.
Impaired insulin production is a stage on the path to type 2 diabetes, the 'lifestyle' disease brought about by an unhealthy diet. The researchers, from the University of California at Los Angeles (UCLA), stumbled upon this after discovering something else about the rats' behaviour: those fed HFCS also had poorer memories and impaired learning capacities.
The UCLA researchers think this may have something to do with insulin blocking, but others have different ideas. One report by an Environmental Health Officer (EHO) from the US Food and Drug Administration found another problem with HFCS back in 2004: HFCS may be tainted with mercury, which interferes with our neurological processes.
This EHO report prompted a study by researcher Renee Dufault, who found mercury in nine of the 20 HFCS samples collected from various US processing plants. It's assumed that the mercury got into the HFCS during production. The processing plants use 'mercury-grade' caustic soda in the manufacture of HFCS, and there's a lot of leakage into our air, water-and the product itself (see box, page 20: Making HFCS).
Dufault discovered levels of mercury ranging from 0.005 to 0.570 mcg/g of HFCS and, as the average daily consumption of the sweetener is around 50 g in the US, consumers are very likely-and unwittingly-ingesting up to 28.5 mcg of mercury every day. As the standard 20-oz bottle of Coca-Cola contains around 17 teaspoons' worth of HFCS, it's easy to see why processed snack foods and soft drinks could easily be a far bigger source of mercury than fish.
Alerted by Dufault and her colleagues' findings, Dr David Wallinga and other researchers at the Institute for Agriculture and Trade Policy (IATP), an independent lobby group based in Minneapolis, Minnesota, went out and bought a range of commonly consumed soft drinks and snack foods sweetened with HFCS, and tested them for mercury.
Of the 55 products they purchased from the local supermarket, the researchers found that one-third contained mercury, including products made by Quaker, Kraft and Nutri-Grain (Kellogg's); all were international and well-known brands. The levels of mercury varied enormously, with the highest being twice that of the lowest. The biggest amounts were found in barbecue sauces, whereas most of the colas and soft drinks contained none.
Know your sugars
Sugar-whether it's sucrose, glucose or fructose-is a carbohydrate found naturally in whole foods and often added to processed foods. Simple sugars (or simple carbohydrates) are made up of either one or two molecules (monosaccharides or disaccharides). Glucose and fructose are monosaccharides, while sucrose is a disaccharide comprising both those sugars.
This is often called 'blood sugar' because it circulates in the bloodstream. The body's insulin processes the carbohydrates we eat into glucose, which is then used for energy or stored in muscle cells or the liver. It's also found in the sap of plants.
Found in many fruits and vegetables, this is often added to sodas and fruit-flavoured drinks. Fructose is metabolized only by the liver and is more lipogenic, or fat-producing, than glucose. Too much fructose could lead to more fat in the body.
Commonly known as 'table sugar', this is derived from sugar cane or sugar beet. Other fruits and vegetables also contain sucrose that, when consumed, is broken down into its constituent parts-fructose and glucose.
Artificial sweeteners and sugar substitutes are all doing the same thing: reducing your intake of sucrose-the stuff we put in our hot drinks. These products come in four forms: artificial sweeteners (like aspartame, sold as NutraSweet), sugar alcohols (lactitol, sorbitol, xylitol), novel sweeteners (stevia, trehalose) and natural sweeteners (agave nectar, date sugar, honey, maple syrup).
The rise of HFCS
The UK's Institute of Food Research has described HFCS as "a brilliant technological invention" as it has many advantages over traditional sweeteners. In addition to its ability to stretch the shelf life of products, it blends more easily into liquids and keeps its sweetness better than sugar.
For this reason, it was quickly adopted by Coca-Cola, Pepsi and other soft-drink manufacturers. It also helps to prevent food 'freezer-burn' as it stops icy crystallization and so is used in frozen products like ice cream. What's more, it helps to turn baked goods brown and so is used in cakes, pastries, bread rolls, crackers and breakfast cereals. Most important of all, it's far cheaper to make than other sweeteners.
Nowadays, it's found in virtually every processed food and drink and, best of all, claim its advocates, it's natural and safe, a view supported by America's foods regulator, the Food and Drug Administration (FDA). Most scientists and commentators apparently agree.
Although its advocates describe HFCS as 'natural' and even 'organic', it's nothing of the sort. While other sweeteners are based on cane and beet sugar, HFCS is a derivative of cornstarch-and it comes about only as a result of several industrial processes.
In 1957, scientists discovered an enzyme that could convert the glucose in corn syrup into fructose (the natural sugar found in fruits and plants), a process finally perfected only in the 1970s, so paving the way for mass-produced HFCS. The process involves several steps and three different enzymes, and the result is a syrup that is 90 per cent fructose. This is blended down with untreated, glucose-only syrup into a mix that is either 42 per cent or 55 per cent fructose.
Around 50 processing plants around the world, including eight in the US and three in the UK, are producing HFCS. And some of these plants-more correctly known as 'industrial chlorine' or 'chlor-alkali' plants-still use caustic soda (sodium hydroxide) in the manufacture of HFCS, although it's an outmoded form of manufacturing and some plants have replaced it with safer technology.
Other food ingredients, such as citric acid, are also manufactured at these plants.
The caustic soda is referred to as 'mercury-grade' or 'rayon-grade', which means that these plants are reliant on mercury for part of the process. Astonishingly, the plants regularly report that some of the mercury mysteriously disappears. In one year, for example, the four plants in the US that still use caustic soda each reported an unaccountable loss amounting to around seven tons of mercury.
The three UK plants report a similar story, although the environmental lobby group Oceana believes that the mercury loss isn't so mysterious, but is being pumped out into the air and into the general water supply.
In fact, according to the group's report Poison Plants, these three plants are responsible for a third of all mercury emissions in the air and nearly half of all emissions in the water supply of the UK.
Nevertheless, the release of mercury into the environment accounts for just a mere fraction of the total mercury 'lost'. Nine of the mercury-using plants around the world have reported that eight tons of the stuff was emitted into the air and water supply.
Reading the label
Consumers are always urged to 'read the label' if they're worried about the contents of the food they're about to buy. But it's not always that easy when it comes to spotting HFCS.
In the UK, the sweetener is more often referred to as 'glucose corn syrup' and, in the US, where the HFCS or high-fructose corn syrup name is more widely used, manufacturers are starting to wise up.
Some are starting to claim that their products are 'HFCS-free'-even when they're not. It's all to do with how you interpret the figures: standard HFCS is either 42 per cent or 55 per cent fructose but, in the processing stage before that, it's 90 per cent fructose. So if manufacturers are using the 90 per cent fructose HFCS, they're claiming it's not HFCS at all!
1 J Nutr, 2015; doi: 10.3945/jn.114.202531
3 Pharmacol Biochem Behav, 2010; 97: 101-6
4 J Physiol, 2012; 590 [Pt 10]: 2485-99
5 Environ Health, 2009; 8: 2; doi: 10. 1186/1476-069X-8-2
6 Wallinga D et al. Not So Sweet: Missing Mercury and High Fructose Corn Syrup. Minneapolis, MN: IATP, 2009
Published in the February 2015 issue