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Wednesday, January 15, 2014

Oh Sugar! Wrong about fructose

Of late, the words “toxic”, “sugar” and “fructose” have been widely used together, implying a most dangerous aspect of sugar on human metabolism. The irony is that in Greek mythology, Cronus, the Titan leader was fed so much honey that he fell into a deep sleep during which time his son Zeus killed him. The original words of the Greek legend refer to the “intoxicating effect” of the large intake of honey on Cronus. Just as we are amused but not troubled by the language or beliefs of Greek mythology, we should not be so troubled by the same nonsense reformulated in modern Californian mythology.  Honey was always held as a truly prized food: hard to harvest, made by bees through some mysterious process foreign to all other plant and animal foods, golden in colour and above all, sweet as nothing else ever known to man. The sweetness of honey was down to a combination of two simple sugars, fructose and glucose present at 55% and 45% respectively. Sugar, as we know it today, is also an ancient food but newer, relatively speaking, than honey. It is plant-derived and the very first commercial facility for the extraction of sugar in crystalline form from sugar cane or sugar beet was located on the Island of Crete.  The Arabian merchants who funded this production facility had another name for Crete, which they called Qandi. Hence the term “candy”, used today mainly in the US for sugar confectionary products. The main component of this sugar derived from cane or beet is the sugar “sucrose” which is a couplet of two sugars joined together, fructose and glucose.

Honey and particularly sugar, dominated the sweetness aspect of the human diet. That was to change in the 1980’s with the advent of high fructose corn syrup (HFCS) production, driven by simple economics. In the period up to the early 1980’s, US and global sugar prices were pretty identical and highly subject to wild fluctuations in market supply. Thus, in 1974 and 1979-1980, US and global sugar prices soared 5 fold in two separate market peaks. The advent of a new technology that could replace sugar with an identical alternative at a stable low price became a simple no-brainer. Sugar was priced out of the US markets with strict import quotas introduced in the early 1980s to maintain very high domestic sugar prices, double the global price.  HFCS was to almost completely replace sugar in the US diet. The manufacture of HFCS is technically simple. Starch, which is a polymer of glucose units, is extracted from corn and enzymes are used to first break down the starch to glucose. Half the glucose is converted to fructose, again using a simple enzyme system.  The glucose and fructose can now be blended together and the most popular blend with consumers was 55% fructose and 45% glucose, an identical blend to that found in honey.  HFCS intakes soared 8-fold in the US from 1975 to the 80s-90s. However, in recent years HFCS intake has fallen in the US and is now back to values in 1980. During the surge in the use of HFCS, that of sugar fell pro rata.

In 2004, some leading US obesity researchers published data to show that the epidemic of obesity in the US coincided with the surge in HFCS use in the food chain. Whilst most scientific commentators have dismissed this putative link, the debate rages on with thousands of doom-laden Internet postings fuelled by a handful of media-friendly scientists. The term “high fructose corn syrup” was in hindsight a foolish name to introduce since HFCS is quite simply not high in fructose, equal in fact to the level found in honey and almost equal to the level found in sugar. Fructose is the element of HFCS that has been singled out as the bad part and the research in this area leaves a lot to be desired. To begin with, humans don’t and never have consumed fructose in isolation. It is always consumed with glucose and thus experiments in humans or animals using diets with high fructose levels with no accompanying glucose are basically unrealistic. They may show what is possible but they have no bearing on what is probable. In a paper presented to the US Experimental Biology conference in 2012[1], the levels of fructose used in these diets was compared to the average daily intake of fructose by US adults. In every one of the 37 human studies and every one of the 21 animal studies, the level of fructose used exceeded the US average intake value (9% of calories). Of course the average hides high consumers so this paper also looked at the fructose intake of the top 5% of fructose consumption (15% of calories). Only 3 human and 1 animal study were at or below this very high level of intake. The majority of animal studies used as much as 55% of calories from fructose, a situation, which is impossible to envisage in the human diet except maybe in the make-believe land of milk and honey.

None of these studies needed to be funded since a natural experiment was being acted out on both sides of the Atlantic. Just as the US jacked up sugar prices to promote HFCS usage, in the EU sugar beet farmers were protected under the CAP limiting the use of HFCS to 5% of total supply. Thus beverages in the US contain HFCS whilst beverages in the EU do not. Nonetheless, obesity levels have grown dramatically either side of the ocean.  While the debate on HFCS rages on the Internet, two key organisations have pinned their colours to the mast. Both the American Medical Association[2] and the American Dietetic Association[3] have issued position statements dismissing any claim that HFCS use contributes to obesity or associated biochemical abnormalities of blood lipids or blood glucose.

[1] White JS (2013) Adv Nutr, 4, 246-256
[3] Journal of the American Dietetic Association, (2004) 104, 255-275

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