Corn Syrup

Corn Syrup / HFCS

Corn syrup (in Hebrew “סירופ תירס”) is made by enzymatically breaking down corn starch into glucose. In its basic form it is almost pure glucose syrup, less sweet than sugar. The version at the center of the health debate is high-fructose corn syrup (HFCS), in which an enzyme called glucose isomerase converts some of the glucose into the sweeter fructose.

The two common versions are HFCS-55 (55% fructose, 42% glucose), used in drinks, and HFCS-42, used in baked goods and processed food.

The syrup was developed in the 1970s and captured a huge market share thanks to three industrial advantages: it is significantly cheaper than cane sugar (mainly because of corn subsidies and tariffs on imported sugar), it is liquid and therefore easy to mix in mass production, and it retains moisture and extends shelf life.

The comparison with sugar — the point worth getting right

A widespread claim holds that HFCS is uniquely harmful, far beyond regular sugar. The evidence does not support the strong version of this claim, and it is worth understanding why.

Table sugar (sucrose) is a disaccharide: a glucose molecule and a fructose molecule bound to each other — that is, 50% fructose. An enzyme in the gut breaks the bond within seconds.

HFCS-55 contains 55% fructose, already in free form.

The difference is 5 percentage points. After digestion, both reach the liver in almost identical composition. Systematic reviews that compared the two directly found no significant difference in their effect on weight, blood lipids or metabolic markers when the calorie amount is the same.

The conclusion is not that HFCS is safe — but that the problem is fructose and the amount, not the source of the sugar. Focusing on HFCS as a unique villain diverts attention from the real question: how much added sugar is consumed overall.

Where HFCS does play a unique role: its low price and ease of use led to it being introduced into a huge range of products that used not to be sweet at all — bread, sauces, ketchup, soups, processed meat. The result is an increase in total sugar intake in the population. This is a real economic-industrial effect, not a biochemical one.

Why fructose behaves differently

• Almost exclusively liver metabolism: while glucose is taken up by almost every cell in the body and regulated by insulin, fructose is handled almost entirely in the liver. The liver receives a concentrated dose without parallel hormonal control.

• Bypassing the control point: in the glucose breakdown pathway there is an enzyme (phosphofructokinase) that acts as a regulating tap — when the cell is saturated with energy, it closes. Fructose enters the pathway below this control point, so its breakdown is unregulated. Excess energy flows directly into fat production.

• De novo lipogenesis (DNL): the result is increased production of fatty acids in the liver. Some are packaged into VLDL and raise blood triglycerides, and some are stored in the liver itself.

• Non-alcoholic fatty liver disease (NAFLD): high, prolonged fructose intake is consistently linked to fat accumulation in the liver and to insulin resistance. Controlled feeding trials showed a measurable increase in liver fat with high fructose intake.

• A weak satiety response: fructose triggers a weaker insulin and leptin response than glucose — two hormones that signal satiety. The calories “don’t register” well, especially when they come in liquid form.

An important note about fruit: all of the above refers to free fructose in concentrated amounts. The fructose in an apple or in blueberries comes packaged with fiber, water and polyphenols, in a much smaller amount and with slow absorption. Do not conclude from this that you should avoid fruit.

Downsides and health considerations

• Empty calories: corn syrup provides energy without vitamins, minerals, fiber or protein.

• Liquid calories: the main use of HFCS-55 is in sweetened drinks — the most problematic form of sugar, because it does not produce satiety and does not reduce intake at the next meal.

• Hidden presence: it appears on labels under many names — “corn syrup”, “high-fructose corn syrup”, “glucose-fructose syrup”, “isoglucose” (the name used in the European Union). Products not perceived as sweet at all contain it.

• Type 2 diabetes and obesity: large cohort studies link sweetened drink consumption with an increased risk of type 2 diabetes, obesity and metabolic syndrome. The link is consistent, although fundamentally observational.

• Tooth decay: like any fermentable sugar, it feeds the mouth bacteria that produce acid.

What the official recommendation says

The World Health Organization recommends limiting free sugars — a category that includes corn syrup, white sugar, honey, date syrup (silan) and fruit juices — to less than 10% of total daily calories, and preferably below 5%.

For a 2,000-calorie diet: under 50 grams a day, and preferably under 25 grams (about 6 teaspoons). A single can of a sweetened drink contains about 35-40 grams — meaning it exceeds the stricter threshold on its own.

Practical use

Reading labels: the ingredient list is ordered by descending weight. Sugar or corn syrup among the first three ingredients is a clear sign. Manufacturers sometimes split different kinds of sugar (corn syrup, cane sugar, dextrose) so that none of them appears high on the list — it is worth adding them up.

Looking at “added sugars” in the table: in Israel and Europe the label shows “of which sugars”, which includes natural sugar too. In a product without fruit or milk, almost all of it is added.

Where the biggest impact is: giving up sweetened drinks is the single most significant step for cutting corn syrup intake — they make up the lion’s share of intake for most people.

Alternatives: water, unsweetened flavored water, unsweetened tea. Replacing HFCS with honey or date syrup changes very little metabolically — they are all free sugars.

Summary

High-fructose corn syrup is not a unique poison, and it is almost identical to table sugar in composition and effect for the same number of calories. But that is no consolation: the fructose in both undergoes unregulated liver metabolism, promotes fat production in the liver and provides weak satiety. The syrup’s unique contribution is economic — its low price made it possible to put sugar into a huge range of products and raise total intake. The practical step is not to replace it with a “natural” sweetener but to cut the total amount, first and foremost by giving up sweetened drinks.