Fructose

Fructose, also called fruit sugar, is the sugar of fruit and honey, and it makes up half of table sugar. It is a simple sugar with the same chemical formula as glucose, C6H12O6. But the body handles it very differently: the liver takes up almost all of it and quickly turns it into glucose, glycogen, lactate and fat.

Table sugar (sucrose) is one glucose joined to one fructose, and high-fructose corn syrup is a mix of the two sugars. Fructose is one of the sugars in food, and no official daily need or limit is set for it on its own.

Most readers have not been told how much the answer depends on calories. When trials swapped fructose for other carbohydrate at equal calories, weight, blood fats, uric acid and liver fat did not rise in pooled results.

When 104 to 250 g a day of fructose was added to the usual diet, weight, triglycerides (blood fats) and liver fat did rise. The authors say the extra calories may be the cause.

Whole fruit has not shown that pattern for weight, liver fat or uric acid in the reviews below. But fruit juice and fructose-rich fruits were linked to gout in two large cohorts, studies that follow people for years.

One more fact most people do not know: many healthy people do not fully absorb free fructose. In a breath test study of 10 healthy adults, 5 of them did not fully absorb 25 g of fructose alone. Yet up to 100 g of sucrose, which holds the same fructose joined to glucose, caused no malabsorption.

That is one reason some people get gas and loose stools from fruit, honey or juice. It is a different matter from hereditary fructose intolerance, a rare inherited condition that is far more serious. This page sets out each at its real evidence level, with the funding of the main trials.

Health effects of fructose

• ★★★Lower blood sugar peak after mealsSwapping glucose or sucrose for fructose at equal energy lowered the blood sugar peak after a meal, most in people with prediabetes or diabetes. The EU allows this claim only when sugars fall by at least 30%, and it covers just the after-meal rise.
• ★★No change in weight at equal caloriesIn 31 trials where fructose was swapped in at equal calories, weight did not change (−0.14 kg). Trials adding 104 to 250 g a day of extra fructose found 0.53 kg of weight gain, which may come from the extra energy.
• ★★More liver fat only with extra caloriesIn trials adding extra fructose (21% to 35% of energy), liver fat rose, but the extra energy may explain it. Sugary drinks that added energy raised liver fat too, while swaps at equal calories changed nothing.
• ★★No change in blood fats at equal caloriesIn 51 trials at equal calories, fructose did not change LDL cholesterol, triglycerides or apolipoprotein B. Added on top (21% to 35% of energy), it raised triglycerides by 0.26 mmol/L.
• ★★Lower long-term blood sugar markers in diabetesIn 18 trials in 209 people with diabetes, fructose swaps lowered glycated blood proteins, like a 0.53% drop in HbA1c (average blood sugar). Fasting glucose and insulin did not change.

Foods high in fructose

Fructose comes from fruit, honey and sweeteners. In our USDA ranking, per serving, dates lead with 15.3 g in 2 dates (48 g). Grapes (12.3 g in 1 cup) and pears (11.4 g in 1 medium) follow. Then come apples, honey, cherries, mango, blueberries, bananas and papaya; the ranking below has each amount.

Per 100 g the order changes: honey has 40.9 g and dates 32 g, then grapes, pears and apples. Per 100 kcal, honey leads with 13.5 g, ahead of grapes, dates, pears and watermelon.

The ranking counts the fructose USDA lists on its own. So table sugar, which is half fructose, does not appear: its fructose is bound to glucose.

How the sugars are counted matters. The WHO defines free sugars as single sugars and sugar pairs added to foods and drinks by the manufacturer, cook or consumer. They also include sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates.

Its guideline leaves out the sugars in fresh fruit and vegetables and in milk, as it found no reported evidence of adverse effects from them. The US Dietary Guidelines say most fruit should be eaten whole rather than as juice. They note that 100% fruit juice is lower in fiber than whole fruit.

Fruits also differ in their mix. The FDA notes that fruit-based sweeteners may hold more fructose than glucose, especially those from apples and pears. Honey has about one fructose to one glucose.

Added fructose arrives mainly as sucrose and high-fructose corn syrup (HFCS). HFCS is made by using enzymes to turn some of the glucose in corn syrup into fructose. The FDA says HFCS 42 is used mainly in processed foods, cereals, baked goods and some drinks, and HFCS 55 mainly in soft drinks.

Our arithmetic: a medium pear (11.4 g) plus a cup of grapes (12.3 g) gives 23.7 g of free fructose. That is close to the 25 g that 5 of 10 healthy adults did not fully absorb in the breath test. But fruit also holds glucose, which helps fructose across the gut wall.

How fructose works

The basic biochemistry is well established, and what extra fructose does in people is tested in the study cards above. Four ideas cover most of it.

Fructose crosses the gut wall by its own carrier, up to a limit. The liver takes up most of it and skips a control step. The pieces end up as glucose, lactate, glycogen and some fat, with uric acid as a by-product. And a missing enzyme makes it dangerous for a few people.

Here is each one, and what has been seen in people.

It crosses the gut wall by its own carrier, up to a limit

The main carrier for fructose in the small intestine is GLUT5, with GLUT2 also involved. A review of past studies in healthy adults found a strong link between dose and malabsorption (r = 0.86). So even healthy people have a limited, dose-dependent capacity, and glucose taken with fructose helps.

A mouse without GLUT5 shows profound fructose malabsorption. Gibson and colleagues put it plainly: up to half of the population cannot completely absorb a 25 g load of free fructose. Average daily intakes run from 11 to 54 g around the world. The chart shows the classic breath test results.

Unabsorbed fructose adds to the water and the fermentable material that reach the colon. Gibson and colleagues describe an increased osmotic load (water drawn into the gut) and fuel for rapid bacterial fermentation. That is more likely to cause symptoms in people with functional gut disorders than in people without them.

Fructose is the “M” in FODMAP, the group of fermentable short-chain carbohydrates (oligosaccharides, disaccharides, monosaccharides and polyols) that a low-FODMAP diet limits. Breath hydrogen tests can show who absorbs a fructose load completely.

In the randomized rechallenge trial above, fructose brought symptoms back in 70% of people with irritable bowel syndrome, and so did fructans and mixes. Glucose did so in only 14%. The symptom link is not simple: in a crossover trial, blood fructose was the same in people with and without symptoms.

The liver takes up most of it and skips a control step

Tappy and Lê describe an almost complete extraction of fructose by the liver and a rapid conversion into glucose, glycogen, lactate and fat. The first step is the phosphorylation of fructose by the enzyme ketohexokinase, also called fructokinase, to fructose-1-phosphate. Aldolase B then splits it into two three-carbon sugars.

Mayes explains why this matters. Most of fructose’s metabolic effects come from its rapid use by the liver and from bypassing phosphofructokinase, a main control step in sugar breakdown. The liver’s output of lactate and pyruvate rises at once, fat is steered from burning toward storage (esterification), and more very-low-density lipoprotein (VLDL) is secreted.

Fructose also does not trigger insulin release the way glucose does. In 12 women, meals with 30% of energy as fructose gave insulin responses that were 65% lower than the same meals with glucose.

In mice, the first enzyme has two forms; form C, found mainly in liver, intestine and kidney, has a high affinity for fructose. It uses fructose so fast that ATP (the cell’s energy molecule) falls sharply. Form A, spread widely and with a lower affinity, protects the mouse from the fructose-induced metabolic syndrome that form C drives. That is mouse and cell work, and it is one of several routes proposed for the harm seen at high doses.

Uric acid is a by-product

Mayes adds a second consequence. A big load of fructose ties up phosphate in fructose-1-phosphate and slows the making of ATP. That lifts the brake ATP puts on the breakdown of adenine nucleotides, so uric acid forms faster.

That chain fits what the trials show. On top of usual food, 213 to 219 g a day raised blood uric acid, and sugary drinks raised it in controlled trials. Fructose-rich drinks went with gout in two large cohorts. At equal calories, the pooled trials found no change in uric acid from fructose.

Uric acid is the molecule that crystallizes in gout, so the signal matters most for people who already have it.

Where the fructose goes in people

Tracer studies follow labeled fructose through the body. Within 3 to 6 hours, a review found, people at rest burned about 45% of the dose for energy and turned about 41% into glucose. About a quarter became lactate, and under 1% went straight into blood triglycerides.

The bars come from different studies, so they do not add up. The same review notes that larger amounts raise fat making when it is measured with labeled acetate over longer periods. It says the reasons for the effect on blood fats remain debated. Both of its authors work for Archer Daniels Midland, a food-ingredient company.

Trials that measure fat making directly agree on the direction. In six healthy adults, an 85 g sugar dose with fructose in it doubled the liver’s fat making compared with glucose alone. In overweight and obese adults, 10 weeks of fructose-sweetened drinks raised liver fat making where glucose-sweetened drinks did not. Both studies gave a lot of sugar at once or on top of the diet.

The gut clears some before it reaches the liver

Mice lacking the fructose enzyme in the small intestine sent more fructose on to the liver and gut bacteria. They became more prone to fatty liver and high blood fat, while mice with extra intestinal enzyme made less fat.

The authors report more fat making when fructose was drunk rather than eaten, and given at once rather than over 45 minutes in small doses. They suggest slower intake could soften the effects, but no human trial has tested that idea.

Hereditary fructose intolerance: when aldolase B is missing

Hereditary fructose intolerance (HFI) is a rare, recessive inherited disorder in which the liver enzyme aldolase B is deficient. A fructose load makes fructose-1-phosphate pile up, which uses up phosphate and ATP. That causes low blood sugar, lactic acidosis, high uric acid and, over time, liver and kidney damage.

Estimates vary: about 1 in 10,000 from gene data, and 1 in 20,000 to 1 in 60,000 in a 2022 review. About 1.3% of UK newborns carry one copy of the common A149P variant.

Symptoms start only when fructose, sucrose or sorbitol is eaten, typically when an infant starts weaning foods. Some children avoid sweets on their own, and the diagnosis can come late.

What has been seen in people

The pooled weight data show the calorie split clearly. In 31 trials at equal calories, swapping other carbohydrate for fructose changed weight by −0.14 kg, a result that could be zero. In 10 trials where fructose was added on top of usual food, weight rose by 0.53 kg.

Putting the cards together: fructose lowers the blood glucose rise when it replaces glucose or sucrose. It does not raise weight, blood fats, uric acid or liver fat when swapped for other carbohydrate at the same calories. It does raise them as a large dose of extra calories, especially in sugary drinks. The trials cannot separate the fructose from the extra calories.

Fruit lowered weight in the 169-trial review and went with slightly lower diabetes risk in cohorts; juice and some fruits were linked to gout. Several lab and small-trial findings, such as the gut-clearance idea and the effects of a single dose, remain open.

The two sides of the argument both have trials. The weight and liver-fat reviews above come largely from one funded group and find no harm at equal calories. The drink trials of Stanhope and colleagues find harm at 25% of energy. The 2021 trial by Stanhope’s group was funded by the NIH, the US National Institutes of Health.

How much fructose is too much?

There is no recommended intake for fructose on its own. The limits that cover it are for free or added sugars. The WHO recommends free sugars under 10% of energy, with a conditional recommendation to go below 5% (roughly 25 g a day). EFSA says added and free sugars should be as low as possible.

The 2025-2030 US Dietary Guidelines recommend no amount of added sugars and no more than 10 g in one meal. The 2020-2025 edition said under 10% of calories from age 2. On a 2,000 kcal diet, 10% is 200 kcal, or 50 g of sugar (our arithmetic, which matches the FDA’s).

Source	Group	Value	Notes
WHO guideline, 2015	Adults and children	Free sugars under 10% of total energy (strong recommendation); below 5%, roughly 25 g a day, for added benefit (conditional)	Free sugars include fructose and sucrose added to foods and drinks, and sugars in honey, syrups, fruit juices and concentrates. Sugars in fresh fruit, vegetables and milk are not covered, because no adverse effects were reported.
EFSA scientific opinion, 2022	Adults and children	Added and free sugars as low as possible within a nutritionally adequate diet	EFSA could not set a tolerable upper intake level for dietary sugars. It says sugar is a known cause of dental caries and links sugar-sweetened beverages, juices and nectars with obesity, fatty liver disease and type 2 diabetes.
Dietary Guidelines for Americans, 2025-2030	Everyone; infants and young children	No amount of added sugars is recommended; one meal should contain no more than 10 g of added sugars	Avoid added sugars during infancy and early childhood. Fructose is named as one of the added sugars on labels.
Dietary Guidelines for Americans, 2020-2025 (previous edition)	People aged 2 and older; under 2	Added sugars under 10% of calories a day from age 2; avoid foods and drinks with added sugars under age 2	About 200 kcal or 50 g on 2,000 kcal, as the FDA states it.
FDA Nutrition Facts label	Packaged foods	Daily Value for added sugars: 50 g a day	Based on a 2,000 kcal diet. Added sugars cover sugars added in processing, sweeteners, syrups, honey and concentrated fruit or vegetable juices, not sugars naturally in milk, fruit and vegetables.
Any authority we found	Fructose on its own	No daily need and no upper limit	The site’s intake box also shows no FDA or EU reference value for fructose.

Gibson and colleagues report average daily fructose intakes of 11 to 54 g around the world. In the United States, estimated intakes of added and total fructose rose in every age and sex group from 1977 to 2004. Naturally occurring fructose stayed flat or fell, and the rise was dwarfed by larger increases in total energy and carbohydrate intake.

For the gut, the number that matters is how much free fructose you take at once. Many healthy adults did not fully absorb 25 g of fructose alone, and glucose in the same meal improved absorption in a dose-dependent way. Breath hydrogen tests can identify people who absorb a fructose load completely, so that restriction can be less strict. The low-FODMAP approach needs a dietitian trained in it.

We found no official report that sets a daily need for fructose, and no deficiency state. Small amounts of fructose are even made in the brain by the body’s polyol pathway, so this page has no deficiency section.

Forms of fructose: absorption and effects

Fructose reaches you as free fructose in fruit, honey, agave and juice, and as crystalline fructose sold as a sweetener. It is also half of table sugar, and 42% to 55% of high-fructose corn syrup.

The forms differ in how much glucose arrives with the fructose. That matters for absorption, because glucose helps fructose across the gut wall, and much less for what the liver does with it.

The honest bottom line: the one trial that compared HFCS-sweetened with sucrose-sweetened drinks found no difference, and fruit behaves differently from drinks. We found no trial for popular claims such as “honey is healthier than sugar” or “agave is better for diabetes”.

Where trials exist, the doses are large: 25% of energy for 2 to 10 weeks in the drink trials. The high-dose trials of pure fructose gave 104 to 250 g a day. Those are not typical of eating fruit, and we found no trial that tested crystalline fructose as an everyday sweetener.

Form	What it is	What studies show	Source
Whole fruit	Free fructose with glucose, fiber, water and other nutrients; apples and pears hold more fructose than glucose	Fruit lowered weight when it replaced other foods in a 169-trial review. In three US cohorts, whole fruit went with slightly lower type 2 diabetes risk (hazard ratio 0.98 per 3 servings a week), though cantaloupe went the other way (1.10). Apples and oranges, like juice, were linked to higher gout risk in men.	1, 9, 8, 16
100% fruit juice	Fruit sugars with most of the fiber removed; counted as free sugars by the WHO	Each daily serving went with a small BMI rise in children (0.03) and no clear weight change in 19 adult trials. Juice went with higher diabetes risk in cohorts (1.08 per 3 servings a week) and lowered uric acid in add-on trials. US guidelines say juice is lower in fiber than whole fruit.	7, 8, 10, 11, 15
Table sugar (sucrose)	One glucose bonded to one fructose, so 50% fructose by weight	No malabsorption in 10 healthy adults at 50, 75 or 100 g, unlike 25 g of free fructose. Sucrose drinks raised liver fat in a 2-week trial in 75 adults. See the page on sucrose.	1, 12, 3
High-fructose corn syrup (HFCS 42 and 55)	A syrup of free glucose and fructose, 42% or 55% fructose, with water and no bond between the sugars	HFCS and sucrose drinks gave the same changes in liver fat, insulin sensitivity and blood lipids in a 2-week trial. HFCS drinks raised LDL as much as fructose drinks did, and glucose drinks did not. A review found no direct evidence that HFCS has more serious effects than sucrose, and the FDA is not aware of any difference in safety.	1, 3, 4, 5
Crystalline fructose	Pure fructose sold as a sweetener and used in trials	The controlled-feeding meta-analyses pooled trials of free fructose. At 25 g in water, more than half of 15 healthy volunteers and 5 of 10 in another test did not absorb it fully.	13, 12, 14
Honey	A mix of glucose and fructose, about one to one	In healthy volunteers, rapeseed honey raised blood fructose more than a matched glucose and fructose solution; acacia honey did not. Honey lowered weight in add-on trials. We found no trial showing honey is healthier than sugar.	1, 6, 9
Agave syrup	A syrup made by hydrolyzing the fructans of agave sap	A 2022 review lists fructose as the main sugar, 71.86% to 92.13% in one analysis, and says research on human metabolism is needed to back health claims. We found no human trial.	2
Sugary drinks	Drinks sweetened with sucrose, HFCS or fructose	When they added energy to the diet, they raised liver fat, uric acid and body weight in pooled trials.	9, 10

Here are the form-specific studies, strongest evidence first, 5 in all.

Is fructose bad for you? Limits and who should watch it

Fructose from whole fruit is not a safety concern for most people. The WHO guideline leaves out the sugars in fresh fruit because it found no reported evidence of harm. No tolerable upper intake level exists for fructose or for dietary sugars as a whole: EFSA could not set one in 2022. It says added and free sugars should be as low as possible.

EFSA adds that sugar is a known cause of dental caries (tooth decay). Sugar-sweetened beverages, juices and nectars are linked with obesity, fatty liver disease and type 2 diabetes, it says.

• Hereditary fructose intolerance. This rare inherited condition needs a doctor’s diagnosis, for which a genetic test is favored. Fructose, sucrose and sorbitol cause vomiting, low blood sugar and liver and kidney injury, and fructose or sorbitol given by vein can be fatal. With strict avoidance the outlook is excellent. In four undiagnosed infants, a sucrose-containing formula caused liver failure.
• Fructose malabsorption and irritable bowel syndrome. Gas, bloating, pain and loose stools after fruit, honey or juice are common. A low-FODMAP diet reduces functional gut symptoms but needs expert delivery by a dietitian, and glucose taken with fructose can help. Tolerance varies, so work out your own threshold.
• Gout and high uric acid. Sugary drinks and orange juice went with more gout in two large cohorts, and sugary drinks raised uric acid in controlled trials. If you have gout, ask your doctor about sugary drinks and juice.
• Diabetes. Swapping other carbohydrate for fructose lowered glycated blood proteins in 18 trials, equal to about 0.53% of HbA1c (long-term blood sugar). It also lowered the peak glucose after a meal. Sugary drinks that add energy are another matter. If you have diabetes, plan sugar changes with your care team.
• Fatty liver disease. In adults with fatty liver disease, daily fructose drinks went with more scarring. In children with obesity, 9 days of cutting sugar lowered liver fat. If you have liver disease, follow your doctor’s advice.
• Drug interactions. We found no report of an interaction between dietary fructose and a medicine.

How to eat less fructose

• Start with drinks. Removing sugary drinks and other sources of added energy lowered body weight by 0.96 kg in trials. Cutting fructose to 4% of energy for 9 days lowered liver fat in children. Water and unsweetened drinks are the swap.
• Keep whole fruit, limit juice. US guidelines say most fruit should be whole, and juice is lower in fiber. In trials, fruit lowered weight when it replaced other foods, while juice went with higher diabetes risk in cohorts.
• Read labels and pace yourself. HFCS, honey, agave, fruit juice concentrate and syrups all count as free sugars. If fruit upsets your gut, spread it through the day, eat it with other food, and ask a dietitian about a breath test.

History of fructose

The French chemist Augustin-Pierre Dubrunfaut described fructose in 1847. The English chemist William Allen Miller named it in 1857, from the Latin for fruit and the suffix for sugars. Its natural sources are fruit and honey, yet Tappy and Lê note that it was virtually absent from the diet a few hundred years ago. It has now become a major constituent.

The medical story starts with a rare disease. In 1956 the Lancet carried a paper titled “Idiosyncrasy to fructose”. By 1963 Froesch and colleagues had named the cause: an inborn defect of the liver enzyme that splits fructose-1-phosphate, now called aldolase B. A 1998 review says sugar’s rise as a major food in western societies may explain why the condition is now recognized more often.

The industrial story begins in 1957, when Marshall and Kooi reported an enzyme that converts D-glucose to D-fructose. High-fructose corn syrup is made by that kind of step: enzymes turn some of the glucose in corn syrup into fructose. In the United States, HFCS rose from 16% of sweeteners in 1978 to 42% in 1998, then stabilized, and sweetener availability peaked in 1999. Researchers estimate that fructose intakes rose from 1977 to 2004, but that the rise was dwarfed by increases in total energy and carbohydrate intake.

The research argument is younger. The equal-calorie trials found little harm, the extra-calorie and drink trials found more, and each side questions the other.

The pooled analyses come largely from a group whose members disclose research support from the Calorie Control Council and Coca-Cola. The drink trials of Stanhope and colleagues use 25% of energy as sugary drinks, a high dose. This page puts both on the cards, with the funding stated.

Frequently asked questions about fructose

Is fructose bad for you?

Not in itself, and not in whole fruit; large amounts of sugary drinks are the concern. In 31 equal-calorie trials, fructose swaps changed weight by −0.14 kg, while 104 to 250 g a day on top added 0.53 kg. The WHO guideline does not cover the sugars in fresh fruit because it found no reported evidence of harm. Sugary drinks that added energy raised liver fat and uric acid in pooled trials.

What is the difference between fructose and glucose?

Both are simple sugars with the formula C6H12O6. Cells throughout the body use glucose, and its rise releases insulin. The liver takes up almost all fructose and turns it into glucose, glycogen, lactate and fat. In 12 women, meals with 30% of energy as fructose gave 66% smaller blood glucose rises than the same meals with glucose. See our page on glucose.

Is fructose the same as high-fructose corn syrup?

No. Fructose is one sugar; HFCS is a syrup of free glucose and fructose, most often 42% or 55% fructose, near table sugar’s 50%. In a 2-week trial in 75 adults, sucrose and HFCS drinks raised liver fat by 0.6% and 0.4%, and no outcome differed between them. The FDA is not aware of any difference in safety. See sucrose.

How much fructose per day is too much?

No official limit exists for fructose alone, so follow the limits for free or added sugars. Those are under 10% of energy (WHO) and as low as possible (EFSA). The 2025-2030 US guidelines recommend no amount of added sugars and no more than 10 g in one meal. On 2,000 kcal that is 50 g of sugar, half of it fructose in table sugar (our arithmetic). For the gut, 5 of 10 healthy adults did not fully absorb 25 g of free fructose at once.

What are the symptoms of fructose intolerance?

The word covers two different conditions. Fructose malabsorption causes gas, bloating, pain and loose stools after fruit, honey or sweetened drinks. Hereditary fructose intolerance is rare and serious, with vomiting, low blood sugar and liver and kidney injury after fructose, sucrose or sorbitol. It often shows when an infant starts weaning foods, and a doctor must diagnose it.

Does fructose cause fatty liver?

At extreme doses of extra calories, yes; at equal calories, pooled trials found no effect. In 13 trials, 104 to 220 g a day on top of usual food raised liver fat, while fructose swapped for other carbohydrate did not. Sugary drinks that added energy raised liver fat in a 51-trial review. In 41 children with obesity, 9 days of lower fructose lowered it from 7.2% to 3.8%.

Does fructose cause gout?

Fructose-rich drinks are linked with gout: in 46,393 men, the top fifth of fructose intake had a relative risk of 2.02. In 78,906 women, one sugar-sweetened soda a day had 1.74. Sugary drinks raised uric acid in trials, while 100% fruit juice lowered it in add-on trials. Cohorts cannot prove cause, and people with gout should ask their doctor.

Is fructose safe for people with diabetes?

In controlled trials it did not worsen blood sugar when it replaced other carbohydrate. In 18 trials, glycated blood proteins fell, equal to about 0.53% of HbA1c, and the after-meal glucose peak was lower. The effect depends on calories, so sugary drinks that add energy are different. Ask your care team before changing how you sweeten food.