What is Hereditary Fructose Intolerance (HFI)?

Hereditary Fructose Intolerance (HFI) is a rare genetic disease in which fructose can’t be properly metabolised in the body. Affected person gets bad abdominal reaction (bloating, diarrhea) after eating fructose-containing foods. HFI is an autosomal recessive disorder of fructose metabolism, due to a deficiency of fructose-1-phosphate aldolase - an enzyme, which converts fructose into glucose in the liver. Incidence of HFI is estimated at 1 / 22-58,000 (1).

HFI should be differed from fructose malabsorption (dietary fructose intolerance - DFI).

Patophysiology of HFI

Fructose in the liver is normally converted into fructose-1-phosphate, and further into glucose. In HFI, fructose-1-phosphate, due to lack of fructose-1-phosphate aldolase, can’t be converted into glucose, so it accumulates in liver, intestine, and kidneys. The accumulated fructose-1-phosphate inhibits glycogen breakdown and glucose synthesis, thus causing hypoglycemia after fructose ingestion. Prolonged fructose ingestion in infants may cause hepatic or renal failure and death.

What are FODMAPs?

FODMAPs (Fermentable Oligo-, Di-, Mono-saccharides And Polyols) are short-chain carbohydrates which have high osmotic activity (they drag water into intestine) and are regularly fermented by small and large intestinal bacteria.

FODMAPs include:

• oligosaccharides: fructans (inulin, fructo-oligo-saccharides (FOS) or oligofructose), galactans, and raffinose;
• disaccharides: lactose;
• monosaccharides: fructose;
• polyols: sorbitol, mannitol, xylitol, isomalt, erithrytol, arabitol, erythritol, glycol, glycerol, lactitol, ribitoll.  

Who Can Benefit from Low Sugar Diet?

People diagnosed with IBS, lactose intolerance, fructose malabsorption (Dietary Fructose Intolerance - DFI), Crohn’s disease, chronic diarrhea, toddler’s diarrhea, and those with ‘indigestion’, ‘dyspepsia’, unexplained bloating, or irregular bowels may all benefit from low sugar (FODMAPs) diet. FODMAP diet may be a way to lose weight in obese but otherwise healthy people.

Can FODMAP Diet be Dangerous?

FODMAP diet should not be introduced by any person with diabetes, hypoglicemia or other metabolic disorders, or in malnutrition without prior consultation with a doctor. It may be necessary to interrupt FODMAP diet in any severe acute disease, after injury or surgery, and in other urgent situations. 

What Symptoms Can FODMAPs Cause

FODMAPs malabsorption may result in bloating, gas, abdominal pain, diarrhea, weight loss, symptoms of vitamin and mineral  deficiency, headache, lethargy, and depression.

Low Fructose Diet (in DFI)

Persons with Fructose malabsorption (Dietary Fructose Intolerance - DFI) should limit foods high in fructose and sorbitol, and possibly foods high in fructans and other FODMAPs (Table 1).  The most problematic foods are those with high fructose : glucose ratio, or high sorbitol (11). 

Glucose enhances absorption of fructose, so moderate amount of foods with equal or low fructose : glucose ratio (e.g table sugar) should be OK…if they don’t contain sorbitol. Especially pre-prepared frozen foods and bakery, canned foods, low-calorie foods, and many artificially sweetened products have to be avoided. Labels should be checked for fructose and sorbitol.

Tolerance threshold for fructose may be as low as 1g of fructose per serving (25g / serving, or more, is considered as normal). Sorbitol: 10g of sorbitol may cause a diarrhea in a sensitive person. When fructose and sorbitol (and other FODMAPs) are combined in one food, relatively lower amount of each is needed to cause symptoms.  Fructose, sorbitol and FODMAPs may be naturally present in the food (fruits, vegetables, wheat) or they may be added during the food processing. On labels, fructose is hidden within ’sugars’, and sorbitol within ’sweeteners’, so their exact amount usually can’t be checked. Therefore, a person with fructose malabsorption should be aware of food ingredients (Table 1).

Below ‘foods to try’ and ‘to avoid’ were most often recommended / disadviced by doctors and fructose malabsorbers. Since each individual with DFI has its own fructose tolerance threshold, everyone has to build his/her personal list. Small amounts of problematic foods can be often safely ingested. Symptoms should lessen considerably in a couple of days after onset of low-fructose diet, and tolerance threshold for fructose may raise after some time. In small children fructose absorption increases with age (11). If symptoms don’t improve after 6-8 weeks of low-fructose diet, other diagnoses, like lactose intolerance and celiac disease, should be considered. Other causes of diarrhea.

Sugars to try: acesulfam pottasium (Nutrinova, Sweet One, Sunnett, Ace-K, Acesulfame K), barley malt syrup, brown rice syrup, corn syrup (if no fructose is added), dextrin, glucose (dextrose, glucodin), glycogen, grape syrup, maltodextrin (modyfied starch), maple syrup, moducal, sorghum syrup, sucrose (table or cane sugar), trehalose.

Sugars to avoid: agave syrup (in Tex-Mex foods, tequila, margaritas, soft drinks), brown sugar, caramel, chinese rock sugar (honey + added sugars), fructose, fruit juice concentrate, golden syrup (cane syrup), High Fructose Corn Syrup (HFCS - isoglucose), honey, invert sugar (treacle), licorice, molasses, raffinose (in legumes), raw sugar (Turbinado, Demerara, jaggery, palm sugar -gur); sugar substitutes: sorbitol, maltitol, mannitol, xylitol, hydrogenated starch hydrolysates (HSH), isomalt, erythritol, dulcitol, lactalol, lacticol, litesse, lycasin, saccharin (Sweet ‘n Low), stevia, sucanat, sucralose (splenda), trimoline (from beets). 

Fructose Malabsorption

In this article, fructose malabsorption, also known as Dietary Fructose Intolerance (DFI), which is a common cause of diarrhea, is described. Another, rare, Hereditary Fructose Intolerance (HFI), which causes impairment of liver, kidneys and small intestine is much more severe. DFI and HFI are NOT allergies.

In fructose malabsorption fructose can’t be efficiantly absorbed from unknown reason. Transport protein GLUT5, responsible for fructose absorption in the small intestine, may not be present or becomes inactive. People with fructose intolerance have fructose absorption limit lower than 25 grams per serving, but this may differ a lot from person to person. Fructose, unabsorbed in the small intestine, reaches the colon, where bacteria ferment it and yield short chain fatty acids, carbon dioxide (CO2), hydrogen and methane, which cause symptoms. It is estimated that about 1/3 of people are fructose intolerant, and about half of them have symptoms. People with fructose intolerance may be also sensitive to other non-digestable carbohydrates, such as sorbitol and xylitol, raffinose (beans) and inulin (polyfructose), (5).

Who Can Get Fructose Intolerant?

Anyone at any time can develop fructose intolerance. Abnormality or lack of GLUT-5, a fructose transporting protein, may be inherited (5). Other causes, suggested so far:

• family predisposition; 
• overuse of High Fructose Corn Syrup (HFCS), or fruit juices in children (toddler’s diarrhea); 
• small intestinal bacterial overgrowth (SIBO);
• celiac disease; 
• chemotherapy or radiation;
• dumping syndrome (rapid stomach emptying).

It has been reported in diabetes special issue of The Lancet that the researchers have demonstrated that early intensive insulin therapy may improve the functions of insulin generating ?-cells in the patients with type-2 diabetes. The schedule of the therapy has also been linked with blood glucose control recovery and restoration.

Type-2 diabetes is considered a disorder related to metabolism which typifies by insulin resistance .Many studies that have been conducted before have recommended that there is an ability in intensive insulin therapy to alter or at least slow down the development of the disease. Professor Jianping Weng of Hospital of Sun Yat-Sen University, Guangzhou, China and co researchers tried to find the true nature of these claims.

Candida Albicans

Candida albicans is a yeast (unicellular fungus), normally present on the human skin and mucosa of the gut, respiratory system and genitals; its amount is controlled by immune system and normal bacterial flora. Under certain circumstances, candida may overgrow, mainly in the vagina, mouth, esophagus, sinuses and rarely colon.

WARNING: Candida is rare in otherwise healthy people. Do not jump easily into a self-diagnosis of intestinal candida, just on the basis of some symptoms mentioned in this article. The only firm proof of intestinal candida is colonoscopy with a biopsy of colonic wall. Next: intestinal candida is NOT already a systemic candida.

What Causes Intestinal Candida Overgrowth?

Triggers of candida overgrowth:

1. During a long term antibiotic treatment many normal bacteria, attached to colonic wall are killed, thus releasing the space for yeasts (1).
2. Lowered immunity due to steroids, birth control pills, antacids, anti-ulcer drugs, chemotherapy, radiation therapy, immuno-suppressant drugs, AIDS, malignancy, diabetes, hypothyroidism, hypoparathyroidism, Addison’s disease, malnutrition, alcoholism, street drugs, or chronic stress, enables uncontrolled candida growth.
3. Sugars and other carbohydrates are food for yeasts and may quickly and markedly boost their growth.
4. Gastric hypo-acidity due to gastric disease, antacids, or anti-ulcer drugs, may allow candida to spread from the mouth into intestine (1).
5. Mouldy environment, like basement appartments in dump builduings, or wet cool climate may enhance yeast infections.

Candida Symptoms

Main symptoms of intestinal candida overgrowth are diarrhea (or constipation), pale or mucous stools, bloating, itchy anus, diaper rash in kids, oral thrush (greasy white patches on the tongue or mouth mucosa, Image 1), and craving for sugar. If candida enters the blood, e.g. in persons with lowered immunity, it causes systemic infection, present with vaginal discharge, burning at urinating, prominent fatigue, irritability, and it may be deadly. Symptoms improve after sugar-free diet and may dramatically worsen after the sugar-rich meal, what can be an useful diagnostic sign.