Fructose is found in:

Fructose is a natural sugar found in fruit, vegetables, and honey.23 Although all fruit (especially fruit juices) contains fructose, the varying amounts of fructose, glucose and sorbitol in different juices may affect absorptive capacities (as demonstrated above with apple, pear and grape juice).8 Because the concentration of the sugars (glucose, fructose and sucrose) in fruit juice is influenced by storage and the particular types of fruit (for example, type of apple) used, each juice will differ in concentration of the different sugars.4
Also, fruit juice manufacturers around the world may use different methods in processing; they may use different concentrations of fruit juice; adding or not adding, for example, deflavoured apple juice, which may be imported or produced locally. Thus, the concentrations of sugars in fruit juices may differ extensively from country to country.
It must be borne in mind that relatively low doses of processed (commercial) fruit juice may cause as much malabsorption as eating excessive amounts of fresh fruit.
Fructose is widely used as a food additive, as it gives many useful attributes to food and beverages, including sweetness, flavour enhancement, humectancy, colour and flavour development, freezing-point depression, and osmotic stability.24

Fructose, sucrose and sorbitol in foods (adapted from Shaw V, Lawson M. Clinical Paediatric Dietetics. Blackwell Science Ltd, UK, 1994.) Apart from the whole food sources, fructose, sucrose and sorbitol is used in many manufactured foods. So much so that very few manufactured foods are allowed in the diet. Sugar is used in obvious products such as sweets, desserts and soft drinks, but also in many other less obvious products such as canned food, bottled sauces, savoury biscuits, etc. Flavourings is another potential trace source of these sugars as they are sometimes used as carriers for flavouring compounds. Only vegetables that contain predominantly starch are allowed in the diet. Cooked vegetables have a lower fructose content and are recommended in preference to raw as the cooking process causes a loss of free sugars. New potatoes have a higher fructose content than old potatoes. Wholemeal flour contains more fructose than white flour because the germ and bran contains sucrose. Similarly other wholegrain foods (e.g. brown rice and wholemeal pasta) contain more sucrose than the refined products. Sorbitol is used as an artificial sweetener, especially in diabetic foods and drinks. These foods should therefore be avoided. Isomalt and lycasin, alternative sweeteners that are predominantly used in confectionary, also contain sorbitol. Glucose can be used as an alternative sweetener and as a source of energy. Sucrose and sorbitol are used in medications as bulking agents or to improve the taste.

Hereditary fructose intolerance (HFI): HFI is a rare autosomal recessive disorder of fructose metabolism, due to a deficiency of fructose-1-phosphate aldolase activity. This condition initiates severe toxic symptoms following ingestion of fructose. Glycogen breakdown and glucose synthesis can be inhibited, causing severe hypoglycemia, which manifests as tremors, disorientation, vomiting and, in the worst cases, severe convulsions and coma. Chronic ingestion of fructose during infancy may also result in clinical findings such as failure to thrive, hepatomegaly, and jaundice, which ultimately leads to hepatic and/or renal failure and death. 5,25,26 Fructose-1,6-diphosphate deficiency is another form of fructose intolerance, which usually presents as neonatal hypoglycemia. With fructose-1-phosphate aldolase deficiency, hypoglycemia is experienced after fructose ingestion, whereas in fructose-1,6-diphosphate deficiency, acidosis and hypoglycemia are experienced during caloric deprivation, in fasting or during intercurrent illness.27

MORE on FRUIT JUICE: In general fruit juice… (adapted from the American Academy of Pediatrics' paper "The Use and Misuse of Fruit Juice in Pediatrics") has no nutritional benefit for infants younger than 6 months.  has no nutritional benefit over fresh fruit for children older than 6 months. In fact, fruit juice contains less fibre than whole fruit; kilocalorie for kilocalorie, fruit juice can be consumed more quickly than whole fruit; and the reliance on fruit juice instead of whole fruit to provide the recommended daily intake of fruits does not promote the healthy eating behaviours associated with consumption of whole fruits. is not appropriate in the treatment of dehydration or management of diarrhoea. Malabsorption may cause diarrhoea to worsen. Additionally, fruit juice is low in electrolytes (with sodium concentrations of 1 - 3 mEq/L) compared to oral electrolyte solutions (which contain 40 - 45 mEq/L). As a replacement for fluid losses, juice may predispose infants to development of hyponatremia. is more than adequate in intakes of 120-180ml per day (if well tolerated). Infants can be encouraged to consume whole fruits that are mashed or pureed. should be given only to infants who can drink from a cup. Teeth begin to erupt at approximately 6 months of age, and prolonged exposure of the teeth to the sugars in fruit juice has been associated with the development of dental caries.15 Other health concerns related to fruit juice consumption: Fruit juice has been shown to account for 50% of all fruit servings consumed by children aged 2 through 18 years, and 1/3 of all fruits and vegetables consumed by preschoolers. With the increase in fruit juice consumption, there has been an overall decline in milk intake, which is a cause for concern, as milk is the major source of calcium in the diet. It was found that 11% of healthy preschoolers consumed > or = 375ml/day of fruit juice, which is considered excessive. Excess fruit juice consumption has been reported as a contributing factor to nonorganic failure to thrive and to decreased stature. In other children, excessive fruit juice consumption has been associated with an increased caloric intake and obesity.9

compiled by Karen du Plessis B.Sc. Diet. karen@allergyadvisor.com Food & Allergy Consulting & Testing Services (FACTS) PO Box 565 Milnerton 7435

E. Comments by our editors

Chronic diarrhoea is a common complaint in children. Often no cause is found despite extensive medical investigations. In very young children soy and milk allergy may be suspected or alternatively, lactose intolerance. I see a number of adults and children, where a restriction of dairy and soy products has not led to a resolution of diarrhoea. Usually a careful history reveals an overconsumption of hyperosmolar fluids, diet sweets, sweets, fruit leathers or fruit. In some cases food intolerances (histamine, salicylates) may play a role. In fructose intolerance the first stools of the day are usually formed and night-time diarrhoea is uncommon. When re-introducing fructose into the diet, it is always an idea to challenge in the pure form to establish a tolerance threshold. Should there be no response to a low fructose diet, it can be assumed that other food intolerances need to be investigated. – Sabine Spiesser

This case report demonstrates clearly that one should pay careful attention to a patient’s history, and illustrates how modifying an allergic child’s diet may have adverse consequences, even if an ostensibly “healthy” food is the replacement. - Dr. Harris Steinman

Editors:
Prof Janice Joneja Ph. D.
Sabine Spiesser B.Sc. Dip. Ther. Diet.
Dr. Harris Steinman M.B.Ch.B.

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