Formula C12H22O11 | Molar mass 342.296 g/mol | |
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Isomaltulose (proprietary name Palatinose) is a disaccharide carbohydrate composed of glucose and fructose linked by an alpha-1,6-glycosidic bond (chemical name: 6-0-α--glucopyranosyl--fructose). It is naturally present in honey and sugar cane extracts. It tastes similar to sucrose with half the sweetness. Isomaltulose is also known by the trade name Palatinose™, which is manufactured by enzymatic rearrangement (isomerization) from sucrose (beet sugar). The enzyme and its source were discovered in Germany in 1950. After evaluation of its basic physiology—reviewed—it has been used as a sugar alternative in foods in Japan since 1985, in the EU since 2005, in the US since 2006, and in Australia and New Zealand since 2007, besides numerous other countries worldwide where isomaltulose can be found today. Characterization, purity and analytical methods for commercial isomaltulose are laid down for example, in the Food Chemicals Codex. Physical and physiological properties of isomaltulose (Palatinose) have been summarised; its physical properties closely resemble those of sucrose making it easy to use in existing recipes and processes.
Contents
- Function
- Available carbohydrate
- Source of energy
- Slow and sustained release
- Lower blood glucose and insulin response
- Improvements to blood glucose control
- Effect on fat oxidation
- Cognitive performance mood and memory
- Oral health
- Use
- References
The last decade has seen considerable interest in isomaltulose. Like sucrose (table sugar) it can be digested to glucose and fructose. However, it differs from sucrose in one highly important respect. While in sucrose the glucose and fructose are bonded together with a linkage called α1-2, in isomaltulose the linkage is α1-6. This difference results in profoundly different effects on human (and animal) physiology with multiple potential health benefits when isomaltulose is consumed in place of sucrose and certain other carbohydrates. The benefits arise because, in comparison with sucrose and most other carbohydrates, isomaltulose is digested slowly and steadily by humans and animals, and is essentially no substrate for oral bacteria (i.e. isomaltulose is kind to teeth by not promoting tooth decay).
Function
Basically, isomaltulose has the same function as sucrose; that is as an energy source that keeps the human body and brain functioning. The similarities even extend to how both of these substances taste and are processed.
Available carbohydrate
Isomaltulose is an available carbohydrate like sucrose and most others sugars or maltodextrins. Available or “nutritive” carbohydrates serve the body as a source of energy for its physiological functions. Whether a carbohydrate becomes available to the body largely depends on its digestion, absorption and metabolism.
When present in foods and beverages that are ingested by humans, isomaltulose is essentially completely digested and absorbed. Its intestinal digestion involves the enzyme isomaltase, which is located in the wall of the small intestine. This enzyme is otherwise involved in the digestion of α-1,6 linkages present in starch. The products of isomaltulose digestion are glucose and fructose, which enter blood. Once absorbed, the glucose and fructose follow the same metabolic routes through the body as if they were derived from sucrose. While fructose is converted to glucose in the liver, glucose from the small intestine and liver is distributed via blood to different parts of the body where it serves cellular metabolism as an energy source.
Source of energy
Based on the heat released on complete burning of isomaltulose, and the essentially complete physiological availability of carbohydrate from isomaltulose, the food energy value of isomaltulose is identical to that of sucrose. For both, the caloric value of 4 kcal/g (17 kJ/g) for available carbohydrates applies in food labelling or dietary planning.
Slow and sustained release
Isomaltulose is a slow- and sustained-release carbohydrate: After ingestion, the enzymatic digestion of sucrose and isomaltulose occur on the same sucrase-isomaltase enzyme complex, which is located in the small intestine. Several studies show this complex to digest isomaltulose (via isomaltase) slowly compared with sucrose (via sucrase) (Vmax differ by a factor of 4.5 fold).
As a result of its slow digestion, isomaltulose occurs more distally in the human small intestine than does sucrose. This is evidenced by their different incretion hormones responses. The hormone GIP (glucose-dependent insulinotropic polypeptide) is secreted from the earlier (proximal) part of the small intestine in lower amounts after isomaltulose than for sucrose ingestion, whereas the hormone GLP-1 (glucagon-like peptide-1) is secreted from later (distal) parts of the small intestine in higher amounts with isomaltulose compared with sucrose.
Compared with sucrose, the absorption of energy as carbohydrate from isomaltulose is prolonged, as was illustrated for example by Ang and Linn in 2014. The resulting steady and sustained energy supply to the body from isomaltulose is reflected in the shape of the blood glucose response, which demonstrates the slow and sustained release of energy from this dietary carbohydrate.
Lower blood glucose and insulin response
Slow digestion and distal absorption of carbohydrate from isomaltulose contributes to the low blood glucose response to isomaltulose ingestion and to the associated low insulin release. In comparison with sucrose, the rise in blood glucose concentration following the ingestion of isomaltulose appears slower and attenuated, with a lower amplitude that is sustained over a longer period of time. Isomaltulose has a low glycaemic index (GI). A GI of 32 for isomaltulose was determined by the University of Sydney Glycaemic Index Research Service, who list isomaltulose (Palatinose™) in their searchable GI database. The GI value of 32 compares with one of 67 for sucrose and 100 for glucose, which makes isomaltulose a very low GI carbohydrate.
The low glycaemic response to isomaltulose has been confirmed in numerous studies for different population groups including healthy people, overweight or obese persons, and individuals in a pre-diabetic state and persons with manifest type 1 or type 2 diabetes (e.g.). Among these studies, all show the lower blood glucose response of isomaltulose and where tested also show the associated reduction in the blood insulin response. A significant role for the incretin hormone GLP-1 has been established, which occurs in response to distal carbohydrate absorption and limits the rise in blood glucose concentration after a meal.
A claim corresponding to the low glycaemic response of isomaltulose and its potential to lower the blood glucose response of foods when replacing other sugars has been approved and laid down in EU legislation following the publication of a positive opinion from the European Food Safety Authority.
Improvements to blood glucose control
In the long-term when eating a diet including carbohydrate, reducing undesirably high concentrations of glucose in blood, and the associated demand for insulin, is supportive of the prevention and management of diabetes mellitus, cardiovascular disease, and possibly overweight and obesity—as indicated by the International Carbohydrate Quality Consortium consensus of expert nutrition scientists. A lower glycemic diet can be achieved by choosing foods with low or reduced glycemic properties instead of many commonly consumed foods. Isomaltulose in place of sucrose and many other carbohydrates has enabled the glycemic profile of foods to be reduced.
Several studies have looked at the longer-term effects of dietary sugar replacement with isomaltulose for the management of both blood glucose control and lipid metabolism in both diabetic and non-diabetic persons. The studies provide evidence of improvements to both aspects of metabolism upon regular isomaltulose consumption when compared with certain other carbohydrates such as sucrose, maltodextrin or glucose (e.g.).
Effect on fat oxidation
When compared with other ingested carbohydrates, isomaltulose allows higher rates of fat oxidation to fuel energy demanding processes in the body—as noted below for various circumstances. Mechanisms for this can be explained: Ingested carbohydrates that cause a higher blood glucose concentration stimulate a higher release of insulin both to facilitate the uptake of glucose by tissues and to normalise the blood glucose concentration. The higher insulin concentration also promotes carbohydrate oxidation at the expense of fat oxidation, thus promoting fat retention and storage in adipose tissue. Thus, ingested isomaltulose with its slower, steadier and longer time for release of glucose into blood allows the supply of carbohydrate energy to be steady for longer—meanwhile creating a more advantageous metabolic profile: That is, demand for insulin is lower after isomaltulose ingestion than it is for higher glycaemic carbohydrates. The associated lower insulin release and concentration thereby allow a person eating isomaltulose to maintain higher rates of fat oxidation in energy metabolism. The lower insulin concentration is also expected to lower the recycling by liver of circulating free-fatty acids back to adipose tissue via plasma triglycerides, a process that supports both fat oxidation and lowering of fat storage. Practical implications seem to be several, higher rates of fat oxidation occur after isomaltulose than after ingestion of higher glycaemic carbohydrates in many studies, yet the studies have different focuses:
Some studies have looked at the effects of replacing sugars with isomaltulose in meals or drinks on metabolic responses and fat oxidation in healthy or overweight to obese adults with normal or impaired glucose tolerance in largely sedentary conditions. These studies evidently see the relevance in weight management and body composition. Longer-term studies suggest, indeed, that isomaltulose has a role in reducing body fatness, at least central obesity. In these studies, abdominal fat decreased with sugar replacement by isomaltulose or when replacing breakfast calories.
Others studies have looked at the potential of the slow and sustained release of carbohydrate energy from isomaltulose compared with other ingested carbohydrates, finding higher rates of fat oxidation in endurance activities when preserving glycogen is important. In addition, recently published trials with a recovery protein drink suggest that the addition of isomaltulose and a nutritional supplement (β-hydroxy- β-methylbutyrate) may enhance recovery from resistance exercise—contributing to reduction of muscle damage and improvement of athletic performance.
In people with type-1 diabetes, the ingestion of isomaltulose instead of glucose during moderate carbohydrate loading before exercise has resulted in improvements in their glycaemic control, protection against hypoglycaemia, and maintenance of their running performance. The reduced risk of exercise-induced hypoglycaemia arises in part from the lower demand for insulin injection (50% lower) when using isomaltulose and in part from the simultaneous higher contribution of fat oxidation to energy metabolism, which reserves energy in carbohydrate to counter the risk of hypoglycaemia.
Cognitive performance (mood and memory)
Carbohydrates and the glucose they supply influence cognitive performance. The sustained glucose release from isomaltulose has particular advantages in the late phase after a meal. Several studies comparing isomaltulose with higher glycaemic carbohydrates when eaten with breakfast by healthy children, middle-age adults, and aged adults, show improvements in mood and memory after the isomaltulose.
Oral health
Isomaltulose is ‘kind to teeth’. The fermentation of carbohydrates by oral bacteria is responsible for the formation of dental plaque and oral acids, which initiate tooth demineralisation and dental caries (tooth decay). Isomaltulose largely resists hydrolysis, digestion and fermentation by oral bacteria and is the first carbohydrate of its kind to show negligible acid production on teeth by pH telemetry. The evidence is strong and has provided the basis for ‘toothkind’ claims approved by both the Food and Drug Administration in the USA and the European Authorities with a respective claim following a positive opinion from the European Food Safety Authority in the EU.
Use
Isomaltulose is used as a food ingredient and alternative to other sugars and maltodextrins in foods and beverages. Thus isomaltulose has a pure and natural sucrose-like sweetness profile, a sweetening power about a half that of sucrose, and no aftertaste. Because isomaltulose has very low hygroscopicity (moisture absorption), in instant powders (e.g. drinks) it maintains free-flowing properties (low risk of lumping). Moreover, isomaltulose is highly stable during processing including acidic conditions and environments where bacteria might grow. In sports beverages, for instance, isotonicity (osmotic pressure equal to that of fluids in the body) can be maintained during storage over the beverage’s shelf-life.
Products in which isomaltulose finds application include, for example, baked goods, pastry glazings and icings, breakfast cereals, cereal bars, dairy produce, sugar confectionery (e.g. chocolates, jellies, chewy confections and chewing or bubble gum), frozen desserts, fruit-juice beverages, malt beverages, sports beverages, energy drinks, instant drinks, special and clinical nutrition feeds and more.
The use of isomaltulose in foods and drinks is recognised in many regions worldwide. For example, it is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration, is approved as a novel food by the European Commission, and in Japan has the status FOSHU (food for specific health use).