What is maltose?
Maltose or malt sugar is a disaccharide composed of two glucose molecules connected with an alpha (1,4) glycosidic bond. Maltose is not an essential nutrient, which means you do not need to get it from food in order to live an be healthy.
Name origin: from malt = soft grain; -ose denotes sugar.
Picture 1. Maltose structure
Nutrition Facts for Maltose
- Calories per gram = 4
- Glycemic index for 50 g (GI) = 105 
- Sweetness, relative to sucrose = 50% 
- Net carbohydrates = 100%
Maltose Function in the Human Body
Maltose is a source of energy; it can provide about 4 Calories per gram,which is about the same as glucose or sucrose.
- Maltose is an intermediate product of the starch digestion.
- Free maltose (as a disaccharide) in significant amounts is naturally present in spelt, kamut and sweet potatoes  .
- Syrups high in maltose: high maltose corn syrup (HMCS), barley malt syrup, also called barley malt sugar or dark malt syrup (which is a thick brown syrup), brown rice syrup, corn syrup  .
- Beverages containing maltose: certain beers, ciders, compotes, kombucha rice malt, “malt beverages” (non-alcoholic).
- Processed foods high in maltose: certain ready-to-eat cereals, jelly candies, chocolates, compotes, caramel sauce, confections (especially in China, Taiwan, Hong Kong) [1,2] .
Chart 1. Foods High in Free Maltose
|Beer, strong ale, 8 vol% alco (12 oz, 355 mL)||22|
|Barley malt syrup (1 tbsp, 20 g)||12-15|
|High maltose corn syrup (HMCS) (1 tbsp, 20 g)||4.5-13.5|
|Sweet potato, baked (1 cup, mashed, 200 g)||13|
|High maltose corn syrup (HMCS, 65% maltose) (1 tbsp, 20 g)||10|
|Beer, lager, 4.7 vol% alco (12 oz, 355 mL)||7.5|
|Brown rice syrup (1 tbsp, 20 g)||7|
|Ready-to-eat cereals (1/2 cup, dry)||6|
|Cider, 4.7 vol% alco (12 oz, 355 mL)||2-6|
|Pears, canned, solids and liquids (1 cup, 265 g)||5|
|Jelly candies (2 oz, 57 g)||4|
|Pizza, meat and vegetables (1 slice, 150 g)||3.5|
|Sundae, caramel (1 piece, 165 g)||3.5|
|Peaches, canned, solids and liquids (1 cup, 250 g)||3.5|
|Shake, strawberry (1 cup, 237 mL)||3.5|
|Bagel, plain (3.5 oz, 100 g)||3|
|Bread, whole wheat (two slices, 6“x 4“ x ½”, 3.5 oz, 100 g)||3|
|Grapes (1 cup, 90 g)||3|
|Light corn syrup (1 tbsp, 20 g)||3|
|Guava nectar, canned (1 cup, 237 mL)||2|
|Dark corn syrup (1 tbsp, 20 g)||2|
|Pancake syrup (1 tbsp, 20 g)||2|
|Nougat candy (1 oz, 28 g)||2|
|Beer, alcohol free (12 oz, 355 mL)||1|
|Steak, breaded (1 piece, 175 g)||1|
|Honey (1 tbsp, 21 g)||Up to 1|
Chart 1 references: USDA.gov  , Fineli.fi 
In the small intestinal lining, the enzymes maltase and isomaltase break down maltose to two glucose molecules, which are then absorbed. Glucose from maltose is absorbed faster than pure glucose  . Some maltose can be absorbed as such, without being broken down into glucose  . Maltose and its digestion product glucose attract water from the intestinal wall (osmotic effect) so they can cause diarrhea if consumed in excess. The laxation threshold for maltose in healthy people is about 120 grams per day [7-p.320] .
Maltose and Dental Caries
Maltose, including maltose released from the digestion of starch in mouth, can promote dental caries.
Individuals with a congenital sucrase-isomaltase deficiency may experience bloating and diarrhea after ingesting maltose, sucrose or starch  .
Maltose, Blood Glucose Levels and Diabetes
- Maltose has a high glycemic index (GI = 105)  and can cause greater blood glucose spikes than sucrose.
- An antidiabetic drug acarbose inhibits the digestion of maltose, which results in slower glucose absorption and lower blood glucose spikes after carbohydrate meals  .
Who can benefit from avoiding/limiting maltose intake?
Individuals with the following conditions can benefit from avoiding maltose:
- Diabetes mellitus
- Celiac disease 
- Reactive hypoglycemia 
- Postprandial hypotension 
- Glucose-galactose malabsorption 
- GLUT-1 deficiency syndrome 
- Congenital sucrase-isomaltase deficiency (CSID) 
Maltose is produced from corn, barley, tapioca or sago palm starch using the enzyme alpha-amylase of fungal origin [3,4,producers] .