Maltose

Maltose is a sugar made of two glucose units joined together. It forms when starch is broken down — in your gut and when grains such as barley sprout (malting) — and is found in malted drinks, malt extract, maltose syrup and beer.

What is it?

Maltose is a disaccharide, also called malt sugar. It is made when amylase breaks down starch, in saliva and the small intestine, in germinating grains, and in cooked sweet potato, and is split into two glucose units by the enzyme maltase. It is about one third to half as sweet as sucrose.

Maltose syrup (also called malt syrup or maltose sugar) is made from starch for confectionery, baking and brewing, and is the traditional sweetener in Chinese maltose candy.

What it does

1. Provides energy at about 4 kilocalories per gram, as glucose
2. Adds mild sweetness and a malty flavour
3. Has a high glycaemic index (about 105), meaning it raises blood glucose very quickly
4. Feeds yeast in brewing and baking

Food sources

Malted drinks and powders (such as Milo and Horlicks), malt extract and malted barley, maltose syrup, sprouted grains, malted cereals and biscuits, beer, cooked sweet potato and some breads and sweets. Maltose is rarely found alone in whole fresh foods.

Singapore food examples

1. Malted chocolate and malt drinks — Milo, Horlicks
2. Maltose candy, dragon's beard candy and maltose-based sweets
3. Barley-based drinks and desserts
4. Roasted or baked sweet potato
5. Malted breakfast cereals and biscuits
6. Beer and malt beverages

How much do I need?

There is no recommended intake for this sugar on its own, and Singapore's RDA table does not list it. Singapore's dietary guidelines advise that added sugar provide no more than 10 percent of daily energy — about 10 teaspoons (around 50 g) on a 2,000-kilocalorie diet, with about 5 teaspoons (25 g) even better — see Singapore's dietary guidelines for adults (HealthHub).

Low intake and deficiency

There is no deficiency; the body does not need maltose and makes glucose from starch and other foods.

Too much and safety

Because maltose is made of glucose and absorbed quickly, large amounts of maltose syrup or sweetened malt drinks raise blood sugar rapidly and add energy without much else. As with other added sugars, limit sweetened malted drinks and sweets — choose unsweetened versions or smaller portions, and check the Nutri-Grade label.

People with diabetes, or on medicines to lower blood sugar, should be aware that maltose can raise blood glucose very fast; check with your doctor or dietitian.

Absorption and bioavailability

Maltase on the lining of the small intestine splits maltose into two glucose molecules, which are absorbed through the SGLT1 transporter and enter the blood very quickly. Deficiency of maltase is rare, as maltase is abundant.

Connection to daily life

1. Energy and exercise: malted drinks supply quick glucose, but are best as a treat — see Exercise
2. Blood sugar: the high glycaemic index makes portion size important
3. Related: see Glucose, Sucrose and Sugars

Sources: 1. HealthHub Singapore — Dietary guidelines for adults: https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/dietary_guidelines_adults 2. HealthHub Singapore — Recommended Dietary Allowances: https://www.healthhub.sg/well-being-and-lifestyle/food-diet-and-nutrition/recommended_dietary_allowances 3. Health Promotion Board — Singapore Food Insights Database (SG FoodID): https://www.hpb.gov.sg/healthy-living/food-and-beverage/sgfoodid/ 4. FAO/INFOODS — Food composition tables and databases: https://www.fao.org/food-composition/tables-and-databases/en/ 5. National Academies of Sciences, Engineering, and Medicine — Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005)