Mannitol

What is mannitol?

Mannitol is a low-calorie sweetener. It is a carbohydrate, a sugar alcohol, made from fructose and hydrogen ^[2,3-p.249]. It is poorly absorbed in the small intestine, so it travels to the large intestine where beneficial intestinal bacteria break it (ferment) into gases and short-chain fatty acids (SCFAs), which can be absorbed and provide some energy.

Nutrition Facts:

Calories per gram = 1.6
Glycemic index (GI) = 0
Sweetness, relative to sucrose = 60%
Net carbs = zero

Mannitol Origin

Mannitol occurs naturally in mushrooms, marine algae, strawberries, celery, onions, pumpkins ^[1,2]. In China, mannitol can be produced from seaweeds ^[3-p.251]. Mannitol as a food additive is semi-artificially produced by adding hydrogen to fructose, which is derived from starch (corn, wheat or tapioca) ^[2,3-p.249]. Prior to conversion to mannitol fructose is converted to mannose, from which mannitol has got its name ^[2].

Foods Containing Mannitol

Mannitol is used as a sweetener, anti-caking agent, emulsifier or thickener in chocolate-flavored coatings for ice cream and confections, chewing gum, butter, frozen fish, pre-cooked pasta, infant formula ^[1,4]. In the European Union, mannitol is labeled as E number E421 ^[5].

Mannitol can be also used as a carrier in certain vitamin supplements, medicinal syrups and medications.

Mannitol Absorption and Metabolism

Mannitol is slowly absorbed in the small intestine and poorly metabolized. It provides only 1.6 kilocalories per gram ^[3-p.59].

Possible Mannitol Benefits

Tooth decay. Mannitol does not promote dental caries ^[1].

Diabetes mellitus. Mannitol has a very low glycemic index (GI = 0) ^[3-p.9] and does not raise blood glucose and insulin levels ^[1].

Mannitol Safety

Mannitol is Generally Recognized As Safe (GRAS) by the US Food and Drug Administration (FDA) ^[6]. Mannitol is approved to use by The Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) ^[1]. JECFA has determined 50 mg mannitol/kg body weight per day as safe for healthy adults ^[1].

During Pregnancy

There appears to be no data about the eventual harmful effects of the sweetener mannitol on the growing fetus.

Side Effects, Dangers

Mannitol attracts water from the intestinal wall (osmotic effect) so it can cause diarrhea if consumed in excess. Mannitol,when ingested in amounts greater than 50 mg/kg body weight (35 g by a 70 kg or 155 lbs person) may cause abdominal pain, excessive gas (flatulence), loose stools or diarrhea. According to one source, the laxation threshold for mannitol in healthy people is about 20 grams per day ^[3-p.257].

There appears to be no evidence about association between mannitol and cancer.

Mannitol and Cooking

Physical properties:

A white crystalline powder ^[7]
60% as sweet as sucrose with a strong cooling effect ^[1]
Non-hygroscopic – does not attract moisture from the air until it exceeds 90% relative humidity ^[1,3-p.254]
Solubility in water at 77° F (25° C) = 20 g/100 g solution ^[3-p.158]; poorly soluble in ethanol ^[7]
Melting point = 329-336° F (164-169° C) ^[1,7]
Does not decompose at 320° F (160° C) ^[3-p.158]

Mannitol as a Drug

Mannitol acts as an osmotic diuretic, which means it drags water from the blood into the urine and can thus quickly reduces blood pressure. As an intravenous drug is used to lower the increased pressure within the skull (intracranial pressure or ICP) and in treatment of increased pressure within the eye (glaucoma).