Many of us will be familiar with cravings for sweet food, after having overindulged in alcohol the night before. It appears that Egyptian fruit bats also crave particular types of sugar to reduce the effects of ethanol toxicity. Francisco Sanchez from the Ben-Gurion University of the Negev (Israel) presented data demonstrating this on Sunday 1st of April at the Society for Experimental Biology's Annual Meeting in Glasgow.
The concentration of ethanol rises in fleshy fruits, such as figs and dates, as they ripen. Egyptian fruit bats prefer these fruits when they are ripe, however high concentrations of ethanol (around 1%) are toxic to the animals. Intoxicated bats may also be less able to respond to attacks from predators, and to avoid obstacles (much like us humans, some might say!). The sugar molecule, fructose, is known to reduce the toxicity of ethanol. Therefore, scientists investigated the effect of consuming fructose on ethanol toxicity in Egyptian fruit bats, and whether the fruit bats preferred food containing sucrose after they had consumed ethanol.
It was found that ethanol levels measured in fruit bat breath declined faster after feeding on fructose-containing food, than when the food contained either sucrose or glucose (two other types of sugar). Furthermore when the amount of ethanol in food increased the fruit bats preferred food which contained fructose over glucose-containing food. Intriguingly the fruit bats preferred food containing sucrose above either of the other two sugars. Thus, although only fructose reduced ethanol toxicity for Egyptian fruit bats, the bats themselves perceived both fructose and sucrose as being beneficial. "We think that this observation may be due to a matter of taste or flavour", explains researcher Francisco Sanchez, "The perception of sweetness versus bitterness may vary according the type of sugar and the amount of ethanol consumed. The combination of sucrose and ethanol may just have tasted better than either ethanol and fructose, or ethanol and glucose".
- Glucose is a simple sugar (termed monosaccharide) found in most plant and animal tissue. It is the principal sugar found in the blood and is a major source of energy.
- Fructose is another monosaccharide which occurs in fruits and honey.
- Sucrose is commonly known as "table sugar", and is composed of one glucose molecule and one fructose molecule (and therefore called a disaccharide).
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