People who drink less than a couple of glasses of water each day may be more likely to develop high blood sugar, a new study suggests.
When someone's blood sugar levels are elevated above the normal range, but not high enough to fit the definition of diabetes, they are said to have impaired fasting glucose or "pre-diabetes" -- which puts them at risk of developing the disease itself.
In the new study, adults who drank only 2 cups (500 ml) of water or less each day were more likely to develop blood sugar levels in the pre-diabetes range, versus people who drank more water.
But whether simply drinking water will cut your risk of blood sugar problems is still not known.
The findings show a correlation between water intake and blood sugar, but do not prove cause-and-effect, said the researcher from the French national research institute INSERM.
A hormone called vasopressin is the potential missing link, according to the researchers. Vasopressin -- also known as antidiuretic hormone -- helps regulate the body's water retention.
When we are dehydrated, vasopressin levels go up, causing the kidneys to conserve water. But research suggests that higher vasopressin levels may also elevate blood sugar.
There are vasopressin receptors in the liver, the organ responsible for producing glucose in the body. One earlier study found that injecting healthy people with vasopressin caused a temporary spike in blood sugar.
The new findings are based on 3,615 French adults who were between the ages of 30 and 65, and had normal blood sugar levels at the start of the study. About 19 percent said they drank less than 2 cups (500 ml) of water each day, while the rest drank up to 4 cups (1 litre) or more.
Over the next nine years, 565 study participants developed abnormally high blood sugar and 202 developed type 2 diabetes.
When the researchers looked at the participants' risk according to water intake, they found that people who drank at least 2 cups of water per day were 28 percent less likely to develop prediabetes than those who drank less than that amount.
There was no strong statistical link between water intake and risk of developing diabetes, however.
One obvious explanation for the connection with high blood sugar would be that people who drink little water may instead be reaching for sugary drinks -- which could lead to weight gain and impaired blood sugar control.
But the researchers accounted for sugary drinks and alcohol, as well as people's body weight at the start of the study, their reported exercise levels and certain other health factors. And the link between low water intake and high blood sugar persisted.
However, they could not account for everything, including generally healthy or less-healthy eating habits.
As for why there was no link between water intake and diabetes itself, the researchers said that the number of diabetes cases in the study was "too small to get a significant result." A larger study might have been able to detect a statistically significant link.
Further studies are needed to confirm the findings on blood sugar.
Source: Diabetes Care, online October 12, 2011.
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