They used to tell us that we should drink eight ounces of water eight times a day. Then the standard advice became to drink only when we are thirsty. Now it seems that this isn’t right for everyone either.
The problem is that as we grow older the sensation of thirst frequently declines, studies show. “Thirst is not a good guide to the need to drink in older people,” writes Lee Hooper, PhD, and other researchers at the University of East Anglia in Norwich, England. Not drinking enough water can lead to disability and even death.
The new study, “Which Frail Older People Are Dehydrated?,” was published last week in The Journal of Gerontology. While only the abstract is free online, Dr. Hooper kindly sent me the full-text. This is the first report that takes into account both a large study group and a large range of health factors. The research took place in 56 residential care homes where the team studied 188 people older than 65.
"Older people tend not to feel thirsty when they drink too little,” Dr. Hooper says. “On top of that, as our kidneys get older we are less able to concentrate our urine to preserve fluid, so the body’s ability to regulate its fluid balance slowly reduces.
The diabetes connection
Until now, there has been limited and contradictory evidence about which health factors are associated with dehydration in older adults. But the study turned out to be especially relevant to people with diabetes. Diabetes is one of the health factors that is associated with dehydration, they write. Obesity, hypertension, and other chronic diseases are additional ones.
The authors of this study write that they were surprised to find that diabetic medication in general is associated with dehydration. They further found that dehydration was likely to be associated with higher blood glucose levels.
The myth exposed
“There’s an old urban myth that you should drink at least eight glasses of water a day,” I wrote here nine years ago. While you will see this advice repeated time and again, it appears to lack any scientific proof.
It looks like the Food and Nutrition Board of the National Research Council started the whole thing in 1945. That’s when the board recommended that we consume about “1 milliliter of water for each calorie of food.” That works out to roughly two to two-and-a-half quarts per day. But most people seem to have missed its next sentence, that “most of this quantity is contained in prepared foods.”
Only drink when thirsty?
So, shouldn’t we just drink when we are thirsty? As recently as this summer that was the recommendation of a consensus panel of experts advising us to do that “before, during and immediately following exercise.”
Unfortunately, for the experts who like to give one-size-fits-all advice, not everyone is the same. When we get older, we tend to lose the sense that we need to drink more and have to consciously decide to have a drink.
See more of my articles about how to manage diabetes:
David Mendosa was a journalist who learned in 1994 that he had type 2 diabetes, which he wrote about exclusively. He died in May 2017 after a short illness unrelated to diabetes. He wrote thousands of diabetes articles, two books about it, created one of the first diabetes websites, and published a monthly newsletter, “Diabetes Update.” His very low-carbohydrate diet, A1C level of 5.3, and BMI of 19.8 kept his diabetes in remission without any drugs until his death.