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Cut calories vs. cut protein intake: the results will surprise you 11/16/22
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All Health and Nutrition Bites


Low-Carb Diets Affect Your Brain
Low-carb diets seem like an easy way to lose weight: just cut out all carbs. No worrying about portion size, balanced meals or avoiding low-quality, fatty foods - it's "dieting without hunger!" Still, you've probably heard that low-carb diets may not be good for your liver.

Healthier and Happier
We've seen that low levels of dehydration can affect people's mood - causing higher levels of anger or hostility, fatigue, and feeling that a given task is more difficult to perform (Drink Water, Feel Better 2/29/12). Following a Mediterranean-style diet also appears to be good for your mood, improving feelings of contentedness, vigor and alertness.

Keep Your Kids Hydrated
Earlier this year I reported on a small study in college students that suggested that mild to moderate dehydration could affect the brain's cognitive functions, including short-term memory, reasoning, and even mood. Indeed, it's been estimated that most adults in Western cultures are chronically mildly dehydrated. 


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Drink Water, Feel Better

We know that severe dehydration can kill, with early signs of serious dehydration including confusion and delirium. Even moderate dehydration has been shown to interfere with thinking processes. The studies that have investigated mild to moderate dehydration have used high temperatures as well as exercise to induce sweating enough to cause dehydration. A recent study performed at the University of Connecticut, however, takes on the issue from a less extreme point of view: are the levels of dehydration that people experience in their daily lives enough to affect their brain's function?

Instead of using high temperatures, the researchers used a combination of diuretic medications and mild exercise in 25 healthy college-age women (J Nutr 2012; 142(2):382-388). On three separate occasions the women visited the research lab and responded to a battery of neurological tests intended to measure brain function in various areas, including memory, learning, reasoning and mood. On one occasion the women were asked to walk on a treadmill in a moderately warm room (80F) for 40 minutes and were also given a diuretic pill to help induce dehydration. On a second occasion they performed the same exercise but were given a placebo, or sugar pill. On the third occasion they did not exercise and were also given a placebo. Before and after the tests the women's blood was tested and their urine collected to measure levels of dehydration.

The amount of exercise and the medications were designed to induce very low levels of dehydration in each participant - on the order of 1%, 2%, or 3% of total body mass - so that the researchers could assess the effects of those levels of dehydration on each participants' performance in the testing.

Given that we know that serious dehydration can affect the brain, it's not surprising that the more dehydrated the women were, the poorer their scores in such areas as short-term memory, attention, and logical reasoning. What is surprising, however, is that their moods were affected as well. The more dehydrated they were, the harder they felt a given task was to perform, the more angry or hostile they felt, and the more fatigued they felt.

What this means for you

Last week I reported on a study that shows that substituting calorie-free beverages like diet soda and water for sugared beverages can help you lose weight. This is just another reason that water should be your beverage of choice: being well hydrated can not only help keep you happier, you'll probably be more likely to feel like exercising - or continuing to exercise if you've already started. In addition to drinking water throughout the day, be sure to take a bottle of water with you when you exercise and sip on it regularly to help keep you motivated.

First posted: February 29, 2012