Nutritional Pearl: How Does Hydration Affect the Brain?

Julie is a 23-year-old healthy college senior. At a recent check-up, she mentions that she has been struggling with the pressure of her last year at school, and asks if there are any lifestyle modifications she can make that could help improve both her mood and her levels of concentration.

How would you advise your patient?
(Answer and discussion on next page)

Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients with evidence-based resources including special diets for coumadin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance. 

Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen with familiar, healthy recipes. He is an assistant dean for clinical services, executive director of The Goldring Center for Culinary Medicine, associate professor of medicine at Tulane University in New Orleans, faculty chair of the all-new Certified Culinary Medicine Specialist program, and co-chair of the Cardiometabolic Risk Summit.

Now, for the first time, Dr. Gourmet is sharing nutritional pearls of wisdom with the Consultant360 audience. Sign up today to receive an update from the literature each week.

Answer: Staying well hydrated is associated with lower levels of tension and confusion.

We’ve covered more than one study that looked at the effects of mild dehydration on the brain. One focused on young women and found that just 1% to 3% dehydration could not only affect their reasoning skills and attention span but also make them feel angrier or hostile.¹ Another found that children's short-term memory was better when they were well hydrated.²

Today's study looks more specifically at water's effect on mood. Instead of inducing dehydration (as they did in the first study), or making sure that the participants were well hydrated (the second), the authors sought to evaluate mood more realistically: by looking at accustomed hydration levels.
______________________________________________________________________________________________________________________________________________________________________

RELATED CONTENT
Diagnosing Dehydration: What Would Osler Do?
Hyperhydration Greater Threat to Athletes than Dehydration
______________________________________________________________________________________________________________________________________________________________________

The Research

The team recruited 120 healthy women from the student body to participate in their study.³ For 5 consecutive days, the women kept detailed records of everything they ate and drank, which allowed the researchers to estimate their total water intake: all of the liquid content of all foods consumed (not just their beverages alone). On those same days, the participants responded to a series of mood questionnaires.

The authors analyzed the women's total water intake and grouped the participants into 3 levels of average daily water intake: low, moderate, and high. The moderate level corresponded to about the daily amount recommended by the Institute of Medicine.

The Results

Compared to the mood questionnaire results that are considered normal for the women's age group, the authors found that those women in the high water intake group tested lower for signs of depression than those in the low intake group. Further, those in the high group reported less tension than the moderate group as well as less confusion. Overall, those in the high group "experienced less mood disturbance" (an overall measure) than the low group and "trended toward" less mood disturbance than the moderate group.

This study's authors did their best to take into account dietary variables that might affect mood. The participants were asked to refrain from drinking alcohol throughout the study, as it not only affects hydration but also is a mood depressor. They also considered protein, carbohydrate, fat, and caffeine intake as well as weekly exercise amounts, none of which appeared to have a role in the participants' moods.

What’s The “Take Home”?

The authors do not specify how much of the participants' water intake was from food (soup or fruit, for example) as opposed to beverages, nor did they specify how much plain water the participants drank—or even if they did. That said, this is certainly another argument in favor of keeping yourself well-hydrated. Water is best, but tea or coffee, even if caffeinated, are also great for you.

References:

1. Fadda R, Rapinett G, Grathwohl D, et al. Effects of drinking supplementary water at school on cognitive performance in children. Appetite. 2012;59(3):730-737.
2. Armstrong LE, Ganio MS, Casa DJ, et al. Mild dehydration affects mood in healthy young women. J. Nutr. 2012;142(2):382-388.
3. Munoz CX, Johnson EC, McKenzie AL, et al. Habitual total water intake and dimensions of mood in healthy young women. Appetite. 2015;92:81-86.