Does Coffee Cause Dehydration?
It is well known that intake of
very large amounts of caffeine can increase blood flow to the kidneys and
inhibit the absorption of sodium and thereby cause dehydration, but do lower
doses of coffee also cause dehydration?
It would be interesting to study
whether a medium intake of coffee would cause dehydration. I believe the experiments will
not be hard to perform. We would need to recruit two groups of volunteers,
probably UK students. Volunteers would be divided into a “coffee group”
(participants would consume a daily 32oz coffee containing 660mg caffeine for a
week) and a “water group” (participants would consume the same normal amount of
water as that of the coffee group and an additional 32oz of water daily for one
week). Both groups of volunteers would be on identical diets, sleep/wake cycles
and physical activity.
First, we would determine
whether there was a significant change in the total amount of body water at the
end of experiments in the two groups. Total body water would be determined
following ingestion of deuterium oxide as described previously (1). Second, we would determine
whether there is a significant difference between the two groups in serum Na+,
serum K+, osmolality and creatinine. Blood for serum would be collected on the
mornings of day 1-day 7. Serum Na+ and K+ levels would be analyzed using a
ILab600(Diamond Diagnostics). Serum creatinine levels would be analyzed using
ilab650 and serum osmolality would be analyzed using advanced Osmometer
765(Advanced Instruments Inc). Third, the 24 h urine volume,
urinary Na+ excretion, K+ excretion, urine osmolality, and urine creatinine
would be compared between the two groups using the same instrumentation. Urine
would be collected on the mornings of day 1-day 7. The results above would help
me determine whether medium doses of coffee do cause dehydration.
Reference:
1. Silva A, Judice P, Matias C, Santos D, Magalhaes J, et al. (2013) Total body
water and its compartments are not affected by ingesting a moderate dose of
caffeine in healthy young adult males. Appl Physiol Nutr Metab Just-IN.
I think this would be a worthwhile study to complete! I feel like excessive coffee intake is extremely common among college students so it would be interesting to see the actual effects on dehyradation because I've always tried to increase my water intake when drinking cofeee in order to prevent dehydration!
ReplyDeletecoffee is considerably the "go to" drink for many individuals; many which consume multiple times daily. i think this would be a very good set up for the actual experiment. however, i do believe that having variable groups for each dosage level: low, medium, high, & none should be tested in the experience that; this way we can determine whether or not the cause of the dehydration is dose dependent. i also think considering recruiting volunteers who have similar lifestyles is something to think about. For example, an individual who is a traveling business man, transporting by flight, could experience a greater chance of becoming dehydrated from altitude changes rather than an individual who is not traveling for business, like a stay home mom; other factors such as these could be considered when recruiting volunteers.
ReplyDeleteThis is an interesting study, and it will add a valuable information to fill this gap. However, I think he needs to consider more controls like; the body temperature and sweating for participants, water may not a good control since it affects hydration to a different level from coffee, the total urine output, and gender for participants.
ReplyDeletethanks! it is nearly impossible to make the two group have the same amount of sweat and exact same body temperature but since Both groups of volunteers would be on identical diets, sleep/wake cycles and physical activity, so the difference will be minimized. caffeine is diluted in water so water is probably the best control and we do not know what solvent has the same hydration level as coffee
DeleteThis would be an interesting study. I am wondering if the coffee intake needs to be 32oz at once or if it can be smaller throughout the day. Personally, I rarely drink coffee so I don't have first hand knowledge of its effects on my body, but I feel like many people that are health conscious would be aware of their hydration and would supplement with extra water. I'm sure many others wouldn't though. Nice piece.
ReplyDeleteGenerally it sounds like a good study, but I think there are several factors that need to be considered. The individuals history of coffee/caffeine consumption would need to be known. Studies have shown that consuming caffeine on a regular basis will inhibit the loss of water through the kidney by becoming tolerant to caffeine. Another factor is the function of the kidney in each volunteer. Age, health, and GFR will play a major factor in this determination. I would hypothesize that due to the incredible fluid volume homeostatic capabilities of the body, that low amounts of caffeine would not cause a significant increase in dehydration. -J. Ohde
ReplyDeleteI have to agree with previous comments, that I don't believe 32oz consumed by the 'coffee' group to be effective or not. I believe you could use a lower amount (i.e. 12 oz) and still have effective and sufficient results. I also believe to consider including observational results (i.e. drinking more, tired, muscle cramps, headaches, etc.) which give indication of possible dehydration.- JS
ReplyDeleteI think this would be an interesting study and would be especially intriguing to college students and athletes. I know a lot of my college teammates were not happy when our coach encouraged us not to drink coffee, especially on game days. I think a study like this could help bridge the gap on the information missing from the idea that drinking coffee will have such severe effects of dehydration.
ReplyDelete