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Study under review: A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index
Study Deep Dives has previously covered the glycemic index and the insulin index, but beverages now also have their own index: namely, the new “hydration index”. People usually think about hydration in the context of sports and exercise, so it may be beneficial to know which beverages can best hydrate you when access to fluids (or bathrooms, see Figure 1 for a rough guide to bathroom-guided hydration statuses) is limited.
Reference: Maughan et al. Am J Clin Nutr. 2015.
Not all beverages are created equal from a hydration standpoint. Absorption is affected by the amount of fluid ingested, electrolyte and carbohydrate content, and the presence of diuretic agents (substances that promote urine production). For example, milk has been shown to be more effective than both water and sports drinks for rehydration after strenuous exercise.
The rehydration process is affected both by the volume of fluid ingested as well as the sodium content. It has long been known that the presence of carbohydrates and electrolytes in a drink increases the rate of fluid absorption after drinking. Coffee is often thought of as negatively affecting hydration status, but this is based on studies examining the acute effects of high levels (more than 300 mg) of caffeine on individuals who had been deprived of caffeine for a period of days or weeks. A tolerance to the diuretic actions of caffeine develops with regular intake, and the amounts of caffeine found in normal sized servings of tea, coffee, soda, etc., do not have diuretic effects.
This study is the first to develop a method for systematically quantifying values for hydration and fluid balance. Similar to how the glycemic index is intended to define the blood glucose response to the ingestion of foods compared to a white bread or glucose standard, a beverage hydration index (BHI) could serve to quantify water excretion from the kidneys in response to various beverages compared with still water. The cumulative volume of urine passed over a fixed period of time can be measured as a marker of fluid absorption and retention. The aim of this new study was to determine the fluid balance responses to the ingestion of a set amount of commonly consumed beverages ingested in a euhydrated state (a normal fluid balance).
The volume and amount of electrolytes and sugars of ingested fluids affect their absorption and retention, but various beverages have yet to be systematically compared. This study set out to determine if a beverage hydration index, similar in principle to the glycemic index, could be established.
Other Articles in Issue #16 (February 2016)
Dieting, with a side of extra protein
For many lifters, it’s been a mantra that you just can’t gain muscle while being in a heavy calorie deficit. That statement was put to the test in this trial of a high protein diet.
Promoting ‘high quality’ weight loss: protein and weights
By Stuart Phillips, PhD
Vitamin E bioavailability isn’t always the same
The vast majority of people don’t meet the recommended intake level for vitamin E. And it turns out that certain people may not absorb vitamin E as well as others, and they might actually be the ones who need it most.
Spice up your satiety?
The active ingredient in spicy food, capsaicin, seems to have some effect on satiety. But researchers weren’t quite sure what it was or how it happens, until this highly controlled experiment was done
Little bugs for big depression
Your gut and your brain communicate much more often than you’d think. In fact, all the time. Hence the potential for consuming gut inhabitants (aka probiotics) and impacting brain-related maladies
Fish oil incorporation: where do other fats fit in?
When you buy and take a fish oil supplement, the story doesn’t end there. It still needs to be incorporated into cell membranes. This study looked at how other fats may impact that process
The Tyranny of the Outlier: Focusing on the best of the best sometimes diminishes the rest of us
By Lou Schuler
Have a nice trip, see you next fall
Some preliminary evidence has pointed to a potentially greater risk of falls for elderly people taking vitamin D. That’s put to the test in this year-long randomized trial.
A vitamin D-efense against multiple sclerosis
MS involves a complex interplay between the nervous and immune systems (and potentially others as well). This is the first trial looking at the safety and immune impact of vitamin D supplementation for MS patients.