Have you had enough water today?
On hydration. 2L of water per day. Beverage Hydration Index. Properties of drinks. Electrolytes.
“Have you had enough water today?”
Sound familiar? A question we’ve all gotten at one point in our lives, usually following statements such as “I’ve got a headache”, “I’m not feeling very well”, “My energy is low”, “I’m feeling quite tired” and so on...
I mean it makes sense, why it may be the culprit of all the statements - the majority of our body is water, around 60% to be precise. More specifically, over 70% of each cell is made up of water.
I guess another reason why we may assume so is the 2-liter or 8-glasses per day water intake recommendation. But do actually we need that much water? The origin of this recommendation can be traced back to three main sources:1
19th Century Hydropathists: practitioner of hydropathy (a traditional alternative medicine practice which involves consuming water for pain relief and treatment of illness) which advocated for water’s curative powers. The movement started in the early 1800s, by Vincent Priessnitz in Austria, as he believed that cold water could invigorate the system and stimulate health. (maybe the origin of cold plunges?)
1945 Food & Nutrition Board Guidelines: there was a guideline issued by this board that suggested for each calorie consumed you should be having 1 millilitre of water, so based on the average caloric consumption of an adult man that would be 2,500 millilitres or 2.5 litres, if on a 2,500 kcal diet. But the catch is, that this guideline did not state that the water source should be plain drinking water, water contained in food would also count, e.g., fruits and vegetables.
Influence of Commercial Interests: there’s suggestions that the bottled water industry also influenced the perception of people when it came to how much they should be consuming. Maybe the 8 glasses of water (or 8x8 for eight 8-ounce glasses in the US) per day may be more commercially driven than health wise.
I, for one, don’t have the best relationship with water. The number of water bottles I've purchased, only to take 2-3 sips from each, is quite high (and hence, why I get nicknames like dehydrated cat). That being said, I’ve improved and I found that using my Chilly’s bottle and having it by my desk means I tend to have sufficient water.
Undoubtedly, water, and thus, hydration is very important as it pretty much impacts every aspect of our bodily functions. Those range from cellular health, to digestion, temperature regulation, cognitive function (our brain is 80% water), skin health, and loads more.
Noticed how I said hydration? Well, nowadays our diet contain so much more than just water, be it coffee, tea, juice, smoothies, energy drinks, soda, or alcohol. Each drink has different hydration properties, or even dehydration in some cases. There’s something called the Beverage Hydration Index (BHI), which assigns various drinks a score benchmarked against still water. This was developed by Maughan et al. in 2015.2 They investigated the effects of 13 different drinks on urine output and fluid balance on well hydrated individuals. The BHI was defined as the volume of urine produced after drinking expressed relative to a standard treatment (still water) for each drink.
The graph above shows the BHI of each beverage tested. It’s to no surprise that coffee and lager scored below 1 as they’re technically dehydrating. For coffee it’s the caffeine in it, as it’s a diuretic (read my post about coffee here). While for alcohol, the diuretic effect is due to the blocking of the release of the hormone vasopressin, an antidiuretic hormone (read my post about alcohol here). But that being said, their BHI values were not that much lower than that of water.
Interestingly, milk was the best hydrator, with a BHI of 1.50 for full fat milk, and 1.58 for skimmed milk. This means, that the body retains half as much fluid after consuming a glass of full fat milk than a glass of water.
You might be wondering what Oral rehydration solution is, and why it scores so high. Well, they’re electrolytes - which they presumably dissolved in water. Which brings me on to my next point, electrolytes for hydration. Electrolytes play a vital role in hydration, and overall bodily functions and not just due to the hydration; they contribute in the hydration properties of beverages.3 Electrolytes are minerals which carry an electric charge when dissolved in bodily fluids; examples include sodium, calcium, potassium, and magnesium. A few weeks back I wrote about collagen, with bone broth being a very good source of it, but it also having excellent hydration properties due to the electrolytes present.
A further study, expanding on the BHI, examined the influence of sodium, caffeine, and sucrose (a carbohydrate) on the fluid potential of beverages. Similar, methodology to the BHI (ie, urine output vs fluid intake). They gave them beverages containing four different concentrations of one of those components (sodium, caffeine, or sucrose). The data demonstrate that beverage sucrose and sodium content influence fluid delivery and retention in the 4-h after ingestion, but caffeine up to 400 mg/L does not.4
Quite ironically, drinking too much water can lead to depletion of electrolytes. This effect is called water intoxication or hyponatremia, which simply means that the sodium levels in your blood below very low. So, water consumption definitely does not fall under “the more the better” after a certain point. Of course, that amount depends, on your age, gender, outside temperature, if you’ve worked out, health conditions (e.g., diabetes). Now, that being said it’s not that drinking 2.8 L of water as opposed to 2.5 L will cause this, but in reality many many more litres. Sources state no more than 0.8 - 1 L of water per hour.5
To wrap up, staying hydrated is not about chugging down litres and litres of water. You’re keeping hydrated by most fluids that you’re drinking - whether that’s a glass of fresh orange juice (my fave) or a smoothie, or even a glass of milk. As with everything nutrition wise, the amount one should consume is not a set value. Also, don’t forget that the food you consume also contains water: vegetables, fruit, soups, bone broth! Maybe if you’re struggling to generally have a high fluid intake, try setting an alarm every couple of hours and have your 1/2 L bottle by you. If the water has not been consumed by the time the alarm goes off, you need to drink up more. Now, don’t go chugging it as suddenly having a huge amount of water ingested does not mean all of it will be actually absorbed.
If I may offer a last piece of advice or two; avoid consuming fluids from plastic bottles. Earlier in 2024, a study showed that the microplastics present in bottled water is at least 10 times worse than what was thought.6 The second one, is to avoid tap water as much as possible - either buy a Brita or install a filter on the tap itself. This tweet explains the why v well. I would love to hear any tips you have on staying hydrated! 🩵
I hope you enjoyed, thank you for taking some time out of your day to read my posts! See you next week! :)
Other posts you may like / mentioned:
Tsindos S. (2012). What drove us to drink 2 litres of water a day?. Australian and New Zealand journal of public health, 36(3), 205–207. https://doi.org/10.1111/j.1753-6405.2012.00866.x
Maughan, R. J., et al. (2016). A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. The American journal of clinical nutrition, 103(3), 717–723. https://doi.org/10.3945/ajcn.115.114769
Millard‐Stafford, M., et al. (2021). The beverage hydration index: influence of electrolytes, carbohydrate and protein. Nutrients, 13(9), 2933. https://doi.org/10.3390/nu13092933
Maughan, R. J., et al. (2019). Sucrose and Sodium but not Caffeine Content Influence the Retention of Beverages in Humans Under Euhydrated Conditions. International journal of sport nutrition and exercise metabolism, 29(1), 51–60. https://doi.org/10.1123/ijsnem.2018-0047
Qian, N., et al. (2024). Rapid single-particle chemical imaging of nanoplastics by srs microscopy. Proceedings of the National Academy of Sciences, 121(3). https://doi.org/10.1073/pnas.2300582121
The other day I was interested in whether or not it mattered when you drink water in a day. I tend to try to drink most of my water by 1 o’clock. But then I thought—maybe having 45 ounces of water between breakfast and lunch isn’t really doing what I think it is? So I read an article that had some of the same data you are presenting here about how some beverages are more hydrating. I think I understood that the reason for this is because orange juice and milk calories involved so it makes our bodies more able to absorb the water? which made me think maybe I should just be drinking more water with my breakfast and my lunch? What do you think?
Traumatized and never touching a plstic bottle every again