Busting Myths About Fluid Intake

There are many commonly held beliefs about fluid intake that actually have no basis in truth. How much fluid is best? Should I drink 8 glasses of water a day? Is caffeine bad for your bladder? What colour should urine be? Read on to learn the difference between fact and fiction!

Myth #1. You should drink 8 glasses of water a day

It is frequently recommended that we should drink 8 glasses or 2 litres of water a day. However, there is no scientific evidence to support this idea in a healthy person^1,2. Many researchers have been unable to find where this myth originated, however it is continually perpetuated by the health and wellness industry, not to mention the bottled water industry!

Myth #2. Only Water Counts Towards Fluid intake

Recommendations about adequate fluid includes all types of fluid, not just water, as well as fluid gained from food^2,3. So, your morning cup of coffee, your soup for lunch and your cup of tea in the afternoon all count towards your total daily fluid intake.

Myth #3. You Can't Drink Too Much

High fluid intake can be harmful. Drinking too much fluid leads to dilution of sodium in the blood, causing a condition called hyponatremia or water intoxication. This causes the body’s salt levels to drop dangerously, increasing the risk of seizures and death. In the medical literature there are documented fatalities due to excessive fluid consumption in athletes⁴.

Contrary to popular belief, there is no scientific evidence that a high fluid intake is beneficial for heart disease, deep vein thrombosis (DVT), constipation, headaches, bladder cancer or cognitive function^2,³. High fluid intake also isn’t associated with preventing kidney stones in people that have never had them before^2,5. There is also no evidence that proves that having a high amount of water intake reduces the risk of developing chronic diseases². It is important to note however, that dehydration could exacerbate conditions such as chronic constipation and headache intensity^2,3.

Myth #4. Caffeine Is Bad For Your Bladder

In some people, caffeine can irritate their bladder, increasing urgency and contributing to incontinence^6,7. This is not the case for every person that experiences bladder problems. Whilst large amounts of caffeine have an immediate diuretic effect, meaning that this increases the amount of urine that the body produces; small amounts of caffeine have little to no diuretic action. In addition, regular caffeine drinkers develop a tolerance to the diuretic effects of caffeine^6,7.

When you see a Pelvic Health Physiotherapist for your bladder, they will ask you to complete a bladder and fluid intake diary, which will can help understand the effect of caffeine on your bladder symptoms.

Myth #5 If You Wait Until You Are Thirsty You Are Already Dehydrated

The theory that if you are thirsty, you are already dehydrated is the same as saying that if you are hungry, you are already malnourished. This of course, is not true! Our bodies have an effective system of maintaining water balance and thirst is a vital part of this system¹. For the average person, thirst is likely a good indicator of fluid requirements. The degree of thirst should be interpreted in the context of your general health, age, activity and environment.

Myth #6. Urine Should Be Very Pale Yellow Or Clear

Not true! Normal urine has a moderately yellow colour¹. The colour may also be affected by what we eat or drink. For example, certain vitamins can turn urine orange, whilst foods like beetroot can turn urine red/pink! Having very clear urine does not necessarily mean you are drinking the right amount of fluid.

Myth #7. Drinking Lots Of Water Will Help To Lose Weight

There is some research that suggests that drinking water along with a meal or incorporating fluid into food can promote satiety (the feeling of being full). This link has not been clearly established, and it is not clear to what extent this effect reduces food intake, how long the effect lasts, and how much fluid might be needed to influence satiety¹.

If you want to lose weight, talk to your doctor about the safest way for you to go about this.

Myth #8. You Should Have A Glass Of Water By Your Bed And Should Drink Through The Night

Drinking an adequate total volume of fluid, spread out over the course of the day is sufficient to maintain adequate hydration. Drinking late in the evening and through the night can lead to waking up more overnight to go to the toilet, a condition called nocturia. It is normal for people of any age to wake up once per night, but any more than that can have significant impacts on their health. To learn more about nocturia, read our blog here.

Recommendation: Everything In Moderation & Drink To Thirst

Unfortunately, there is no magic answer to the question, “how much should I drink?”. The amount depends on your age, your general health, your height and weight, the environment in which you live and work, your food intake and your exercise levels, amongst other factors.

Keep in mind that a balance between water and caffeinated, sugary or alcoholic drinks is important. Spreading fluids throughout the day, rather than having large amounts at once can also be a helpful strategy if you have bladder problems.

A common sense approach for a healthy person is to have a drink with meals, have a drink between meals, and more if you are thirsty. If you are playing sport or the weather is very hot you may need more.

References

1 Valtin, H. (2002). "Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 x 8"? Am J Physiol Regul Integr Comp Physiol, 283, R993.
2. Wood, L., Markowitz, M., Parameshwar, P., Hannemann, A., Ogawa, S., Anger, J., & Eilber, K. (2018). Is it safe to reduce water intake in the overactive bladder population? A systematic review. The Journal of Urology, 200, 375-381.
3. Institute of Medicine: Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, D.C.: The National Academies Press 2005.
4. Noakes, T. (2003). Overconsumption of fluids by athletes. BMJ, 327, 113-114.
5. Bao Y, Tu X and Wei Q. Water for preventing urinary stones. Cochrane Database of Systematic Reviews Review – Intervention. 2020. https://doi.org/10.1002/14651858.CD004292.pub4
6. Dumoulin C, Booth J, Cacciari, L, Campbell P, Hagen, S, Homsi J et al. Adult Conservative Management. In: Cardozo L, Rovner E, Wagg A, Wein A and Abrams P, ed. In: Incontinence: 7th Edition. International Continence Society; 2023: pp795-1038
7. Maughan, R. & Griffin, J. (2003). Caffeine ingestion and fluid balance: a review. J Hum Nutr Dietet, 16, 411-420.

September 2023