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For decades, the ‘8 glasses of water a day’ rule has been the universal standard for hydration advice. As climate change intensifies and the world continues to become warmer, especially South Africa, is this guideline still sufficient. And was this guideline even the right advice to begin with?

The 8-glass rule – Who gave this advice?

The advice to drink eight glasses of water, or around 2 – 2.5l a day, is an oversimplification of a recommendation made by the U.S. Food and Nutrition Board in 1945. The guideline mentioned that people need around 64 fl. ounces (1.89l) of water per day, but specifically mentioned that this combines the water in the food we eat as well as beverages, a detail that is often overlooked.

Over time, this one guideline became the gold standard, a simplified and rigid prescription that seemed easy enough to follow, but didn’t take into consideration individual hydration needs based on body size, age, climate and activity levels and more.

Critics of this ‘rule’ have also pointed out that the original recommendation made in 1945 wasn’t based on any real science or experiments, and that it’s impossible to have a set rule for water intake.

Climate change and hydration needs

Global warming is causing temperatures to rise in many parts of the world, including South Africa. The Western Cape, for instance, has experienced severe droughts over the past decade, culminating in Cape Town nearly running out of water in 2018.

The human body naturally loses around 1.5l – 2l of water a day through sweating, breathing, urination and more. Warmer temperatures result in a greater water loss, so you’ll naturally need to drink more water.

Heat also places a lot more stress on the body’s ability to regulate temperature which may lead to dehydration. This can cause heat exhaustion, place strain on your kidneys and reduce your ability to think clearly.

Hydration – the socioeconomic hurdles

Unfortunately, access to clean, running water isn’t a reality for many South Africans. Rural areas and informal settlements are often the areas with the least reliable access to potable water. For the people in these areas, proper hydration can be difficult, not just based on access to water, but the quality of the water when they get it can further complicate their situation.

So, how do you figure out how much water to drink?

Rather than strictly sticking to the eight-glass rule, most hydration experts recommend an individualised approach based on your age, body type, activity levels and the climate you live in. Here’s how.

Monitor your fluid loss – The more you sweat the more fluid you should replace. Keep an eye out for signs of dehydration, like increased thirst, headaches, loss of energy and dark urine.

Add hydrating foods to your diet – Watermelon, oranges, cucumbers, spinach and more are all great options that are both hydrating and nutritious.

Electrolytes! – When you sweat, you lose electrolytes like sodium and potassium. It is recommended that you consider an alternative to plain water, like coconut water or add an electrolyte solution to your water to help keep your body in the best shape when under stress.

So, while the 8-glass rule has served as a general guideline for ages, it’s not a true reflection of your hydration needs. Your hydration needs fluctuate and are influenced your body, your age, where you live and how active you are. Listen to your body and adapt your water intake accordingly. Remember, it’s not just about water. Everything you eat and drink will have an effect, so adapt and pivot as needed.

References:

The Water Myth. McGill University. 2018. Available here.

Why you don’t need to drink 8 cups of water a day. The Washington Post. 2022. Available here.

Variation in human water turnover associated with environmental and lifestyle factors. Science. 2022. Available here.

Water Researchers Do Not Have a Strategic Plan for Gathering Evidence to Inform Water Intake Recommendations to Prevent Chronic Disease. National Library of Medicine. 2020. Available here.

How much water should you drink a day? Brita. Accessed 2025. Available here.

Everything You Need to Know About Sweat. TrainingPeaks. Accessed 2025. Available here.