Your mum wasn't completely wrong about the need to stay hydrated in hot weather. However, she and many others have been needlessly worrying about the wrong things. Here are four hydration myths you can safely discard.
Myth #1: Drink eight glasses of water a day
Snopes.com does a great job breaking open this health advice snippet that everybody and their grandparents (and especially your grandparents) offer up when nearby people say they're parched. It might have started as a reference point for the easily dehydrated, like infants and the elderly, or it might have derived from measuring IV drip output over a day. Either way, it is, at best, akin to stating that you should cook all your food to a healthy 120 degrees, just to ensure every single living thing is dead inside it; at worst, you're over-spending on bottled water and working your kidneys a bit too hard.
Myth #2: Caffeinated beverages are ineffective at hydration
The centre for Human Nutrition released their study results after monitoring the hydration of 18 healthy men drinking water, coffee, caffeinated and caffeine-free sodas, and juices. Their results "found no significant differences" in hydration with any combination of drinks, and suggests that those who normally take in caffeine retain at least half the fluid in their coffees, Coke Zeros, or other boosters of choice. Of course, that study is based on drinking a "normal" amount of coffee by a "normal" person, and it doesn't quite extend to alcohol - that actually produces a net loss of fluid, but that's at a "noticeable" level after more than one drink.
Myth #3: If you feel thirsty you've left it too late
Some of us sit at a desk for most of our working day. Some of us get serious exercise. Some of us break a sweat just heading out to our car at noon. The one common denominator of how much water you need? Your mouth and its ability to tell you you're thirsty. Those nutritionists and doctors who don't believe in arbitrary fluid amounts say that drinking for thirst is fine, and that being thirsty is not "too late".
Myth #4: Sports drinks are best for outdoor exercise
As WebMD points out, and as almost every coach we've ever had will tell you, plain old tap water is fine for the vast majority of sweat-inducing outdoor activities. If you're running or undertaking another strenuous activity for an hour or more, you might consider one of those crazy-colored liquids to replace the sodium, potassium, and magnesium you're losing through sweat - but watered-down fruit juice can often get the same trick done, and it definitely sells at a much lower mark-up.
This article has been updated since its original publication.