Be Sure to Drink Plenty of Water
- , by SANUSq Research team
- 9 min reading time
It's the simplest health advice there is — drink more water — and yet most of us drift through the day a little more dehydrated than we should be.
Why water matters so much
The benefits of drinking water are unglamorous but foundational. Water makes up around 60% of your body weight and is involved in almost everything your body does. It carries nutrients and oxygen to your cells, regulates your temperature through sweat, cushions your joints and organs, keeps your skin and tissues healthy, and allows your kidneys to flush waste. Because water is lost continuously — through breathing, sweating and urination — it has to be replaced continuously. When it isn't, even mildly, the effects show up quickly: tiredness, poor concentration, headaches and low mood are all common signs of not drinking enough.
Water is essential to a wide range of bodily functions, and beverages such as tea and coffee count towards daily fluid intake, with individual needs varying rather than following a single fixed rule (Harvard T.H. Chan School of Public Health, The Nutrition Source).
How much water should you drink?
The famous "eight glasses a day" is a handy rule of thumb, not a scientific law. Actual needs vary with your body size, activity level, the climate and your health.
Guidance from the US National Academies suggests around 2.7 litres of total daily fluid for women and 3.7 litres for men from all sources — including food and other drinks — with needs rising in heat, during exercise or illness (Mayo Clinic).
Crucially, that total includes the water in food (fruit and vegetables can contribute a fair amount) and in other drinks. And despite the old myth, moderate tea and coffee count too — their mild diuretic effect doesn't cancel out the fluid they provide.
A simple way to check
Rather than counting glasses, the easiest guide is to watch two things: your thirst and your urine. Pale straw-coloured urine usually means you're well hydrated; dark yellow suggests you need to drink more. Thirst is a reasonable prompt for most people, though it becomes less reliable with age, which is one reason older adults are more prone to dehydration. One caveat on the urine test: B vitamins can turn urine a bright yellow, and some foods and medicines change its colour too, so judge it against your own usual rather than a chart alone.
In older adults, the body's regulation of fluid balance and the sense of thirst decline, raising the risk of low-intake dehydration and making conscious attention to fluids more important with age (Li et al., 2023).
Dehydration symptoms: signs you might not be drinking enough
Dehydration doesn't always announce itself as thirst. Common early signs include fatigue and flagging energy, difficulty concentrating or "brain fog", headaches, dry mouth and lips, and dark urine. Because these are easy to misread — that mid-afternoon slump might be dehydration rather than a need for more coffee — simply drinking a glass of water is often a sensible first response. Losses also rise sharply with fever, vomiting or diarrhoea, in hot weather, and for anyone working or training outdoors, so those are the times to drink more deliberately rather than waiting for thirst. Good hydration also supports digestion and helps prevent constipation, and keeping urine dilute is a recognised way to lower the risk of kidney stones, as we discuss in our guide to kidney stones.
It doesn't all have to be plain water
If plain water feels like a chore, it helps to know that hydration comes from more than the glass. All fluids contribute — herbal teas, milk, and even the tea and coffee people often assume are "dehydrating" all count toward your total. Water-rich foods pull real weight too: cucumber, tomatoes, lettuce, courgette, melon, oranges, strawberries and soups are mostly water, and fruit and vegetables can supply a meaningful share of your daily fluid while delivering fibre, vitamins and minerals at the same time. What's worth limiting rather than relying on is sugary drinks and large amounts of alcohol — the former add a lot of sugar for their fluid, and alcohol actually promotes fluid loss. So the practical message isn't "force down eight glasses" but "let a variety of fluids and water-rich foods, with plain water as the mainstay, keep you topped up through the day".
Hydration, the brain and exercise
Two areas deserve a special mention because the effects of even mild dehydration show up so clearly. The first is the brain. Your brain is around three-quarters water, and studies consistently show that being even slightly under-hydrated impairs concentration, alertness, short-term memory and mood, and can bring on headaches. This is why a glass of water is so often the real answer to mid-afternoon fog or a nagging head. The second is physical activity. When you exercise you lose fluid through sweat, and losing even a small percentage of body weight in fluid measurably reduces physical performance and endurance while raising the strain on your heart. The practical takeaway is simple: drink a little before you exercise, sip during longer or hotter sessions, and rehydrate afterwards. For everyday activity, water is all most people need; it's only during prolonged, intense exercise or heavy sweating that replacing salts — with an electrolyte drink or salty food — becomes genuinely useful. For most workouts, plain water and common sense do the job.
Easy ways to drink more
If you struggle to drink enough, a few simple habits help. Keep a reusable water bottle within reach and sip through the day rather than gulping occasionally. Start the morning with a glass of water, and tie drinking to things you already do — a glass with every meal, one after brushing your teeth, one when you sit down at your desk — since an existing habit is a far more reliable reminder than good intentions. Flavour it naturally with lemon, cucumber or mint if plain water bores you. Eat plenty of water-rich fruit and vegetables. And drink a little extra around exercise and in hot weather. One caution for balance: it is possible, though rare, to drink too much too fast, diluting the body's salts — so the goal is steady, sensible hydration, not forcing down litres in one go. For most people, gently drinking a bit more than you currently do is one of the easiest wins in health, and minerals like magnesium and potassium work alongside water to keep you balanced, as covered in the benefits of magnesium.
Frequently asked questions
How much water should I drink a day?
There's no single rule. Guidance suggests roughly 2.7 litres of total daily fluid for women and 3.7 litres for men from all sources, including food and other drinks, with more needed in heat, during exercise or when unwell. Your size, activity and health all affect the amount.
Do tea and coffee count towards hydration?
Yes. Despite the old myth, moderate tea and coffee contribute to your daily fluid intake — their mild diuretic effect doesn't outweigh the fluid they provide. Water is ideal, but other drinks and water-rich foods count too.
How can I tell if I'm dehydrated?
Watch your urine and thirst: pale straw-coloured urine usually means good hydration, while dark yellow suggests you need more. Fatigue, poor concentration, headaches and dry mouth are common early signs. Thirst is a useful prompt but becomes less reliable with age.
Can you drink too much water?
It's possible but rare. Drinking very large amounts very quickly can dilute the body's salts, which can be dangerous. The goal is steady, sensible hydration through the day rather than forcing down large volumes at once.
Why are older adults more prone to dehydration?
With age, the body's regulation of fluid balance and the sense of thirst both decline, so older adults may not feel thirsty even when they need fluids. This makes it more important to drink regularly by habit rather than waiting for thirst.
Should I drink more when it is hot or when I am unwell?
Yes. Heat, exercise and illness — particularly with a fever, vomiting or diarrhoea — all increase fluid losses, and guidance recognises that needs rise in those situations. Sip regularly rather than drinking a large amount at once, and seek medical advice if someone cannot keep fluids down.
References
- Harvard T.H. Chan School of Public Health. Water. The Nutrition Source. The Nutrition Source
- Mayo Clinic. Water: nutrition and healthy eating. Mayo Clinic
- Li S, Xiao X, Zhang X. Hydration status in older adults: current knowledge and future challenges. Nutrients. 2023;15(11):2609. doi:10.3390/nu15112609
Read more on the blog
Watch on YouTube
Explore more on our channel, @SANUSqHealthSupplements.
We wish you good health on your terms.
The team at SANUSq.
PS. Curious what's currently on offer? Take a look at our latest promotions.
The health information in this article is provided for educational purposes only. Consult your healthcare professional before making any medical decisions.
Regulatory Notice
The information on our websites, blogs, and emails is provided for informational purposes only and has not been evaluated by the EMA, EFSA, or FDA. It is not intended to replace medical advice provided by your healthcare professional, and is not intended to diagnose, treat, cure, or prevent any disease. Our products are intended for adults aged 18 and over. While the vitamins and supplements mentioned may offer various health benefits, supplements and dietary changes should be considered part of an overall health plan and not a substitute for professional medical treatment. Only a qualified healthcare professional can provide personalized advice and treatment plans based on your individual health needs and medical history; you should consult your healthcare professional before taking any product(s) if you are pregnant or breastfeeding.