Hydration in Summer: Health Benefits of Pure and Filtered Water

Why is hydration in summer so important?

Your hydration status reflects the balance between water intake and water loss. In summer, with higher temperatures, sun exposure and outdoor activities, the body loses more water and minerals through sweat. If you sweat heavily and that loss is not replaced, the risk of dehydration increases.

Water is the main component of the body and, as a nutrient, it affects how every system and organ works. That is why, according to Portugal’s Directorate-General of Health (DGS), dehydration can cause headaches, tiredness and irritability.

Drinking more water than usual in summer, on holiday or during outdoor sporting and work activities, is essential for wellbeing and health. As a reference, the European Food Safety Authority (EFSA) suggests a total water intake of around 2 litres a day for adult women and 2.5 litres for adult men, including the water in food. These values were set for moderate ambient temperatures and moderate physical activity, so your needs increase with heat and physical exertion.

What are the signs of dehydration and how does it affect the body?

Dehydration occurs when you lose more water than you take in, especially when the temperature or physical activity increases. According to the DGS and the NHS, the most common signs include:

• intense thirst and a dry mouth;
• darker urine, in smaller amounts;
• dizziness and headaches;
• tiredness and lack of energy;
• difficulty with concentration, attention and memory;
• mood changes, such as irritability;
• dry skin.

Who is most vulnerable to dehydration?

Some groups need extra care on hot days. The DGS heat recommendations also include people with chronic illnesses and those who work outdoors:

• Children and people with physical or cognitive dependency, who rely on others to help them drink water regularly.
• Older people, because they tend to be less sensitive to fluid loss and to feel less thirsty.
• Athletes, because exercising in high temperatures requires greater hydration to make up for heavy sweating.

If you train in the heat, it may be useful to learn about the benefits of hydrogen water in sport and what research has found so far about its effect on fatigue and recovery.

When should you seek medical help?

Seek medical help if symptoms persist despite drinking fluids or if warning signs appear, such as confusion, fainting, not passing urine, or a fast heartbeat and fast breathing. A high temperature with hot, red, dry skin may indicate heatstroke: in that case, call the emergency number (112 in Portugal). If in doubt, in Portugal you can contact the SNS 24 helpline (808 24 24 24). In young children and older people, assessment should be carried out as early as possible. If you have a chronic illness, follow a low-salt diet or have been told to restrict fluids, the DGS recommends seeking your doctor’s advice.

Practical tips for staying hydrated on hot days

We are made up largely of water, which is why it is essential to life. As the DGS explains, water is the main component of cells, transports nutrients and is involved in all the body’s metabolic reactions. Without adequate intake, it becomes harder to regulate body temperature and keep the organs working normally.

According to the DGS, around 75% of the water we take in comes from drinks and the rest from food. In a European study of healthy adults, food provided on average about a quarter of total water intake. As fruit and vegetables contain 80% to 95% water, this summer you can also boost your hydration with foods such as:

• watermelon, honeydew melon and cantaloupe;
• oranges, pineapple and plums;
• cucumber and tomatoes;
• raw leafy greens, among others.

You should avoid or cut down on alcoholic and sugary drinks, as the DGS recommends on hot days. Drinking too much alcohol is one of the causes of dehydration, and a clinical trial showed that stronger drinks, such as wine and spirits, increase urine output in the following hours, although only slightly and briefly. Soft drinks, although they contain a lot of water, are high in sugar, which contributes to tooth decay and obesity, and should not replace water.

How to create a hydration routine on holiday

This holiday, create a healthy routine of drinking enough water. Some practical suggestions:

• At the start of each day, set the amount of water you will drink and commit to reaching it.
• Drink small amounts throughout the day, without waiting until you feel thirsty.
• Carry a safe, reusable, BPA-free bottle (bisphenol A is a substance used in some plastics that can migrate out of these materials; in the European Union, its use in food contact materials was banned in December 2024, taking into account EFSA’s risk assessment). Look for the “BPA free” label or choose reusable glass bottles.
• If the taste of chlorine puts you off drinking tap water, let it stand in a jug for about half an hour or keep it in the fridge, as suggested by ERSAR, Portugal’s water services regulator, or choose a filter that reduces chlorine.

Water quality matters too: why choose pure or hydrogenated water?

When we think about hydration, we think about drinking water. However, each water has its own characteristics and not all waters are the same, because they all carry substances invisible to the naked eye.

Tap water meets legal standards and is safe to drink: according to ERSAR, 98.84% of mains water in mainland Portugal is safe water (2025 data). Residual chlorine ensures disinfection and, according to the same regulator, poses no danger to health, although it can leave a taste and smell. Water may also contain traces of other substances, resulting from treatment or already present before abstraction, generally at concentrations below legal limits, and some consumers prefer to reduce this exposure.

Bottled natural mineral and spring waters cannot be subjected to disinfection treatments, according to Portugal’s food and veterinary authority (DGAV), and many people enjoy their taste. The drawbacks are the price, the environmental footprint and the fact that most are packaged in single-use plastic bottles. Microplastics have been found in both bottled and tap water; according to the World Health Organization (WHO), based on the limited information available, they do not appear to pose a health risk at current levels, but more research is needed.

A practical alternative is to filter water at home, with lower costs and less plastic than bottled water. At home or in the office, a dispenser such as the Juman HG provides filtered water that is chilled, hot, at room temperature or sparkling. Mains water is safe, but meeting the parametric values set in Directive (EU) 2020/2184 does not mean a complete absence of substances: treatment ensures they stay below these limits without removing them all. Water quality can also be affected inside the home since, according to ERSAR, the upkeep of a building’s internal plumbing is the owner’s responsibility and some cases of non-compliance are due to poor maintenance or unsuitable pipe materials. A specialised, certified home filtration system can reduce some of these substances even further.

Filtered water: what it is and its health benefits

Filtered water is water that has undergone a process to remove some of its constituents, whether microbiological, physical, chemical or radioactive, depending on the system used. For mains water, filtering can further reduce substances present within legal limits, such as residual chlorine, disinfection by-products (for example trihalomethanes, which the WHO recommends keeping as low as practicable without ever compromising disinfection), lead from old pipes or PFAS, provided the system, for example activated carbon or reverse osmosis, is chosen according to the substances to be reduced, is certified for them and is properly maintained.

Filtering is particularly important for water from private sources such as wells or boreholes. In that case, ERSAR warns that the water, even if it looks good and tastes pleasant, is generally unfit for consumption and may contain microorganisms or substances harmful to health. You should therefore have it tested at least once a year and whenever you notice a change in taste, colour or smell, and choose the treatment according to the results.

That is why it is worth paying attention not only to how much water you drink, but also to the quality of the water you drink and cook with.

What substances can mains water contain?

Mains water is treated to make it safe. Chlorine disinfection produces by-products and, as explained in an analysis published in Environmental Health Perspectives, the aim is to strike a balance between disinfecting the water and reducing these by-products. The groups of substances that may be present in trace concentrations, and whose exposure has been studied, include:

• Trihalomethanes: these form mainly during chlorination, when chlorine reacts with natural organic matter in the water. According to the WHO, high doses of chloroform, the most common trihalomethane, cause liver and kidney damage in laboratory animals; in human studies, the results on bladder cancer risk are not consistent.
• Endocrine disruptors: substances such as bisphenol A (BPA) and phthalates, used in plastics, some pesticides and certain disinfection by-products. According to a scientific review, they can interfere with the hormone system and affect development and fertility. In Portugal, BPA has been detected in several rivers.
• Polycyclic aromatic hydrocarbons: these form during combustion and can reach soils and groundwater, for example after wildfires. A study of springs in the Braga region found an increase in these compounds, especially those considered carcinogenic, after a wildfire, although levels remained below drinking water guideline values.
• Pesticides: Portuguese studies have detected pesticides with potential endocrine-disrupting effects in surface waters in the north and centre of the country and in groundwater used in small supply systems, in some cases above the legal limit. These compounds can interfere with the hormone system.
• Heavy metals: such as lead or arsenic. According to the WHO, there is no known level of lead exposure without harmful effects: it can affect the brain, kidneys and cardiovascular system and reach water through plumbing that contains lead. Long-term exposure to arsenic, mainly from contaminated groundwater, is associated with skin lesions and several types of cancer.

In mains water, these substances are generally within legal limits. If you want to reduce your exposure to some of them even further, you can choose a filter, as long as it is certified for the contaminants in question, and you should start by finding out the quality of the water you have at home.

What are the main water filtration systems?

There are several filtration systems, each suited to the type of substances you want to remove:

• Mechanical filtration: uses materials such as compacted cotton or polypropylene fibres to trap sand, sediment and suspended particles.
• Activated carbon: used in many jug and fridge filters, it reduces chlorine and, according to the US CDC, mainly improves the taste and smell of water rather than its safety.
• Ion exchange: reduces water hardness, caused mainly by calcium and magnesium (limescale); it does not remove bacteria or viruses.
• KDF (Kinetic Degradation Fluxion): a filter medium used in some filters, usually combined with other media; check the filter’s certification to see which substances it reduces.
• Reverse osmosis: uses a semi-permeable membrane with very fine pores which, according to the CDC, removes parasites, bacteria and viruses and several chemicals such as lead, copper and sodium, making it one of the most complete purification systems.

There are also solutions that change the properties of the water after filtration, such as ionised alkaline water or hydrogenated water.

What are the benefits of drinking filtered water?

Depending on the system and the quality of the starting water, drinking filtered water can offer some advantages:

• lower exposure to specific contaminants, such as lead, some pesticides or chlorine by-products, if the filter is certified to reduce them;
• water without the taste or smell of chlorine, which many people find more pleasant to drink, something useful for staying hydrated in summer;
• teas, soups and other dishes with a more natural taste;
• a barrier against microorganisms in systems designed for this, such as reverse osmosis, since most jug or fridge filters are not designed to remove germs;
• fewer plastic bottles and lower costs than bottled water;
• for private water sources, the possibility of treating specific problems identified by testing.

To keep these advantages, the filter must be cleaned and replaced according to the manufacturer’s instructions, as ERSAR points out. The CDC warns that a filter that removes the disinfectant and is not properly maintained can encourage germs to grow in the plumbing.

Hydrogenated water: pure water with molecular hydrogen

Hydrogenated water is pure water, purified by reverse osmosis, light and pleasant-tasting, to which a hydrogenator adds molecular hydrogen. A 2007 study, carried out in cells and in an animal model, showed that molecular hydrogen has a selective antioxidant action, and research has grown since then, although most studies have been carried out in animals and many are still preliminary. Find out more about the benefits of hydrogenated water for hydration.

In the context of summer and holidays, this is what is known so far about hydrogenated water:

• it hydrates like any good-quality water, with no evidence that it hydrates better than ordinary water;
• in a small trial in healthy adults, drinking hydrogenated water for four weeks was associated with improvements in mood and anxiety;
• there are studies, mostly in animal models, on the effect of hydrogen on skin damage caused by ultraviolet radiation, but none of this replaces sun protection;
• in healthy adults who exercise, a meta-analysis indicates that it may reduce feelings of fatigue, without improving aerobic capacity.

Some people also put it in a spray bottle to refresh their skin after sun exposure, although the effect of hydrogen applied to the skin has been little studied. Learn more about the health applications of molecular hydrogen.

On the move? A practical way to have hydrogenated water wherever you go

On holiday, access to quality water can be limited. If you value water quality first and foremost, followed closely by low environmental impact and a fair cost, a good choice may be to drink hydrogenated water prepared in a portable hydrogenator.

It is a practical option if you want to ensure good hydration and maintain healthy habits in summer, while continuing to drink pure water with molecular hydrogen, whose antioxidant potential is still being researched. Compact in size, the portable hydrogenator lets you prepare hydrogenated water easily and can go with you on holiday, to work or on your travels.

Frequently asked questions about hydration in summer

How much water should you drink a day in summer?

EFSA suggests a total water intake of around 2 litres a day for adult women and 2.5 litres for adult men, including the water in food, under moderate temperature and physical activity conditions. With heat and more physical activity, your needs increase, so you should drink regularly throughout the day, even when you are not thirsty, as the DGS recommends.

How can you tell if you are dehydrated?

Thirst, a dry mouth, dark urine and passing less urine, dizziness, headaches, tiredness and difficulty concentrating are common signs. If symptoms are severe or persist, or if confusion, fainting or not passing urine occur, seek medical help.

Is filtered water better than tap water?

Tap water is safe to drink and meets legal standards: according to ERSAR, 98.84% is safe water. Meeting legal limits does not, however, mean a complete absence of substances. Tap water may contain residual chlorine and disinfection by-products such as trihalomethanes, traces of pesticides, lead and other metals such as iron from old building plumbing, whose upkeep is the owner’s responsibility rather than the water supplier’s, and emerging substances such as PFAS, with limits set by Directive (EU) 2020/2184 that have applied since January 2026, or microplastics, on which the WHO considers the data still limited. A specialised, certified filtration system, such as activated carbon or reverse osmosis, can reduce these substances further: according to the US Environmental Protection Agency (EPA), these systems can reduce PFAS, and the agency advises choosing filters certified to NSF/ANSI 53 or 58 for this purpose and maintaining them according to the manufacturer’s instructions. For private sources such as wells or boreholes, the water should be tested before choosing a treatment.

Does hydrogenated water hydrate better than regular water?

There is no evidence that hydrogenated water hydrates better than ordinary water: any good-quality water contributes to hydration. Hydrogenated water adds molecular hydrogen, whose antioxidant potential has been studied mainly in the laboratory and in small human trials. It can be an option if you enjoy this water, without replacing other health care.

Hydration in summer: make pure water a priority

Our body is our main companion and deserves attention to ensure health, vitality and wellbeing. In summer, on holiday or not, the heat calls for more care with hydration, because the body loses more water through sweat to regulate its temperature.

Setting the amount of water to drink at the start of the day, based on your planned activities, and meeting that goal is essential. Within a few days, the routine becomes a habit and it is easy to keep it up.

Remember that not all waters are the same in their composition and in the substances dissolved in them. If you want to further reduce the substances that mains water contains within legal limits, choose water filtered with a certified, well-maintained system and, if possible, hydrogenated water, and take it with you wherever you go, in “BPA free” bottles.

If you want quality filtered water at home, see how to choose the water purifier best suited to your family.

Make hydration a priority this summer!

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By the Filtrarte Expert Team
The information in this article is not intended to recommend any treatment for symptoms or diseases. Consult your doctor for specialist advice.