Don’t be misled: can I boil water twice for coffee?

Scare tactics of the internet: why should you allegedly not boil water twice for coffee?

The internet is teeming with articles warning about reboiling water. Some of these articles claim that reboiling water can allegedly lead to serious health issues, as chemicals become more concentrated. To appear more reliable, they use scientific jargon, throwing names such as nitrates, arsenic and fluoride.

However, those claims are not necessarily true. Why? Because reboiling water twice or three times cannot create the type of concentration that would activate harmful effects of these chemicals.

Possible in the lab, but unlikely in the real world

Studies show that harmful levels of chemical concentrations are nearly impossible to obtain in normal conditions. Why? In order to become harmful, water would need to satisfy all three requirements:

• Boil for an extended period of time.
• Boil at extremely high temperatures.
• Contain elevated levels of harmful chemicals.

Furthermore, a human-being would need to ingest such water daily for an extended period of time to suffer any consequences. In the case of arsenic, for instance, a study showed that acute toxicity occurs when an individual consumes 0.6 mg of arsenic per kg of body weight per day.

This means that an average American woman (166 lbs / 75 kg) would need to consume an equivalent of 2,600 gallons (almost 10,000 litres) boiled down to a regular cup of water for several days in a row.

Debunking myths associated with reboiling water for coffee

Reboiling can only make water toxic if that water was toxic even before the first boil. The claims that boiling water twice causes cancer are mostly inaccurate. Let’s look more closely at the three chemicals that are the main characters of the debate: arsenic, nitrates and fluoride.

✔️ Arsenic can be poisonous but only if 2600 gallons of water boils down to 1 cup of coffee

Myth: reboiling water can cause arsenic to accumulate, which can result in cancer, heart disease, infertility and neurological problems.

Truth: arsenic is a powerful poisonous chemical that is naturally found in the public water supplies. In some places, like Bangladesh, the water supply contains arsenic in higher concentrations, due to the local geology.

Despite potential poisonous effect, the World Health Organization (WHO) concluded that high concentrations of inorganic arsenic can cause some adverse effects. However, elevated concentrations of arsenic would cause a low incidence rate that would be difficult to detect in epidemiological studies.

The Risk Assessment Information System database states that “the acute lethal dose of inorganic arsenic to humans has been estimated to be about 0.6 mg/kg/day.” In normal conditions, this would require boiling down 10,000 liters / 2,600 gallons of water to fit one cup of coffee in order to obtain a highly toxic dose of arsenic.

✔️ Nitrates can cause carcinogenic nitrosamines, but it has to do with environmental conditions (and not reboiling)

Myth: when water reboils, the nitrates can turn into nitrosamines and become carcinogenic.

Truth:Nitrates are another group of chemicals in public water supplies. Some claim that boiling water twice for coffee can cause nitrates to transform into nitrosamines, a group of carcinogens.

However, that appears to be inaccurate.

The research shows that formation of nitrosamines has nothing to do with boiling and reboiling water. Instead, it has to do with water contamination and the presence of specific molecules and environmental conditions.

✔️ Fluoride can become dangerous if you boil 4 gallons of water down to a 12oz cup

Myth: when water evaporates during boiling, an increase in the level of fluoride can have damaging effects on the cognitive and neurological development of children.

Truth: the fluoride concentration can hardly be influenced by boiling water twice. In order to be poisonous, 4 gallons of water with elevated levels of fluoride would need to be boiled down to 12oz. This would require an enormous amount of time and energy.

Fluoride exists in public water supplies to help fight cavities around the country. Conspiracy theorists claim that exposure to fluoride is linked to neurological and cognitive function in children, as well as to infertility in adult men.

However, the type of concentration that can be dangerous to human health is more than 4X the concentration that can usually be found in the public water supplies.

It is true, however, that a concentration of 2 mg or more per liter can lead to fluorosis (staining and weakening of the teeth) in children under 8. In such cases, it is recommended that the children should consume water from a different source.

How to boil water twice for coffee safely?

There are a couple of steps we can take to ensure that boiling water twice for coffee or tea is safe and fine:

• Pay attention to the source of water.
• Ensure that a coffee maker or a kettle are clean and bacteria-free.
• Avoid reboiling water in plastic coffee makers or plastic kettles.
• Avoid letting water sit in the recipient for too long between boils.
• Ensure that the water you are using is safe to drink.
• Try to use filtered water if you are not sure about about how safe your tap water is.

Water purifiers and filters to reboil water even more safely

If you still have doubts about boiling water twice for coffee, there are a couple of excellent filters and water purifiers. They vary in quality, materials and endurance. While some of them are able to filter out even the smallest particles, some others only do well with large elements.

Here are some examples for you to explore:

Owly’s conclusion

So how is it? Is it ok or not to boil water twice for coffee?

Reboiling water for a cup of coffee should not be a big problem.

For the pure enjoyment of coffee, we encourage the use of fresh water. After all, there is nothing better than a cup of freshly brewed coffee from fresh and clean water.

Other than that, concerns surrounding chemicals when water has been boiled twice are nothing but skillfully crafted marketing tactics. Yes, drinking good water is important. However, lets not allow ungrounded hysteria get the best of us. Water is still water, even after it has been boiled twice.

What do you think?

Do you think it is ok to boil water twice for coffee? Do you sometimes reboil water for coffee or tea? What do you typically do with any leftover boiled water? What did you think?

Let us know in the comments!