Calcium, magnesium and sodium in water: log it in one tap

The water you drink is not just water: it carries dissolved minerals, mainly calcium, magnesium and sodium, and they count towards what you take in each day. In vitaloop you log it with one tap, choose which water you drink, and its minerals are added to your day’s totals. Here is where those minerals come from, what a bottled-water label tells you, and where you see it all in the app.

vitaloop is free by default. Logging food, drinks and supplements, seeing the day’s macros and micronutrients (5 in view at a time, swap them whenever you like) and logging water by type cost nothing. Pro adds AI on top: logging with a photo or your voice, the weekly report and patterns.

Where the minerals in water come from

Rainwater carries almost no minerals. Water picks them up from the ground it flows through: passing through limestone or dolomite, it dissolves calcium and magnesium, which is why a water reflects the area or the spring it comes from. What we call water hardness is exactly that, calcium and magnesium together. Sodium comes from the ground too, and some waters carry a fair amount of it.

To put these minerals in context, EFSA’s reference values for adults are:

• Calcium: 950 mg a day from age 25 (EFSA, 2015).
• Magnesium: 300 mg a day for women and 350 mg for men, as an adequate intake (EFSA, 2015).
• Sodium: 2 g a day is considered a safe and adequate intake (EFSA, 2019).

For water itself, EFSA sets an adequate intake of 2.0 L a day for women and 2.5 L for men, counting drinks and the water in food together. Since you drink throughout the day, whatever a water carries adds up glass by glass.

Is the calcium in water absorbed?

Published studies say yes, at a rate similar to milk. In a trial with nine young women, 23.8% of the calcium in a high-calcium water was absorbed, against 25.0% from milk, a difference that was not significant (Couzy et al., 1995; the authors worked at the Nestlé Research Centre). A later review reached the same conclusion (Heaney, 2006). These are small studies, and absorption varies from person to person.

What a bottled-water label tells you

In the EU, a natural mineral water must state its analytical composition, in mg/L; in Spain the rule is set out in Royal Decree 1798/2010 (art. 9.2.b), which transposes Directive 2009/54/EC. The same rules define the claims a label may carry:

• “Very low mineral content” or “low mineral content”: up to 50 or 500 mg/L of dry residue, the total of dissolved salts.
• “Contains calcium”: more than 150 mg/L of calcium.
• “Contains magnesium”: more than 50 mg/L of magnesium.
• “Contains sodium”: more than 200 mg/L of sodium. “Suitable for a low-sodium diet”: up to 20 mg/L.

How to log water in vitaloop

On the Log screen, next to Search, is the water button. One tap logs the amount you have chosen, which the button itself shows (+250 in the picture). Hold it down and the Water sheet opens, where you choose two things:

• Which water you drink: tap, bottled, low-mineral or sparkling. Underneath, you see the calcium, magnesium and sodium of the type you picked, per 100 ml.
• How much each tap adds: 200, 250, 330, 500 or 750 ml, or 1 L.

Press Done and your choice is saved: from then on, every tap logs that water in that amount. There is nothing to search for and no millilitres to type, and a whole day’s water takes a few taps.

Each glass is logged with its minerals, which are added to those from your food and supplements. The calcium, magnesium and sodium you see in the day’s micronutrients already include the water you drank.

Where you see the water you drink

On Home, the day’s summary has a water bar against your target, based on EFSA’s adequate intake for total water: 2 L if you are a woman and 2.5 L if you are a man. The bar counts all the water you log: the glasses, your other drinks and the water in your food.

With Pro, among the AI patterns there is the Hydration & electrolytes card, which looks at your last 7 days:

• Your daily average of water against the same target, with a bar for each day so you can see at a glance which days you reached it.
• Your sodium–potassium balance: how much of each you take in on average, and their ratio, sodium divided by potassium. You can compare it with two reference points: about 0.6, the ratio you get by following both WHO guidelines at once, no more than 2 g of sodium a day (WHO, 2012) and at least 3.5 g of potassium (WHO, 2012), and 1, where you take in as much sodium as potassium.

Logging 4 of those 7 days is enough to see the card with your numbers. How patterns work is explained in how vitaloop finds patterns in what you eat.

One practical note to finish: calcium, including the calcium in water, can reduce iron absorption when the two meet in the same meal, as we explain in how much iron you need a day.

vitaloop is a free download on the App Store and Google Play, with no ads.