We got this question earlier this year and we admit we were interested. In general, fluoride in water has irked a lot of people, sparking all sorts of conspiracies (like that it causes cancer). These are usually unfounded: fluoride probably doesn't cause cancer, for instance. But whether it is actually good for you is the real question. After all, since calcium fluoride is a naturally occurring mineral and both calcium and fluoride have always been in the water, calcium fluoride must be okay, right?
Well, sort of. To be fair, most people aren't worried about eating calcium fluoride. They're worried about fluoride being added to their water in other ways, such as adding sodium fluoride to water.
When did we start adding fluoride to our water? It turns out the U.S. has been regularly adding fluoride, or fluoridating, its water officially as far back as 1951, guided by the U.S. Public Health service. Initially, it might make sense to be concerned about this. Fluorides can cause death in high doses. But does this mineral pose a real threat to us?
To understand this better, we need to know some basics about ions and their compounds. Ionic compounds all pretty much fall under the same umbrella, as they each have a positively charged element or compound which is bound to a negatively charged compound or element by the illustrious “ionic bond.”
You've probably heard of this before. When an ionic compound dissolves, as in water, the ions separate. Chemists typically called this process “dissociation,” and we see it all the time in our own lives when we dissolve table salt in water.
When table salt dissolves, sodium chloride dissociates into positively charged sodium ions and negatively charged chloride ions which bounce around in the solution. This salty solution doesn't contain complete sodium chloride salt molecules anymore; it's just an evenly blended soup of sodium and chloride ions.
Now, sodium chloride is not the only ionic compound that can dissolve in water. You could add other ionic compounds to this water solution, maybe some baking soda (sodium bicarbonate), possibly some cream of tartar or even some sodium acetate, which would give it a salt and vinegar taste.
Imagine that you could make your solution so complicated that people would never be able to tell what ionic compounds you started with without having made the solution themselves. That's kind of how the Earth's water is, but the ions' sources are much more ambiguous. It's still a soup of many ions, like sodium, calcium, magnesium, chloride and fluoride, but in very small concentrations.
So what about calcium fluoride?
Well, calcium fluoride itself doesn't dissolve well in regular water. Like we discussed earlier, both calcium ions and fluoride ions can come from other compounds. In the soup of drinking water, it's hard to pinpoint exactly where any fluoride ions come from, especially if extra are added.
Thankfully, because our bodies don't sort ions back into their initial compounds, it doesn't actually matter in the end; to our bodies, water is just an evenly mixed solution with multiple ions floating around in it. What does matter are the individual ions and the ways they interact with each other and our bodies.
To find the answer to the question of calcium fluoride's benefit to us, we need to ask ourselves if the ions it splits into are good for us.
Let's look at the amounts present in water and amounts you need of each individual ion, calcium and fluoride.
You need calcium, for sure; to be precise, you need about a gram of calcium a day. We all probably remember lectures about the importance of drinking milk so we can strengthen our bones with its calcium. But the amount of calcium we need is far more than the amount we would get by drinking calcium fluoride dissolved in water.
However, you need far less fluoride than you do calcium. For fluoride, anywhere from 0.7 to 1.2 milligrams per liter of water is considered optimal. More could be dangerous.
Yes, that's as tiny an amount as it sounds. For every gram of fluoride, there are a million grams of pure water. That would be like identifying one person in a stadium at full capacity that is ten times as big as Neyland Stadium.
Water with dissolved calcium fluoride can only really provide you with the amount of fluoride you need daily.
But if we only need a little fluoride and can't get enough calcium to help, is it a big deal if we just leave calcium fluoride out of our water entirely?
Perhaps not, but it is easy to see why people started fluoridating their water. In small concentrations, fluoride can prevent tooth decay, and it was very good at doing that at first in the 1950s. If you don't have good dental hygiene, getting cavities is pretty easy. Getting some source of fluoride can make a big difference.
But water isn't the only source of fluoride; most people these days get plenty by regularly brushing their teeth. There's a lot of fluoride in toothpaste, so much so that it would be poisonous if eaten. But brushing with it and spitting it out? Great idea. Youshould totally brush your teeth with fluoride toothpaste. Do that, and you'll get all the fluoride you need.
If most people brush their teeth with fluoride toothpaste, do we need to have fluoride in our water? Maybe not, and the science behind this stance has been discussed for more than a decade. A review published in 2007concluded that fluoridating water probably wasn't helpful in industrialized countries. Since then, other scientific studies have been published criticizing water fluoridation's usefulness. Today, many countries have abandoned fluoridation entirely. We can only imagine that natural sources have questionable effectiveness as well.
So in general, is calcium fluoride a beneficial micromineral? Well, given that calcium fluoride isn't very water soluble, and given that it's only good for providing fluoride, it's probably not any more beneficial than other sources of calcium or fluoride. Still, the U.S. fluoridates its water to give us the fluoride we need, and whether or not we should stop remains a contentious debate.
We don't have an answer for the policy question, but from the looks of it, the fluoride we put in our water might not be as essential as we once thought. Eating vegetables and regularly brushing your teeth will probably treat any calcium and fluoride deficiencies you might have that would otherwise be fixed by calcium fluoride in your water. That seems a lot more accessible — and tasty — to us than getting a supplement.
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Scott Satinover is a PhD student in Bioenergy and Biofuels and can be reached at email@example.com. Brooke Dulka is a PhD student in Biological Psychology and can be reached at firstname.lastname@example.org.
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