Is fluoride really linked to lower IQ, as a recent study suggested? Here’s why you shouldn’t worry
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Fluoride is a common natural element found in water, soil, rocks and food. For the past several decades, fluoride has also been a cornerstone of dentistry and public health, owing to its ability to protect against tooth decay.
Water fluoridation is a population-based program where a precise, small amount of fluoride is added to public drinking water systems. Water fluoridation began in Australia in the 1950s. Today more than 90% of Australia’s population has access to fluoridated tap water.
But a recently published review found higher fluoride exposure is linked to lower intelligence quotient (IQ) in children. So how can we interpret the results?
Much of the data analysed in this review is poor quality. Overall, the findings don’t give us reason to be concerned about the fluoride levels in our water supplies.
Not a new controversy
Tooth decay (also known as caries or cavities) can have negative effects on dental health, overall health and quality of life. Fluoride strengthens our teeth, making them more resistant to decay. There is scientific consensus water fluoridation is a safe, effective and equitable way to improve oral health.
Nonetheless, water fluoridation has historically been somewhat controversial.
A potential link between fluoride and IQ (and cognitive function more broadly) has been a contentious topic for more than a decade. This started with reports from studies in China and India.
But it’s important to note these studies were limited by poor methodology, and water in these countries had high levels of natural fluoride when the studies were conducted – many times higher than the levels recommended for water fluoridation programs. Also, the studies did not control for other contaminants in the water supply.
Recent reviews focusing on the level of fluoride used in water fluoridation have concluded fluoride is not linked to lower IQ.
Despite this, some have continued to raise concerns. The United States National Toxicology Program conducted a review of the potential link. However, this review did not pass the quality assessment by the US National Academies of Sciences, Engineering and Medicine due to significant limitations in the conduct of the review.
The authors followed through with their study and published it as an independent publication in the journal JAMA Paediatrics last week. This is the study which has been generating media attention in recent days.
What the study did
This study was a systematic review and meta-analysis, where the researchers evaluated 74 studies from different parts of the world.
A total of 52 studies were rated as having a high risk of bias, and 64 were cross-sectional studies, which often can’t provide evidence of causal relationship.
Most of the studies were conducted in developing countries, such as China (45), India (12), Iran (4), Mexico (4) and Pakistan (2). Only a few studies were conducted in developed countries with established public water systems, where regular monitoring and treatment of drinking water ensures it’s free from contaminants.
The vast majority of studies were conducted in populations with high to very high levels of natural fluoride and without water fluoridation programs, where fluoride levels are controlled within recommended levels.
The study concluded there was an inverse association between fluoride levels and IQ in children. This means those children who had a higher intake of fluoride had lower IQ scores than their counterparts.
Limitations to consider
While this review combined many studies, there are several limitations that cast serious doubt over its conclusion. Scientists immediately raised concerns about the quality of the review, including in a linked editorial published in JAMA.
The low quality of the majority of included studies is a major concern, rendering the quality of the review equally low. Importantly, most studies were not relevant to the recommended levels of fluoride in water fluoridation programs.
Several included studies from countries with controlled public water systems (Canada, New Zealand, Taiwan) showed no negative effects. Other recent studies from comparable populations (such as Spain and Denmark) also have not shown any negative effect of fluoride on IQ, but they were not included in the meta-analysis.
For context, the review found there was no significant association with IQ when fluoride was measured at less than 1.5mg per litre in water. In Australia, the recommended levels of fluoride in public water supplies range from 0.6 to 1.1 mg/L.
Also, the primary outcome, IQ score, is difficult to collect. Most included studies varied widely on the methods used to collect IQ data and did not specify their focus on ensuring reliable and consistent IQ data. Though this is a challenge in most research on this topic, the significant variations between studies in this review raise further doubts about the combined results.
No cause for alarm
Although no Australian studies were included in the review, Australia has its own studies investigating a potential link between fluoride exposure in early childhood and child development.
I’ve been involved in population-based longitudinal studies investigating a link between fluoride and child behavioural development and executive functioning and between fluoride and IQ. The IQ data in the second study were collected by qualified, trained psychologists – and calibrated against a senior psychologist – to ensure quality and consistency. Both studies have provided strong evidence fluoride exposure in Australia does not negatively impact child development.
This new review is not a reason to be concerned about fluoride levels in Australia and other developed countries with water fluoridation programs. Fluoride remains important in maintaining the public’s dental health, particularly that of more vulnerable groups.
That said, high and uncontrolled levels of fluoride in water supplies in less developed countries warrant attention. There are programs underway in a range of countries to reduce natural fluoride to the recommended level.
Loc Do, Professor of Dental Public Health, The University of Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Food Expiration Dates Don’t Mean What Most People Think They Mean
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Have you ever wondered why rock salt that formed during the Precambrian era has a label on it saying that it expires next month? To take something more delicate, how about eggs that expire next Thursday; isn’t that oddly specific for something that is surely affected by many variables? What matters, and what doesn’t?
Covering their assets
The US in particular wastes huge amounts of food, with 37% of food waste coming from households. Confusion over date labels is a major contributor, accounting for 20% of household food waste. Many people misinterpret these labels, often discarding food that is still safe to eat—which is good for the companies selling the food, because then they get to sell you more.
Date labels were introduced in the 70s with the “open dating” system to indicate optimal freshness, not safety. These dates are often conservative, set by manufacturers to ensure food is consumed at its best quality and encourage repeat purchases. However, many foods remain safe well past their labeled dates, including shelf-stable items like pasta, rice, and canned goods, as well as frozen foods stored properly.
Some foods do pose safety risks, especially meat and dairy products, as well as many grain-based foods, all of which which can harbor harmful bacteria. Infant formula labels are strictly regulated for safety. However, most date labels are not linked to health risks, leading to unnecessary waste.
When it comes down to it, our senses of sight, smell, and taste are more reliable than dates on packaging. Some quick pointers and caveats:
- If it has changed color in some way that’s not associated with a healthily ripening fruit or vegetable, that’s probably bad
- If it is moldy, that’s probably bad (but the degree of badness varies from food to food; see the link beneath today’s video for more on that)
- If a container has developed droplets of water on the inside when it didn’t have those before, that’s probably bad (it means something is respiring, and is thus alive, that probably shouldn’t be)
- If it smells bad, that’s probably bad—however this is not a good safety test, because a bad smell may often mean you are inhaling mold spores, which are not good for your lungs.
- If it tastes different than that food usually does, that’s probably bad (especially if it became bitter, pungent, tangy, sour, or cheesy, and does nor normally taste that way).
Some places have trialled clearer labelling, for example a distinction between “expires” and merely “best before”, but public awareness about the distinction is low. Some places have trialled removing dates entirely, to oblige the consumer to use their own senses instead. This is good for the seller in a different way than household food waste is, because it means the seller will have less in-store waste (because they can still sell something that might previously have been labelled as expired).
For more on all of this, enjoy:
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like to read:
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Fruit & Veg In The Fridge: Pros & Cons
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It’s Q&A Day at 10almonds!
Have a question or a request? We love to hear from you!
In cases where we’ve already covered something, we might link to what we wrote before, but will always be happy to revisit any of our topics again in the future too—there’s always more to say!
As ever: if the question/request can be answered briefly, we’ll do it here in our Q&A Thursday edition. If not, we’ll make a main feature of it shortly afterwards!
So, no question/request too big or small
❝What effect does refrigeration have on the nutritional value of fruit and vegetables??❞
It’s difficult to give a single definitive answer, because naturally there are a lot of different fruits and vegetables, and a lot of different climates. The answer may be different for tomatoes in Alaska vs bananas in Arizona!
However, we can still generalize at least somewhat
Refrigeration will generally slow down any degradation process, and in the case of fruit and vegetables, that can mean slowing down their “ripening” too, as applicable.
However…
Refrigeration will also impede helpful bioactivity too, and that includes quite a list of things.
Here’s a good study that’s quite illustrative; we’d summarize the conclusions but the rather long title already does that nicely:
So, this really is a case of “there are pros and cons, but probably more cons on balance”.
In practical terms, a good take-away from this can be twofold:
- don’t keep fruit and veg in the fridge unless the ambient temperature really requires it
- if the ambient temperature does require it, it’s best to get the produce in fresh each day if that’s feasible, to minimize time spent in the fridge
An extra thing not included there: often when it comes to the spoilage of fruit and veg, the problem is that it respires and oxidizes; reducing the temperature does lower the rate of those, but often a far better way is to remove the oxygen. So for example, if you get carried away and chop too many carrot batons for your hummus night, then putting them in a sealed container can go a long way to keeping them fresh.
See also: How Does the Nutritional Value of Fruits and Vegetables Change Over Time?
Enjoy!
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The Body: A Guide for Occupants – by Bill Bryson
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Better known for his writings on geography and history, here Bryson puts his mind to anatomy and physiology. How well does he do?
Very well, actually—thanks no doubt to the oversight of the veritable flock of consulting scientists mentioned in the acknowledgements. To this reviewer’s knowledge, no mistakes made it through into publication.
That said, Bryson’s love of history does shine through, and in this case, the book is as much a telling of medical history, as it is of the human body. That’s a feature not a bug, though, as not only is it fascinating in and of itself, but also, it’d be difficult to fully understand where we’re at in science, without understanding how we got here.
The style of the book is easy-reading narrative prose, but packed with lots of quirky facts, captivating anecdotes, and thought-provoking statistics. For example:
- The least effective way to spread germs is kissing. It proved ineffective among volunteers (in what sounds like a fun study) who had been successfully infected with the cold virus. Sneezes and coughs weren’t much better. The only really reliable way to transfer cold germs was physically by touch.
- The United States has 4% of the world’s population but consumes 80% of its opiates.
- Allowing a fever to run its course (within limits) could be the wisest thing. An increase of only a degree or so in body temperature slows the replication rate of viruses by a factor of 200.
Still, these kinds of things are woven together so well, that it doesn’t feel at all like reading a trivia list!
Bottom line: if you’d like to know a lot more about anatomy and physiology, but prefer a very casual style rather than sitting down with a stack of textbooks, this book is a great option.
Click here to check out The Body, and learn more about yours!
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Luxurious Longevity Risotto
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Pearl barley is not only tasty and fiber-rich, but also, it contains propionic acid, which lowers cholesterol. The fiber content also lowers cholesterol too, of course, by the usual mechanism. The dish’s health benefits don’t end there, though; check out the science section at the end of the recipe!
You will need
- 2 cups pearl barley
- 3 cups sliced chestnut mushrooms
- 2 onions, finely chopped
- 6 large leaves collard greens, shredded
- ½ bulb garlic, finely chopped
- 8 spring onions, sliced
- 1½ quarts low-sodium vegetable stock
- 2 tbsp nutritional yeast
- 1 tbsp chia seeds
- 1 tbsp black pepper, coarse ground
- 1 tsp MSG or 2 tsp low-sodium salt
- 1 tsp rosemary
- 1 tsp thyme
- Extra virgin olive oil, for cooking
- Optional garnish: fresh basil leaves
Method
(we suggest you read everything at least once before doing anything)
1) Heat a little oil in a large sauté pan; add the onions and garlic and cook for 5 minutes; add the mushrooms and cook for another 5 minutes.
2) Add the pearl barley and a cup of the vegetable stock. Cook, stirring, until the liquid is nearly all absorbed, and add more stock every few minutes, as per any other risotto. You may or may not use all the stock you had ready. Pearl barley takes longer to cook than rice, so be patient—it’ll be worth the wait!
Alternative: an alternative is to use a slow cooker, adding a quart of the stock at once and coming back about 4 hours later—thus, it’ll take a lot longer, but will require minimal/no supervision.
3) When the pearl barley has softened, become pearl-like, and the dish is taking on a creamy texture, stir in the rest of the ingredients. Once the greens have softened, the dish is done, and it’s time to serve. Add the garnish if using one:
Enjoy!
Want to learn more?
For those interested in some of the science of what we have going on today:
- The Magic Of Mushrooms: “The Longevity Vitamin” (That’s Not A Vitamin)
- The Many Health Benefits Of Garlic
- Chia: The Tiniest Seeds With The Most Value
- Black Pepper’s Impressive Anti-Cancer Arsenal (And More)
- Monosodium Glutamate: Sinless Flavor-Enhancer Or Terrible Health Risk?
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Red Bell Peppers vs Tomatoes – Which is Healthier?
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Our Verdict
When comparing red bell peppers to tomatoes, we picked the peppers.
Why?
In terms of macronutrients, these two fruits-that-get-used-as-vegetables are similar in most respects; they’re mostly water, negligible protein and fat, similar amounts of carbs, even a similar carb breakdown (mostly fructose and glucose). One thing that does set them apart is that peppers* have about 2x the fiber, which difference results in peppers having the lower Glycemic Index—though tomatoes are quite low in GI too.
*for brevity we’re just going to write “peppers”, but we are still talking about sweet red bell peppers throughout. This is important, as different color peppers have different nutrient profiles.
In the category of vitamins, peppers have much more of vitamins A, B1, B2, B3, B5, B6, B9, C, and E. In contrast, tomatoes have more vitamin K. An easy win for peppers.
When it comes to minerals, the margins are narrower, but peppers have more iron, zinc, and selenium, while tomatoes have more calcium and copper. They’re approximately equal on other minerals they both contain, making this category a slight (3:2) win for peppers.
As for phytochemical benefits, both are good sources of lycopene (both better when cooked) and other carotenes (for example lutein), and both have an array of assorted flavonoids.
All in all, a win for peppers, but both are great!
Want to learn more?
You might like to read:
- Brain Food? The Eyes Have It!
- Bell Peppers: A Spectrum Of Specialties
- Lycopene’s Benefits For The Gut, Heart, Brain, & More
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Monosodium Glutamate: Sinless Flavor-Enhancer Or Terrible Health Risk?
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What’s The Deal With MSG?
There are a lot of popular beliefs about MSG. Is there a grain of truth, or should we take them with a grain of salt? We’ll leap straight into myth-busting:
MSG is high in salt
True (technically) False (practically)
- MSG is a salt (a monosodium salt of L-glutamic acid), but to call it “full of salt” in practical terms is like calling coffee “full of fruit”. (Coffee beans are botanically fruit)
- It does contain sodium, though which is what the S stands for!
- We talked previously about how MSG’s sodium content is much lower than that of (table) salt. Specifically, it’s about one third of that of sodium chloride (e.g. table salt).
MSG triggers gluten sensitivity
False!
Or at least, because this kind of absolute negative is hard to prove in science, what we can say categorically is: it does not contain gluten. We understand that the similar name can cause that confusion. However:
- Gluten is a protein, found in wheat (and thus wheat-based foods).
- Glutamate is an amino acid, found in protein-rich foods.
- If you’re thinking “but proteins are made from amino acids”, yes, they are, but the foundational amino acid of gluten is glutamine, not glutamate. Different bricks → different house!
The body can’t process MSG correctly
False!
The body has glutamate receptors throughout the gut and nervous system.
The body metabolizes glutamate from MSG just the same as from any other food that contains it naturally.
Read: Update on food safety of monosodium l-glutamate (MSG) ← evidence-based safety review
MSG causes “Chinese Restaurant Syndrome”
False!
Racism causes that. It finds its origins in what was originally intended as a satirical joke, that the papers picked up and ran with, giving it that name in the 1960s. As to why it grew and persisted, that has more to do with US politics (the US has been often at odds with China for a long time) and xenophobia (people distrust immigrants, such as those who opened restaurants), including nationalistic rhetoric associating immigrants with diseases.
Read: Xenophobia in America in the Age of Coronavirus and Beyond ← academic paper that gives quite a compact yet comprehensive overview
Research science, meanwhile, has not found any such correlation, in more than 40 years of looking.
PS: we realize this item in the list is very US-centric. Apologies to our non-US subscribers. We know that this belief isn’t so much of a thing outside the US—though it certainly can crop up elsewhere sometimes, too.
Are there any health risks associated with MSG, then?
Well, as noted, it does contain sodium, albeit much less than table salt. So… do go easy on it, all the same.
Aside from that, the LD50 (a way of measuring toxicity) of MSG is 15.8g/kg, so if for example you weigh 150lb (68 kg), don’t eat 2.2lb (a kilogram) of MSG.
There have been some studies on rats (or in one case, fruit flies) that found high doses of MSG could cause heart problems and/or promote obesity. However:
- this has not been observed to be the case in humans
- those doses were really high, ranging from 1g/kg to 8g/kg. So that’d be the equivalent of our 150lb person eating it by the cupful
- it was injected (as a solution) into the rats, not ingested by them
- so don’t let someone inject you with a cup of MSG!
Read: A review of the alleged health hazards of monosodium glutamate
Bottom line on MSG and health:
Enjoy in moderation, but enjoy if you wish! MSG is just the salt form of the amino acid glutamate, which is found naturally in many foods, including shrimp, seaweed, and tomatoes.
Scientists have spent more than 40 years trying to find health risks for MSG, and will probably keep trying (which is as science should be), but for now… Everything has either come up negative, or has been the result of injecting laboratory animals with megadoses.
If you’d like to try it in your cooking as a low-sodium way to bring out the flavor of your dishes, you can order it online. Cheapest in bulk, but try it and see if you like it first!
(I’ll be real with you… I have 5 kg in the pantry myself and use about half a teaspoon a day, cooking for two)
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