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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A short history of sunscreen, from basting like a chook to preventing skin cancer
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Australians have used commercial creams, lotions or gels to manage our skin’s sun exposure for nearly a century.
But why we do it, the preparations themselves, and whether they work, has changed over time.
In this short history of sunscreen in Australia, we look at how we’ve slathered, slopped and spritzed our skin for sometimes surprising reasons.
At first, suncreams helped you ‘tan with ease’
This early sunscreen claimed you could ‘tan with ease’.
Trove/NLASunscreens have been available in Australia since the 30s. Chemist Milton Blake made one of the first.
He used a kerosene heater to cook batches of “sunburn vanishing cream”, scented with French perfume.
His backyard business became H.A. Milton (Hamilton) Laboratories, which still makes sunscreens today.
Hamilton’s first cream claimed you could “
Sunbathe in Comfort and TAN with ease”. According to modern standards, it would have had an SPF (or sun protection factor) of 2.The mirage of ‘safe tanning’
A tan was considered a “modern complexion” and for most of the 20th century, you might put something on your skin to help gain one. That’s when “safe tanning” (without burning) was thought possible.
This 1967 Coppertone advertisement urged you to ‘tan, not burn’.
SenseiAlan/Flickr, CC BY-SASunburn was known to be caused by the UVB component of ultraviolet (UV) light. UVA, however, was thought not to be involved in burning; it was just thought to darken the skin pigment melanin. So, medical authorities advised that by using a sunscreen that filtered out UVB, you could “safely tan” without burning.
But that was wrong.
From the 70s, medical research suggested UVA penetrated damagingly deep into the skin, causing ageing effects such as sunspots and wrinkles. And both UVA and UVB could cause skin cancer.
Sunscreens from the 80s sought to be “broad spectrum” – they filtered both UVB and UVA.
Researchers consequently recommended sunscreens for all skin tones, including for preventing sun damage in people with dark skin.
Delaying burning … or encouraging it?
Up to the 80s, sun preparations ranged from something that claimed to delay burning, to preparations that actively encouraged it to get that desirable tan – think, baby oil or coconut oil. Sun-worshippers even raided the kitchen cabinet, slicking olive oil on their skin.
One manufacturer’s “sun lotion” might effectively filter UVB; another’s merely basted you like a roast chicken.
Since labelling laws before the 80s didn’t require manufacturers to list the ingredients, it was often hard for consumers to tell which was which.
At last, SPF arrives to guide consumers
In the 70s, two Queensland researchers, Gordon Groves and Don Robertson, developed tests for sunscreens – sometimes experimenting on students or colleagues. They printed their ranking in the newspaper, which the public could use to choose a product.
An Australian sunscreen manufacturer then asked the federal health department to regulate the industry. The company wanted standard definitions to market their products, backed up by consistent lab testing methods.
In 1986, after years of consultation with manufacturers, researchers and consumers, Australian Standard AS2604 gave a specified a testing method, based on the Queensland researchers’ work. We also had a way of expressing how well sunscreens worked – the sun protection factor or SPF.
This is the ratio of how long it takes a fair-skinned person to burn using the product compared with how long it takes to burn without it. So a cream that protects the skin sufficiently so it takes 40 minutes to burn instead of 20 minutes has an SPF of 2.
Manufacturers liked SPF because businesses that invested in clever chemistry could distinguish themselves in marketing. Consumers liked SPF because it was easy to understand – the higher the number, the better the protection.
Australians, encouraged from 1981 by the Slip! Slop! Slap! nationwide skin cancer campaign, could now “slop” on a sunscreen knowing the degree of protection it offered.
How about skin cancer?
It wasn’t until 1999 that research proved that using sunscreen prevents skin cancer. Again, we have Queensland to thank, specifically the residents of Nambour. They took part in a trial for nearly five years, carried out by a research team led by Adele Green of the Queensland Institute of Medical Research. Using sunscreen daily over that time reduced rates of squamous cell carcinoma (a common form of skin cancer) by about 60%.
Follow-up studies in 2011 and 2013 showed regular sunscreen use almost halved the rate of melanoma and slowed skin ageing. But there was no impact on rates of basal cell carcinoma, another common skin cancer.
By then, researchers had shown sunscreen stopped sunburn, and stopping sunburn would prevent at least some types of skin cancer.
What’s in sunscreen today?
An effective sunscreen uses one or more active ingredients in a cream, lotion or gel. The active ingredient either works:
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“chemically” by absorbing UV and converting it to heat. Examples include PABA (para-aminobenzoic acid) and benzyl salicylate, or
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“physically” by blocking the UV, such as zinc oxide or titanium dioxide.
Physical blockers at first had limited cosmetic appeal because they were opaque pastes. (Think cricketers with zinc smeared on their noses.)
With microfine particle technology from the 90s, sunscreen manufacturers could then use a combination of chemical absorbers and physical blockers to achieve high degrees of sun protection in a cosmetically acceptable formulation.
Where now?
Australians have embraced sunscreen, but they still don’t apply enough or reapply often enough.
Although some people are concerned sunscreen will block the skin’s ability to make vitamin D this is unlikely. That’s because even SPF50 sunscreen doesn’t filter out all UVB.
There’s also concern about the active ingredients in sunscreen getting into the environment and whether their absorption by our bodies is a problem.
Sunscreens have evolved from something that at best offered mild protection to effective, easy-to-use products that stave off the harmful effects of UV. They’ve evolved from something only people with fair skin used to a product for anyone.
Remember, slopping on sunscreen is just one part of sun protection. Don’t forget to also slip (protective clothing), slap (hat), seek (shade) and slide (sunglasses).
Laura Dawes, Research Fellow in Medico-Legal History, Australian National University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Natural Alternatives for Depression Treatment
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Questions and Answers at 10almonds
Have a question or a request? You can always hit “reply” to any of our emails, or use the feedback widget at the bottom!
This newsletter has been growing a lot lately, and so have the questions/requests, and we love that! 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
Natural alternatives to medication for depression?
Great question! We did a mean feature a while back, but we definitely have much more to say! We’ll do another main feature soon, but in the meantime, here’s what we previously wrote:
See: The Mental Health First-Aid That You’ll Hopefully Never Need
^This covers not just the obvious, but also why the most common advice is not helpful, and practical tips to actually make manageable steps back to wellness, on days when “literally just survive the day” is one’s default goal.
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What Your Mucus Says About Your Health
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It’s not a sexy topic (unless perhaps you have a fetish), but it is a useful topic to know about.
So, let’s get down to business with this much-maligned bodily fluid:
What is mucus? And why?
Sometimes, it can seem that mucus only exists to be an inconvenience, and to convey disease.
And… Actually, that’s mostly true.
While some kinds of mucus have other jobs beyond the scope of today’s article (did you know semen is mostly mucus? If not, now you do), the primary job of most of our mucus is to stop things (especially pathogens) going where they shouldn’t.
So, in essence, it really does exist to be an inconvenience—to pathogens. And to convey those pathogens to where they can be disposed of safely, either outside of the body, or to be an easy meal (what with being stuck in mucus, and thus at least moderately immobilized) for our various active immune cells. To make matters worse for the pathogens, there are (usually) enzymes in our mucus that have antimicrobial properties, too.
Some of mucus’s protective role can be in other ways too, such as by lining our stomach. You know, the stomach that contains the acid that can dissolve meat, despite us also being made of meat.
The slimiest rainbow
Ok, maybe not the slimiest rainbow—there’s probably a YouTube slime channel producing more colors. But, our noses are capable of dispensing astonishing quantities of mucus sometimes, and the color can vary widely, so here’s what we can know from that:
Clear
This is as it should be, in good health. If you’re getting lots of it but it’s clear, then it’s usually allergies, but watch out in case it changes color, heralding an infection. This “clear is how it looks when in ideal health”, by the way, is why when someone is sobbing in abject grief, any mucus that shows up to add to that picture will generally be clear.
White
As above, but now inflamed. Inflammation is usually something we don’t want, but in the case of a threat from a pathogen, we actually do want acute inflammation like this—the body is assembling its armies, of which, the most visible (when they appear in mass) are white blood cells. Because of their abundant presence at this stage, the mucus will also become thicker.
Yellow
As above, but the battle is now truly underway, and the yellow color comes from dead white blood cells. This does not, however, mean the battle is necessarily going badly—the body treats its white blood cells as very disposable fighters, and their deaths in large numbers are expected and normal when doing battle.
Green
As above, but neutrophils (a specific kind of white blood cell) have joined the party. They release an enzyme that colors the mucus green—and kills a lot of pathogens. Popular lore says that green mucus means a bacterial infection, but it’s not always so; these can be deployed against viruses too, depending on various factors beyond the scope of this article (but generally pertaining to severity). In any case, this too does not mean the battle is necessarily going badly, but it does express that your body is taking it very seriously—and you should, too.
Red
Nothing to do with infections, usually—it’s just a little blood (the red kind, this time). Usually it got into the mucus because the mucus membrane got damaged, usually due to some kind of physical trauma (e.g. very vigorous nose-blowing, poking things up the nose, etc) or sometimes if the air is very dry (then the mucus itself can dry out, and become stabby inside the nose; when more mucus is produced, it gets infused with blood from the injury).
Pink
As above, but combined with the “white” stage of infection response.
Orange
As above, but combined with the “yellow” stage of infection response.
Brown
As above, but the blood has oxidized—or, as a completely alterative possibility, it could mean you have been breathing a lot of pollutants. Smoke of various kinds (from fires, from smoking, etc) can cause this.
Black
There are various possible explanations here and all of them are bad. Get thee to a doctor. Superficial examples include:
- Fungal infection (you thought toxic black mold was bad when it was on the wall of the house, wait until it’s on the walls of your respiratory system)
- Blood, in abundance, oxidized (which begs the question of what caused that, but certainly: something wrong is not right)
- Pollutants again, but this time at absurd levels of exposure
That last one might sound very transient and self-correcting, but it’s not, and it comes with many increased short- and long-term health risks.
Want to know more?
Knowledge is power, so read up, and stay well:
- Beyond Supplements: The Real Immune-Boosters!
- The Cold Truth About Respiratory Infections
- Why Some People Get Sick More (And How To Not Be One Of Them)
Take care!
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The Vitamin Solution – by Dr. Romy Block & Dr. Arielle Levitan
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A quick note: it would be remiss of us not to mention that the authors of this book are also the founders of a vitamin company, thus presenting a potential conflict of interest.
That said… In this reviewer’s opinion, the book does seem balanced and objective, regardless.
We talk a lot about supplements here at 10almonds, especially in our Monday Research Review editions. And yesterday, we featured a book by a doctor who hates supplements. Today, we feature a book by two doctors who have made them their business.
The authors cover all the most common vitamins and minerals popularly enjoyed as supplements, and examine:
- why people take them
- factors affecting whether they help
- problems that can arise
- complicating factors
The “complicating factors” include, for example, the way many vitamins and/or minerals interplay with each other, either by requiring the presence of another, or else competing for resources for absorption, or needing to be delicately balanced on pain of diverse woes.
This is the greatest value of the book, perhaps; it’s where most people go wrong with supplementation, if they go wrong.
While both authors are medical doctors, Dr. Romy Block is an endocrinologist specifically, and she clearly brought a lot of extra attention to relevant metabolic/thyroid issues, and how vitamins and minerals (such as thiamin and iron) can improve or sabotage such, depending on various factors that she explains. Informative, and so far as this reviewer could see, objective and well-balanced.
Bottom line: supplementation is a vast and complex topic, but this book does a fine job of demystifying and simplifying it in a clear and objective fashion, without resorting to either scaremongering or hype.
Click here to check out The Vitamin Solution, and upgrade your knowledge!
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Spirulina vs Nori – Which is Healthier?
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Our Verdict
When comparing spirulina to nori, we picked the nori.
Why?
In the battle of the seaweeds, if spirulina is a superfood (and it is), then nori is a super-dooperfood. So today is one of those “a very nutritious food making another very nutritious food look bad by standing next to it” days. With that in mind…
In terms of macros, they’re close to identical. They’re both mostly water with protein, carbs, and fiber. Technically nori is higher in carbs, but we’re talking about 2.5g/100g difference.
In the category of vitamins, spirulina has more vitamin B1, while nori has a lot more of vitamins A, B2, B3, B5, B6, B9, C, E, K, and choline.
When it comes to minerals, it’s a little closer but still a clear win for nori; spirulina has more copper, iron, and magnesium, while nori has more calcium, manganese, phosphorus, potassium, and zinc.
Want to try some nori? Here’s an example product on Amazon 😎
Want to learn more?
You might like to read:
21% Stronger Bones in a Year at 62? Yes, It’s Possible (No Calcium Supplements Needed!) ← nori was an important part of the diet enjoyed here
Take care!
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The Brain As A Work-In-Progress
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And The Brain Goes Marching On!
In Tuesday’s newsletter, we asked you “when does the human brain stop developing?” and got the above-depicted, below-described, set of responses:
- About 64% of people said “Never”
- About 16% of people said “25 years”
- About 9% of people said “65 years”
- About 5% of people said “13 years”
- About 3% of people said “18 years”
- About 3% of people said “45 years”
Some thoughts, before we get into the science:
An alternative wording for the original question was “when does the human brain finish developing”; the meaning is the same but the feeling is slightly different:
- “When does the human brain stop developing?” focuses attention on the idea of cessation, and will skew responses to later ages
- When does the human brain finish developing?” focuses on attention on a kind of “is it done yet?” and will skew responses to earlier ages
Ultimately, since we had to chose one word or another, we picked the shortest one, but it would have been interesting if we could have done an A/B test, and asked half one way, and half the other way!
Why we picked those ages
We picked those ages as poll options for reasons people might be drawn to them:
- 13 years: in English-speaking cultures, an important milestone of entering adolescence (note that the concept of a “teenager” is not precisely universal as most languages do not have “-teen” numbers in the same way; the concept of “adolescent” may thus be tied to other milestones)
- 18 years: age of legal majority in N. America and many other places
- 25 years: age popularly believed to be when the brain is finished developing, due to a study that we’ll talk about shortly (we guess that’s why there’s a spike in our results for this, too!)
- 45 years: age where many midlife hormonal changes occur, and many professionals are considered to have peaked in competence and start looking towards retirement
- 65 years: age considered “senior” in much of N. America and many other places, as well as the cut-off and/or starting point for a lot of medical research
Notice, therefore, how a lot of things are coming from places they really shouldn’t. For example, because there are many studies saying “n% of people over 65 get Alzheimer’s” or “n% of people over 65 get age-related cognitive decline”, etc, 65 becomes the age where we start expecting this—because of an arbitrary human choice of where to draw the cut-off for the study enrollment!
Similarly, we may look at common ages of legal majority, or retirement pensions, and assume “well it must be for a good reason”, and dear reader, those reasons are more often economically motivated than they are biologically reasoned.
So, what does the science say?
Our brains are never finished developing: True or False?
True! If we define “finished developing” as “we cease doing neurogenesis and neuroplasticity is no longer in effect”.
Glossary:
- Neurogenesis: the process of creating new brain cells
- Neuroplasticity: the process of the brain adapting to changes by essentially rebuilding itself to suit our perceived current needs
We say “perceived” because sometimes neuroplasticity can do very unhelpful things to us (e.g: psychological trauma, or even just bad habits), but on a biological level, it is always doing its best to serve our overall success as an organism.
For a long time it was thought that we don’t do neurogenesis at all as adults, but this was found to be untrue:
How To Grow New Brain Cells (At Any Age)
Summary of conclusions of the above: we’re all growing new brain cells at every age, even if we be in our 80s and with Alzheimer’s disease, but there are things we can do to enhance our neurogenic potential along the way.
Neuroplasticity will always be somewhat enhanced by neurogenesis (after all, new neurons get given jobs to do), and we reviewed a great book about the marvels of neuroplasticity including in older age:
Our brains are still developing up to the age of 25: True or False?
True! And then it keeps on developing after that, too. Now this is abundantly obvious considering what we just talked about, but see what a difference the phrasing makes? Now it makes it sound like it stops at 25, which this statement doesn’t claim at all—it only speaks for the time up to that age.
A lot of the popular press about “the brain isn’t fully mature until the age of 25” stems from a 2006 study that found:
❝For instance, frontal gray matter volume peaks at about age 11.0 years in girls and 12.1 years in boys, whereas temporal gray matter volume peaks at about age at 16.7 years in girls and 16.2 years in boys. The dorsal lateral prefrontal cortex, important for controlling impulses, is among the latest brain regions to mature without reaching adult dimensions until the early 20s.❞
Source: Structural Magnetic Resonance Imaging of the Adolescent Brain
There are several things to note here:
- The above statement is talking about the physical size of the brain growing
- Nowhere does he say “and stops developing at 25”
However… The study only looked at brains up to the age of 25. After that, they stopped looking, because the study was about “the adolescent brain” so there has to be a cut-off somewhere, and that was the cut-off they chose.
This is the equivalent of saying “it didn’t stop raining until four o’clock” when the reality is that four o’clock is simply when you gave up on checking.
The study didn’t misrepresent this, by the way, but the popular press did!
Another 2012 study looked at various metrics of brain development, and found:
- Synapse overproduction into the teens
- Cortex pruning into the late 20s
- Prefrontal pruning into middle age at least (they stopped looking)
- Myelination beyond middle age (they stopped looking)
Source: Experience and the developing prefrontal cortex ← check out figure 1, and make sure you’re looking at the human data not the rat data
So how’s the most recent research looking?
Here’s a 2022 study that looked at 123,984 brain scans spanning the age range from mid-gestation to 100 postnatal years, and as you can see from its own figure 1… Most (if not all) brain-things keep growing for life, even though most slow down at some point, they don’t stop:
Brain charts for the human lifespan ← check out figure 1; don’t get too excited about the ventricular volume column as that is basically “brain that isn’t being a brain”. Do get excited about the rest, though!
Want to know how not to get caught out by science being misrepresented by the popular press? Check out:
How Science News Outlets Can Lie To You (Yes, Even If They Cite Studies!)
Take care!
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