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.

If you’ve spent time on social media recently you have probably been exposed to questionable “wellness” content. You may have been instructed to dip your toes in icy water or let the sun shine where it usually doesn’t.

Wellness trends such as drinking “loaded” water or taking ice baths may be benign for most people, while others such as drinking raw milk, eating raw organ meats, or taping your mouth while you sleep carry real risks.

The online spaces where they circulate can also be harmful, serving as breeding grounds for conspiracy theories, anti-vaccination sentiment, and misuse of appearance- and performance-enhancing drugs.

It’s easy to dismiss followers of extreme wellness trends as gullible or misinformed. But research suggests personality traits may help explain why some educated, well-intentioned people sometimes reject conventional medicine in favour of fringe practices.

The big five personality traits

Psychologists have shown that many aspects of human personality can be described via five fundamental dimensions, of which we all have varying levels.

Two of these “big five” traits – openness and agreeableness – are particularly relevant to people’s interest in alternative health practices. (The remaining three traits are conscientiousness, extraversion and neuroticism.)

People high in openness are curious, imaginative and adventurous. They question tradition and are attracted to novelty and unconventional ideas. As a result, they are more likely to try new and unorthodox diets or treatments.

Highly agreeable people are trusting, cooperative and empathetic. They are very receptive to emotional messages, especially when they appeal to ideas of caring for others and benefiting the community.

These personality traits also influence how people search for and evaluate online information. People higher in openness tend to adopt an exploratory search strategy, preferring to seek novel or unconventional sources rather than relying on established information channels.

Because they value harmony, trust and maintaining relationships, highly agreeable people tend to give greater weight to information that comes from familiar or socially endorsed sources. They do so even when this information has not been critically evaluated.

Personality and persuasive influence

In the online wellness ecosystem, high levels of openness and agreeableness can make people susceptible to persuasion.

Influencers have a powerful advantage. They can position themselves as both novel and trustworthy. Open people can be seduced by original, eye-catching content, and agreeable people by community-focused narratives.

Influencers cultivate one-sided “parasocial” relationships in which followers feel an intimate connection with someone they have never met. These close bonds, coupled with the open personality’s attraction to unconventional ideas, can draw people into extreme, untested and unsafe health practices.

Openness to new experiences and being interpersonally agreeable are usually seen as strengths. However, in the buzzing, emotionally charged environment of online wellness culture they can become vulnerabilities.

From ice baths to anti-vax

Not all wellness practices peddled by online influencers are harmful. But some relatively innocuous trends can be a gateway to more extreme practices.

Someone might start taking ice baths for a mood boost, move on to restrictive raw diets for “clean eating”, and eventually arrive at anti-vaccine beliefs grounded in deep mistrust of health authorities.

Gateway effects can occur if a trusted influencer makes increasingly extreme recommendations. If the influencer pivots to more dangerous ideas, many followers will follow.

Over time, exposure to fringe wellness narratives can erode trust in mainstream institutions. What began as curiosity and warmth may, through repeated exposure to extreme content, shift towards cynicism and institutional mistrust.

How can public health messages adapt?

Public health campaigns sometimes assume people reject mainstream health advice because they lack knowledge or have low “health literacy”.

But if personality traits influence receptiveness to alternative wellness claims, simply giving people more information may not produce positive change.

Public health campaigns should consider personality traits for more effective preventive interventions. They can target people high in openness, for example, by presenting health science as dynamic and evolving, not just a set of rules and prescriptions. They can reach highly agreeable people with health messages that emphasise empathy and community.

To be effective for all of us, public health communication needs to be as engaging as the messages emanating from influencers. It must use eye-catching visuals, personal stories, and moral hooks while remaining truthful.

People who engage in extreme or unusual wellness practices aren’t merely misinformed. Often, they’re driven by the same urge to explore, connect, and live well as everyone else. The challenge we face is to steer that drive toward health, not harm.

Samuel Cornell, PhD Candidate in Public Health & Community Medicine, School of Population Health, UNSW Sydney and Nick Haslam, Professor of Psychology, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.