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.

We’re hearing a lot about ultra-processed foods and the health effects of eating too many. And we know plant-based foods are popular for health or other reasons.

So it’s not surprising new research out this week including the health effects of ultra-processed, plant-based foods is going to attract global attention.

And the headlines can be scary if that research and the publicity surrounding it suggests eating these foods increases your risk of heart disease, stroke or dying early.

Here’s how some media outlets interpreted the research. The Daily Mail ran with:

Vegan fake meats are linked to increase in heart deaths, study suggests: Experts say plant-based diets can boost health – but NOT if they are ultra-processed

The New York Post’s headline was:

Vegan fake meats linked to heart disease, early death: study

But when we look at the study itself, it seems the media coverage has focused on a tiny aspect of the research, and is misleading.

So does eating supermarket plant-based burgers and other plant-based, ultra-processed foods really put you at greater risk of heart disease, stroke and premature death?

Here’s what prompted the research and what the study actually found.

Remind me, what are ultra-processed foods?

Ultra-processed foods undergo processing and reformulation with additives to enhance flavour, shelf-life and appeal. These include everything from packet macaroni cheese and pork sausages, to supermarket pastries and plant-based mince.

There is now strong and extensive evidence showing ultra-processed foods are linked with an increased risk of many physical and mental chronic health conditions.

Although researchers question which foods should be counted as ultra-processed, or if all of them are linked to poorer health, the consensus is that, generally, we should be eating less of them.

We also know plant-based diets are popular. These are linked with a reduced risk of chronic health conditions such as heart disease and stroke, cancer and diabetes. And supermarkets are stocking more plant-based, ultra-processed food options.

How about the new study?

The study looked for any health differences between eating plant-based, ultra-processed foods compared to eating non-plant based, ultra-processed foods. The researchers focused on the risk of cardiovascular disease (such as heart disease and stroke) and deaths from it.

Plant-based, ultra-processed foods in this study included mass-produced packaged bread, pastries, buns, cakes, biscuits, cereals and meat alternatives (fake meats). Ultra-processed foods that were not plant-based included milk-based drinks and desserts, sausages, nuggets and other reconstituted meat products.

The researchers used data from the UK Biobank. This is a large biomedical database that contains de-identified genetic, lifestyle (diet and exercise) and health information and biological samples from half a million UK participants. This databank allows researchers to determine links between this data and a wide range of diseases, including heart disease and stroke.

They used data from nearly 127,000 people who provided details of their diet between 2009 and 2012. The researchers linked this to their hospital records and death records. On average, the researchers followed each participant’s diet and health for nine years.

What did the study find?

With every 10% increase of total energy from plant-sourced, ultra-processed foods there was an associated 5% increased risk of cardiovascular disease (such as heart disease or stroke) and a 12% higher risk of dying from cardiovascular disease.

But for every 10% increase in plant-sourced, non-ultra-processed foods consumed there was an associated 7% lower risk of cardiovascular disease and a 13% lower risk of dying from cardiovascular disease.

The researchers found no evidence for an association between all plant-sourced foods (whether or not they were ultra-processed) and either an increased or decreased risk of cardiovascular disease or dying from it.

This was an observational study, where people recalled their diet using questionnaires. When coupled with other data, this can only tell us if someone’s diet is associated with a particular risk of a health outcome. So we cannot say that, in this case, the ultra-processed foods caused the heart disease and deaths from it.

Why has media coverage focused on fake meats?

Much of the media coverage has focused on the apparent health risks associated with eating fake meats, such as sausages, burgers, nuggets and even steaks.

These are considered ultra-processed foods. They are made by deconstructing whole plant foods such as pea, soy, wheat protein, nuts and mushrooms, and extracting the protein. They are then reformulated with additives to make the products look, taste and feel like traditional red and white meats.

However this was only one type of plant-based, ultra-processed food analysed in this study. This only accounted for an average 0.2% of the dietary energy intake of all the participants.

Compare this to bread, pastries, buns, cakes and biscuits, which are other types of plant-based, ultra-processed foods. These accounted for 20.7% of total energy intake in the study.

It’s hard to say why the media focused on fake meat. But there is one clue in the media release issued to promote the research.

Although the media release did not mention the words “fake meat”, an image of plant-based burgers, sausages and meat balls or rissoles featured prominently.

The introduction of the study itself also mentions plant-sourced, ultra-processed foods, such as sausages, nuggets and burgers.

So it’s no wonder people can be confused.

Does this mean fake meats are fine?

Not necessarily. This study analysed the total intake of plant-based, ultra-processed foods, which included fake meats, albeit a very small proportion of people’s diets.

From this study alone we cannot tell if there would be a different outcome if someone ate large amounts of fake meats.

In fact, a recent review of fake meats found there was not enough evidence to determine their impact on health.

We also need more recent data to reflect current eating patterns of fake meats. This study used dietary data collected from 2009 to 2012, and fake meats have become more popular since.

What if I really like fake meat?

We have known for a while that ultra-processed foods can harm our health. This study tells us that regardless if an ultra-processed food is plant-based or not, it may still be harmful.

We know fake meat can contain large amounts of saturated fats (from coconut or palm oil), salt and sugar.

So like other ultra-processed foods, they should be eaten infrequently. The Australian Dietary Guidelines currently recommends people should only consume foods like this sometimes and in small amounts.

Are some fake meats healthier than others?

Check the labels and nutrition information panels. Look for those lowest in fat and salt. Burgers and sausages that are a “pressed cake” of minced ingredients such as nuts, beans and vegetables will be preferable to reformulated products that look identical to meat.

You can also eat whole plant-based protein foods such as legumes. These include beans, lentils, chickpeas and soy beans. As well as being high in protein and fibre, they also provide essential nutrients such as iron and zinc. Using spices and mushrooms alongside these in your recipes can replicate some of the umami taste associated with meat.

Evangeline Mantzioris, Program Director of Nutrition and Food Sciences, Accredited Practising Dietitian, University of South Australia

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