Could drinking fruit tea be bad for your teeth?

"Sipping acidic fruit teas can wear away teeth, says study," reports BBC News on a new review on the role of diet in tooth erosion – where the tooth's enamel coating is worn down by acid.

Two researchers from King's College London looked at a number of existing studies on the topic of dietary causes of tooth erosion. The studies ranged from those looking at which foods and drinks contained the most acids, to those considering how the way in which people sipped and tasted drinks might affect their risk of tooth enamel erosion.

Although we know that acidic foods can cause tooth erosion, many of the studies included in this review were quite small and some were likely to be less reliable than others. The review gives no methods, so we can't be sure that all relevant research on the topic has been identified. A systematic review of all the available evidence would give a clearer understanding of the relationship between how and what people eat and drink, and their risk of tooth enamel erosion.

As such it's not possible to state with confidence that fruit tea is bad for your teeth. The best way to prevent tooth decay is to brush your teeth twice a day and cut down on sugary and starchy foods.

Where did the story come from?

This review article was written by researchers from King's College London and was published in the peer-reviewed British Dental Journal. No funding was mentioned. One of the authors contributed to one of the studies discussed in the review.

Although this was a review of a number of pieces of research, the news outlets mostly focused on one study that compared 300 people with tooth erosion and 300 people without. This was actually a piece of research published by the same authors over a year ago, which featured heavily in an accompanying press release. Unfortunately, this latest review article did not go into much detail on the previous study, making it hard to evaluate.

What kind of research was this?

The report was a narrative review in which the authors selected a number of studies on the theme of diet in tooth erosion to compare and discuss.

Narrative review articles can be useful for getting a broad overview of some key studies on a topic. However, the researchers provided no methods, so it's unclear why the particular studies were selected. We don't know whether other relevant studies on this topic may have been left out, and whether or not they agreed with the ones chosen. For the individual selected studies, there is generally not enough information for the reader to fully understand the strengths and weaknesses without reading the original research.

This review is therefore a useful overview of a selection of research on tooth erosion, but does not enable us to draw any definitive conclusions. For that, we would need to see a systematic review where the researchers are clear about the question they are looking at and include all relevant studies on the topic.

What did the research involve?

The authors selected studies across a range of tooth-erosion topics. The themes of these papers included:

identifying dietary sources of potentially eroding acids
how often people consumed dietary acids
habits such as how food or drink is held in the mouth before swallowing
how much dietary acid was found in specific types of diet that some people follow
whether giving people dietary advice is effective at reducing tooth erosion

The included studies involved a range of methods and populations. Some involved hundreds of people, while others were quite small.

There was often no description of the individual study designs, making it hard to tell whether they are reliable or not. For example, there are different ways of monitoring and recording how much people consume of specific foods and drinks, and some are more accurate than others.

What were the basic results?

Foods listed as containing dietary acids included citrus fruits, chillies, tomatoes, drinks containing fruit or fruit flavourings (including slices of lemon or lime), fizzy drinks (including diet versions), vinegars and pickles.

Some other findings of the review are as follows:

A small study of 55 adults suggested that consuming dietary acids 4 or more times a day was associated with the wearing away of tooth enamel over the course of 6 years.
Some studies looking at whether it mattered if acidic foods and drinks were consumed during meals or between them concluded that the risks of erosion were lower if consumed with meals. There was no explanation given for why this is the case.
One study found people who take a long time to eat fruit (more than 10 minutes at a single sitting) were more likely to have tooth erosion than those who did not.
The same study also looked at the effect of sipping drinks and found that those who spent more than 10 minutes drinking were more likely to have tooth erosion. Another study found a single boy who had the habit of holding soft drinks in his mouth for a long while before swallowing had tooth erosion and needed extractions.
One trial was said to find that increasing the temperature of fruit tea increased tooth wear. The number of people in this study, its methods, and its duration are unclear.
Another study on teeth in the laboratory found that higher temperatures of tea were associated with greater softening of tooth enamel.
One study of people on a "raw food diet" found they had higher rates of dental erosion compared to those not on that diet. The link was put down to eating more fruit.

How did the researchers interpret the results?

The authors noted that there is "an established role between dietary acids and erosive tooth wear".

They noted that this was a preventable aspect of tooth wear and speculated that addressing this might also delay erosion caused by less preventable or unavoidable causes (for example vomiting and reflux). However, no evidence on this matter was discussed in the review.

They also discuss that it is difficult to encourage people to change their diet solely by giving advice, without providing individualised support.

Conclusion

This review gives a broad overview of some interesting pieces of research in the field of dietary causes of tooth erosion. Broadly, the review has told us that dietary acids found in some foods have the potential to contribute towards tooth erosion. We have also learnt that the way in which food and drink is consumed, rather than just the content, might also play a part.

However, with no methods on how the reviewers searched for, selected, and assessed the studies they included, this piece must largely be considered the opinion of the authors. Very little information is given on the design and methods of most studies discussed. However, just from size alone it seems many are not good enough to give any certainty of effects or draw firm conclusions. For example, a single case report of an individual boy who liked to sip drinks slowly tells us very little.

A systematic review, covering all relevant literature on this topic, is needed to get a proper answer. Without this it is hard to attach specific risks to particular habits or to particular foods and drinks, or give definitive advice on exactly how to reduce the risk of dietary tooth erosion, aside from the general advice of limiting your consumption of sugary and starchy foods.