The use of blood sugar monitors in people without diabetes is not supported by research and may cause anxiety, experts have warned.
The monitors are being widely advertised as a way of personalising diets and are being marketed by several firms, including as part of Professor Tim Spector’s Zoe programme.
Zoe says on its website that blood sugar spikes can, over time, lead to an increased risk of heart disease.
Its programme assesses a person’s blood sugar responses to food and also looks at blood fat levels and gut bacteria.
“From this information, we can provide personalised nutrition advice to help you minimise blood sugar spikes and move toward your long-term health goals,” it says.
However, several experts have questioned the research evidence behind Zoe, together with other programmes using continuous glucose monitors for people without diabetes.
The monitors are often used by people with diabetes who are reliant on insulin pumps to ensure their blood sugar remains stable.
In the new review, researchers at University College London and Birmingham Children’s Hospital concluded there is a lack of evidence to support the use of CGMs in people without diabetes.
They said the devices may also cause people anxiety and lead to them restricting certain foods, such as with orthorexia, a “pure food” obsession, and argued that “spikes” in blood sugar after eating are perfectly normal.
Senior author on the study and dietitian Dr Adrian Brown, from UCL’s division of medicine, told the PA news agency: “Our review found that there was a lack of consistent and high-quality evidence to demonstrate the effective use of continuous glucose monitors in people not living with diabetes.
“At the present time, CGMs can be sold by companies but they are without a medical use.
“We have good evidence that they have transformed the lives of people with type 1 diabetes, and with good effect for people with type 2 diabetes on insulin therapy.
“But for people not living with diabetes, we don’t have the same data.”
Dr Brown said when companies are advertising “personalised nutrition to help people tailor their diet and keep their blood glucose within a normal range, the data is challenged, it’s not fully there.”
He added: “We are not saying CGMs might not have benefit. However, currently, there remains limited evidence to support the claims being made by commercial companies regarding the use of CGMs in people not living with diabetes.”
He added: “What constitutes a normal blood glucose level varies between individuals, it varies within the same individual at different times of the day.
“And CGM accuracy varies between the model of CGM that’s used.
“Even with good CGMs, there’s still variation in accuracy of around 20% on blood glucose being shown.
“A person not living with diabetes has a normal blood glucose ranging from between around 3.8 and 7.8.
“However, on the monitor that could display at readings between 2.6 to 9.4, therefore showing a potential low blood glucose or a high blood glucose, despite (the person) having normal blood glucose.
“This could impact people seeing results that are in fact normal blood glucose readings, and altering their diets accordingly.”
Dr Brown said people without diabetes will experience brief periods of having elevated blood glucose after meals but – as they generally have good blood glucose control anyway – these often return back to normal within one to two hours.
And while people with diabetes may have long periods of elevated blood glucose, which can put their health at risk in the long term, the shorter-term spikes after meals have not been linked to long-term poor health outcomes at the present time, he said.
He added: “I think there needs to be evidence behind some of the advertisement by CGM companies related to the evidence that is currently available.
“There’s a lot of anecdotal benefits being reported by people that might have used companies.
“However, what’s important is that companies stick to what the published data says.”
Dr Brown also said there needs to be better regulation of the devices.
“The review found evidence that, in people not living with diabetes using CGMs, this potentially could cause anxiety about what normal blood glucose is and also how that impacts on their diet,” he said.
“So there is a potential risk for the development of eating disorders such as orthorexia – an unhealthy obsession with eating ‘pure’ food.
“So, for example, there might be foods that they consume that elevate their blood glucose higher than they wish, and there is the potential that people might end up avoiding healthy foods that ‘spike their blood glucose’, but are healthy according to national dietary guidelines, in the idea that these spikes in blood glucose are actually a negative thing as opposed to a normal response to eating a food high in carbohydrate.”
Dr Brown called for more independent research into CGMs, adding that the majority of personalised nutrition data has come from industry-funded research.
“Particularly around CGMs, the vast majority of data even in people living with diabetes is industry-funded … So there is the need for more independent research to be conducted outside of commercially funded research,” he said.
CGMs are designed for people with diabetes and work by monitoring blood glucose levels in real time.
Readings can delivered to an insulin pump in people with type 1 diabetes, which delivers the correct amount of insulin required to keep blood sugar levels steady, and can be useful for people with type 2 diabetes.
The new study, published in Diabetic Medicine, included a review of 25 existing pieces of research and warned that CGMs are “gaining traction among people not living with diabetes”.
The researchers said: “We argue that there is a regulatory inadequacy that fuels ‘off-label’ CGM distribution and calls for the strengthening of post-market clinical follow-up oversight.
“We hope this will help to avert the continued misinformation risk to people not living with diabetes and ‘off-label’ exacerbation of health disparities.”
Prof Spector said: “Tracking our health data is the future of health and personalised medicine.
“We wouldn’t think twice about monitoring our blood pressure and how it changes; tracking blood glucose changes is likely to be as powerful a tool for prevention.
“The use of CGMs in people with diabetes and impaired glucose response has well-established benefits.
“Research of their use in people without diabetes is ongoing and points to being a useful approach, especially in the context of growing metabolic disease burden.
“Our research, and that of other colleagues, points to a benefit in understanding postprandial and diurnal changes in blood glucose levels.
“We welcome more research on the topic to personalise advice and improve metabolic health – this is definitely the future.”
