Two new studies published in The BMJ claim to have identified factors associated with increased risk of type 2 diabetes: regular sugary drink consumption and a combination of low birth weight and an unhealthy lifestyle in adulthood.

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Higher consumption of sugary drinks - defined as one 250 ml serving daily - was associated with an 18% increased risk of type 2 diabetes before adjusting for obesity and a 13% increased risk after adjustment.

Around 29.1 million people in the US have diabetes, with type 2 diabetes accounting for around 90-95% of all cases.

Some well-established risk factors for type 2 diabetes include overweight and obesity, lack of physical activity and family history of the condition. But increasingly, studies are identifying other factors that may influence a person's likelihood of developing type 2 diabetes.

In January, for example, Medical News Today reported on a study associating vitamin A deficiency with increased risk of type 2 diabetes, while another study found use of the cholesterol-lowering drugs statins may raise risk for the condition.

In the first of these latest studies, study co-author Fumiaki Imamura, of the School of Clinical Medicine at the University of Cambridge in the UK, and colleagues set out to investigate whether regular consumption of sugar-sweetened drinks, fruit juice or artificially sweetened drinks may influence the risk of type 2 diabetes.

Sugary drinks have been associated with greater risk of obesity - a major risk factor for type 2 diabetes - though Imamura and colleagues note it was unclear whether the beverages influence diabetes risk after accounting for obesity status.

Fruit juice and artificially sweetened beverages are often seen as healthier alternatives to sugar-sweetened drinks, the team notes, but it is unclear whether consuming such drinks can prevent type 2 diabetes.

Regular sugary drink consumption 'increases type 2 diabetes risk by up to 18%'

To reach their findings, the team conducted a systematic review and meta-analysis of 17 observational studies involving 38,253 cases of type 2 diabetes.

All studies reported participants' consumption of sugary drinks, fruit juice and artificially sweetened drinks, and none of the studies included were industry funded, the researchers note.

The results of the analysis revealed that higher consumption of sugary drinks - defined as one 250 ml serving daily - was associated with an 18% increased risk of type 2 diabetes before adjusting for obesity and a 13% increased risk after adjustment.

The researchers used their data to estimate the risk of type 2 diabetes risk attributable to sugar-sweetened beverages among the UK and US populations between 2010 and 2020.

They estimate that regular consumption of sugary drinks may account for around 2 million new cases of type 2 diabetes in the US and 80,000 new cases in the UK over the 10-year period.

The researchers also identified a positive link between regular consumption of fruit juice and artificially sweetened drinks and greater type 2 diabetes risk, though they say these findings were likely to involve bias.

They note, however, that they found no evidence supporting the consumption of these drinks for prevention of type 2 diabetes.

Commenting on their overall findings, the researchers say:

"Although causality has not been established and precision needs to be improved, this study informs the potential efficacy of reducing the consumption of sugar-sweetened beverages in a contemporary population.

Moreover, findings support that neither artificially sweetened beverages nor fruit juice are suitable alternatives to sugar-sweetened beverages for the prevention of type 2 diabetes."

Combination of low birth weight, unhealthy lifestyle boosts type 2 diabetes risk

The second study, conducted by Yanping Li of the Harvard School of Public Health in Boston, MA, and colleagues, is the first to investigate whether birth weight combined with lifestyle in adulthood affects the risk of type 2 diabetes.

According to the background of the study, past research has indicated that early life factors that raise the risk for type 2 diabetes and other metabolic disorders may be modified by lifestyle changes in adulthood.

"However, very few studies have comprehensively explored the joint effect of prenatal and postnatal factors on risk of diabetes," say the authors.

The researchers assessed data from three ongoing trials involving 149,794 healthy men and women. Participants were followed-up for around 20-30 years, during which time 11,709 new cases of type 2 diabetes were identified.

The birth weight of all participants was recorded, and medical questionnaires were completed every 2 years, disclosing information on participants' health and lifestyle.

An unhealthy lifestyle score was given to each subject, calculated using five lifestyle factors: smoking, diet, physical activity, alcohol consumption and body mass index (BMI).

The team found that independently, low birth weight and an unhealthy lifestyle in adulthood were associated with greater risk of type 2 diabetes. However, an even greater risk was identified for subjects with both factors combined.

"The joint effect could be decomposed to 22% for a lower birth weight alone, 59% for an unhealthier lifestyle alone, and 18% for an additive interaction between low birth weight and unhealthy lifestyle," say the authors.

In other words, the findings indicate that 18% of type 2 diabetes cases would occur as a result of low birth weight and an unhealthy lifestyle in adulthood combined, but these cases would not occur if just one of these factors was present.

Commenting on their study results, Li and colleagues say:

"The finding suggests that most cases of type 2 diabetes could be prevented by the adoption of a healthier lifestyle, but simultaneous improvement of both prenatal and postnatal factors could further prevent additional cases."

This research supports findings from another study reported by MNT earlier this month, which suggests type 2 diabetes can be averted through eating healthily and increasing physical activity.