Findings from a large prospective study suggest that regular consumption of yoghurt may help protect against the development of type 2 diabetes.

The EPIC study is a European multicentre trial that has been prospectively investigating the link between diet and cancer. The branch of the trial sited in Norfolk had a nested cohort of patients who were also followed up for incident diabetes.

Between 1993 and 1997, the EPIC-Norfolk study recruited a UK-based population cohort of 25,639 men and women aged between 40 and 79 at baseline. The participants attended a baseline health examination at their GP's surgery, after which follow-up data collection points included a postal questionnaire at 18 months.

A second health examination visit in 1998-2000 and a postal questionnaire in 2002-2004.

The study was designed to link dietary patterns with disease, and the data were gathered from a highly detailed diet diary, kept for a week at the start of the study.

Food weights and content were estimated from photographs of standard portion sizes, household measures and standard units.

Nurses trained in the study helped participants complete the initial diary entry based on recall of the previous day, and this was the first of the seven days of recording. Other lifestyle and health characteristics were gathered by a self-administered questionnaire and baseline recordings of height, weight, BMI, waist circumference, blood pressure and blood chemistry were taken.

From this population a nested case cohort of 4,000 participants was randomly selected for the diabetes study. After exclusions, 3,502 participants remained eligible and 128 cases of type 2 diabetes were diagnosed by the time the study closed at the end of July 2006.

The intake of dairy food was calculated in total, and sub-classified into high fat (≥ 3.9% fat) and low fat and also divided into milk, cheese and yoghurt. Yoghurt is the main component of the category of ‘low fat fermented dairy products’.

The largest contributors to dairy intake were milk (81.7%), cheese (8.7%) and yoghurt (7.6%). The mean dairy intake in the cohort was 269 g/day, and 65% on average was from low-fat sources. Interestingly, high total dairy intake equated with men with lifestyles that were healthier than average. High yoghurt consumption was found more often in women, and was associated with lower intakes of saturated fat.

When adjustment for confounding variables was made, the only dietary fat component with a significant association with diabetes incidence was the yoghurt group. Increased intake of yoghurt was associated with a reduced incidence of type 2 diabetes, HR 0.72 (95% CI: 0.55-0.95; Ptrend = 0.017).

The power of this study compared with many others was the prospective completion of the food frequency questionnaire, and the higher level of detail about subgroups of the main dietary components.

The conventional perception of the saturated fat in dairy produce is of association with adverse health outcomes. Although mechanisms are speculative the fermentation of yoghurt may be adding other beneficial compounds to the vitamins and minerals that are also a positive feature of dairy produce in the diet.

It may explain the mixture of findings from previous studies that have not divided the dietary fat intake in such detail.

There is a lot of interest at present in preventing diabetes in at-risk populations, and a need for clear public health messages. As well as exercise, a healthy, balanced diet remains the cornerstone of prevention. However, some helpful messages are coming from recent studies, that suggest the intake of coffee, specific fruits and now yoghurt may be especially beneficial food choices to prevent type 2 diabetes.

Dr Matthew Lockyer