Fish diet best for reducing risk of developing type 2 diabetes

27th April 2022

A fish diet rather than any other type of diet appears to be associated with the greatest reduction in the risk of developing type 2 diabetes

A fish diet appears to be the best way of reducing the risk of developing type 2 diabetes in comparison to either a poultry, meat-based or even a vegetarian diet. This was the conclusion of an analysis of the UK Biobank by researchers from the UK, Thailand and Chile.

Type 2 diabetes is a metabolic disorder that results in hyperglycaemia and is a global health concern. One estimate from 2017 suggested that approximately 462 million individuals were affected (6.28% of the world’s population), leading to 1 million deaths per year.

Many cases of type 2 diabetes could potentially be prevented by lifestyle changes, including maintaining a healthy body weight, consuming a healthy diet, staying physically active, not smoking and drinking alcohol in moderation. 

In fact, a 2017 systemic review identified how the risk of diabetes is reduced by increased consumption of whole grains, fruits and dairy, but that the risk is increased by greater consumption of red meat, processed meat and sugar sweetened beverages. However, there is some uncertainty over whether any specific type of eating pattern e.g., fish diet, poultry or vegetarianism, has a greater impact on the risk of developing diabetes.

For the present analysis, the team turned to the UK Biobank database to explore the associations between different diets and the risk of incident type 2 diabetes. In addition, the researchers examined the extent to which adiposity might impact on these associations.

Within the UK Biobank, participants complete food frequency questionnaires and based on responses, individuals were categorised as vegetarian, fish eaters, fish and poultry eaters and finally meat eaters. A number of participants reported eating a varied diet and the effect on this type of diet was analysed separately.

The results were analysed using Cox-proportional hazard models which provided a measure of the association between the different diets and the risk of type 2 diabetes and models were adjusted for several factors including age, sex, alcohol intake, smoking status etc.

Fish diet and the risk of type 2 diabetes

A total of 203,790 individuals were included in the analysis with 1.6% who were vegetarian, 2.2% fish diet, 1.1% fish and poultry eaters, 87.3% meat eaters and 7.8% who reported eating a varied diet. The mean age of the groups ranged from 52.8 to 56.5 years and after excluding the first two years, individuals were followed-up for a median of 5.4 years. During the follow-up, 5,067 (2.5%) participants developed type 2 diabetes.

Using meat eaters as the reference, a fish diet had the lowest risk of developing type 2 diabetes (hazard ratio, HR = 0.41, 95% CI 0.31 – 0.55, p < 0.0001), followed by fish and poultry eaters (HR = 0.61, 95% CI 0.44 – 0.86). The association with vegetarian and a varied diet were non-significant. However, in the fully adjusted models, a significant association remained only for a fish diet but not for fish and poultry eaters or any of the other diets.

Interestingly, general obesity was a partial mediator for fish diets, accounting for 49.8% of their lower risk of developing type 2 diabetes.

The authors concluded that fish diets produced the greatest reduction in the risk of developing diabetes and that this effect was largely due to the fact that fish eaters had a lower level of adiposity.

Citation
Boonpor J et al. Types of Diet, Obesity, and Incident Type 2 Diabetes: Findings from The UK Biobank Prospective Cohort Study Diabetes Obes Metab 2022

Prospective analysis shows regular meat eaters at higher risk of several types of cancer

21st March 2022

A UK study has found that meat eaters have an increased risk of developing cancer compared with either low meat eaters, pescatarians or vegetarians

Individuals who are regular meat eaters have been found to be at a higher risk of all and some specific cancers compared to those who are either low meat eaters, pescatarians or vegetarians. This was the finding of a study of the UK Biobank database by researchers from the Cancer Epidemiology Unit, University of Oxford, Oxford, UK.

Cancer has been declared by the World Health Organization (WHO) as a leading cause of death worldwide accounting for nearly one in six of all deaths (10 million in 2020). Moreover, according to WHO, breast, lung, colorectal and prostate cancers are the most common forms of the disease.

Understanding the causal relationship between dietary patterns or even particular dietary components and cancer aetiology and prevention is a challenge.

For example, undertaking randomised controlled intervention trials to examine the association between diet and cancer outcomes are not feasible, for a number of reasons including cost, the difficulty of ensuring compliance among control and intervention groups as well as the long time-frame and exposure necessary to affect the carcinogenesis process.

Although it has been shown that the risk of some cancers is lower in fish eaters and vegetarians than in meat eaters, it is not universally true with other work showing no statistically significant associations with dietary pattern and risk of premenopausal breast cancer.

For the present analysis, the Oxford team examined the relationship between those who ate meat at least 5 times a week, low meat consumers (< 5 times/week), pescatarians and vegetarians and the risk of all cancers and in particular, colorectal, postmenopausal breast and prostate cancers.

They used data held in the UK Biobank and excluded individuals with a cancer diagnosis at recruitment. Participants completed an online questionnaire at recruitment into the database which asked about consumption and frequency of meat intake.

The team also assessed whether specific hormones such as insulin-like growth factor-1 and testosterone as well as body mass index, might have potential mediator effects on the association between dietary patterns and cancer risk. The risks for the development of all and any of the specific cancers, were assessed using meat eaters as the reference group.

Meat eaters and cancer risk

A total of 247,571 individuals with a mean age of 56 years (46.4% female) were classed as meat eaters, 205,385 as low-meat eaters, 10,696 as pescatarians and 8,685 as vegetarians. After an average follow-up of 11.4 years, 54,861 incidence cases of cancer occurred; 5882 colorectal, 7537 women with postmenopausal breast cancer, 9501 men with prostate cancer.

After adjustment for several factors such as smoking status, physical activity etc, a vegetarian diet was associated with a 14% lower risk of all cancers compared to the reference group. (hazard ratio, HR = 0.86, 95% CI 0.80 – 0.93). This risk was also significantly reduced for breast cancer (HR = 0.82) and prostate cancer (HR = 0.69).

For pescatarians, there was also a lower risk of all cancers (HR = 0.90) compared to the reference meat group and for prostate cancer (HR = 0.80). For those categorised as low-meat eaters, the risks were only significantly lower for colorectal cancer (HR = 0.91).

After adjustment for possible mediators, only body mass index was found to be relevant and the risk of all cancers was slightly attenuated for vegetarians (HR = 0.88) and pescatarians (HR = 0.92) but remained significant.

Furthermore, the reduced cancer risk remained significant among pescatarians and vegetarians but only for prostate cancer.

The authors concluded that being a pescatarian or vegetarian was associated with a lower risk of all cancers and that this might be attributable to differences in dietary factors in comparison to those who regularly eat meat.

However, they added that it was unclear if these associations are causal or due to residual confounding, i.e., due to other, but unmeasured factors.

Citation
Watling CZ et al. Risk of cancer in regular and low meat-eaters, fish-eaters, and vegetarians: a prospective analysis of UK Biobank participants BMC Med 2022