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Healthy Diet Linked to Better Blood Glucose, Lower Type 2 Diabetes Risk in Genetically Susceptible Individuals

Somi Igbene PhD ANutrNovember 21, 2021

Sticking to a healthy diet may improve blood glucose control and lower the odds of type 2 diabetes (T2D) in individuals with a high genetic risk of the disease, a new study has found. 

Notably, in individuals with a high genetic risk, each standard deviation increase in diet quality reduced the risk of type 2 diabetes by nine per cent and lowered glycated haemoglobin (HbA1c) levels by 0.146 mmol/mol. 

The study, “Effect of diet quality and genetic predisposition on haemoglobin A1C and type 2 diabetes risk: gene-diet interaction in 357,419 individuals,” was published in Diabetes Care

T2D arises from a complex interaction between genetic and lifestyle factors, including diet. So far, scientists have identified over 500 gene mutations that increase the odds of T2D. Combining these mutations have allowed scientists to create genetic risk scores to predict risk. 

Research has consistently shown that healthy dietary patterns such as the Mediterranean diet and the Dietary Approach to Stop Hypertension (DASH) diet can reduce the risk of developing T2D. These diets recommend consuming whole grains, vegetables, fruits, legumes, fish, and nuts and limiting refined grains, processed meats and sugar-sweetened beverages. 

However, these diets don’t have equal health benefits for all individuals because of genetic variations and how diet and genes interact to affect their responses. If scientists understand how gene-diet interactions affect T2D development, they can identify high-risk populations and effectively develop personalised nutrition plans to prevent T2D. 

However, scientists are unsure how overall diet quality affects the risk of T2D in people who are genetically prone to the disease. 

To better understand, a team of researchers in the United Kingdom (UK) evaluated data from the UK Biobank study, a cohort of around half a million adults aged 40-69 in the UK.  All study participants completed questionnaires, provided biological samples, and underwent physical examinations before enrolling. 

The scientists calculated dietary quality scores for each participant based on information provided in their food frequency questionnaires. They also calculated genetic risk scores for each participant. The scientists then examined how diet quality and genetic risk scores affected HbA1c levels and T2D development. 

A total of 357,419 adults aged 40–69 years were included in the analysis. Participants with higher diet quality scores were generally older, mostly women, highly educated, and more physically active with lower body mass index. They also had high cholesterol levels, took multivitamin supplements, aspirin, and lipid-lowering medication. 

After a mean follow-up period of 8.1 years, 5,663 participants developed T2D. There was a significant link between diet quality, genetic risk and the risk of type 2 diabetes. Participants with a higher genetic risk had a higher risk of type 2 diabetes; this link was more evident in people with low diet quality. 

Compared to participants with the lowest genetic risk and highest diet quality, those with the highest genetic risk and lowest diet quality had a 2.29-fold increase in T2D risk. And after adjusting for various factors, the scientists found that for each standard deviation increase in genetic risk, there was a 54% higher risk of T2D. Conversely, for each standard deviation increase in diet quality, there was a nine per cent decrease in T2D risk. 

Notably, a simultaneous increase in diet quality and genetic risk scores was linked to a three per cent decrease in T2D risk.

There was also a significant link between diet quality score, genetic risk score and HbA1c levels. While each standard deviation increase in genetic risk score was associated with a 0.544 mmol/mol increase in HbA1c levels, each standard deviation increase in diet quality score was associated with a 0.146 mmol/mol decrease in HbA1c.

Interestingly, a simultaneous increase in diet quality and genetic risk score was linked with a 0.050 mmol/mol decrease in HbA1clevels. 

It is worth noting that there were no significant links between diet quality and T2D risk in individuals with low genetic risk. 

“Higher diet quality was significantly associated with reductions in HbA1C and T2D risk among individuals at higher genetic risk for T2D but not among those at lower genetic risk,” the researchers wrote. 

“Besides, individuals at an extremely high genetic risk (greater than 95%) had a sharp reduction in T2D risk related to improved diet quality,” they wrote. 

“We also detected that the protective associations of the diet quality score with T2D risk were not significant among those with a genetic risk score less than 40%, which implied that for individuals with relatively low genetic risk, the effect of a high-quality diet might be weak and that modifications of other lifestyle factors, such as physical activity and smoking may be considered,” the researchers wrote. 

Further analysis of the data showed a significant link between diet quality score, genetic risk score and T2D risk in only men. However, the association between diet quality score, genetic risk score and HbA1c levels was significant for men and women. 

One limitation of the study was that the cohort consisted of White Europeans only, so the findings may not be generalised to other ethnic groups. 

“We showed that the protective associations of diet quality with T2D and blood HbA1C were modified by the genetic risk. These results indicate that individuals with higher genetic risk, especially extremely high genetic risk, may benefit more from adherence to a healthy diet in T2D prevention,” the researchers wrote. 

“Our findings provide important evidence to support tailoring dietary recommendations to an individual’s genetic makeup for T2D prevention,” they wrote. 

The researchers also wrote that more studies with large cohorts are needed to support the findings of their research. 

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