Medical Nutrition therapy can improve blood sugar levels in adults living with prediabetes

Dudzik JM, Senkus, KE, Evert AB, et al. The effectiveness of medical nutrition therapy provided by a dietitian in adults with prediabetes: A systematic review and meta-analysis Am J Clin Nutr. 2023; 118:892-910.

Review question

Is medical nutrition therapy from a registered dietitian effective in improving blood sugar levels, physical body measurements, measures of fat in the blood, and blood pressure in adults living with prediabetes, when compared to standard care?

Background

Prediabetes refers to blood sugar levels that are higher than normal but not yet high enough for a type 2 diabetes diagnosis. It increases the risk of developing type 2 diabetes but can be managed or even reversed with lifestyle changes, such as to diet and physical activity. Medical nutrition therapy delivered by a registered dietitian encourages healthy diets and behaviours, so investigating whether it can support people living with prediabetes is important.           

How the review was done

This is a systematic review and meta-analysis of 13 randomized controlled trails. These studies were published between 2008 and 2022 and included a total of 2308 participants.   

Key features of the studies:

• Participants were adults living with prediabetes, including those with overweight or obesity.
• Participants received either medical nutrition therapy alone or as a part of a multi-component strategy from a trained registered dietitian.
• Medical nutrition therapy generally lasted 3-6 months and consisted of both group and individual sessions that were delivered in-person and remotely. 
• Researchers measured changes in blood sugar levels (e.g., average blood sugar and fasting blood sugar), physical body measurements (e.g., weight, body mass index, waist circumference), measures of fat in the blood (e.g., total cholesterol, LDL “bad” cholesterol, HDL “good” cholesterol, triglycerides), and blood pressure (e.g., diastolic, systolic).
• Participants engaging in medical nutrition therapy were compared to control groups who received standard care (e.g., advice or care provided via educational booklets, newsletters, physicians, etc.).

What the researchers found

Moderate certainty evidence shows that compared to standard care, medical nutrition therapy with a registered dietitian likely reduces fasting blood sugar, weight, waist circumference, total cholesterol, and blood pressure, but likely doesn’t influence triglycerides. What's more, low certainty evidence shows this strategy may reduce average blood sugar, body mass index, and LDL “bad” cholesterol, and increase HDL “good” cholesterol. There is also low certainty, limited evidence of its impact on the occurrence of type 2 diabetes. Low certainty indicates that future research may change these results. More research is needed to increase certainty in some outcomes and provide a better understanding of optimal program characteristics.      

Conclusion

In adults living with prediabetes, medical nutrition therapy delivered by a registered dietitian appears to improve various types of blood sugar and fat in the blood, body measurements, and blood pressure compared to standard care.