Unfortunately, not many clinical trials have been conducted to investigate the link between diet and the various mental health disorders such as depression and anxiety. However, there are enough case reports and anecdotal evidence to suggest that there may be some benefits to reducing intake of processed foods, but there’s still more research to be done to investigate the impact of low carbohydrate diets.

What’s the latest study say?

A recent Dutch study investigated the links between insulin resistance and the development of major depressive disorders. In the study, 601 participants (18–65 years old) without a lifetime history of depression or anxiety disorders were followed for 9 years.

Three surrogate markers of insulin resistance – high triglyceride-HDL (high-density lipoprotein) ratio; prediabetes, as indicated by fasting plasma glucose level; and high central adiposity, as measured by waist circumference) – were measured.

What did the study entail?

• 14% of the sample developed a major depressive disorder during the nine year follow-up period.
• Higher triglyceride-HDL ratio was positively associated with an increased risk for incident major depression, as were higher fasting plasma glucose levels and higher waist circumference.
• Specifically they found that a moderate clinical increase in a surrogate measure of insulin resistance (i.e., a one-unit change in triglyceride-HDL ratio) corresponded to an 89% increase in the rate of incident major depressive disorder in the a 9-year follow-up period.

What does it mean?

The study shows a clear association between insulin resistance and depression. In recent years, there has been considerable interest in the link between diet and depression, and this study is a further indication of that link.

There have been a number of studies, including one from Felice Jacka and her colleagues at Deakin University, which have demonstrated that reducing intake of ‘extras’ foods, such as sweets, refined cereals, fried food, fast food, processed meats and sugary drinks can have a significant impact on depression. The impact of improving diet is at least as powerful as anti-depressant medication.

What now?

We know that a low carbohydrate diet can reduce, and even reverse insulin resistance, so the logical next step is further to study the impact of a low carb diet on depression.

References

Watson KT, Simard JF, Henderson VW, Nutkiewicz L, Lamers F, Nasca C, Rasgon N, Penninx BWJH. Incident major depressive disorder predicted by three measures of insulin resistance: A Dutch cohort study. Am J Psychiatry. 2021 Oct 1;178(10):914-920.

Jacka FN, O’Neil A, Opie R, Itsiopoulos C, Cotton S, Mohebbi M, Castle D, Dash S, Mihalopoulos C, Chatterton ML, Brazionis L, Dean OM, Hodge AM, Berk M. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med. 2017 Jan 30;15(1):23.