Vitamin D deficiency may increase the risk of depression symptoms in Chinese women with prediabetes, a new study has found.

Prediabetic women with sufficient vitamin D levels had a 72% lower risk of reporting depression symptoms than those with deficiencies.

“This study provides the first evidence that an association exists between vitamin D and depression in prediabetes,” the researchers wrote. “Vitamin D supplementation may be an effective way to decrease the risk of depression symptoms in adults with prediabetes and to prevent the development of prediabetes to diabetes.”

The study, “Association between serum (OH) D levels and depression symptoms in adults with prediabetes,” was published in Diabetes & Metabolic Syndrome: Clinical Research & Reviews.

Depression is a significant public health problem and economic burden associated with disability and early mortality. According to the World Health Organisation (WHO), it affects an estimated 264 million people globally, with people with prediabetes twice as likely to develop depression.

Vitamin D, a fat-soluble vitamin that regulates blood sugar levels, promotes communication between nerve cells and maintains blood levels of calcium and phosphate to support bone and muscle health, also plays a vital role in brain health. It activates serotonin ­– the feel-good hormone – that regulates dopamine and norepinephrine production. Of note, dopamine regulates pleasure and motivation, while norepinephrine controls alertness, arousal and attention.

Recent studies have tied low vitamin D levels to depression, but no studies have investigated the link between vitamin D levels and depression in Chinese individuals with prediabetes.

Chinese researchers analysed data from participants enrolled on the Tianjin Chronic Low-grade Systemic Inflammation and Health (TCLSIH) study. After exclusions, the researchers included 4051 individuals (56.5% male) with prediabetes aged 20–65 years in the study. Their weight, blood fats, waist circumference, blood pressure and body mass index (BMI) were measured. All participants completed the Chinese version of the Self-Rating Depression Scale (SDS) to assess their symptoms of depression, and their blood levels of vitamin D (measured as serum 25 (OH) D concentration) were evaluated. Participants’ serum vitamin D levels were grouped into three categories: less than 50 nmol/L (deficient), 50-75 nmol/L (insufficient) and greater than 75 nmol/L (sufficient).

Women More Likely to Report Depression Symptoms

The rates of vitamin D deficiency were higher in females (70.9%) compared to men (62.4%). Males with vitamin D deficiency were more likely to have higher waist circumferences, triglycerides and lower high-density lipoprotein cholesterol (HDL-C) than men with vitamin D sufficiency. These correlations were absent in females.

The prevalence of depression in the cohort was 14.2%, 12.5% in males and 16.4% in females. Vitamin D levels were unrelated to depression symptoms in males after the researchers considered confounding factors. In contrast, vitamin D deficiency was significantly linked to depression symptoms in women, increasing the risk of depression symptoms by 72%.

“After adjustment for age, BMI and other confounding factors, we identified a negative correlation between serum 25 (OH) D concentrations and symptoms of depression in females but not in males. To our knowledge, this is the first study to examine the relationship between vitamin D and symptoms of depression in prediabetic people,” the researchers wrote.

According to the researchers, an explanation for the sex differences in the impact of vitamin D status on depression may be differences in oestrogen and progesterone production. Another could be that women internalise symptoms more often than men.

One limitation of the study was that the researchers assessed depression via self-report questionnaires rather than interviews with qualified psychologists.

“The correlation between low 25-hydroxyvitamin D levels and increased depressed symptoms shows that vitamin D insufficiency may be a risk factor for late-life depression,” the researchers wrote.

“Further large prospective epidemiological research will be necessary to elucidate this conclusion.”

Key Message

More studies are needed to confirm the link between vitamin D, depression and prediabetes.

But it is worth noting that many people of Black descent and those who live in cold climates, cover their skin for religious reasons, or otherwise have an increased risk of vitamin D deficiency.

Ask your physician/doctor for a vitamin D blood test if you haven’t had one recently and to check your levels. They will prescribe a vitamin D supplement if needed.