Unstable Blood Sugar Linked to Low Mood? Doctor Warns Against Eating Sweets or Drinking Sugary Beverages at This Time

When feeling stressed or down, many people instinctively reach for sweets to feel better. While this 'sweet comfort' may provide brief relief, its effects are short-lived. High-sugar foods might offer momentary satisfaction, but for some individuals, they can cause blood glucose levels to swing wildly like a rollercoaster after meals, resulting in post-meal fatigue, reduced attention, and stronger cravings.

A study published in Acta Diabetologica does not prove a causal relationship between blood sugar and mood, but it found that the less time people spent with stable glucose levels, the more frequently words related to sadness and depression appeared in their personal writings.

Dr. Chou Chien-An, a metabolism and weight management specialist at Chuyi Clinic, points out that dietary adjustments don't mean completely eliminating sugar from daily life, nor should all emotional issues be blamed on blood sugar. Conditions like depression, anxiety, or chronic stress require professional evaluation. However, if someone habitually relies on high-sugar foods to relieve stress, leading to chronically unstable blood glucose, it may increase the brain's emotional regulation burden. This is primarily linked to four key mechanisms:

- Neuroinflammation and oxidative stress: Long-term consumption of high-sugar, high-fat, and processed foods may lead to chronic inflammation and metabolic dysfunction. In individuals with diabetes or metabolic abnormalities, glucose fluctuations generate oxidative stress, which is associated with neuroinflammation and cognitive changes.

- Impaired neurotransmitter synthesis: Serotonin, dopamine, and GABA are key neurotransmitters for emotional stability. Their synthesis and regulation require nutrients like magnesium, zinc, and B vitamins—especially B6, B12, and folate. Regularly replacing meals with sweets or sugary drinks may deprive the body of these nutrients, worsening anxiety and low mood.

- HPA axis dysregulation: Stress, poor sleep, and blood sugar fluctuations can mutually affect the hypothalamic-pituitary-adrenal (HPA) axis. Cortisol promotes gluconeogenesis in the liver, raises blood glucose, and reduces glucose uptake in peripheral tissues.

- Gut-brain axis imbalance: The enteric nervous system in the gut, often called the 'second brain,' communicates bidirectionally with the brain via neural, immune, and microbial metabolic pathways. Research shows that long-term excessive intake of added sugars may alter gut microbiota and intestinal barrier function, disrupting signals from the gut to the brain and impairing emotional regulation.

The Acta Diabetologica study observed 58 adult patients with type 1 diabetes who used continuous glucose monitoring (CGM) devices long-term. Researchers analyzed 14 days of CGM data and the participants' personal written reflections on their CGM experience. Results showed that the longer glucose levels remained within the target range (TIR), the fewer expressions of sadness and depression appeared in their writings. Conversely, longer time in hyperglycemia (TAR) correlated with more negative emotions.

To maintain emotional stability and metabolic health, Dr. Chou recommends starting with simple dietary changes to reduce glucose fluctuations. Avoid eating sweets or drinking sugary beverages on an empty stomach. If cravings arise, consume small amounts after a meal. Prioritize protein and vegetables at each meal—such as eggs, tofu, fish, chicken, or unsweetened soy milk—before finishing with moderate portions of starches and whole grains. This approach enhances satiety and slows post-meal glucose spikes.

Frequent post-meal drowsiness, afternoon fatigue, poor concentration, uncontrollable cravings, or significant mood swings may be linked to sleep, stress, or meal composition—and could signal unstable blood sugar or metabolic imbalance. If combined with overweight, high waist circumference, fatty liver, family history of diabetes, hypertension, or abnormal blood lipids, individuals should consult a physician or dietitian. Tests like fasting glucose and HbA1c may be recommended to assess metabolic health.