Depression and Anxiety: Debunking the Sugar Myth on Mental Health

Back in 1989, a “groundbreaking” study suggested that carbohydrates might help alleviate depression symptoms. [1] The theory, presented by Dr. Judith Wurtman, then the research director for women’s health at MIT, proposed that when we feel down or anxious, we tend to crave carbs like sweets or cakes. This is because depression can lead to a serotonin deficiency in the central nervous system, and serotonin’s precursor, tryptophan, often gets sidelined after a high-protein meal. As a result, it struggles to cross the blood-brain barrier and reach the central nervous system.

Carbohydrates, however, trigger insulin release, which carries glucose and various amino acids, including tryptophan, into muscle tissues. This provides tryptophan an opportunity to enter the central nervous system, potentially helping to increase serotonin levels and improve mood. So the theory goes that consuming carbohydrates might help in treating depression.

Does LNAA Lower Serotonin Synthesis?

Now, let’s explain the concept of large neutral amino acids (LNAA). LNAA, due to their “bulky size,” cannot easily pass through the blood-brain barrier by themselves and need specific carriers and pathways to enter the brain.

Tryptophan is one of these LNAA, and you can think of it as being on the south bank of a river. It can only cross over to the north bank, where the central nervous system is, by taking a “bus” through a bridge. However, tryptophan is not the only passenger waiting for the bus; other LNAA, such as leucine, phenylalanine, and threonine, are also in line.

When you consume protein, you ingest various amino acids, and tryptophan is usually the least abundant among them. So, when you eat protein, different LNAA compete with tryptophan for a spot on the “bus” to the central nervous system, making it less effective in increasing serotonin levels. Hence, the dietary protein is not the best way to increase tryptophan in the central nervous system. This part of Wurtman’s logic makes sense so far. [2]

But does this theory hold up? Over the years, many studies have sought to validate Wurtman’s idea, but results have been inconclusive. It’s important to consider that increasing tryptophan in the blood and brain through diet changes is challenging. Several research reviews have debunked the myth that altering blood tryptophan levels significantly affects mood. [3-4]

How Sugar and Other Refined Carb Affect Mental Health

Carbohydrates can impact mental health. Studies on mice showed that a diet high in refined carbs led to obesity, anxiety, and signs of depression. [5]

In humans, research found that those who consumed more sugary desserts and drinks had a 23% higher risk of developing mental health issues.[6]  

Drinking sugary beverages, like soda, daily could increase depression risk by 5-25%. So, reducing refined carbs and sugary foods may benefit mental well-being. [7]

Moreover, Wurtman’s theory of “comfort foods” being a remedy for stress and anxiety might not be as simple as it seems. Recent animal studies suggest that eating sweet treats during times of stress could create a psychological dependency through dopamine’s reward mechanisms. When the treats are removed, this can lead to feelings of depression and anxiety. Thus, relying on sugary foods as a coping mechanism might not be a healthy solution. [8]

Summary.

While the initial idea of carbohydrates positively affecting depression might not be fully supported, it’s crucial to adopt a balanced approach to diet and mental well-being. Instead of indulging in sugary treats for relief, consider adding more fruits, vegetables, and whole grains to your diet.

Let’s debunk the sugar myth and focus on nourishing both body and mind for better overall well-being.