There is scientific evidence that an insufficient intake of carbohydrates can cause anxiety. This phenomenon might give you a reason to avoid low-carb diets, especially if you are prone to getting anxiety disorders. However, anxiety and depression are also prominent in people with insulin resistance. In this patient population, fewer carbs might significantly improve mood disorders.
Carbohydrates and Mood
An insufficient intake of carbohydrates has been linked to a reduced amount of serotonin. Low levels of serotonin are a common trigger of anxiety. Judith Wurtman, director of the MIT Program in Women's Health, and colleagues found that carb restriction can make the brain stop regulating serotonin, which is directly correlated with mood disorders. Carbs are crucial to the maintenance of adequate serotonin levels, Wurtman says.
Mechanism of Action
According to biologist Judith Wurtman, founder of TRIAD, a Harvard Hospital weight loss center, although the amino acid tryptophan is essential to the synthesis of serotonin, carbs, not protein, can serve as a trigger of serotonin synthesis. One reason for this might be that serotonin doesn't just play a role as a mood regulator -- it also controls appetite. High amounts of glucose could signal to the brain that it needs to synthesize serotonin. Amino acids can be converted into glucose, but it is a much more difficult process and one that doesn't take place unless there is a serious energy deficiency. The presence of glucose appears to signal to the serotonin-producing cells that it is time to stop eating. These cells then respond by secreting serotonin.
Insulin Resistance
Even though a high intake of carbs might be an important factor in guaranteeing adequate levels of serotonin, there are some circumstances in which anxiety is better controlled through a low-carb diet. People resistant to insulin cannot easily lower their blood sugar. Because blood sugar does not reach the body's cells in insulin-resistant individuals, the cells are starving, in spite of the high blood glucose levels. In this case, it will not help to start eating loads of carbs, as this will just result in high amounts of glucose floating around in the blood. Restricting carbs and eating mostly fat and protein can help stabilize blood glucose and insulin levels. That by itself might be sufficient to raise brain levels of serotonin.
Stress
Insulin resistance and the accompanying low levels of insulin and high levels of glucose stimulate the adrenal glands, located atop the kidneys, which then produce stress hormones. Cortisol, in particular, plays a role in body metabolism. It normally ensures that muscles have enough energy in fight-and-flight situations. In cases of insulin resistance, the lack of insulin leads the body to react as if there is a shortage of insulin, so the adrenal glands secrete high levels of cortisol. Cortisol is a stress hormone which, if secreted constantly, will lead to, or maintain, anxiety. Breaking this vicious cycle of insulin resistance leading to a state of stress requires controlling the insulin resistance through diet.
References
- Mayo Clinic: Anxiety
- MIT News: Carbs are essential for effective dieting and good mood, Wurtman says
- Mayo Clinic: Atkins diet -- What's behind the claims?
- "Obesity Research"; "Brain serotonin, carbohydrate-craving, obesity and depression"; R.J. Wurtman et al; November 1995
- "The Serotonin Power Diet"; Judith Wurtman and Nina Frusztajer; 2006
