Sugar & Mental Health

photo credit: kurtis garbutt

photo credit: kurtis garbutt

It’s common knowledge that sugar can contribute to mood swings and hyperactivity.  It’s now been shown that sugar can be directly related to certain mental health disorders as well. 

Sugar and Mental Illness:

Psychiatric researcher Malcolm Peet did a cross cultural analysis of the relationship between diet and mental illness.  He found that increased sugar is correlated with increased risk of depression, and worse 2 year outcomes of schizophrenia symptoms.  

  •  One theory is that sugar suppresses a growth hormone (BDNF) that is very low in people with both depression and schizophrenia.  BDNF is vital in both the maintenance of healthy neurons and in the growth of new connections between neurons, which relates to the creation and maintenance of memory. 
  • Sugar is also a cause of chronic inflammation, which disrupts brain function, and the immune system.  Chronic inflammation is also positively correlated with depression and schizophrenia.

In one study by the University of Toronto it was found that depression patients displayed a 30% increase in some markers of brain inflammation.  The rates of inflammation correlated strongly with the severity of the patients’ depression.

Sugar Addiction:

Sugar floods the brain with its own natural opioids (like endorphins), and the feel-good neurotransmitters dopamine, and serotonin (that act as hormones), activating the same reward centers as many drugs, like cocaine.  People with addictive eating patterns feel a high merely by looking at sugary foods.  A study at UCSD used brain scans of obese children to show that they have a higher sense of food-reward when tasting sugar than do children in a healthy weight range; this could indicate a predisposition to crave sugar throughout their lives.

One study presented at the annual meeting of the Society for Neuroscience in SanDiego (2007) showed that rats will prefer sugar water to that laced with cocaine, and they will exhibit tolerance and withdrawal symptoms when denied sugar; this is true even for rats already addicted to cocaine.  

"The brain's pleasure center, called the nucleus accumbens, is essential for our survival as a species... Turn off pleasure, and you turn off the will to live... But long-term stimulation of the pleasure center drives the process of addiction... When you consume any substance of abuse, including sugar, the nucleus accumbens receives a dopamine signal, from which you experience pleasure. And so you consume more. The problem is that with prolonged exposure, the signal attenuates, gets weaker. So you have to consume more to get the same effect -- tolerance."

Sugar rich diets overstimulate these neurotransmitter pathways, draining the body’s reserves, and can contribute to symptoms of depression.

"And if you pull back on the substance, you go into withdrawal. Tolerance and withdrawal constitute addiction. And make no mistake, sugar is addictive." – Dr Lustig, UCSF

Increased anxiety and susceptibility to stress:

Sugar inhibits the body’s ability to regulate stress.  Panic, including hypervigilance, shaking, tension, brain fog, irritability, blurry vision, and fatigue can all be the result of sugar consumption.  Blood sugar levels spike, and then crash.  The crash when sugar intake is limited can appear very much like opiate withdrawal in terms of brain chemistry.

Severe or long-lasting traumatic early childhood experiences are risk factors for susceptibility to psychiatric disorders; they are correlated with increased cortisol, a stress hormone, and decreased volume in certain areas of the brain, including the hippocampus, a region of the brain vital to memory function and particularly susceptible to cortisol.  A recent rat study conducted by the University of New South Wales, Australia, and the Indian Council of Medical Research, India found that chronic consumption of sugar produced similar changes in hippocampal gene expression to those derived from early life stress.  “[diets rich in sugar promote] the expression of inflammation-related genes, and [reduce] the expression of genes involved in neurogenesis and neuroplasticity.” These changes directly affect the ability to recover from stressful situations. 

Cognitive function – A diet high in sugar will negatively affect learning and memory:

A study by UCLA showed that rats previously trained on a maze were unable to remember their way out after six weeks of consuming a diet rich in fructose.  Insulin resistance caused by the high sugar diet damaged communication, or synaptic activity, between brain cells which affects memory and learning.  In general insulin strengthens synaptic activity allowing better communication between cells and improved memory, so it makes sense that insulin resistance would damage it.  In contrast, rats fed a healthy diet, and rats fed a diet high in fructose but that also included omega 3 fatty acids were able to remember their way out of the maze faster.  The omega 3’s seemed to lessen cognitive impairment by protecting the synapses between brain cells.

80% of foods in the American diet contain sugar.  Foods high in sugar and fat have been shown to relieve stress and anxiety; it’s no surprise that stress and poor diet often appear together.  Furthermore, food addiction is frequently connected to unresolved emotional patterns.

All this is to say:

The more I learn about sugar and its relationship to mental health, the more I encourage my clients to take a close look at their diet and develop awareness of how their diet is related to their mood.  For some, we even go the extra step of trying to limit the consumption of sugar, at least for a while to track if they notice any effect.

For more interesting information about the effects of sugar on the brain and body: