Foods have an immense impact on your brain, and eating whole foods as described in my nutrition plan is the best way to support both your physical and mental health. Based on the evidence, avoiding sugar (particularly fructose) is an important prevention and treatment strategy for anxiety and depression, both of which are rising in prevalence.
A number of studies have linked high-sugar diets to a higher risk of depression. Most recently, men consuming more than 67 grams of sugar per day were found to be 23 percent more likely to develop anxiety or depression over the course of five years compared to those whose sugar consumption was less than 40 grams per day.1,2,3
This held true even after accounting for other contributing factors, such as socioeconomic status, exercise, alcohol use, smoking, other eating habits, body weight and general physical health. As noted by lead author Anika Knüppel,4 a Ph.D. student at the Institute of Epidemiology and Public Health at University College London:5
“Sweet food has been found to induce positive feelings in the short-term. People experiencing low mood may eat sugary foods in the hope of alleviating negative feelings. Our study suggests a high intake of sugary foods is more likely to have the opposite effect on mental health in the long-term.”
Other Research Showing High-Sugar Diets Promote Depression
While the featured study could neither ascertain a mechanism for the link between sugar consumption and depression risk, nor could it establish causation, it adds support to other studies that have found the same link. For example, research6 published in 2002, which correlated per capita consumption of sugar with prevalence of major depression in six countries, found “a highly significant correlation between sugar consumption and the annual rate of depression.”
A Spanish study7 published in 2011 linked depression specifically to consumption of baked goods. Those who ate the most baked goods had a 38 percent higher risk of depression than those who ate the least.
Similarly, a 2016 study,8 summarized in the video above, found a strong link between high-sugar diets (high-glycemic foods such as processed foods, sweetened beverages and refined grains) and depression in postmenopausal women. The higher the women’s dietary glycemic index, the higher their risk of depression. A diet high in whole fruit, fiber, vegetables and lactose was associated with lowered odds of depression.
How Sugar Raises Your Depression Risk
A number of other studies have also identified mechanisms by which excessive sugar consumption can wreak havoc with your mental health. For example, eating excessive amounts of sugar:
•Contributes to insulin and leptin resistance and impaired signaling, which play a significant role in mental health.
•Suppresses activity of brain derived neurotrophic factor (BDNF), a key growth hormone that promotes healthy brain neurons. BDNF levels tend to be critically low in both depression and schizophrenia, and animal models suggest this may actually be a causative factor.
•Affects dopamine, a neurotransmitter that fuels your brain’s reward system9 (hence sugar’s addictive potential10,11,12) and is known to play a role in mood disorders.13
•Damages your mitochondria, which can have body-wide effects. Your mitochondria generate the vast majority of the energy (adenosine triphosphate or ATP) in your body. When sugar is your primary fuel, excessive reactive oxygen species (ROS) and secondary free radicals are created, which damage cellular mitochondrial membranes and DNA.
Needless to say, as your mitochondria are damaged, the energy currency in your body declines and your brain will struggle to work properly. Healthy dietary fats, on the other hand, create far fewer ROS and free radicals. Fats are also critical for the health of cellular membranes and many other biological functions, including and especially the functioning of your brain.
Among the most important fats for brain function and mental health are the long-chained animal-based omega-3 fats DHA and EPA. Not only are they anti-inflammatory, but DHA is actually a component in every cell of your body, and 90 percent of the omega-3 fat found in brain tissue is DHA.
•Promotes chronic inflammation which, in the long term, disrupts the normal functioning of your immune system, thereby raising your risk of depression. A 2004 cross-cultural analysis14 of the relationship between diet and mental illness found a strong link between high sugar consumption and the risk for depression and schizophrenia.
It also concluded that dietary predictors of depression are similar to those for diabetes and heart disease. One of the hallmarks of these diseases is chronic inflammation, which sugar is a primary driver of. So, excessive amounts of sugar can truly set off an avalanche of negative health events — both physical and mental.