Noted British psychiatric researcher Malcolm Peet has conducted a provocative cross-cultural analysis of the relationship between diet and mental illness. His primary finding may surprise you: There is a strong link between high sugar consumption and the risk of both depression and schizophrenia.
In fact, there are two known mechanisms through which sugar intake could exert a toxic effect on mental health.
First, eating sugar actually suppresses the activity of a key growth hormone in the brain called BDNF. This hormone promotes the health and maintenance of neurons in the brain, and it plays a vital role in memory function by triggering the growth of new connections between neurons. BDNF levels are critically low in both depression and schizophrenia, which explains why both syndromes often lead to shrinkage of key brain regions over time (yes, chronic depression actually leads to brain damage). There's also evidence from animal models that low BDNF can trigger depression.
Second, sugar consumption triggers a cascade of chemical reactions in the body that promote chronic inflammation. Now, under certain circumstances (like when your body needs to heal a bug bite), a little inflammation can be a good thing, since it can increase immune activity and blood flow to a wound. But in the long term, inflammation is a big problem. It disrupts the normal functioning of the immune system, and wreaks havoc on the brain.
Inflammation is associated with an increased risk of heart disease, diabetes, and cancer . . . and also linked to a much greater risk of depression and schizophrenia. And again, eating sugar triggers inflammation. So does eating ubiquitous processed sugars like 'high fructose corn syrup'.
If you think about it, it makes sense that our bodies don't handle sugar very well. After all, for the vast majority (99.9%) of our existence as a species, there simply was no sugar. We were endowed with a sweet tooth so that we'd crave the highly nutritious fruits that were in rare supply in the ancestral environment. But with the advent of processed sugar cane a few centuries ago, the blessing of our formerly adaptive sweet tooth suddenly turned into a curse - causing us to crave foods that we were simply never designed to process.
As I've become increasingly convinced by these research data, I've begun gently encouraging my depressed patients to simply try cutting out sugars for a week to see if they notice any effect. (I also ask them to cut out simple starches - like crackers and white bread - which the body converts directly to sugars). Many patients have given it a go . . . often with rather remarkable improvements in mood, energy level, and mental clarity.
And, even though I've been very fortunate to escape the debilitating scourge of depression, I tried cutting out sugar myself a few months ago. Although one can never rule out placebo effects in such self-directed trials (!) . . . I've definitely noticed a nice improvement in energy and mental sharpness (I used to get a little foggy for an hour or two after lunch, and that just doesn't happen any more).
If you decide to give it a try, please be sure to pass along the results under the blog's Comments section. Good luck!