Our body’s reaction to the food we eat can sometimes warn us that something is wrong. One day we’re eating our favorite food without consequence; the next day, the same food produces nausea, dizziness and mental confusion. Why? Sometimes the constituents of our diet can induce toxic reactions when they are not being properly metabolized and excreted. A recent example was published in a one of the world’s leading chemistry journals, Angewandte Chemie International Edition.

I am a big fan of starfruit (Averrhoa carambola). You’ve probably seen these small, yellow or green, clear-skinned fruits in the grocery store; they’re very tasty but not that popular. Their true name is carambola and they likely originated in Sri Lanka or India; their colloquial name originated from the star like shape produced when the fruit is cut in cross section. They contain an impressive variety of vitamins, minerals and dietary fibers and they are a rich source of antioxidants. However, they pose a serious risk for individuals with kidney failure or kidney stones.  The consequences of eating starfruit when the kidneys are not functioning adequately is an array of symptoms that might easily be ignored or misinterpreted as unrelated to eating the fruit, including vomiting, hiccups, mental confusion and seizures. Deaths have also been reported.

In the past, these symptoms were blamed on oxalic acid, a component of the starfruit. Oxalic acid is a relatively strong acid that can damage the kidneys and is a key component of kidney stones.  Now before you decide to avoid starfruit you should also consider that many other healthy foods contain oxalic acid as well, including spinach, chives, cassava and rhubarb.  

However, this recent study demonstrated that oxalic acid is not responsible for the dangerous cognitive effects of eating the fruit. First of all, oxalic acid does not easily cross the blood brain barrier. The true villain of the story is a new compound named caramboxin. Caramboxin appears to mimic one of the brain’s own neurotransmitters, glutamate. This action induces the brain to become extremely excitable, thus leading to the seizures and mental confusion. There are two important lessons that this story offers. First, food contains quite powerful chemicals and if those chemicals are able to enter the brain they may produce negative consequences upon mental function.  Second, how we respond to the components of our diet is greatly influenced by the status of our health.  Sometimes, our body’s response to a specific food can warn us about the health of specific organs. Here’s yet another reason to pay close attention to what you eat.

© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford University Press)

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