Episode 150

You probably ate something toxic today.  But don’t panic!  It was actually good for you.

Turns out, many plants produce chemicals that are poisonous in large amounts, but have health benefits in small doses.

Dr. Mark Mattson, Professor at the Johns Hopkins University School of Medicine and Chief of the Laboratory of Neurosciences at the National Institute on Aging, is back on the podcast to talk to us about plant toxins — how our bodies protect us against those toxins and actually benefit from them.

Toxic Phytochemicals

Phytochemicals are chemicals naturally produced in plants.  Many of them function to protect plants from being eaten, especially before the seeds are fully formed and ready to be dispersed.

That’s why unripe fruit is so bitter.  The plant doesn’t want anyone eating the fruit until the seed(s) inside are mature.  Of course, once it is mature, all that sugar in the ripe fruit is there to entice passing animals to take a bite and help scatter the seeds.

But even though green fruit is bitter to eat, small amounts are really good for you.  One example:  a chemical in green tomatoes is neuroprotective and has been found to increase the lifespan of worms.  But it disappears once the tomato ripens to red.

Adaptive Response to Stress

So what’s going on?  Our bodies have a couple of protective mechanisms to prevent overdosing on plant toxins:

  1. Avoidance of bitter tastes.  Most of these toxins are bitter, and most people instinctively don’t like bitter tastes.
  2. Vomiting.  If you’ve ever eaten too much unripe fruit, you might have noticed your body forced you to expel it.
  3. Enzymes that metabolize and eliminate toxins from your body quickly, so they don’t accumulate in your cells.  Ever noticed how quickly asparagus causes your pee to smell?  That’s because your body has metabolized the toxins and targeted them for quick elimination.

The most relevant protective mechanism for our purposes is the adaptive stress response.  When our cells are exposed to low doses of toxins like caffeine, curcumin, or selenium, they have learned to benefit from the stress the toxins cause.  It’s a good stress, if you will.

When organisms live in environments with high levels of toxins, the ones that survive are those whose cells are able to use the stress to become stronger, more able to resist oxidative or metabolic stress.

Our cells have learned to respond adaptively to stressors, like toxins, and benefit from them.  It’s a classic hormetic dose-response:  a little is good, a lot is poison.

Benefiting from Toxins

Caffeine is a perfect example of turning lemons into lemonade.  In high concentrations, caffeine is toxic (one tip off is the incredibly bitter taste of pure caffeine).  After all, plants produce caffeine to stop bugs from eating them.

Despite its toxicity, our brains actually function better for neurons having experienced exposure to caffeine.

Caffeine has the same effects on nerve cells as exercise and engaging in intellectually challenging activities.  It promotes CREB, a protein that plays a critical role in learning and memory, promoting the formation and growth of synapses.

The same is true of sulforaphane — found in cruciferous veggies like broccoli and cabbage — and curcumin.  Consuming either causes our neurons to produce Nrf2, which stimulates the production of antioxidant enzymes in cells, protecting against oxidative damage.

Episode Highlights

0:22Plant toxins
1:27This Week in Neuroscience: Brain scan study reveals dogs attend to word meaning, not just intonation
4:36The audience interaction section
6:02Introduction to Dr. Mark Mattson
7:48The health benefits of plant toxins
10:44Hormesis and how we’ve evolved to keep from overdosing
14:10Insect antifeedants
15:20Why do humans have workarounds for toxic chemicals and insects don’t?
17:17Sugar in fruit
18:15How can we use this information to our advantage?
22:34“Mono meals”
24:39Why don’t we eat coffee fruit?
28:21When addiction could be beneficial
31:31Health consciousness at NIH
32:41We benefit more from eating fruits and vegetables that contain toxins than simply the toxins themselves
34:40Should kids be consuming the same chemicals as adults?
37:08Ruthless Listener-Retention Gimmick: A Science-Backed Guide to Taking Truly Restful Breaks

PS:  Join our free weekly emails – pure benefit, no poison.

Oh yeah, one more thing: 
The image above is the “Abrus seed pod.”  One of the most deadly plant toxins, abrin, is produced by rosary pea (Abrus precatorius).  As little as 0.00015% of toxin per body weight will cause fatality in humans (a single seed).  Strangely, birds appear to be unaffected by the deadly toxin.

Written by Hannah Sabih
Hannah believes there's nothing 8 hours of sleep and some kale can't cure (yes, she's from California). She's an avid runner, reader, and traveler, who brings you the latest and greatest in neuroscience via our social media channels.
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