Sunday, October 24, 2010

Monday WOD - Banana peels, plant defenses, and saponins...

How saponins destroy cell membranes.

So what do banana peels and saponins have to do with health or peformance? Well bananas are surely a delicious way to get some carbs after a tough workout, but there are surely better choices like yams, sweet potatoes, and other tubers, right? But why are we talking about their peels, and what the heck are saponins?

Banana peels offer a great example of how plants have evolved chemical protection mechanisms for lack of physical protection(plants can't run away from animals, and they can't fight back physically, except for thorns and such).

On ThePaleoDiet.com, a reader stumbled upon the nutrient content of banana peels, was amazed at the rich nutrient profile, and posed a question asking for more information about the nutrition of banana peels.

At first glance, it looks like banana peels are the holy grail of nutrient density, eating only 50g of banana peel would provide you with 3900mg of potassium(110% RDA), 1200mg of sodium, 30 mg of iron(200%), 960mg of calcium(80%), and 3800mg of manganese(78,000%).


Sounds great right? To paraphrase from Dr. Cordain's response, however: the devil is in the details. The banana peel serves to protect the fruit from physical damage, and more importantly, from predators (birds, mammals, insects, etc) and pathogens (fungi, bacteria, etc).

The banana inside contains the reproductive material, it's seeds, which have to eventually make it into the ground intact and unharmed, so that they can produce offspring of the original plant. If the seeds are destroyed, then the banana plant could not reproduce, and would become extinct. However, the banana plant, as all other plants, has developed an evolutionary strategy involving chemical defense that allows it to survive and reproduce.

Banana peels contain a number of toxic substances to ward off predation and infection by bacteria and fungi. These substances are called antinutrients, and we have touched on a few of them in particular in the past, such as phytate, and lectins. Here's a new one though that banana peels, as well as legumes, potatoes and other nightshades, and grains contain in high quantities: Saponins.

Saponins are a class of compounds that have a lipid-soluble side, and a water-soluble side, giving them unique characteristics. They derive their name from their tendency to produce soap-like foaming when mixed with water. They are often bitter, and act in many ways to deter plant predation. What gives banana peels the bitter taste is that they contain 8 times the safe concentration limit of saponins (24mg/g).

Saponins also have toxic effects on ALL cells. They cause the membranes of all living cells to breakdown, killing the cells. If saponins are consumed in large enough quantities, saponins rapidly breakdown the cells lining the intestine, and enter blood circulation where they can destroy the membranes of red blood cells, which can cause death.

This is not simple theory either, in experiments with animals, even low doses of banana peel extract added to their normal food caused damage to their red and white blood cells, severely impaired growth, and strongly inhibited the production of thyroid hormone, necessary for a healthy metabolic rate.

To sum it up: Don't eat your banana peels, and don't eat grains or legumes either.


Strength WOD
3 X 5 Front Squat

WOD
15-12-9 of:
DB Clean & Jerk (50lb DB's)
Burpees

MWOD
Wide Squat Stretch - 2 min
Calf Stretch - 2 min/leg
Hamstring Stretch - 2 min/leg

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