Phytochemicals, Natural Antibiotics and Antioxidants

Plants are mean and sneaky.  They are natural organic chemists and make the nastiest toxins on earth.  Never trust a plant.  Eat them at your peril… or because they taste good.

Phytoalexins

Plants are Fast and Lethal

I was shocked when people started to laud the virtues of phytochemicals.  I thought that they must have alkaloid poisoning.  My PhD training involved separating and measuring the antifungal chemicals produced by soybean cotyledons exposed to the wall polysaccharides of a pathogenic fungus.  The plants would go crazy and produce a witch’s brew of toxins to provide protection from the fungus.  I eventually wrote a chapter on these toxic natural antibiotics, phytoalexins, for the Encyclopedia of Science and Engineering.  All plants produce these chemicals and as one might expect, seeds/nuts are provided with special protection to avoid being digested.

Lignin

Plants are Natural Chemical Killers

I developed a profound respect for the ability of plants to protect themselves.  Fungal spores germinate on the surface of leaves and their slender, threadlike hyphae attach and glue themselves to the waxy outer surface and then forcefully and enzymatically penetrate to the spongy cells below.  When the tip of the hypha touches the wall of the underlying cell, the plant nucleus lurches as its cytoskeleton reorients.  The surrounding plant cells respond in sympathy and all of these neighbors mobilize their biochemical processes to kill everything in their vicinity.  In a few hours, the plant chemicals kill the cells producing them along with the pathogen, and would continue to kill more and more of the leaf, but plant cell walls also contain enzymes that convert the phytoalexins to more wall material, lignin, and protect cells outside of the influence of the fungus.  As lignin in wood and plant litter is slowly degraded by microorganisms, it forms humus, the natural organic material in compost and soil, and also releases a potpourri of potent plant phenolics like BPA.  Compost is also a rich source of cell wall polysaccharides, a.k.a. soluble fiber, that feeds soil bacteria.

Phytochemicals are Natural Antibiotics

Most phytochemicals have evolved in plants as pathogen or herbivore defenses.  Since the nervous system is adapted to detect other organisms, it is not surprising that plants target the sensory system, brain and nerves of herbivores, and we detect the flavor and smell of plants/herbs/spices by their defensive molecules.  All of the flavor and taste components of herbs and spices are phytochemicals that kill bacteria, fungi and other pathogens.  Nicotine and caffeine are insecticides.  A detailed, worldwide study showed that spices are used in specific global areas, because of the local availability of the spices and their effectiveness against local food storage pathogens.  People develop a taste for the plant defensive chemicals that they must be exposed to for sustenance.  Cuisine represents a knife edge that separates attractive stimulation from death.  Natural or organic does not mean safe or healthy.  Plants are as dangerous to eat as pufferfish.

Phytoalexins are Useful, but Be Very Careful

Perfume Ingredients

If a grape notices a nearby fungal pathogen, it produces its phytoalexins, including resveritrol, which is a notable “antioxidant” that has been recognized as contributing to longevity.  People are encouraged to drink red wine for the health benefits of its phytoalexins.  Most of the pharmaceuticals derived from plants are phytoalexins in disguise.  Of course, the evolutionary origins of phytoalexins as natural broad spectrum antibiotics, makes it no surprise that phytoalexins are commonly toxic, carcinogenic and very dangerous to fetuses.  Morning sickness has been explained as nature’s way of telling a mother carrying a vulnerable fetus to not eat plants and potentially phytoalexins.  It is wise for women to avoid plants, perfumes and essential oils during their first trimester.  Essential oils are phytoalexin extracts from plants and many of these components are the essence of perfumes.  These same chemicals, e.g. limonene, serve dual purposes as fragrances and paint strippers, recreational drugs and insecticides.  We can smell these natural plant chemicals, because they are attacking our nervous system.  Multipurpose mixtures of essential oils, such as Vick’s Vaporub, contain menthol, camphor, eucalyptus oil and terpentine that kill bacteria and fungi (toe nail fungus) and also stimulate cold/hot sensing nerves in the skin, which triggers endorphin production and reduces underlying joint inflammation.

Fruits are Fake Seduction

Fructose is fruit sugar.  That is very appropriate.  Fructose derivatives are the most central intermediates of central metabolism, glycolysis; glucose is immediately converted to fructose after it enters a cell as the fundamental source of energy and carbon building blocks.  Fructose is not normally transported in plants or animals, because it is too chemically reactive and toxic.  It rapidly bonds and crosslinks proteins and is ten times worse than glucose in forming AGE (advanced glycation end products) such as hemoglobin A1C.  If you feed fructose to cattle, it makes their meat tough by cross linking protein fibers and it does the same thing to human skin.  Fructose in fruit is a fake, because it is cheap and sweet.  Animals eat fruit hoping to find starch, which is the only polysaccharide that animals can convert to glucose with their own (not bacterial gut flora) enzymes.  Starch quickly becomes sweet, because amylase in saliva digests the long chains of glucose molecules of starch into shorter dextrins that trigger sweet sensors in the tongue.  Fructose masquerades as starch by binding to sweet sensors a hundred times more strongly than dextrins.  The evolutionary advantage to using fructose to make plants sweet is that it takes much less energy and carbon, and it also poisons insects and microorganisms.  That is why honey is made of equal amounts of fructose and glucose, rather than sucrose, for example.  Fructose in high concentrations is toxic to microorganisms and honey can be used to dress wounds.  I can’t understand why fruits, especially juices, are recommended as part of a nutritional diet.  At best, fruit should be converted into juice.  The juice should be discarded and the pulp eaten as a source of soluble fiber, pectin, to feed gut flora. 

Phytochemicals Must be Detoxified to be Edible

Bacterial and fungal pathogens must avoid detection by plants to avoid death by phytoalexins.  Insects, similarly must avoid preformed phytochemicals that would kill or poison them with their first bite.  Pathogens and pests that are effective on one species of plant cannot eat others with different chemical defenses; plants and their pests/pathogens are mutually adapted.  Primates browse on new shoots of many different types of plants, to avoid building up lethal doses of particular phytochemicals.  The same is true of humans, who also have intestines and livers that chemically treat and neutralize plant toxins.  These same human defenses determine the rate at which other related chemicals, i.e. pharmaceuticals, most of which are derived from phytoalexins, are transformed and excreted.  Turmeric contains curcumin, which is the most potent inhibitor of inflammation yet identified.  Unfortunately, curcumin is “detoxified” in the intestine and large amounts must be eaten to suppress inflammation.  Fortunately, pepper contains another phytoalexin, piperine, which inhibits the detox system, so that most cuisines that use turmeric combine it with black pepper.

Trade Your Liver for Vegetables

The liver is the only organ that can be continually regenerated and that is because humans have evolved to eat plants, and phytoalexins take their toll on the liver.  As plants are digested and absorbed in the small intestines and transported to the liver, phytoalexins accompany the nutrients.  Most of the phytochemicals are chemically detoxified by liver enzymes, but the phytoalexins kill some liver cells with each meal and some of the phytoalexins circulate in the blood and reach other tissues.  The phytoalexins are evolutionarily adapted to bind to proteins to disrupt essential enzymes of microorganisms and herbivores, and like pharmaceuticals to which they are chemically and functionally related, they have numerous side effects.  The chemical reactivity is what is detected as the “antioxidant” property of phytoalexins.  Antioxidant is nutritionally meaningless and basically reflects the chemical toxicity of phytochemicals.  After all, you can’t easily sell chemicals that are inherently toxic.  Meat and humans are made of the same easily digestible stuff, i.e. protein, fat, plus indigestible polysaccharides in connective tissue, i.e. chondroitin sulfate and heparan sulfate.  Plants are essentially anti-human and are made of protein, vegetable oils (omega-6), digestible starch, undigestible cell wall polysaccharides, undigestible lignin and toxic phytoalexins.  Humans have adapted to eating plants with liver enzymes, liver regeneration, gut flora (to eat otherwise indigestible polysaccharides, soluble fiber to produce short chain fatty acids) and elaborate cultural habits.  We avoid most plants as too toxic and have domesticated some to produce reduced and tolerable levels of phytochemicals.  Of course this also means that the domesticated, defanged crop plants have a hard time defending themselves and we have to continually worry about blights and pestilences, and end up applying our own witch’s brew of fungicides, pesticides, and herbicides.

Polyphenols and Hormesis
I am going to add a few comments on the benefits of phytochemical "antioxidants", a.k.a. polyphenols, to clarify what I think is a misuse of the term "hormesis", which I thought meant the dilution of a toxin until it reached a magic lower concentration which was beneficial.  The trade offs of phytochemicals are nicely discussed by the Whole Health Source blogger, Dr. Stephan Guyenet.  I just don't think that the benefit of toxic chemicals stimulating the body's own antioxidant arsenal is an example of hormesis.  The point is that phytochemicals always act as toxins and stimulate toxin defenses.  Phytochemicals don't act as anti-oxidants in the body, even though they stimulate antioxidant defenses at all concentrations.  They provide a dubious benefit of unnecessarily heightening defenses with concomitant energy expenditure at low amounts and net damage at higher amounts.

Hakuna Matata and Sip the Tea

Tea Fanatic

I seem to have painted a compromising picture of plants as less than the perfect food.  They are tough and potentially toxic.  Plants clearly don’t like to be eaten and the best that can come of eaten plants is a full belly and a damaged liver.  But if you cook or ferment the plants first and bacteria start to digest and dull the chemical arsenal, plants can be safely and perhaps even enjoyably eaten.  We need not eat just safe meat.  We can also kick back and sip the tea.