When talking about nutrition it is often assumed that certain species exist for the sole purpose to be food. You can bet there isn't a single organism who wants to willfully die only to serve as a food donor. Everyone wants to live. That’s the burning highlight of the ego.
Food is a complex relationship. It is a hierarchy of survival strategies, it is a hierarchy of adaptation and proliferation, it is a competition.
To be eaten is not a pleasant experience I can imagine, so anyone going through the process is putting up a good fight. This is toxicology in a nutshell:
“ All things are poison and nothing is without poison; only the dose makes a thing not a poison.”,
says Paracelsus, known as the father of toxicology.
Most survival strategies of the animal kingdom are easy to see. Some run to hunt, some run not to get hunted and some do both. Some eat plants, some eat other animals and some do both.
Whatever the scenario, developing specific skills such as climbing, swimming, flying, digging, fighting, sprinting and so on is crucial. If living energy has a limit then specific skills are indeed the key for survival because one has better chance of prevailing. Spending the energy in one direction is the secret of mastery.
The survival strategies of the plant kingdom seem to be mercilessly restricted. I say mercilessly because with a few exceptions plants can’t move. They are just there - under the sun or in the shade for everyone to find them and eat them.
So what do you do when you can’t move?
You protect yourself through various kinds of poisons and a whole lot of trickery.
Before I open the door to what plants do to survive I should confirm that animals in terms of food should be considered almost non-toxic. The organization and structure of animal matter is very similar to ours which is easy to translate into our biological language. Up the chain herbivores have already counteracted the majority of the toxins from the plants through their survival adaptations.
Let’s go back to plants.
Plants are on the border of sunlight translation and should be looked at as the core of primary energy formation and preservation. Everyone wants a piece of them. Based on how well living forms have adapted to eat plants determines what acts as a poison or an antinutrient and what acts as a nutrient. There is a huge gray area since there is always a dancing mixture between the two. This makes the dose the most important factor: “The dose makes the poison “.
This is to say that substances considered toxic, in small doses could be harmless and even beneficial - a phenomenon known as hormesis, while other perfectly harmless substances in huge doses could be deadly. Drinking a large enough amount of water at one time can kill you and on the contrary, you may ingest a miniature amount of cobra venom and it can improve and even erase your arthritis symptoms.
The primary purpose of antinutrients is to prevent destruction of the plant by microorganisms, insects, birds, rodents, and large mammals. There are thousands of different natural pesticides produced by plants. Defense against microorganisms, fungi and insects does not have the same strength as the one produced against large animals. In fact many organisms have adapted to use the protection themselves against microbial invasions and excessive overgrowth.
The cost and energy expenditure dictates the specificity of defense and toxin production. Plants focus on their major predators first. This is why the most dangerous toxins for humans or any other omnivore are the ones protecting from herbivores. One reason is herbivores are very close to our biology. Another is the fact that omnivores because of a wider food choice have lost many of their specific toxin neutralizing mechanisms. Our guts are shorter, the coexisting species of microorganisms are a lot less, and we did not develop organs such as rumens in order to ferment, detoxify and transform.
The evolution of chemical defenses in plants that are not involved in essential photosynthetic and metabolic activities are called secondary metabolites. Most of these antiherbivory metabolites can be classified into three sub-groups: Nitrogen compounds ( alkaloids, cyanogenic glycosides, glucosinolates and benzoxazinoids.), terpenoids and phenolics. Proteins, enzymes and fatty acid derivatives also play an important role in protection.
Alkaloids are derived from amino acids and scientists have labeled over 3000 of them. The most famous players are caffeine, nicotine, morphine, strychnine, quinine. Alkaloids can inhibit or activate enzymes, alter carbohydrate and fat storage, affect DNA repair, cell membrane, inner cell structure and nerve transmission. Wow, what else can one possibly do to life?
Cyanogenic glycosides are stored in a dormant state in plant vacuoles and become toxic only when herbivores eat the plant and crash the cell membranes allowing the glycosides to come into contact with enzymes releasing hydrogen cyanide which blocks respiration.
Glucosinolates are triggered in a similar way but their main playfield is the digestive system.
Benzoxazinoids are present in grasses and are also stored in an inactive form in the vacuoles. When activated through digestion they get into contact with b-glucosidases which releases the toxic aglucones.
Terpenoids are organic chemicals similar to terpenes, derived from five-carbon isoprene units. There are more than 10,000 distinctions. Monoterpenoids are volatile essential oils such as limonene, menthol, camphor citronella etc. Diterpenes are responsible for making a variety of leaf poisons. Plant steroids and sterols are also made from terpenoid precursors, including vitamin D, glycosides and saponins. Saponins are found in almost all legumes. They have soaplike properties that crack holes in the membrane of the cell, compromising communication which is what is called low-level inflammation.
Phenolics, sometimes called phenols, have an aromatic 6-carbon ring bonded to a hydroxy group. Phenols are extremely diverse in function and represent a co-evolutionary relationship between plants and their predators. Flavonoids are the phenolics which paint the world in red, blue, yellow and white. Even more complex than flavonoids, polyphenols are the ones animals abuse the most for their own protection. Flavonoids and polyphenols are plant’s defense from the sun radiation which is used by the rest as antioxidants. Resveratrol, to name one, is a polyphenol found in red grapes which protects from ultraviolet radiation. Tannins and isoflavones are also polyphenols which inhibit digestibility and disturb absorption. Tannins bind to iron and other minerals, preventing their absorption, they also damage the intestines, compromising the permeability of the gut. Isoflavones are even more creative. They act like female hormones in the predator’s body in order to stop the aggressor from reproduction. Isoflavones from soy , called phytoestrogens, attack the thyroid gland, causing major hormonal disbalance.
The attractive power of phenolics is a brilliant survival strategy aiming to spread seeds, to cross-pollinate, and to reproduce. Fruit is attractive, colorful and tempting, smells heavenly and tastes sweet, it is there to be eaten so the animal can spread the seed of the mother plant.
While fruit is meant to be eaten seed is not. It carries the future of the species and it is best defended by plant’s toxins.
This is the main reason plants and seeds contain proteins and enzymes that block normal digestion and absorption of nutrients. Especially the cereal grains which are the seeds of grasses and legumes which are the seeds of leguminosae family.
Defensins are small cysteine-rich proteins that inhibit growth of many fungi and bacteria, as well as digestive proteins in herbivores by acting upon targets in cell membrane and altering ion balance.
Alpha-amylase inhibitors are proteins found in legumes that bind to amylase enzymes and inhibit starch digestion.
Lectins are carbohydrate-binding proteins which also inhibit digestion, cellular signaling and alter gut permeability. Lectins have the power to damage the intestinal barrier, to impair growth and reproduction, to disrupt normal immune function, and to cause inflammation.
Wheat Germ Agglutinin (WGA) as just one of many lectins which binds to certain sugars causing damage in the gut lining. This lectin changes the behaviour of the immune system leading to autoimmune attacks. WGA crosses cell membranes and connects easily to the cell nucleus in order to block the action of many hormones including the metabolism of vitamin D.
Protease Inhibitors are yet another successful defense mechanism that disturbs digestive enzymes including trypsin and chymotrypsin causing intestinal damage and low-level inflammation.
Gluten is the composite of a gliadin and a glutenin, which is connected with starch in the endosperm ( the area surrounding the embryo ) of grass seeds. Gluten makes up 80 percent of the protein in wheat, rye, and barley. It inhibits cell growth, increases cellular oxidation, and compromises the communication in the cell membrane. It affects the intestinal walls by reducing the height of villi - small finger-like projections of the gut lining which serve to increase the surface area for better absorption. Gluten weakens the filtration structure of the gut allowing undigested particles to enter the blood causing variety of immune responses ( allergies, autoimmune disorders, systemic inflammation... ).
Phytic Acid or phytate is the main storage form of phosphorus, especially in seeds. Phytate blocks the absorption of iron, zinc, calcium and magnesium which leads to anemia, infertility, and osteoporosis.
To finish properly this defense classification I should say most toxins are still unknown to us. This is because we so eagerly want to put labels on everything, call it good or bad, and draw a clear line. Clear lines are a human illusion and nothing comes separated. The good comes with the bad, toxins are mixed with nutrients. A powerful toxin can transform into a healing nutrient once the host adapts to it. The idea of a toxin is nothing more than the refusal of a living form to die. The complexity of this idea is tightly related to adaptation. It gives beginning of natural medicine, herbalism, natural healing, homeopathy and nutrition.
Understanding life in all forms and relationships is impossible for us and this is the good news. It ensures an ever pleasant journey. I applaud anyone who realizes that.
