The other day, I was reading a book, Leaf Defence by Edward Farmer. It’s a book about how plants defend themselves against insects and other animals.
Why am I reading about that, you ask? Well, I’m a drug developer, and most drugs are defense chemicals from plants. To understand drugs, you need to understand their provenance, and their provenance is plants. Developing drugs without understanding plant defense systems would be like trying to study Western art without understanding the Bible or trying to study Renaissance works without understanding the precedent Arabic works.
I’m pretty well-versed in plant chemodefenses–I know that for example yams from the Amazon (not the internet store, the rain forest) produce high levels of estrogen to prevent herbivores that eat them from reproducing (and that those yams were the source of first birth control pills)–but I didn’t know wild carrots and certain parsleys were natural abortifactants. Obviously for the same reason, the plants are practicing population control of animals that eat them.
I knew ancient ferns took up silica into their tissue but I didn’t know that modern plants did the same thing–essentially incorporate glass into their leaves to grind down the teeth of herbivores–and in some cases make sand stick to the undersides of their leaves to accomplish the same thing.
I knew that there were high levels of protease inhibitors in seeds to present digestion of the seeds, but I didn’t know there were enzymes in plants that specifically degrades essential amino acids to starve herbivores of those amino acids. I didn’t know that plants made diuretics to induce animals to lose sodium–and that sodium is often the rate-limiting nutrient in many herbivorous diets. I did know microbiome often made essential nutrients for their hosts but didn’t know that they are often reconstructing the amino acids that plants manage to degrade when the plant is eaten. There are enzymes that plants produce that are inactive until the plant is eaten. In the stomach of the animal, they activate, and they degrade the essential amino acids, rendering them useless to the animal (for example, threonine deaminase 2).
The take-away from the the above paragraph is that plant matter(food) is biologically active. What this means that there is an emergent phenoma associated with food–that the food is not just a collection of proteins, fat, and carbohydrate. As Pollan notes in Omnivore’s Dilemma, you can’t understand a particular food’s nutritional value just by looking at the constituent protein, fat, and carbohydrate content. Food is a complex chemical soup of very potent and active biological molecules. Depending on those molecules, your microbiome, and your genetics, the nutritional value can be very different. We also know there is microRNA in plants that seem designed to manipulate the herbivores’ gene expression–although there is debate about how well such microRNAs invade into the animals’ systemic circulation.
This goes along with several other theories and observations. For example, even with same caloric intake, people and animals can gain or lose weight, depending on what they eat. As another example, cooking food substantially increases nutritional value. This is probably partially due to the destruction of the plant’s defense chemicals and proteins.
In other words, calories in != calories out.