An Unrecognised Paradox.
Nutrients and toxins, and what defines, divides and unite these semantic opposites in biology
There are two basic premisses that unites all schools of dietetics, how diet relates to disease and that is the concept of nutrient deficiency and nutrient toxicity. Because we need nutrients to survive and function properly, the first premise can be considered self-evident, a true axiom, and we’ll get to the specifics later in the coming sections of this chapter. However, the idea of nutrient-toxicity, that nutrients when eaten in excess behave like a poison in the body seems to be self-contradictory, since the definition of a nutrient is a substance that organisms need in order to live and grow while a poison is defined as a substance that can kill organisms or make them ill.1)https://dictionary.cambridge.org/dictionary/english/nutrient2)https://dictionary.cambridge.org/dictionary/english/poison In logical deduction this simple semantic contradiction is usually dismissed by applying a principle of toxicology that states that “it is the dose that makes the poison”, that getting to much of something good can make it bad. This seems to explain away the inherent contradiction in considering that nutrients can be synonymous with poison when they are in fact opposites by definition. The practical utility of this toxicology-principle is undeniable, however, like all other principles it is only true in a practical sense and is not meant to be taken literally and can definitely not be said to be a theoretical axiom.
Temporarily disregarding the value of theoretical truth, what organisms fundamentally care about are to function in the world, hence the why and how of a principle is not important as long as the outcome can be somewhat reliably predicted by acting in accordance with it. In the case of the toxicology-principle, people who overeat tend to get metabolic issues and when they eat less they seam to get healthier. To find the answer as to why and how this seams to be the case is therefore often portrayed as being of trivial importance, and a matter of intellectual curiosity rather than a practical necessity and it is often stated that if we just acted on this principle things would sufficiently improve. The problem is that we currently don’t, and even when we do our health don’t seam to improve sufficiently (and sometimes it even gets worse), and if a principle, no matter how well it worked in the past, stops being of sufficient practical use, it is time to re-examine it, bring it closer to theoretical truth.
Toxicology is intimately related to nutrition, but nutrients themselves such as glucose and fatty acids actually don’t behave like toxins in the body, even when eaten in excess. In biology, all living things are potential nutrients for one-another, and true toxins are therefore associated with offensive or defensive or functions. For snakes it facilitates predation, and in plants they allow them to interact with microbes, insects and animals while lowering the chance of having their vital-parts consumed in the process. Once the defence of an organism has been breached or a symbiotic interaction has been established, nutrients are simply nutrients. Like the bee in the picture extracting nectar from one of our most poisonous flower-plants (digitalis). If organisms could poison themselves on nutrients simply through continually and accidentally overshooting their daily needs, which are highly variable, this would severely undermine reproductive success which actually fundamentally depend on the continual accumulation of a resource-surplus.
Appetite is only one mechanism that organisms use to regulate nutrient-intake to changing needs but since digestion poses a time-delay in terms of direct feedback on feeding-behaviour related to the nutrient status of serum and tissues this poses an apparent problem that appetite simply can’t solve which is precisely why appetite is not the only regulatory mechanism governing nutrient-absorption. In fact, and this is rarely mention in standard text-books on nutrition-physiology, absorption on nutrients is regulated, through several different mechanisms, and for nutrients to have toxic effects on an organism it requires the integration of another team of ecological players going in offence or defence in relation to the aforementioned organism, namely the microbiome.
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