“Virtually all of the major tomato volatiles can be linked to compounds providing health benefits to humans.”[i]
There is little scientific evidence to support claims that chemical extracts from plants act as rapid and effective medicines. Herbal supplements do not (and cannot) overtly claim that cancers or allergies or other diseases can be prevented, reduced, or cured. This isn’t to say that plants can’t or don’t have these qualities, but unfortunately our comparison system is one that is oriented around modern chemical medicine. To date, research on plant-based supplements has provided little evidence for substantial changes in metabolic and physiologic processes in comparison to synthetic medicines designed for addressing specific medical issues.
This is true. And it misses the point.
Medicines are short-term technological solutions for acute biological problems. Medicines are designed to replace biological processes whenever the body is unable to overcome a dangerous situation or condition. Medicines rarely boost the natural processes of the body. In fact, those medicines taken for chronic health issues are not intended to correct the medical problem and are used as permanent substitutes.
New medicinal compounds are tested for rapid effectiveness, for low toxicity, and for obvious side effects, and the testing period is rarely longer than 2-3 years because the development and testing of new medicines is incredibly expensive. There is an implicit assumption in the pharmaceutical industry (and regulatory agencies) that negative side effects can be detected within that short testing period.
Health supplements are typically materials or extracts from plants that contain particular secondary compounds that are perceived to have a beneficial effect on human physiology. They are bioactive molecules that affect animal physiology in some way. Most plants have dozens to hundreds of them. Examples are caffeine, nicotine, and morphine. These compounds are typically in relatively low doses in the plants because, let’s remember, secondary compounds in plants are toxins produced by the plant to kill or ward off herbivores, usually small insects.
The majority of medicines existing today are derived from or inspired by these toxins. Pharmaceutical companies employ chemists to identify and extract the bio-active compounds from plants, purify them, magnify the dose, and then design a delivery system that can be tolerated by humans. It is important to note that the process is one of isolating the active molecule from its natural context, which eliminates possible important interactions with other compounds in the plant. However, this is done because pharmaceutical effectiveness is based on a testing procedure that demands rapid response and demonstrable effects of a single variable. Plant extracts cannot be tested in this way and rarely meet the criteria for being “effective”.
However, by eating a plant-based diet, we get small doses of a large number of bioactive compounds every time we eat. If a certain plant is a normal part of the human diet and we are exposed to it regularly and over long periods of time, we are receiving a low dose of a potentially medicinal stimulus from that plant every time we eat it. That stimulus could be from a single compound, from several compounds, or from interactions among the compounds. Almost certainly, the stimulus will be subtle and the benefits will be expressed slowly.
If the Mediterranean cuisine or Indian cuisine or other ethnic food palettes are considered intrinsically healthy, it is because of the characteristic plants and plant-derived seasonings that comprise those foods. Every meal contains low doses of medicinal chemicals in which people of those cultures are immersed over the course of their lives.
Is food medicine? Yes. Can plant-based supplements be medicine? Yes. If you take supplements for an extended period of time, it is certainly possible there will be subtle and even large positive effects. It is also possible that if you were not raised from childhood on foods containing those compounds, the effectiveness may be different from those who were raised on that diet.
What we can say is this: a long-term diet that is based on a variety of strongly flavored plants and plant seasonings is probably providing a medicinal boost to the human body. Plants are food for the microbiome and the microbiome is part of the foundation of our immune system. Secondary compounds in plants taken in small amounts may influence the diversity and functioning of the microbiome and thereby have indirect effects on human health. But it doesn’t happen overnight and the testing methodology of modern medicine is incapable of detecting it.
Therefore, if we assume that humans have possessed a microbiome for a million years, and the microbiome contains large numbers of mutualistic species, and plant materials are the food for the microbiome, then a diet that provides our microbiome with a variety of plants and plant compounds will be heathier for us than a diet without such variety.
[i] Goff, S.A. and Klee, H.J., 2006. Plant volatile compounds: sensory cues for health and nutritional value? Science, 311:815-819.