Herbal Supplements and the Brain: Understanding Their Health Benefits and Hazards
The Gifts of Eden
Adam wasn’t hungry and was apprehensive about the potential consequences of eating the forbidden fruit. He was, however, convinced the plant material could provide benefits beyond its nutritional value. On the one hand, God told him that its consumption would be fatal, while the serpent contended the plant would impart new knowledge. Both were right. After eating the fruit Adam lost his home and immortality, and was made aware of the concepts of good and evil. He would need this new knowledge to survive in the world outside of Eden.
Besides its allegorical importance for Jews, Christians, and Muslims, this biblical account provides lessons for those interested in the therapeutic benefits of herbal supplements, also known as nutritional, dietary, or food supplements. Defined as a product that contains a vitamin, mineral, herb or other botanical, an amino acid, an extract, or any combination of these materials, the United States government considers dietary supplements to be foods rather than drugs. This has significant implications with regard to their regulation and the assurances provided to consumers. Because of this categorization, potential users must obtain on their own objective data about these products. The aim of this book is to provide such information.
The most fundamental question pertaining to dietary supplements is whether there is any evidence that they provide benefits beyond possible nutritional value. Written some 2,500 years ago, the Genesis account of Adam’s introduction to these products indicates that humans have been familiar with the possible mystical and therapeutic powers of plants for quite some time. Moreover, the Old Testament account demonstrates that then, as now, there was uncertainty, and therefore risk, associated with the consumption of plants and plant products for religious, therapeutic, or, as in Adam’s case, educational purposes.
The fruit consumed by Adam is unknown. In Old English, the word “apple” is simply a synonym for fruit. Regardless, when tempted to eat the plant product, Adam was at a distinct disadvantage to today’s consumer. There was no historical record on its possible effects and no scientific data on its safety. Moreover, as the basic principles of pharmacology, the science of drugs, had not yet been established, he was unable to assess these properties himself. Rather, Adam had to rely solely on the word of others.
The constraints experienced by Adam remained for thousands of years until written records were maintained on the medicinal value of plants. More centuries passed before chemists were able to identify, and pharmacologists objectively study, the therapeutically active constituents in plant and animal products. Only during the past century has research revealed the diseases and disorders that are most responsive to these constituents, and to define precisely the appropriate doses to maximize safety and effectiveness in most individuals.
Anecdotal accounts about the potential benefits of dietary supplements have existed for thousands of years. Evidence includes pollen grains found on Neanderthal (Homo neanderthalensis) graves that were from plants lacking showy flowers, such as the yarrow (Achillea millefolium). It is inferred that these plants were placed there not for adornment, but to provide the departed a supply of medications in the afterlife.1 This concept is based, in part, on the fact that many of the plants deposited on Neanderthal gravesites were subsequently described as therapeutics in early medical books, indicating that word of their therapeutic powers was passed on for millennia. For example, yarrow is mentioned in the Assyrian Herbal (800 BC), one of the oldest listings of therapeutically active plant products,2 as well as in the Ebers papyrus (1500 BC) from Egypt. The Greek poet Homer described in The Iliad (800 BC) the use of yarrow to cure wounds, as did the Roman naturalist Pliny the Elder in his writings during the first century AD.3
A conservative estimate is that plants have been used as therapeutics at least since the appearance of modern man, some 200,000 years ago. It seems reasonable that as early humans foraged for food they would accidently discover the curative powers of some plants or take note of the fact that consumption of a certain type of seed, root, or fruit produced discernable effects on mood, sensory input, or alleviated general aches and pains. Indeed, as a species, humans are indebted to the many thousands of forgotten ancestors who became ill or died in the process of identifying plants and animals suitable for consumption. Thus, through trial and error, early man was able to identify plants that possess useful medicinal properties.
In addition to using plants to cure disease, they were also consumed in the ongoing quest for immortality. Recipes for “elixirs of life” were described in ancient writings. An example is the Epic of Gilgamesh, the story of a Sumarian hero that was recorded in 2000 BC.4 After many travails, Gilgamesh obtained the plant of immortality from deep in the sea. Unfortunately for Gilgamesh, the plant was subsequently stolen by a serpent. This tale has many of the features of the biblical account of Adam and Eve. In the end, Gilgamesh returned home to Sumer to, like the rest of us, spend the remainder of his days as a mortal, awaiting the inevitable.
As in Genesis, ancient medical texts demonstrate that plant products have been used for therapeutic purposes for millennia. During most of this time no concerted effort was made to understand the reason for their effectiveness, or, in modern terminology, their mechanism of action. The first recorded attempts to synthesize therapeutics were made by European alchemists during the Middle Ages.5 Besides their efforts to transform base metals into gold, the alchemists were interested in what made substances therapeutically useful as they wanted the power to transform basic materials into drugs. They were hindered in this quest, however, by the prevailing theories about the nature of matter and the causes of disease.
From the time of Aristotle to the seventeenth century, the use of plants in European medicine was based on the idea that all nature was composed of four basic elements: earth, air, fire, and water. Disease resulted from an imbalance of bodily humors. It was believed this imbalance could be countered by one or more of the four plant classes—cold, dry, hot, and wet—that corresponded to the four basic elements of nature. Mixtures of plants, usually from the same class, were preferred over a single specimen for treating medical conditions. For example, combinations of “cold” plants were used to treat fevers. Given these theories, drug discovery remained an empirical enterprise for thousands of years, with the identification of active plants and plant products left solely to chance.
By the seventeenth century, belief in the Aristotelian four elements was being challenged, most notably by the Irish chemist Robert Boyle.6 Boyle understood that the precise identification and classification of the basic elements of nature were absolutely essential for understanding the universe, including drug actions. Thanks to his efforts, and those of many others, modern chemistry emerged in the nineteenth century. This made it possible to isolate, chemically define, and study the biological responses to plant constituents. As a result of these efforts, drugs were identified in plants that were first discovered by our distant ancestors. Many of these compounds, or their chemical derivatives, are still used today.
Given the historical records, and contemporary scientific data, there is no question that plants produce an abundance of substances that provide benefits beyond their nutritional value. However, not all plant constituents have been isolated and properly tested for effectiveness, and, unlike drugs, there is no government requirement that a manufacturer demonstrate effectiveness before marketing an herbal supplement. Like Adam, the consumer must rely on the word of others about the benefits of these products.
This book is designed to address this issue by providing basic information needed to assess the potential therapeutic value of plant products. Included are fundamental principles of pharmacology and about how drugs and natural products can affect various organs and organ systems. Explanations and examples are provided about what determines whether an ingested substance will find its way into the bloodstream, and then to the targeted site in the body at a concentration sufficient to have a beneficial effect. Other topics include the ways in which natural products may influence the blood levels of other substances, including drugs, and the likelihood that such interactions may diminish the effectiveness of prescription medications or alter normal body chemistry. While the principles described apply to all dietary supplements and drugs, emphasis is placed on factors that relate especially to herbal supplements purported to influence brain function. Individual chapters are devoted to a discussion of selected nutritional supplements that are said to enhance memory, or to aid in the treatment of depression, anxiety, insomnia, and alcoholism. These products were chosen because the promised benefits can be difficult to quantify and are more subject to influence by the power of persuasion than is the case with other therapeutics. This is why the use of such substances has been exploited over the centuries by shamans to maintain their social standing, and by charlatans for monetary gain. The properties of these products are described in the context of the basic principles of pharmacology and the results of scientific studies, both human and laboratory animal, aimed at determining effectiveness and mechanism of action. The approach taken in objectively evaluating these products can be used by the reader as a guide for assessing the information available on any dietary supplement. This work is intended for those who are curious about the potential benefits and risks associated with the use of food supplements. The information provided will be of particular value for individuals who, like Adam, are interested in how drugs and natural products affect us for good and evil.