Jennings, Issac. (1847). Medical reform; a Treatise on Man’s Physical Being and Disorders: Embracing an Outline of a Theory of Human Life, and a Theory of Disease, its Nature, Cause, and Remedy. Oberlin [Ohio]: Fitch & Jennings. Hathitrust – https://babel.hathitrust.org/cgi/pt?id=hvd.hc3vs5&seq=7&_ga=2.186671656.1669541545.1706398529-220661866.1701970530

• In this book of 392 pages, Dr. Jennings gives his views on medical reform. He starts with a general outline of Human Life followed by a discussion of his Laws of Life (Law of Action, repose, economy, distribution, economy, accommodation, stimulation, limitation, equilibrium). He next defines what disease is, analyzes various diseases, and discusses their cause and treatment. He highlights the use of alcohol, tea, coffee, tobacco, animal, food, butter, and cheese, etc. He sees these points from experience and observations with reflections and remarks.

Jennings, Issac. (1852). The Philosophy of Human Life. Cleveland, Ohio: Jewett, Proctor & Worthington. Internet Archive –

• Jennings starts by discussing the basis of the old systems of medicine.  He then writes chapters on human physiology, general and special pathology, and reasons for rejecting heteropathy (method of treating disease with remedies) and adopting orthopathy (An alternative-medicine philosophy advocating a vegetarian raw-food diet with periods of intermittent fasting) over 284 pages.

Jennings, Issac.  (1867). The Tree of Life: or, Human Degeneracy, its Nature and Remedy: Based on the Elevating Principle of Orthopathy. New York: Miller, Wood. Internet Archive –

• Jennings shares that this book was monumental in its approach to the problems of life. He begins with man’s spiritual degeneracy, nature, and remedy. Next, he shifts his focus to physiology, the organic laws of life, and disease.  He shared the symptoms, general causation, and treatment protocols for specific diseases. 300 pages.

Jennings, I. (1955, Apr/May). General Operations of the Law of Animal Life. Journal of Natural Hygiene, V1(N8-9), pg40, 41, 44.
https://www.healthscience.org/wp-content/uploads/2023/03/Volume-1-N8-9-Natural-Hygiene.pdf

• Jennings emphasizes the importance of understanding the natural harmony of the body and its innate capacity for healing and adaptation, urging a view of life that aligns with these principles rather than relying on forced or artificial interventions.
• Dr. Isaac Jennings outlines the law of the animal economy, emphasizing nature’s inherent drive to maintain and repair the body, striving for its perfection despite various challenges. He argues that the body is continuously working towards healing and strengthening itself, adapting to changes and circumstances through a process called accommodation. This capacity allows individuals to recover from injuries, resist harmful influences, and maintain health when functioning optimally.
• Jennings stresses that human life is a unit—the body is a cohesive system, where all parts work together under one governing principle, which he identifies as elective attraction. The body responds to the most urgent needs, sending vital forces to where they are most required. The law governing the human system is natural and harmonious, without external intervention, as the body inherently knows how to maintain balance and health.

Jennings, Issac. (1960). “What Is Disease.” Eternal Health Truths of a Century Ago., no. June 1960, pp. 16-24, out of print/Edited by Christopher Gian-Cursio. Accessed 8 Feb. 2024.

• A copy of this out-of-print book was donated to the Internet Archive. Check to see if this has been added to the Internet Archive,
• “What is a disease?” asked Jennings. It was and is the question of the day. Jennings believed that disease is the abatement of health–nothing more, nothing less.
• With good health, the organs perform their parts, untiring with undeviating steadiness, as the planets move in their orbits.
• The first step on the descending scale of health is the reduction of power; second, functional derangement; third, structural derangement, or organic disease. As the force abates, action, enfeebles, and vacillates, the composition or decomposing functions of organs begin to fail to a greater or lesser degree.
• No artificial or unnatural means can make anyone feel better than he or she is in the constant habit of feeling. People of sound constitution and figure of health who live on a simple healthy diet never perceive any good effect from the use of stimulants (e.g., drugs, alcohol). It is actually the reverse.
• Dr. Jennings discusses the foundation of disease, or predisposition, as it was called. This condition has been produced by a long, persistent course of violation of the laws of life. He goes on to discuss that this predisposition or depressed state of the body differs greatly in each individual. 

Jennings, Issac. (1978) “Analysis of the Law of the Animal Economy, or Law of Life.” Health Science – Official Journal of the American Natural Hygiene Society, Inc. Timeless Teachings, 1 Nov. 1978, pp. 2-6. Excerpted from Dr. Jennings’ book Medical Reform: A Treatise on Man’s Physical Being and Disorders, Oberlin: Fitch and Jennings, 1847, pp. 48-75.
https://www.healthscience.org/wp-content/uploads/2023/03/V1-N8-Health-Science-nov.-1978.pdf

The NHA wishes to remind the readers that nothing in this or other publications is intended to constitute medical treatment or advice. Readers should be aware that some previous publications do not reflect the NHA’s current health teachings or approach to health in several areas.

Our Mission

The mission of the National Health Association is to educate and empower individuals to understand that health results from healthy living. We recognize the integration of all aspects of health: personal, environmental, and social.

We communicate the benefits of a plant-based diet, exercise and rest, a healthy environment, psychological well-being, and when indicated, the use of fasting.