The Good Foods' Blog

The Science Behind “Different People, Different Diets”

Dr. Linda Isaacs

Linda L. Isaacs, M.D., is a nationally-renowned physician and sought-after speaker who is a leader in the field of individualized nutritional protocols and currently practices in New York City. Dr. Isaacs is a Lexington native who will be returning to the Bluegrass to share her insights into how specialized diets can be used to reach optimal health in her class “Different People, Different Diets” on February 28 in our Community Room.

Dr. Isaacs received her Bachelor of Science degree from the University of Kentucky and went on to Vanderbilt University School of Medicine to receive her medical degree in 1985. She then completed a residency in Internal Medicine at the Department of Veteran’s Affairs Medical Center at New York University Medical School. She is Board Certified in Internal Medicine, most recently completing recertification in 2011.

Dr. Nicholas Gonzalez, photo credit:

For more than 20 years Dr. Isaacs worked alongside her colleague Nicholas J. Gonzalez, M.D., another leader in the field of individualized nutritional protocols, developing a nutritional approach for treating patients diagnosed with cancer and other serious degenerative illnesses. After his untimely death in July 2015, she has continued with the work they shared. The treatment involves diet, which varies from patient to patient and can range from almost exclusively vegetarian to one that is heavy in animal protein and fat; individualized nutritional supplement protocols, which include large doses of pancreatic enzymes; and procedures such as coffee enemas that help the body rid itself of metabolic wastes.

The basic idea behind tailoring a diet plan for an individual’s needs is outlined in the foreword Dr. Isaacs wrote for Dr. Gonzalez’s book, Nutrition and the Autonomic Nervous System:

The autonomic nervous system is in charge of the functions of our bodies that we do not consciously direct, such as digestion or heart rate. The autonomic system has two parts, the sympathetic and parasympathetic nervous systems, with different and frequently opposing actions. The sympathetic nervous system, the “fight-flight-freeze” system, is in charge of the stress response. Among other activities, it raises heart rate and blood pressure and slows digestion so that the body’s resources can go toward dealing with immediate threats. The parasympathetic system is in charge of the “rest-digest” functions. It stimulates the digestive tract and all its accessory organs such as the pancreas, but it slows the heart and drops the blood pressure. In normal physiology, these two systems take turns depending on the need of the hour, the sympathetic system being active in times of stress and the parasympathetic system being dominant when repair is needed.

While all this is well known to any first- or second-year medical student, by the time most of us graduate and move on to our clinical work, we do not consider the functions of the autonomic nervous system on a day-to-day basis. But in [William Donald Kelley, DDS]’s work, and subsequently in [Dr. Nicholas Gonzalez]’s practice and my own, the autonomic nervous system is the core of the recommendations we make. As described in this book, Dr. Kelley empirically found that some patients did well on an alkalinizing, plant-based diet, with supplementation of magnesium and potassium, while other patients prospered on an acid-forming diet, high in protein and fat, with calcium supplementation.

Using these guidelines, Dr. Isaacs and her peers have been able to treat patients with a variety of health problems, many of them fighting some form of cancer. She continues in her foreword:

In contrast to Kelley, Nick, and myself, others in the integrative nutritional world state that everyone should be on the same diet, which might be anywhere from vegan to low-carb—usually the diet that the prescribing practitioners feel best eating for themselves. With our methods, I will find myself recommending for some patients a diet with less animal protein than works for me, and for others a diet with much, much more. Two of my patients, who were included in our article in “Alternative Therapies in Health and Medicine”, illustrate this point. One, with pancreatic cancer, was told to eat a near-vegetarian diet; the other, with lymphoma, was told to eat large amounts of animal protein. Both patients are alive and well today, nearly ten years since the publication of this article. Each continues to eat the prescribed diet with relish. The vast majority of the time, patients feel well with the recommendations we give.

However, in some cases, patients will modify things not because they feel unwell, but because they have read something that contradicts our advice. As an example, a few months after Nick’s death, I saw one of his patients, a parasympathetic-dominant patient with a low-grade lymphoma of the skin. His disease had improved at first, but it then stabilized with a small patch of disease remaining. As most clinicians know, with a change of physicians sometimes new information comes forward. I routinely ask whether patients are having any trouble tolerating their supplements.

He said no, rather tentatively, and paused. Then he said, “Well, I’m not actually taking the calcium supplements that Dr. Gonzalez told me to take. I read that calcium needs to be balanced with magnesium, so I’ve been taking a product with extra magnesium.” The extra magnesium was making his system too alkaline and suppressing his weak sympathetic system, keeping his parasympathetic system relatively overactive and preventing the protocol from bringing his system into balance. The advice he found about balancing calcium with magnesium is valid for people with other metabolic types, but not for him. From my point of view, his modification of his protocol was preventing progress against his disease.

. . .

Balanced patients, those whose sympathetic and parasympathetic systems are equally or nearly equally active, need only to have this balance maintained with their nutritional supplements. The diets for balanced patients have a great deal of flexibility; such patients will at times crave red meat and other acid-forming foods, and at other times desire only salads, citrus, and other more alkalinizing foods. I saw one such patient recently, a long-term patient of Nick’s who is a health professional. She reported that she did indeed have shifts in her food preferences, with days of eating meat followed by days of eating leafy greens.

She then told me enthusiastically about a meditation program that she had begun. I started to feel a little nervous as she spoke. Some forms of meditation have been shown to stimulate the parasympathetic nervous system, which could cause a balanced patient to shift into parasympathetic dominance. Dr. Kelley once told me that meditation was bad for people with an overactive parasympathetic system, and that such patients should instead consider watching action movies or playing video games to stimulate the underactive sympathetic system.

As I started to express my reservations, she said, “Oh, I don’t meditate every day. There are some days that it just doesn’t seem like the right thing to do.” I then told her that it would be interesting to see if her preferences about meditation correlated with her food choices, and asked her to keep track of that going forward. She said, “I can already answer that. The days I want to meditate, I don’t want red meat. The days that meditation doesn’t feel right, I want to eat a steak.”

After many years on her protocol, she was able to recognize how her metabolism was functioning on any given day and adjust both her diet and her activities to bring her system into balance, almost instinctively. On days when her sympathetic system was a trifle overactive, she would meditate and eat more lightly; on days when her parasympathetic system was overactive, she would eat more animal protein and skip the meditation.

To learn more about Dr. Isaacs, visit her website

To reserve your tickets to see her speak at the Co-op, visit Eventbrite.

To read the foreword in its entirety with full annotation, click here.