By Gaia Kile
Call me a science geek: I enjoy delving into the scientific literature about topics I'm interested in. This often includes looking at studies from the previous year that relate to plant-based nutrition. I search my favorite database for articles about vegetarian and vegan diets and then settle in for a good read.
This past year’s research makes the case that there are specific advantages to a vegetarian or vegan diet. A review of general nutrition that I came across from this past year is titled “Can We Say What Diet Is Best for Health?” (Katz, Meller) It took on the ambitious task of reviewing six major nutritional strategies, including Paleolithic, low-carb, Mediterranean, low-fat vegan/vegetarian, and a couple of others. The author’s conclusion followed Michael Pollan's dictum: “Eat food. Not too much. Mostly plants.” This is an okay start, but sometimes it makes sense to say: “Eat only plants” or “No meat.” Let's take a look at some research.
In demonstrating that plant-based nutrition has definitive advantages over other healthy eating approaches, the most important study of this past year was “A Way to Reverse CAD?” by Caldwell Esselstyn and his associates. CAD stands for coronary artery disease, or the blockages of blood vessels to the heart. Dr. Esselstyn is a cardiologist from the Cleveland Clinic. He has been using a whole food low-fat vegan diet to treat cardiovascular disease for over 25 years. The intent of this particular study was to show that people can adhere to this type of diet. The study enrolled 198 participants and followed them for an average of 3.7 years. At the end of the study, almost 90 percent of the participants were still on the diet. Since this group of participants was self-selected, this is not incredibly surprising. But let's compare the two groups: those who stayed with the diet and those who resumed eating meat. In the group that discontinued the recommended plant-based diet, 10 percent died of heart disease, and 62 percent had evidence that their disease was getting worse. Among those who stayed on the vegan diet, no one died from cardiovascular disease, perhaps as many as 10 percent had some evidence of worsening health, but only one patient had a related cardiovascular incident, a stroke. The vast majority of patients, 81 percent, felt better and their heart disease improved. Some of these patients had ultrasounds of their heart that showed an actual reversal of blood vessel blockage.
Physician Dean Ornish is famous for demonstrating that it is possible to reverse coronary artery disease. He did this using a vegan diet as part of a comprehensive lifestyle program. This raises the question, was it the diet or the other lifestyle changes, exercise, meditation, and group support activities? Caldwell Esselstyn demonstrated that cardiovascular disease could be reversed with only using a vegan diet. While medications and other therapies may be useful in “managing” heart disease, a low-fat vegan diet, either as part of a total lifestyle program or on its own, is the only strategy that has demonstrated actually reversing the blockages in blood vessels in heart disease.
Type II diabetes is a disease caused by excessive fat in your muscle tissues. This prevents cells from being able to use the glucose in your blood stream and results in high blood sugar. A review of vegetarian nutrition published this year states “studies found that vegetarians have lower prevalence of type II diabetes compared with non-vegetarians.” The review backs this up with a discussion of nine different studies. As that review was going to press, another study was being published demonstrating the same principle again. In a study of 4,384 Taiwanese, among women we see diabetes almost four times as often in omnivores as in vegetarians. Among men diabetes was about two times as common for omnivores.
Ten years ago, a clinical trial showed greater improvements in diabetes in groups randomly assigned to a low-fat, low-glycemic vegan diet than groups assigned to a conventional therapeutic diabetes diet. Again this past year, there was another trial showing a vegetarian diet reversing blood sugar among diabetics. A paper titled “Ma-Pi 2 macrobiotic diet and type 2 diabetes mellitus” (Porrata-Maury et al.) described a four-country study that used a specific macrobiotic diet (70 percent carbohydrates, 18 percent fats, and 12 percent protein) with a 40 to 50 percent rate of the diet consisting of whole grains. Participants had an average improvement in their blood sugar of 32 percent in the space of 21 days. Participants also lost on average five pounds.
Another article published last year looks at diabetes from the other direction, arguing that meat consumption is a risk factor for diabetes. Looking at a number of large studies, the article shows that the risk is greatest for eating processed meats, followed by red meats, then chicken, then fish. Among vegans diabetes is nearly half as likely compared to those who eat meat.
A number of sources have suggested that a vegan or vegetarian diet may reduce your risk of cancer. But not all cancers are the same. There is relatively strong evidence that a plant-based diet protects against colorectal cancer. This past year a study from Korea compared the rates of colorectal adenomas (pre-cancerous polyps) between vegetarian Buddhist priests and omnivores from the general population. Although this doesn't strike me as an even comparison, the Buddhist priests did in fact have a lower rate of adenomas. An interesting side note is that the vegetarian Buddhist priests had a higher rate of metabolic syndrome, a precursor to diabetes. This may have to do with greater consumption of sweets among the Buddhist priests. It is certainly possible to have a vegetarian or vegan diet that is out of balance or unhealthy.
Preliminary dietary guidelines for preventing Alzheimer's were developed and published by the International Conference on Nutrition and the Brain. These guidelines suggest avoiding saturated and trans-fats, eating vegetables, legumes, fruits, and whole grains as the staple of the diet, getting vitamin E from food, including seeds, nuts, green leafy vegetables, and whole grains, and getting adequate supplementation of vitamin B12.
As is typical for any year, the medical literature discussed vitamin B12 and neurological development. One review of B12 levels in vegetarians and vegans suggested that B12 supplementation is important not only for vegans but also for vegetarians. Another review that looked at plant sources of vitamin B12 suggested that the only way plant-based food might provide enough B12 would be to eat a lot of Nori seaweed on a daily basis. For most of us, a supplement probably makes more sense.
A balanced vegetarian or vegan diet is a healthy way of eating. When faced with certain diseases, a vegan diet may be the best choice, especially as it offers the only research-demonstrated way of reversing heart disease.
As a health professional, I focus on sustaining and restoring my patients’ health. Often a plant-based diet is a good strategy toward that goal, but that is an individual decision for my patients to make. I don’t expect my patients to address issues of the environment, but changing to a plant-based diet is also more sustainable for the environment. Just one example of this connection is that estimates of the greenhouse gas emissions due to livestock range from 11 percent, according to the Food and Agriculture Organization, to 51 percent, according to a paper by the World Watch Institute. That’s right, over half of all greenhouse gas effects may be caused by livestock production. While there may be more ecological ways to raise livestock, even by best estimates livestock would still have a significant impact. When the best medical care lines up with what’s best for the biosphere, I’d call that sustainable medicine.
Gaia Kile is a Family Nurse Practitioner with a practice in Ann Arbor. He is dedicated to holistic patient-centered care grounded in science-based information and the individuality of each patient. Depending on a patient’s needs he will: encourage lifestyle modification; provide emotional support; use mind-body therapies; engage energy healing; recommend herbs and nutritional supplements; and prescribe hormones and conventional medications.