THE ARGUMENT FOR Plant-Based Diets

By: 
Chris K. Guerin, MD, FNLA, FAC and Rajasreepai Ramachandra Pai, MD

By Chris K. Guerin, MD, FNLA, FAC and Rajasreepai Ramachandra Pai, MD

Plant-based diets are a relatively new concept – or, rather, a return to dietary habits followed by our ancestors before weapons were invented for hunting animals. And as unconventional as it may seem, more and more people in the Western world are adopting a plantbased diet due to the many health benefits it promises.

Worldwide, an estimated 2 billion people live primarily on a meat-based diet, while an estimated 4 billion live primarily on a plant-based diet, often by necessity rather than specific choice, due to food availability. Here in the U.S., food production systems use about 50 percent of the total U.S. land area, approximately 80 percent of the fresh water, and 17 percent of the fossil energy. The heavy dependence on our natural resources suggests that our country’s food system, whether meat-based or plant-based, is not sustainable. So why consider a plant-based diet for yourself at this time? Quite simply, for better health.

Adopting a plant-based diet is mostly based on the theory of promoting healthy gut microbiomes. Gut microbiomes refer to the type of bacteria and microbes we have in our GI (gastrointestinal) tract. By adopting a plant-based diet, a person can positively alter the gut microbiome by eating optimal foods, i.e., plants.

The typical American diet is high in carnitine, lecithin and other substances which promote bacteria that produce compounds that are atherogenic (promote artery clogging). Eating meat and other animal products also contributes to weight gain. And in addition to saturated fat, meat contains a high amount of food preservative sulfur dioxide, which can cause a number of adverse effects; arachidonic acid, which can generate inflammatory responses in the body; and heme iron, which can be harmful in large amounts. Meat, fish, dairy and eggs may also increase our exposure to dietary antibiotics; industrial toxins; mercury and other toxic heavy metals; advanced glycation end-products (AGEs), which can be a factor in aging and in the development or worsening of many degenerative diseases, such as diabetes, atherosclerosis, chronic kidney disease and Alzheimer's; cadmium, a toxic metal which can cause kidney problems and bone softening with long-term exposure; and xenoestrogens in fish and estrogenic meat carcinogens, which both can impact proper hormone balance.

So what specific benefits have actually been shown by making a dietary change? Let’s take a look at vegetarian diets, which have been studied extensively.

Vegetarian Diets and Weight Loss

A 2006 review reported that a vegan or vegetarian diet can be very successful in achieving weight loss, accompanied by the additional benefit of lower rates of heart disease, high blood pressure and diabetes. This review presented evidence that weight loss in vegetarians was not dependent on exercise and suggested a diet-only weekly weight loss of approximately 1 pound. The study authors further noted that a vegan diet seemed to cause more calories to be burned after meals in contrast to non-vegan diets, where food was being stored as fat. During the 1999 to 2004 time span, the National Health and Nutrition Examination Survey (NHANES) – a research program conducted by the National Center for Health Statistics (NCHS) to assess the health and nutritional status of adults and children in the United States and to track changes over time – reported that the more meat in a diet, the more likely the person was to be obese. Other studies have further supported this finding. The Oxford component of the European Prospective Investigation into Cancer and Nutrition found over a five-year period that mean annual weight gain was lowest among individuals who had changed to a diet containing fewer animal foods. And compared with non-vegetarians, vegetarian children are leaner, and their BMI (body mass index) difference becomes greater during adolescence, so a plant-based diet seems to be a sensible approach for the prevention of obesity in children as well.

Plant-based diets are low in energy density and high in complex carbohydrates, fiber and water, which may increase satiety (the feeling of being full) and resting energy expenditure, in turn preventing weight gain by fewer calories taken in overall and better “burning” of the calories actually eaten. Plus, vegetarian diets offer the added bonus of being more nutritious than diets that include meat, typically containing more magnesium, potassium, iron, thiamin, riboflavin, folate and vitamins.

Diabetes and a Vegetarian Diet

Plant-based diets may prevent diabetes, and if it has already developed, help manage the condition.

Adventist Health Studies reports that vegetarians have approximately half the risk of developing diabetes as nonvegetarians. Another study in 2008 reported that nonvegetarians were 74 percent more likely to develop diabetes over a 17-year period than vegetarians. A low-fat, plantbased diet with no or little meat may help prevent and treat diabetes by allowing insulin to work better in the body.

And if you already have developed diabetes, changing to a low-fat vegan diet can reduce your HbA1C levels (a measure of average blood sugars over the previous three months) by 1.23 points, compared with 0.38 points for those on just a carbohydrate-restricted diet. In addition, 43 percent of people on the low-fat vegan diet were able to reduce their medication, compared with 26 percent of those on the carbohydrate-restricted diet.

Reducing Heart Disease

In the LIFESTYLE Heart Trial, the first randomized clinical trial to investigate whether ambulatory patients could be motivated to make and sustain comprehensive lifestyle changes and, if so, whether the progression of coronary atherosclerosis (hardening and narrowing of the arteries) could be stopped or reversed without using lipid-lowering drugs, lead researcher Dr. Dean Ornish reported that 82 percent of patients with diagnosed heart disease who followed his program had some level of regression of atherosclerosis. Although his program involved diet changes, it also focused on stress management and physical activity. His prescribed plant-based regimen allowed a very low 10 percent of calories from fat, but 15 to 20 percent from protein, and 70 to 75 percent from carbohydrates. Cholesterol was restricted.

Interestingly, 53 percent of the control group in the study had progression of atherosclerosis. After five years, this narrowing in the experimental group decreased from 37.8 percent to 34.7 percent (a 7.9 percent relative improvement).

Low-density lipoprotein (LDL cholesterol) decreased 40 percent at one year and was maintained at 20 percent less than baseline after five years. These reductions are similar to results with lipid-lowering medications. The control group experienced a progression of stenosis from 46.1 percent to 57.9 percent (a 27.7 percent relative worsening).

In those placed on a Mediterranean-style diet, which included more plant foods, vegetables, fruits and fish than meat, with butter and cream replaced by canola oil margarine (canola oil and olive oil were the only fats recommended), this diet group had a 73 percent decrease in coronary events at 27 months and a 70 percent decrease in all-cause mortality as compared to the group eating their usual diet.

Yet more data comparing heart disease-specific death rate ratios of vegetarians and non-vegetarians showed a 24 percent reduction in coronary heart disease death in vegetarians as compared with non-vegetarians. Some of this effect might be due to lower cholesterol blood levels, but vegetarian diets are also known to decrease blood pressure.

The Plant-Based Diet: A Step Beyond Vegetarian Diets

Although vegetarian diets are associated with lower risk of several chronic diseases, different types of vegetarians may not experience the same effects on health. The key is to focus on eating a healthy diet, not simply a vegan or vegetarian diet. Healthy eating may be best achieved with a plant-based diet, which is a dietary regimen that encourages whole, plant-based foods and discourages meats, dairy products and eggs, as well as all refined and processed foods. It encourages lots of vegetables (cooked or raw), fruits, beans, peas, lentils, soybeans, seeds and nuts (in smaller amounts) and is generally low in fat. And a true plant-based diet really takes the vegetarian diet a step forward. Unlike the vegan diet, processed foods, including oil, white flour, and refined sugars, are eliminated entirely.

The easiest way to remember the distinction between the vegan diet and a whole food, plant-based diet: people who are vegan can eat cookies and crackers, while people who consume whole food, plant-based diets choose not to eat those. And water replaces fruit juices and milk.

In short, a plant-based diet excludes processed foods and sweets, which makes it unique among other diets for better health.

Another plant-based diet option is to use olives and avocados for fat sources instead of processed oils like olive oil or canola oil and cheese. Again, beans and legumes can be chosen instead of veggie patties, which come under the category of processed foods.

For those who are worried about getting enough protein from a plant-based diet, about three to five servings of legumes, three to five servings of whole grains, and one to three servings of nuts will provide 20 to 25 grams of protein per day. Some essential nutrients that can be missing on plantbased diet are vitamin B12 and vitamin D. These deficiencies can be compensated by choosing products that are fortified and possibly taking vitamin B12 and vitamin D supplements.

Plant-based diets help with weight loss similar to other diets such as the Atkins diet and Paleo diet. In addition to helping treat obesity, plant-based diets have been show to help with reducing mortality, improving and preventing cardiovascular diseases, diabetes and high blood pressure. Fifty percent of all cancers are thought to be due to our diet, and a plant-based diet can reduce this risk.

Plant-based diets also lessen food cost by reducing the purchase of processed food and supports local farmers to grow fresh grains and produce. On a global level, plantbased diets also help lessen greenhouse gas emissions and have a much smaller impact on the environment.

There’s no doubt that reducing your intake of meat and embracing a plant-based diet is not only good for you, but the environment as well. So, whether you’re planning on making a dramatic change to enhance your well-being or prefer to ease into such a significant lifestyle change, there are plenty of resources available on the internet and in your local bookstore to help you embrace a new, healthier way of eating.