Concerns about the rising cost of health care are being voiced nationwide, even as unhealthy lifestyles are contributing to the spread of obesity, diabetes, and cardiovascular disease. For these reasons, physicians looking for cost-effective interventions to improve health outcomes are becoming more involved in helping their patients adopt healthier lifestyles. Healthy eating may be best achieved with a plant-based diet, which encourages whole, plant-based foods and discourages meats, dairy products, and eggs as well as all refined and processed foods. The goal of this article is to review the evidence supporting plant-based diets and to provide a guideline for presenting them to patients.
Plant-based or plant-forward eating patterns focus on foods primarily from plants. This includes not only fruits and vegetables, but also nuts, seeds, oils, whole grains, legumes, and beans. It doesn't mean that you are vegetarian or vegan and never eat meat or dairy.
Understanding Plant-Based Diets
It should be noted that the term plant-based is sometimes used interchangeably with vegetarian or vegan. Vegetarian or vegan diets adopted for ethical or religious reasons may or may not be healthy. It is thus important to know the specific definitions of related diets and to ascertain the details of a patient’s diet rather than making assumptions about how healthy it is. The following is a brief summary of typical diets that restrict animal products.
- Vegan (or total vegetarian): Excludes all animal products, especially meat, seafood, poultry, eggs, and dairy products.
- Mediterranean: Similar to whole-foods, plant-based diet but allows small amounts of chicken, dairy products, eggs, and red meat once or twice per month. Fish and olive oil are encouraged.
- Whole-foods, plant-based, low-fat: Encourages plant foods in their whole form, especially vegetables, fruits, legumes, and seeds and nuts (in smaller amounts). For maximal health benefits this diet limits animal products.
A healthy, plant-based diet aims to maximize consumption of nutrient-dense plant foods while minimizing processed foods, oils, and animal foods (including dairy products and eggs). It encourages lots of vegetables (cooked or raw), fruits, beans, peas, lentils, soybeans, seeds, and nuts (in smaller amounts) and is generally low fat. Leading proponents in the field have varying opinions as to what comprises the optimal plant-based diet. Despite these smaller differences, there is evidence that a broadly defined plant-based diet has significant health benefits.
Whole Foods vs. Processed Foods
Whole foods are the opposite of processed foods. They are kept as close to their natural state as possible. Examples include fresh fruits, vegetables, whole grains, legumes, nuts, and seeds. Processed foods have been changed from their natural state through processes such as adding other ingredients like preservatives.
Read also: Delicious Plant Paradox Breakfasts
Refined grains are not whole because one or more of their three key parts (bran, germ, or endosperm) has been removed. Replace refined grains with whole grains to slow your body’s breakdown of food, improve cholesterol levels, and improve blood sugar levels: For example, try choosing brown rice over white rice, or eating oatmeal with fruit for breakfast instead of sugary cereals.
Health Benefits of Plant-Based Diets
There’s excellent scientific evidence that many chronic diseases can be prevented, controlled, or even reversed with a whole-food, plant-based diet. Scientific research highlighted in the landmark book The China Study shows that a plant-based diet can reduce the risk of Type 2 diabetes, heart disease, certain types of cancer, and other major illnesses.
Weight Management
People who eat a plant-based diet tend to be leaner than those who don’t, and the diet makes it easy to lose weight and keep it off-without counting calories. A 2020 review looked at 19 intervention studies and found that in each one, participants assigned to plant-based diets lost weight.
Research suggests that the crux is calorie density. Meat, dairy products, and highly processed foods are high in calories yet low in the fiber that helps us feel full and fuels a healthy gut microbiome. Whole plant-based foods are low in calories, meaning you can eat a high volume of food without exceeding your calorie needs.
In 2006, after reviewing data from 87 published studies, authors Berkow and Barnard13 reported in Nutrition Reviews that a vegan or vegetarian diet is highly effective for weight loss. They also found that vegetarian populations have lower rates of heart disease, high blood pressure, diabetes, and obesity. In addition, their review suggests that weight loss in vegetarians is not dependent on exercise and occurs at a rate of approximately 1 pound per week.
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Farmer et al14 suggest that vegetarian diets may be better for weight management and may be more nutritious than diets that include meat. In their study, they showed that vegetarians were slimmer than their meat-eating counterparts. Vegetarians were also found to consume more magnesium, potassium, iron, thiamin, riboflavin, folate, and vitamins and less total fat.
In 2009, Wang and Beysoun15 analyzed the nationally representative data collected in the 1999-2004 National Health and Nutrition Examination Survey. The aim of their study was to analyze the associations between meat consumption and obesity. The Oxford component of the European Prospective Investigation into Cancer and Nutrition assessed changes in weight and BMI over a five-year period in meat-eating, fish-eating, vegetarian, and vegan men and women in the United Kingdom. During the five years of the study, mean annual weight gain was lowest among individuals who had changed to a diet containing fewer animal foods.
According to Sabaté and Wien,18 “Epidemiologic studies indicate that vegetarian diets are associated with a lower BMI and a lower prevalence of obesity in adults and children. A meta-analysis of adult vegetarian diet studies estimated a reduced weight difference of 7.6 kg for men and 3.3 kg for women, which resulted in a 2-point lower BMI. Similarly, compared with nonvegetarians, vegetarian children are leaner, and their BMI difference becomes greater during adolescence. Studies exploring the risk of overweight and food groups and dietary patterns indicate that a plant-based diet seems to be a sensible approach for the prevention of obesity in children.
Cardiovascular Health
A whole-food, plant-based diet is extremely effective at promoting cardiovascular health and preventing, halting, and in some cases reversing heart disease, the leading cause of death in the United States. A 2021 review of 99 studies found that diets rich in whole and minimally processed plant-based foods were associated with significantly lower risk of cardiovascular disease compared with diets high in meat and dairy products.
Animal-based foods are high in saturated fat and cholesterol, which raise blood cholesterol levels, causing fatty, wax-like plaque to build up in the arteries. Highly processed foods often contain excessive salt, which raises blood pressure, damaging the lining of the arteries over time. By eliminating these harmful foods from your diet and replacing them with whole plant-based foods, you can bring down your cholesterol levels, blood pressure, and risk of heart disease.
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In the Lifestyle Heart Trial, Ornish10 found that 82% of patients with diagnosed heart disease who followed his program had some level of regression of atherosclerosis. Comprehensive lifestyle changes appear to be the catalyst that brought about this regression of even severe coronary atherosclerosis after only 1 year. Interestingly, 53% of the control group had progression of atherosclerosis. After 5 years, stenosis in the experimental group decreased from 37.8% to 34.7% (a 7.9% relative improvement). The control group experienced a progression of stenosis from 46.1% to 57.9% (a 27.7% relative worsening). Low-density lipoprotein had decreased 40% at 1 year and was maintained at 20% less than baseline after 5 years.
In the Lyon Diet Heart Study, a prospective, randomized, secondary prevention trial, de Lorgeril found that the intervention group (at 27 months) experienced a 73% decrease in coronary events and a 70% decrease in all-cause mortality. The intervention group’s Mediterranean-style diet included more plant foods, vegetables, fruits, and fish than meat. Butter and cream were replaced with canola oil margarine.
In 2012, Huang et al31 performed a meta-analysis to investigate cardiovascular disease mortality among vegetarians and nonvegetarians. They only included studies that reported relative risks and corresponding 95% confidence intervals. Seven studies with a combined total of 124,706 participants were analyzed.
Diabetes Prevention and Management
Healthy plant-centered diets are associated with significantly lower rates of Type 2 diabetes and improved outcomes in those who already have this dangerous chronic condition. A 2018 report in BMJ Open Diabetes Research & Care found that for people with Type 2 diabetes, plant-based diets were more beneficial than the diets recommended by several diabetes associations, offering greater improvements in physical and emotional well-being.
Plant-based diets are low in saturated fat (a culprit behind insulin resistance) and high in fiber, which helps the body to regulate blood sugar and properly absorb nutrients. Plant-based diets also reduce the risk of being overweight or obese, a primary risk factor for Type 2 diabetes.
Plant-based diets may offer an advantage over those that are not plant based with respect to prevention and management of diabetes. The Adventist Health Studies found that vegetarians have approximately half the risk of developing diabetes as nonvegetarians.19 In 2008, Vang et al20 reported that nonvegetarians were 74% more likely to develop diabetes over a 17-year period than vegetarians.
Barnard et al21 reported in 2006 the results of a randomized clinical trial comparing a low-fat vegan diet with a diet based on the American Diabetes Association guidelines. People on the low-fat vegan diet reduced their HbA1C levels by 1.23 points, compared with 0.38 points for the people on the American Diabetes Association diet.
Environmental Impact
Plant-based diet benefits also extend beyond your own body: Switching to a WFPB lifestyle is one of the best things you can do for the environment. The main reason is that raising animals for food is an incredibly inefficient use of resources. Growing crops to feed animals “introduces a major extra step of waste relative to the efficiency of us just eating the plant foods directly,” explains David L. Katz, M.D., MPH, FACPM, FACP, FACLM. “If you just eat the plants, you cut out the middleman.” A 2018 analysis found that livestock provides just 18% of calories consumed globally but takes up 83% of farmland.
Cost-Effectiveness
Whole and minimally processed plant-based foods are not only the healthiest and most sustainable foods around; they’re also some of the most affordable. In fact, going plant-based can cut grocery bills by $750 a year per person, according to research published in the Journal of Hunger & Environmental Nutrition. When you stock your kitchen with WFPB staples such as brown rice, potatoes, and dried beans, you can assemble nutritious, satisfying meals for just a few dollars.
Case Study
A 63-year-old man with a history of hypertension presented to his primary care physician with complaints of fatigue, nausea, and muscle cramps. The result of a random blood glucose test was 524 mg/dL, and HbA1C was 11.1%. Type 2 diabetes was diagnosed. His total cholesterol was 283 mg/dL, blood pressure was 132/66 mmHg, and body mass index (BMI) was 25 kg/m2. He was taking lisinopril, 40 mg daily; hydrochlorothiazide, 50 mg daily; amlodipine, 5 mg daily; and atorvastatin, 20 mg daily.
He was prescribed metformin, 1000 mg twice daily; glipizide, 5 mg daily; and 10 units of neutral protamine Hagedom insulin at bedtime. His physician also prescribed a low-sodium, plant-based diet that excluded all animal products and refined sugars and limited bread, rice, potatoes, and tortillas to a single daily serving. He was advised to consume unlimited non-starchy vegetables, legumes, and beans, in addition to up to 2 ounces of nuts and seeds daily.
The patient was seen monthly in his primary care clinic. Over a 16-week period, significant improvement in biometric outcome measures was observed. He was completely weaned off of amlodipine, hydrochlorothiazide, glipizide, and neutral protamine Hagedorn insulin. Follow-up blood pressure remained below 125/60 mmHg, HbA1C improved to 6.3%, and total cholesterol improved to 138 mg/dL.
The presented case is a dramatic example of the effect a plant-based diet can have on biometric outcomes like blood pressure, diabetes, and lipid profile. The reduction in HbA1C from 11.1% to 6.3% in 3 months is much better than would be expected with monotherapy with metformin6 or daily exercise.7 The improvement in blood pressure observed over a 4-month period with few medications is also rarely encountered in clinical practice and is likely related to a low-sodium diet and the avoidance of red meat.
Nutritional Considerations for Plant-Based Diets
Though previously associated with undernutrition, poor diet is now often correlated with excess calories, saturated fats, trans fats, added sugars, and sodium. Overall, nutrition from plant-based diets is typically of higher quality than omnivorous diets, as assessed by the Alternative Healthy Eating Index (AHEI). A whole food plant-based (WFPB) diet is one made up of predominantly unprocessed fruits, vegetables, whole grains legumes, nuts and seeds, and excludes animal foods, with certain selective supplementation of vitamins B12. Sometimes D.
Macronutrients
All macronutrients (protein, carbohydrate, and fat) are present in whole plant foods in varying proportions.
Protein: The nine essential amino acids (leucine, isoleucine, methionine, phenylalanine, histidine, tryptophan, valine, threonine, and lysine) are synthesized only by plants. Those consuming a plant-based diet are more likely to achieve a healthy fat intake than most omnivorous diets.
Fat: Fat requirements are very low, and plant foods are able to supply all essential fat requirements. The AIs for linoleic acid (LA, an omega-6 fatty acid) is only 12 grams per day for adult women under 70 years and 17 grams for men under 51 or 14 grams for those 51-70 years. Dietary intakes of ALA, the precursor to n-3 fatty acids eicosatetraenoic acid (EPA) and docosahexaenoic acid (DHA) include cold-water fish and seafood. Plant-based eaters generally have lower blood levels of EPA and DHA, and these nutrients may be virtually absent in vegans.
Carbohydrates: Dietary fiber is found exclusively in plant foods. The AI for fiber is 14 g per 1,000 calories per day,3 which translates to 25 g per day for women <50 yrs and 21 g for those >50 yrs. For men, it is 38 g <50 yrs and 30 g for >50 yrs. On average, American adults consume half the recommended amount of fiber. A predominantly plant-based diet rich in whole foods allows for plenty of fiber in the diet.29 Foods high in fiber include black beans, split peas, lentils, avocado, raspberries, dried figs, flaxseeds, oatmeal, and whole wheat pasta.
Micronutrients
Vitamin B12: Vitamin B12 or cobalamin is a group of complex molecules with a single cobalt atom at their center. B12 is one of the eight B vitamins making up the water-soluble vitamins, which are absorbed easily into the bloodstream. Vitamin B12 is made by microorganisms found in the soil and water, as well as produced by microorganisms in the intestines of animals. Vitamin B12 is stored in the liver and muscle tissue, so it is naturally found in animal foods and not plant foods. The amount made in the intestines is not adequately absorbed, so it is recommended that people consume B12 in food or supplementation. Vegetarians and the elderly have a high risk of vitamin B12 deficiency due to low consumption, as well as lower absorption.
Vitamin D: Vitamin D, or calcitriol, is an exception to the list of nutrients provided completely by plant food sources in that it is a fat-soluble steroid hormone produced endogenously from sun exposure. Sunlight is a better source of vitamin D than dietary sources as ultraviolet (UV) B radiation transforms the precursor of vitamin D in the skin into vitamin D3. It is assumed that most people do not make enough D from sun exposure due to indoor living. Deficiency can result in brittle bones, rickets, osteomalacia,73 and/or osteoporosis.74 Symptoms of low vitamin D include fatigue, bone, joint, or muscle pain, and anxiety.
Calcium: Calcium is found in many plant foods. Though cow’s milk is often touted as the best source, our bodies may absorb calcium from plant foods at a higher rate. Plant sources of calcium are adequate to meet needs. For example, calcium-set tofu has the same calcium availability as cow’s milk.56 Plant-based sources of calcium include bok choy, broccoli, Brussels sprouts, kale, collard greens, tofu, winter squash, and almonds.
Iron: Iron is needed to build hemoglobin for red blood cells to carry oxygen from lungs to body tissue. It is vital to muscle function and ATP energy production and as a cofactor for several enzyme systems. The RDA for iron is 18 mg/day for adult women under the age of 51 and 8 mg/day for older women, as well as all adult men,3 though RDAs for vegetarians are 1.8 times higher than for meat-eaters, as heme iron from meat is more bioavailable than nonheme iron from plant-based foods, and meat, poultry, and seafood increase the absorption of nonheme iron.
Iodine: Iodine is an essential component of the two thyroid hormones, thyroxine and triiodothyronine, which regulate many biochemical functions, including protein synthesis and enzyme activity.101 It is a trace element found in soil and the sea and, thus, obtained from plants and sea vegetables.
Vitamin A: Vitamin A is vital for cell reproduction and differentiation, immune function, and good vision. It comes from two sources: plant sources provide carotenoids, and animal sources provide retinol.
Vitamin C: Vitamin C or L-ascorbic acid is required to turn fat into energy and make collagen. It is needed to create certain neurotransmitters and is involved in protein metabolism.
Vitamin E: Vitamin E refers to a collection of fat-soluble compounds with distinctive antioxidant properties. They protect cells from the damaging effects of unstable free radicals that can damage cells and can contribute to cardiovascular disease and certain cancers.
Magnesium: Magnesium is needed for many chemical reactions in the body as well as for neuromuscular connections.
Potassium: Potassium is easily found in many plant foods and is needed for blood pressure regulation and bone health; thus, lower intake is associated with cardiovascular, renal, and bone health risks.
Zinc: Zinc is a mineral and is found in the soil and sea. It competes for transporters with other minerals, so absorption is affected by the balance of other minerals (iron, manganese, nickel, calcium, and phosphate). Zinc is involved in many functions, including brain cell communication, hemoglobin activity, male reproductive cell function, night vision, immunity, and wound healing.
Foods to Limit
Added Sugar: Excess intake of added sugars is associated with weight gain, excess body weight and obesity, type 2 diabetes, high serum triglycerides, higher cholesterol, high blood pressure and hypertension; stroke; coronary heart disease, cancers, and dental caries.52 The recommendation in the 2020 Dietary Guidelines for Americans is to limit added sugar intake to no more than 10% of calories.3 A whole food diet that avoids refined grains and prepared foods is naturally low in added sugars.
Sodium: The ubiquitous intake of processed foods has led to an excess in sodium intake. The CDRR is <2,300 mg/day. consume more than 3,400 mg each day.77 Though the body needs very small amounts of sodium to function, evidence points to an association with excess salt consumed and elevated blood pressure levels, a major risk factor for cardiovascular disease.78 Limiting consumption of commercially processed foods is an important strategy to reduce excess sodium intake.
Saturated Fats: Because they are found primarily in animal foods, plant-based diets are naturally low in saturated fats, which are associated with risk of cardiovascular disease and diabetes.
Tips for Transitioning to a Plant-Based Diet
If you find it difficult to reduce animal products and processed foods: No need to give them up entirely! If other members of your household follow different diets: Find common ground. If you don’t enjoy the taste of plant-based meals: Use seasonings such as garlic, lemon juice, soy sauce, and spices for more flavor.
- Eat lots of vegetables. Fill half your plate with vegetables at lunch and dinner. Make sure you include plenty of colors in choosing your vegetables.
- Change the way you think about meat. Have smaller amounts.
- Choose good fats.
- Cook a vegetarian meal at least one night a week.
- Include whole grains for breakfast. Start with oatmeal, quinoa, buckwheat, or barley.
- Go for greens. Try a variety of green leafy vegetables such as kale, collards, Swiss chard, spinach, and other greens each day.
- Build a meal around a salad. Fill a bowl with salad greens such as romaine, spinach, Bibb, or red leafy greens.
- Eat fruit for dessert.
Over time, eating a plant-based diet will become second nature.
Overcoming Challenges
A plant-based diet requires planning, reading labels, and discipline. The recommendations for patients who want to follow a plant-based diet may include eating a variety of fruits and vegetables that may include beans, legumes, seeds, nuts, and whole grains and avoiding or limiting animal products, added fats, oils, and refined, processed carbohydrates.
It may be especially beneficial for those with obesity, Type 2 diabetes, high blood pressure, lipid disorders, or cardiovascular disease. The benefits realized will be relative to the level of adherence and the amount of animal products consumed. Strict forms of plant-based diets with little or no animal products may be needed for individuals with inoperable or severe coronary artery disease.