Plants May Have the Power to Prevent Chronic Disease: Review
Plants May Have the Power to Prevent Chronic Disease: Review

By Theresa Sam Houghton

Eating more plants could be the key to avoiding heart disease and some types of cancer, according to a recent review of nearly 50 studies.

The umbrella review, published in May in PLOS One, evaluated 48 previous reviews and meta-analyses published between 2000 and 2023 and concluded that vegetarian or vegan diets “significantly reduce the risk” of ischemic heart disease, gastrointestinal cancer, and prostate cancer, as well as associated mortality.

Eat More Plants to Lower Disease Risk

The review’s findings add to a growing body of research linking plant-based dietary patterns with better health outcomes.

“There is massive scientific data that a well-balanced, whole-food, plant-based diet emphasizing fruits, vegetables, whole grains, and the whole spectrum of legumes, peas, beans, lentils” has health benefits, according to Dr. Joel Kahn, cardiologist and author of “The Plant-Based Solution.” “Literally—we’ve had data since the 1940s and 1950s.”

Recent data confirm these benefits, including a 2017 review showing a correlation between plant-based diets and lower cardiovascular disease and cancer risk. Additionally, a 2023 review found a lower risk of Type 2 diabetes, cardiovascular disease, and some types of cancer in people eating diets that prioritize whole plant foods over refined carbohydrates.

Additional evidence suggests that a plant-based diet may promote weight loss and reduce the risk of Type 2 diabetes, cardiovascular disease, and related mortality.

The power of plant-based diets seems to stem from how they affect markers of chronic disease. In the umbrella review, researchers noted that “vegetarian and vegan diets are significantly associated with better lipid profile, glycemic control, body weight/BMI, [and] inflammation”—all critical factors in cardiometabolic health. Changes in these factors influence the development of metabolic syndrome, a cluster of symptoms that can progress to cardiovascular disease or Type 2 diabetes over time.

Whole Plant Foods Are the Key to Better Health

Not all plant-based diets are created equal. The rising popularity of plant-based foods in recent years has given birth to a plethora of products, from “bleeding” plant burgers to faux ribs complete with edible bones—many of which fall into the category of ultra-processed foods.

Studies comparing plant-based diets centered around whole, minimally processed foods to ultra-processed alternatives show that only whole-food dietary patterns improve health outcomes and reduce disease risk.

To incorporate more of these foods into daily meals, Dr. Kahn recommends following a framework like “G-BOMBS,” popularized by plant-based doctor Joel Fuhrman. Short for greens, beans, onions, mushrooms, berries, and seeds, G-BOMBS encompasses a wide range of nutrient-dense plant foods containing antioxidant, anti-inflammatory, and anti-cancer compounds.

Dr. Michael Greger, creator of, provides additional guidance with his “Dining by Traffic Light“ system, which classifies foods based on how much processing they’ve undergone. ”Green light“ foods are unprocessed plant foods in their natural forms. ”Yellow light“ foods include processed plant foods and unprocessed animal foods. Ultra-processed plant foods and processed meats get a ”red light“ designation. Diets made up mostly of ”green light” foods are thought to provide the most significant benefits.

Fiber, Polyphenols, and Other Disease Fighters

Fiber intake may be one possible mechanism by which unprocessed plants affect health. Fruits, vegetables, legumes, and whole grains contain soluble fiber, which interacts with the gut microbiome in complex ways that may impact body weight and influence systemic health.

Plant-based foods also contain a variety of unique nutrients and compounds, such as polyphenols and sulforaphane, which may help control inflammation, reduce cardiovascular disease risk, and protect against developing cancers of the breast, prostate, colon, skin, lung, and stomach.

But despite the significant body of evidence, researchers involved in the umbrella review advise that their findings “should be taken with caution.” They pointed out that current research has several limitations—including highly variable study designs, participant demographics, and lifestyle factors—and noted that restrictive or unbalanced plant-based diets carry “potential risks associated with insufficient intake of vitamin and other elements.”

Supplement Strategically to Avoid Deficiencies on a Plant-Based Diet

The No. 1 nutrient of concern for vegetarians and vegans? Vitamin B12.

“Anybody who is eating a vegan diet or a vegetarian diet or just a mostly plant-based diet should be taking a vitamin B12 supplement,” says Ginny Messina, a vegan registered dietician and co-author of “Vegan for Life.” Vitamin B12 is only found in significant amounts in animal products and fortified foods, and a deficiency can cause anemia, mood changes, or permanent neurological damage.

Plant-based diets may also be low in vitamin D, omega-3 fatty acids, and minerals like iodine, selenium, iron, and zinc. But Dr. Kahn points out that these deficiencies—and others—aren’t unique to plant-based diets.

“When you do vitamin blood levels in the standard American public on all kinds of diets, there’s widespread deficiencies,” he said. This, he says, can be inferred from surveys like the 2005–2016 National Health and Nutrition Examination Surveys (NHANES), which showed that 95 percent of Americans don’t get enough vitamin D, 46 percent fall short on vitamin C, and 45 percent don’t meet adequate intakes for vitamin A.

To ensure proper nutrient levels, Dr. Kahn recommends that people switching to mainly or wholly plant-based diets take a multivitamin formulated for vegans that combines vital vitamins and minerals with omega-3s.

Need Protein? Plants Have It

Protein, not vitamins, is often the focus of concern for those considering a plant-based diet—even though it’s one nutrient most people don’t need to supplement.

While it’s true that protein from plant sources like lentils, beans, peas, nuts, and whole soy products isn’t absorbed as readily as protein from animal products, the difference is slight. To compensate, dieticians like Ms. Messina recommend eating about 10 percent more than the recommended dietary allowance (RDA) of 0.8 grams per kilogram, which amounts to about six additional grams of protein per day for someone weighing 150 pounds.

However, age and activity level can affect protein requirements. Adults over 50 appear to respond less readily to protein’s muscle-building properties, so Ms. Messina suggests increasing intake to 1 to 1.2 grams per kilogram to maintain bone and muscle mass. Up to 2.7 grams of protein per kilogram may be necessary for athletes to build muscle and support intense training.

For the general population, though, eating a variety of plant-based foods appears to be the best approach to improving overall health. According to Ms. Messina, going plant-based doesn’t have to be all or nothing.

“I don’t know that we have real strong evidence to suggest that you have to be vegan in order to have a very healthy diet,” she pointed out. “I would say probably somewhere between 90 and 95 percent plant-based … would be something that people should aim for if their main concern is about health.”

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