A well-planned vegetarian diet is healthy and associated with meaningful reductions in heart disease, type 2 diabetes, and overall mortality. The largest study on the topic, tracking over 73,000 people, found that vegetarians had a 12% lower risk of dying from any cause compared to non-vegetarians. But the key phrase is “well-planned.” A vegetarian diet built around whole foods delivers clear advantages, while one heavy on processed meat substitutes and refined carbs can fall short. The difference comes down to what you’re actually eating.
Heart Disease and Diabetes Risk
The strongest evidence for vegetarian diets sits in cardiovascular health. Vegetarians have roughly a 25% lower risk of developing or dying from ischemic heart disease, the type caused by narrowed arteries. A meta-analysis of 13 prospective cohort studies found a 15% reduction in overall cardiovascular disease risk and a 21% reduction in ischemic heart disease specifically. These are large, consistent effects seen across multiple populations.
The diabetes picture is similarly strong. People who follow a vegetarian diet from an early age show a 35% lower risk of developing type 2 diabetes compared to regular meat eaters. In some populations, lifelong vegetarians had up to a 74% reduced risk. Even switching to a vegetarian diet later in life made a difference: people who adopted a meat-free diet after years of eating meat had a 53% lower risk than those who continued eating meat. These associations held up even after researchers accounted for body weight, which suggests the diet itself, not just being thinner, plays a role.
Weight and Body Composition
Vegetarians tend to weigh less than omnivores. The Adventist Health Study 2, which followed more than 60,000 participants, found that vegetarians had a lower average BMI than meat eaters, with vegans coming in lowest. The EPIC-Oxford cohort study confirmed this pattern over five years of follow-up: vegetarians and vegans gained less weight over time than meat eaters. This likely contributes to some of the disease-risk benefits, though as the diabetes research shows, the advantages persist even when weight is factored out.
Longevity: A Mixed Picture
Whether vegetarians actually live longer depends, interestingly, on which vegetarians you study. The Adventist Health Study 2, following a large American cohort, found that vegetarians had a 12% lower all-cause mortality risk. But the EPIC-Oxford study, tracking over 47,000 British participants, found no longevity advantage for vegetarians at all.
The difference may come down to diet quality. American Adventist vegetarians consumed nearly twice the fiber and vitamin C of their British counterparts. Adventist vegan men averaged about 46 grams of fiber per day compared to 28 grams in EPIC-Oxford vegans. Being vegetarian alone isn’t a guarantee; it matters whether you’re eating legumes, whole grains, fruits, and vegetables or just avoiding meat.
Nutrients That Need Attention
A vegetarian diet has a few genuine nutritional gaps that require planning. None of them are dealbreakers, but ignoring them can cause real problems over time.
Vitamin B12
B12 is the most critical concern. This vitamin is found almost exclusively in animal products, and deficiency rates among U.S. adult vegetarians range from 30% to 47%. Even vegetarians who eat eggs and dairy may not get enough. B12 deficiency develops slowly but can cause nerve damage and fatigue. A B12 supplement or fortified foods (like nutritional yeast or fortified plant milks) is essentially non-negotiable for anyone on a long-term vegetarian diet.
Iron
Plant-based iron is absorbed less efficiently than the iron in meat. Your body absorbs about 25% of the iron from animal sources but 17% or less from plant sources like beans, lentils, spinach, and fortified grains. The practical fix is simple: eat iron-rich plant foods alongside something high in vitamin C, like citrus fruit, bell peppers, or tomatoes. Vitamin C converts plant iron into a form your body absorbs more readily, and it counteracts compounds in tea, coffee, and grains that block absorption. Drinking tea or coffee with meals, on the other hand, works against you.
Bone Health
Several large prospective studies have found that vegetarians, and especially vegans, face a modestly higher risk of bone fractures. Earlier research noted slightly lower bone mineral density in vegetarians, though those studies had significant limitations. Adequate calcium and vitamin D intake, whether from dairy, fortified foods, or supplements, is important. This is one area where lacto-ovo vegetarians (those who eat dairy and eggs) have a clear advantage over vegans.
The Protein Question
Concerns about vegetarian protein are largely outdated. All plant foods contain all 20 amino acids, including the 9 your body can’t make on its own. The idea that plant proteins are “incomplete” is misleading. While grains are lower in one amino acid (lysine) and legumes are slightly lower in sulfur-containing amino acids, this only matters if you eat a single food every day. In practice, vegetarians who eat a reasonable variety of legumes, nuts, seeds, and whole grains easily exceed protein requirements.
Studies of vegetarian diets consistently find average protein intakes of 62 to 82 grams per day, well above the approximate 50-gram reference value. Protein typically makes up about 13 to 14% of total calories in vegetarian diets, comfortably above the 10% lower bound considered acceptable. You don’t need to carefully combine foods at every meal. Just eat a mix of protein-rich plants throughout the day.
Processed Vegetarian Foods
The growing market of plant-based burgers, sausages, and nuggets deserves scrutiny. These products are often ultra-processed and can be high in sodium and saturated fat. A useful rule of thumb from Harvard nutrition researchers: check that saturated fat is less than a third of total fat, and sodium sits at roughly one milligram per calorie. A plant-based patty with 250 calories and 800 milligrams of sodium, for example, doesn’t pass that test.
These products can make transitioning to a vegetarian diet easier, and using them occasionally is fine. But building your diet around them misses the point. The health benefits seen in the research come from diets centered on whole plant foods: beans, lentils, vegetables, fruits, nuts, seeds, and whole grains. A vegetarian diet heavy on processed meat alternatives and refined carbohydrates won’t deliver the same results as one built around these staples.
What a Healthy Vegetarian Diet Looks Like
The 2025 U.S. Dietary Guidelines explicitly address vegetarian and vegan eating patterns, providing tailored recommendations to ensure nutritional adequacy across every life stage, from infancy through older adulthood, including pregnancy. This reflects the mainstream medical consensus: a vegetarian diet is nutritionally adequate when reasonably planned.
In practical terms, “well-planned” means three things. First, eat a genuine variety of whole plant foods, especially legumes, which are the nutritional backbone of a healthy vegetarian diet. Second, supplement B12 or eat B12-fortified foods consistently. Third, pay attention to calcium and vitamin D, particularly if you don’t consume dairy. Beyond that, the evidence is clear: vegetarians who eat real food enjoy lower rates of heart disease, diabetes, and obesity, with a strong signal toward living longer.