A vegetarian diet is an eating pattern that excludes meat, poultry, and fish, relying instead on plant foods like vegetables, fruits, grains, legumes, nuts, and seeds. Some versions include dairy, eggs, or both. Roughly 4.2% of Americans follow a vegetarian diet, while the Asia-Pacific region leads globally with about 19% of the population eating vegetarian.
Types of Vegetarian Diets
Not all vegetarian diets look the same. The three main categories differ based on which animal products stay on the plate:
- Lacto-ovo vegetarian: Includes plant foods plus dairy products and eggs. This is the most common form in Western countries.
- Lacto vegetarian: Includes plant foods and dairy but no eggs.
- Vegan: Excludes all animal-derived foods, including dairy, eggs, and honey.
You’ll also hear terms like “pescatarian” (adds fish) and “flexitarian” (mostly plant-based with occasional meat), though these fall outside the strict vegetarian definition. The health outcomes vary across these categories, with some benefits becoming more pronounced in stricter plant-based patterns.
Heart Disease and Metabolic Benefits
Vegetarian diets are consistently linked to better cardiovascular health. A meta-analysis of 13 prospective cohort studies found that vegetarians had a 21% lower risk of ischemic heart disease compared to non-vegetarians. Vegetarians also tend to carry lower total cholesterol, lower LDL (“bad”) cholesterol, and lower BMI than omnivores, all of which contribute to heart protection. The data on stroke, however, shows no clear advantage.
The effect on blood sugar regulation is even more striking. In the Adventist Health Study-2, which tracked over 41,000 people, vegans had a 62% lower risk of developing type 2 diabetes after controlling for BMI and lifestyle factors, while lacto-ovo vegetarians had a 38% lower risk. A separate study of Taiwanese Buddhist vegetarians found a 51% lower diabetes risk in men and a 75% lower risk in postmenopausal women. Even a generally healthy plant-based diet, one rich in whole grains, fruits, and vegetables while low in refined grains and sugary drinks, was associated with a 34% reduction in diabetes risk.
Longevity and Mortality Risk
A meta-analysis pooling data from 14 studies found that a plant-based diet was associated with a 16% reduction in overall mortality risk, a 19% reduction in cardiovascular death, and a 12% reduction in cancer death. The quality of the diet matters enormously, though. A plant-based pattern built around whole foods showed similar protective effects, while an unhealthy plant-based diet heavy in refined grains, sugary drinks, and processed snacks actually increased the risk of death by 18%.
The protective effect was more pronounced in people over 55. In that age group, a healthy plant-based diet was associated with an 18% lower risk of dying from any cause, compared to a 10% reduction in younger adults. Simply cutting out meat isn’t enough. What you replace it with determines whether the diet helps or harms.
Nutrients That Need Attention
A well-planned vegetarian diet provides most nutrients without trouble, but a few require deliberate effort.
Vitamin B12
B12 is the nutrient most likely to fall short, especially for vegans. Adults need 2.4 micrograms per day, and B12 occurs naturally almost exclusively in animal products. Lacto-ovo vegetarians can get some from dairy and eggs, but most experts recommend that all vegetarians eat B12-fortified foods (like breakfast cereals or plant milks) or take a supplement. Some microalgae supplements contain biologically active B12, though fortified foods and standard supplements remain the most reliable sources.
Iron and Zinc
Plant foods contain a form of iron that your body absorbs less efficiently than the type found in meat. The same is true for zinc, particularly because legumes and whole grains contain compounds called phytates that further reduce absorption. Pairing iron-rich foods like lentils or spinach with a source of vitamin C (citrus, tomatoes, bell peppers) significantly improves uptake. Despite lower iron stores, vegetarians in developed countries eating varied diets don’t show higher rates of iron-deficiency complications. Some researchers have even suggested that moderately lower iron stores may reduce the risk of certain chronic diseases.
Calcium and Bone Health
Bone density in vegetarians is about 4% lower at the spine and hip compared to omnivores. In vegans, that gap widens to about 6% at the hip, though researchers have described even this difference as not clinically meaningful for fracture risk, provided calcium and protein intake are adequate. The key finding: vegetarian women who ate plant proteins like beans, soy, and nuts more than once a day had a 68% lower risk of wrist fracture compared to vegetarian women who ate these foods only three times a week. If you skip dairy, fortified plant milks, tofu made with calcium, leafy greens like kale, and broccoli become essential daily staples.
Getting Enough Protein
Protein is the nutrient vegetarians get asked about most, and it’s typically the easiest to manage. One cup of cooked lentils delivers 18 grams of protein. A cup of firm tofu provides 22 grams. A serving of tempeh packs 27 grams. Beans, chickpeas, quinoa, nuts, seeds, and eggs (for lacto-ovo vegetarians) round out the options.
Plant proteins are sometimes called “incomplete” because individual sources may be low in one or two amino acids. In practice, eating a variety of protein sources throughout the day covers all your needs without any precise food combining at each meal. A lunch with lentils and a dinner with tofu, for instance, gives your body the full range of amino acids it requires.
Environmental Impact
Food choices have a measurable effect on carbon emissions, and the data is straightforward. In one study comparing dietary patterns, meat eaters generated a daily carbon footprint of 3.62 kg of CO2 equivalent, while vegetarians produced 2.45 kg and vegans 1.38 kg. Over a week, a group of 10 vegetarians produced roughly 73 kg less CO2 equivalent than the same number of meat eaters. Per 1,000 calories consumed, a meat-based diet generated about 58% more greenhouse gas emissions than a vegetarian one.
The trend scales with how many animal products you remove. Each step away from animal-derived foods corresponds to a measurable drop in carbon output, with vegan diets showing the lowest footprint and meat-heavy diets the highest. For someone looking to reduce their environmental impact without going fully vegan, a vegetarian diet represents a significant middle ground.