Option A
Plant-Based Diet
The whole-food, predominantly or exclusively plant-derived eating pattern.
Best for: People seeking to reduce chronic disease risk and lower their environmental footprint through vegetables, legumes, grains, nuts, and seeds.
Option B
Omnivore Diet
The flexible, varied eating pattern that includes both animal and plant foods.
Best for: People who want broad dietary flexibility and find certain nutrients — like complete proteins and B12 — most accessible through animal foods.
How These Two Eating Patterns Differ in Practice
A plant-based diet prioritizes foods derived from plants — vegetables, fruits, whole grains, legumes, nuts, and seeds. The term spans a spectrum: some people follow a fully vegan approach that excludes all animal products, while others adopt a predominantly plant-based pattern that allows small amounts of animal foods. What unites these approaches is a deliberate shift away from animal products as the center of every meal.
An omnivore diet, by contrast, includes both animal and plant foods without systematic exclusion of either category. In practice, the quality of an omnivore diet varies enormously — from heavily processed meat-centered meals to Mediterranean-style plates rich in fish, vegetables, whole grains, and olive oil.
This distinction matters because much of the research comparing these patterns is complicated by diet quality within each category. A poorly constructed plant-based diet built on refined carbohydrates and processed meat substitutes performs differently from one centered on whole foods — and the same applies to omnivore eating. For a closer look at how popular structured eating frameworks compare, see our side-by-side comparison of Mediterranean, DASH, and low-carb approaches.
| Criterion | Plant-Based Diet | Omnivore Diet |
|---|---|---|
| Cardiovascular disease risk | Generally lower in research cohorts | Varies widely with diet quality |
| Type 2 diabetes risk | Consistently lower in studies | Lower when diet is whole-food-focused |
| Vitamin B12 access | Requires fortified foods or supplements | Readily available from animal foods |
| Complete protein access | Requires food combining or varied legumes | Readily available from meat, eggs, dairy |
| Dietary fiber intake | Typically high | Often below recommended levels |
| Saturated fat intake | Typically low | Can be high depending on food choices |
| Diet planning complexity | Moderate to high — nutrient gaps need attention | Low to moderate — broad food access |
| Environmental footprint | Generally lower | Generally higher, varies by food choices |
What Long-Term Research Reveals on Key Health Markers
The evidence base comparing plant-based and omnivore diets has grown substantially over the past two decades, largely driven by large cohort studies and systematic reviews.
Cardiovascular Health
Multiple large prospective studies — including data from the Adventist Health Study-2 and the EPIC-Oxford cohort — find that vegetarian and vegan participants tend to have lower rates of ischemic heart disease and hypertension compared to omnivores. Researchers attribute much of this to lower saturated fat intake, higher fiber consumption, and better body weight profiles on average. However, some analyses (including a 2019 BMJ study) found higher stroke risk in vegetarians, possibly related to lower vitamin B12 levels — a finding that underscores the importance of nutrient planning.
Type 2 Diabetes and Metabolic Health
A consistent body of research links plant-rich diets to better insulin sensitivity and a reduced risk of developing type 2 diabetes. A 2019 meta-analysis in JAMA Internal Medicine found that plant-based dietary patterns were associated with significantly lower type 2 diabetes risk. Whole-food omnivore diets with high vegetable intake show similar benefits compared to processed-meat-heavy patterns.
Cancer Risk
The World Health Organization classifies processed meat as a Group 1 carcinogen (meaning there is strong evidence of a causal link to colorectal cancer) and red meat as Group 2A (probably carcinogenic). Plant-based diets, by reducing or eliminating these foods, may lower colorectal cancer risk. That said, plant-based diets are not universally protective — overall diet quality, body weight, and lifestyle factors all contribute meaningfully.
~25%
Lower heart disease risk in vegetarians
A pooled analysis of prospective studies published in the American Journal of Clinical Nutrition found vegetarians had approximately 25% lower risk of ischemic heart disease mortality.
23%
Reduced type 2 diabetes risk
A 2019 meta-analysis in JAMA Internal Medicine found plant-based dietary patterns associated with a 23% lower risk of type 2 diabetes compared to non-plant-based diets.
17g
Average daily fiber intake in the US
According to USDA dietary data, Americans average roughly 17 grams of fiber per day — well below the recommended 25–38 grams, a gap common in both plant-based and omnivore eaters who rely on processed foods.
Nutrient Considerations: Where Each Pattern Has Advantages
No single dietary pattern is nutritionally complete without attention to food choices. Both plant-based and omnivore eaters face specific nutrient considerations.
Nutrients That Require Planning on Plant-Based Diets
- Vitamin B12: Found almost exclusively in animal products; plant-based eaters generally need fortified foods or supplements.
- Iron: Plant foods contain non-heme iron, which is absorbed less efficiently than heme iron from meat. Pairing iron-rich plants with vitamin C improves absorption.
- Omega-3 fatty acids (EPA and DHA): Primarily found in fatty fish; plant sources like flaxseed and walnuts provide ALA, which the body converts to EPA and DHA at low rates. Algae-based supplements bridge this gap.
- Calcium and Zinc: Achievable through plants but require deliberate food choices (fortified plant milks, legumes, seeds).
Nutrients That Require Attention on Omnivore Diets
- Fiber: Omnivore diets in the US average well below the recommended daily intake. Low fiber intake is linked to poorer gut microbiome diversity and higher colorectal cancer risk.
- Saturated fat: High intake from animal products is associated with elevated LDL cholesterol in most people.
For a detailed breakdown of protein options across eating patterns, see our nutritional snapshot of protein sources. And if you're considering supplements to fill gaps, our grounded look at dietary supplements covers what the evidence supports.
This article is for general informational purposes only and does not constitute medical or nutritional advice. Consult a registered dietitian or qualified healthcare professional before making significant changes to your diet, especially if you have an existing health condition.
Diet Quality Matters More Than Category
Research increasingly shows that a 'healthy' plant-based diet score — one emphasizing whole, minimally processed plant foods — is associated with better outcomes than simply being vegan or vegetarian. Similarly, an omnivore diet rich in vegetables, legumes, and whole grains performs much better than one heavy in processed meats and refined grains. The binary of plant-based versus omnivore is a useful starting framework, but the specific foods within your pattern are what drive long-term health. For more on how dietary myths can muddy this picture, see common nutrition myths that science has largely debunked.
The content on this site is provided for informational purposes only and should not be considered a substitute for professional advice. While we strive to provide accurate and up-to-date information, we make no guarantees regarding its completeness or accuracy. Always consult a qualified professional for advice specific to your circumstances before making any decisions.