Researchers compared four different eating styles to see if plant-based diets could be as nutritious and better for the environment than traditional Mediterranean diets. They created week-long meal plans for each diet type, all containing about 2,000 calories per day. The good news: plant-based diets had similar amounts of protein and most important nutrients, and they were much better for the planet—producing up to 46% less pollution and using 33% less land. However, people following these diets need to pay special attention to getting enough vitamin D, iodine, and vitamin B12. The study shows that with careful planning, eating more plants can be both healthy for you and healthy for Earth.

The Quick Take

  • What they studied: Whether plant-based diets (vegetarian and vegan) can provide the same nutrition as Mediterranean diets while being better for the environment
  • Who participated: This wasn’t a study with people—researchers created four different 7-day meal plans (Mediterranean, pescatarian, vegetarian, and vegan) and analyzed their nutrition and environmental impact using computer models
  • Key finding: Plant-based diets had similar protein and most nutrients as Mediterranean diets, but produced 46% less greenhouse gas pollution, used 33% less land, and required 6.6% less water
  • What it means for you: If you’re thinking about eating more plants, you can get the nutrition you need—but you’ll want to make sure you’re getting enough vitamin D, iodine, and B12, either through food choices or supplements

The Research Details

Researchers didn’t study actual people eating these diets. Instead, they created four different week-long meal plans based on official nutrition guidelines from Spain. Each plan had about 2,000 calories per day, which is typical for many adults. They used detailed food databases to calculate exactly how much of each nutrient was in each meal plan. They also used a special tool called Agribalyse to measure the environmental impact of each diet—things like greenhouse gas emissions, water use, and land needed to grow the food.

The four diets they compared were: a Mediterranean diet (eating fish and some meat), a pescatarian diet (eating fish but not meat), an ovo-lacto-vegetarian diet (eating eggs and dairy but not meat or fish), and a vegan diet (eating only plants). All the meal plans followed official recommendations for healthy eating from nutrition organizations.

They used statistical tests to compare the diets and see if the differences were meaningful or just random variation.

This type of study is important because it lets researchers compare diets fairly without asking real people to change their eating habits for weeks or months. By using the same calorie level and official guidelines for all diets, they could see real differences without other factors getting in the way. The environmental measurements are especially valuable because they show the full picture of how different diets affect our planet.

This study is a modeling study, which means it’s based on calculations and databases rather than following real people. This is both a strength and a limitation. The strength is that it’s fair and controlled—all diets have the same calories and follow official guidelines. The limitation is that it doesn’t show how people actually eat these diets in real life, which can be different from a perfect meal plan. The researchers used well-established databases and tools, which makes the results more reliable. However, the study doesn’t tell us whether people would actually stick to these diets or feel satisfied eating them.

What the Results Show

The most important finding was that all four diet types provided enough protein and met most of the daily nutrient needs. This surprised some people who worry that plant-based diets don’t have enough protein. The amount of carbohydrates, fats, and protein were very similar across all four diets.

When it came to helping the environment, plant-based diets were clearly the winners. Vegan diets produced 46% less greenhouse gas pollution compared to Mediterranean diets—that’s almost half the pollution. They also used 33% less land and 6.6% less water. Even the pescatarian and vegetarian diets showed significant improvements over the Mediterranean diet.

However, there were some nutrients that fell short across all diets, not just plant-based ones. Vitamin D and iodine were below recommended levels in all four meal plans. This is actually a common problem in many countries because vitamin D is hard to get from food, and iodine depends on where your food is grown. The vegan diet specifically had too little vitamin B12, which is important for nerve health and energy. Omega-3 fatty acids (healthy fats from fish and some plants) were also below the recommended amount in all diets.

Saturated fat (the less healthy type of fat) stayed below 8% of total calories in all diets, which is good for heart health.

The study found that when plant-based foods replace animal products, the overall nutritional quality stays similar. This suggests that with good planning, you can swap animal products for plant alternatives without losing nutrition. The environmental benefits were consistent across all plant-based options—even just reducing meat and fish (pescatarian diet) made a big difference. The study also showed that the environmental benefits came from multiple sources: less pollution from farming, less water needed, and less land required.

Previous research has suggested that plant-based diets might lack certain nutrients, especially B12, iron, and calcium. This study confirms that B12 needs special attention in vegan diets but shows that iron and calcium can be adequate with good planning. The environmental benefits of plant-based diets have been shown in other studies, but this research provides specific numbers for comparison. The finding that vitamin D and iodine are low across all diet types suggests this is a broader public health issue, not specific to plant-based eating.

The biggest limitation is that this study used computer models and meal plans, not real people eating real food. People might not follow these plans perfectly, might eat different portion sizes, or might choose different plant-based foods than the researchers assumed. The study was based on Spanish nutrition guidelines and food databases, so results might be different in other countries where foods and farming practices are different. The study didn’t account for how food is processed, packaged, or transported, which can affect environmental impact. It also didn’t measure whether people would feel satisfied or healthy eating these diets long-term. Finally, the environmental calculations depend on current farming practices, which might change in the future.

The Bottom Line

If you’re interested in eating more plant-based foods, this research suggests you can do it while staying healthy. Make sure to pay special attention to getting enough vitamin B12 (through fortified foods or supplements if you’re vegan), vitamin D (through supplements or fortified foods, since it’s hard to get from food), and iodine (through iodized salt or supplements). Try to include omega-3 rich plant foods like flaxseeds, chia seeds, and walnuts. These recommendations have moderate confidence because the study was based on meal plans, not real people eating over time.

This research is relevant for anyone thinking about eating more plants, whether for health or environmental reasons. It’s especially useful for people who are vegetarian or vegan and want to make sure they’re getting good nutrition. It’s also important for people who care about the environment and want to understand how their food choices affect the planet. Parents considering plant-based diets for their children should talk to a doctor or nutritionist, since children have different nutrient needs than adults. People with certain health conditions should also check with their healthcare provider before making major diet changes.

You won’t feel immediate changes from switching to a plant-based diet. Some people feel more energy within a few weeks, while others take several months to adjust. Environmental benefits happen immediately in the sense that each meal you eat has a smaller footprint, but you won’t see global environmental changes quickly. If you’re concerned about specific nutrients like B12, you should start supplementing right away rather than waiting to see if you develop a deficiency, since B12 deficiency can take months or years to show symptoms.

Want to Apply This Research?

  • Track your weekly intake of vitamin B12 sources (fortified plant milks, nutritional yeast, supplements), vitamin D sources, and iodine sources. Set a goal to include at least 3 servings per week of omega-3 rich foods like flaxseeds, chia seeds, or walnuts.
  • Use the app to plan one plant-based meal per day or per week, starting small. Log your meals to see how much protein, B12, and other key nutrients you’re getting. Set reminders to take vitamin D and B12 supplements if you’re following a vegan diet.
  • Every month, review your nutrient intake to make sure you’re hitting targets for B12, vitamin D, iodine, and omega-3s. Track your energy levels and how you feel to notice any changes. Consider getting blood work done annually to check B12 and vitamin D levels if you follow a vegan diet long-term.

This research is based on computer models of meal plans, not studies of real people eating these diets over time. Before making significant changes to your diet, especially if you have health conditions, take medications, or are pregnant or nursing, please consult with your doctor or a registered dietitian. This article is for educational purposes and should not replace professional medical advice. If you choose to follow a vegan or vegetarian diet, work with a healthcare provider to ensure you’re getting adequate vitamin B12, vitamin D, iodine, and other essential nutrients through food or supplements.