Researchers wanted to know if eating in a way that’s better for the planet could still give your body all the vitamins and minerals it needs. They had 355 healthy adults follow either an eco-friendly diet or a regular healthy diet for 12 weeks. The results showed that while the sustainable diet was better for the environment, it actually lowered several important nutrients in people’s bodies, including B vitamins, calcium, and zinc. This research suggests that when we try to eat in ways that help the Earth, we need to be careful to make sure we’re still getting all the nutrients our bodies require.

The Quick Take

  • What they studied: Whether a sustainable diet (one designed to be better for the environment) could provide all the vitamins and minerals people need to stay healthy
  • Who participated: 355 healthy adults between ages 18 and 64 from three different locations who received personalized nutrition advice for 12 weeks
  • Key finding: The sustainable diet reduced greenhouse gas emissions by 22% and lowered energy intake by 8%, but it also decreased important nutrients like vitamin B12 (down 36%), vitamin D (down 28%), iodine (down 26%), and several others. More people on the sustainable diet ended up not getting enough riboflavin, B6, B12, calcium, and zinc
  • What it means for you: Eating for the planet is important, but you may need to plan more carefully or add supplements to make sure you’re getting all your nutrients. This doesn’t mean sustainable eating is bad—it just means it requires more thoughtful choices

The Research Details

This was a carefully controlled experiment where researchers split 355 healthy adults into two groups. One group received personalized nutrition counseling to follow a sustainable diet (one that’s better for the environment), while the other group received counseling for a standard healthy diet. Both groups were followed for 12 weeks. The researchers measured what people ate, tracked their nutrient intake, and tested their blood to see if they had enough vitamins and minerals. They also calculated how much greenhouse gas emissions each diet produced. The study was ‘single-blind,’ meaning the participants didn’t know which diet was being tested as the main focus, which helps prevent bias in the results.

This type of study design is important because it lets researchers see cause-and-effect relationships. By comparing two similar groups with only one difference (the type of diet), scientists can be more confident that any changes in nutrients are actually caused by the diet itself, not by other factors. Testing actual blood levels of nutrients is more reliable than just asking people what they ate, because it shows what’s really happening in their bodies.

This study has several strengths: it used a randomized design (randomly assigning people to groups), it measured actual nutrient levels in blood rather than just asking people what they ate, and it had a decent-sized group of 355 participants. However, the study only lasted 12 weeks, which is relatively short for seeing long-term effects. The study also didn’t follow people after the counseling ended, so we don’t know if the nutrient problems would continue or improve over time.

What the Results Show

People who followed the sustainable diet had significantly lower intakes of many important nutrients compared to the control group. Vitamin B12 dropped the most (36% lower), followed by vitamin D (28% lower) and iodine (26% lower). Other nutrients that decreased included retinol (a form of vitamin A), thiamin, riboflavin, niacin, calcium, zinc, potassium, selenium, vitamins B6, C, and K1. The sustainable diet did successfully reduce greenhouse gas emissions by 22% and overall energy intake by 8%.

When researchers looked at how many people weren’t getting enough of each nutrient, the picture became clearer. By the end of the study, more people in the sustainable diet group had inadequate intakes of riboflavin, vitamins B6 and B12, calcium, zinc, and selenium compared to the control group. Interestingly, some nutrients like iron, vitamin A, vitamin E, and vitamin C status (measured in blood) didn’t actually change significantly, even though intake decreased.

The sustainable diet included dairy products, three servings of animal protein per week, and two servings of fish per week, which are good sources of many nutrients. Despite including these foods, the diet still resulted in lower nutrient intakes, suggesting that the overall pattern of the sustainable diet—which likely emphasized more plant-based foods—naturally contains fewer of certain nutrients.

One interesting finding was that vitamin K1 actually increased by 30% in the sustainable diet group, likely because plant-based foods are rich in this nutrient. The study also found that some nutrient status markers (measured in blood) didn’t change even when intake decreased, suggesting the body may have had enough stored reserves for a 12-week period. However, this doesn’t mean long-term deficiencies wouldn’t develop if the diet continued.

Previous research has shown that plant-based and environmentally sustainable diets can be healthy, but this study adds important evidence that they require careful planning to ensure adequate micronutrients. The findings align with other research suggesting that reducing animal products—a key part of sustainable eating—can lower intake of nutrients like B12, calcium, and zinc, which are naturally abundant in animal foods. This research emphasizes what nutritionists have long known: sustainable eating is possible and beneficial, but it needs to be done thoughtfully.

The study only lasted 12 weeks, which is relatively short for determining long-term effects. We don’t know if nutrient levels would continue to drop, stabilize, or improve with longer-term adherence. The study also only measured people while they were receiving counseling and support; we don’t know what would happen if people tried to follow these diets on their own without professional guidance. Additionally, the study didn’t test whether adding supplements or making specific food choices could solve the nutrient gaps identified. The participants were all healthy adults, so results may not apply to children, elderly people, or those with health conditions.

The Bottom Line

If you want to eat in a way that’s better for the environment, you can do so, but plan carefully to ensure you get enough nutrients. Consider: eating a variety of plant-based foods, including fortified foods (foods with added nutrients), consulting with a registered dietitian to ensure you’re meeting your nutrient needs, and possibly taking supplements for nutrients that are hard to get from sustainable diets (like B12, vitamin D, and iodine). These recommendations are moderately supported by this research and align with current nutrition science.

Anyone interested in eating sustainably should pay attention to these findings. This is especially important for vegetarians and vegans, people trying to reduce their environmental impact, and those planning long-term dietary changes. People with specific health conditions, pregnant women, children, and older adults should work with a healthcare provider or dietitian before making major dietary changes. If you’re generally healthy and just want to eat better for the planet, you can absolutely do this—you just need to be intentional about nutrition.

The nutrient decreases in this study happened over 12 weeks. Some nutrients like B12 and vitamin D can take months to years to become truly deficient in your body because you have stores. However, some nutrients like iodine and selenium are needed regularly. If you’re making dietary changes, it’s wise to check your nutrient status after 3-6 months and then regularly, especially if you’re making significant changes to your diet.

Want to Apply This Research?

  • Track daily intake of key nutrients that decreased in this study: vitamin B12 (aim for 2.4 mcg), vitamin D (aim for 600-800 IU), calcium (aim for 1000-1200 mg), zinc (aim for 8-11 mg), and iodine (aim for 150 mcg). Use the app to log these nutrients weekly and set reminders to include specific foods like fortified plant milks, legumes, nuts, and seeds.
  • If following a sustainable diet, use the app to: (1) identify and log at least 3 plant-based sources of B vitamins, calcium, and zinc daily, (2) set reminders to include fortified foods, (3) track supplement intake if taking B12, vitamin D, or iodine supplements, and (4) monitor energy levels and any symptoms that might indicate nutrient deficiency
  • Set up monthly nutrient reports in the app to track trends in key micronutrients over time. Schedule quarterly check-ins to review whether you’re meeting targets for the nutrients that decreased in this study. Consider getting blood work done every 6-12 months if making significant dietary changes, and share results with the app to adjust your tracking goals accordingly.

This research suggests that sustainable diets may lower certain nutrient intakes, but this does not mean sustainable eating is unhealthy or should be avoided. Rather, it highlights the importance of thoughtful planning when adopting any major dietary change. Before making significant changes to your diet, especially if you have health conditions, are pregnant, nursing, or taking medications, consult with your healthcare provider or a registered dietitian. This study lasted only 12 weeks and may not reflect long-term outcomes. Individual nutrient needs vary based on age, sex, health status, and other factors. If you choose to follow a sustainable diet, work with a nutrition professional to ensure you’re meeting all your nutrient needs, and consider periodic blood work to monitor your nutritional status.