Researchers at the University of Minnesota created a complete system for measuring two types of iron in 19,500 foods, with heme iron from meat and seafood separated from non-heme iron from plants and dairy. According to Gram Research analysis, this matters because your body absorbs heme iron much more efficiently than non-heme iron, sometimes up to three times better. The new database assigns iron values to every food with no missing data, helping nutrition apps and dietitians give you more accurate information about whether you’re getting enough usable iron from your diet.
Researchers at the University of Minnesota created a better way to track two types of iron in food databases. According to Gram Research analysis, they added detailed information about heme iron (found in meat and seafood) and non-heme iron (found in plants and dairy) to a database of 19,500 foods. This matters because your body absorbs heme iron much more easily than non-heme iron. The new system helps nutritionists and health apps give you more accurate information about whether you’re getting enough iron from your diet, which is important for preventing anemia and keeping your energy levels up.
Key Statistics
A 2026 research article in the Journal of the Academy of Nutrition and Dietetics successfully assigned heme and non-heme iron values to all 19,500 foods in the University of Minnesota Nutrition Coordinating Center Database with zero missing values.
In the updated database, 68% of core foods (eggs, dairy, and plant foods) were assigned 100% non-heme iron, while 18% of core foods (meats and seafood) contained both heme and non-heme iron in proportions based on scientific literature.
About 14% of core foods in the database contained zero iron and were assigned 0 mg for both heme and non-heme iron, while 24% of meat and seafood values required imputation based on similar foods due to limited direct measurement data.
The Quick Take
- What they studied: How to properly categorize and measure two different types of iron in foods so that nutrition databases and apps can give people better information about their iron intake.
- Who participated: This wasn’t a study with human participants. Instead, researchers analyzed 19,500 different foods and assigned them accurate iron values based on scientific literature and international food databases.
- Key finding: Researchers successfully assigned both heme and non-heme iron values to every single food in the database with no missing data. For meats and seafood, they calculated what percentage was heme iron (the easily absorbed type) versus non-heme iron (the harder-to-absorb type).
- What it means for you: If you use nutrition apps or work with a dietitian, they now have more accurate information about the iron you’re eating. This helps explain why eating a steak gives you more usable iron than eating the same amount of spinach, even if the spinach has more total iron.
The Research Details
This research describes a systematic process for improving how iron is measured in food databases. The team at the University of Minnesota took their existing database of 19,500 foods and added two new pieces of information to each one: how much heme iron it contains and how much non-heme iron it contains. They did this by reviewing scientific studies, checking international food databases, and using specific rules to fill in gaps where data was missing.
The process had four main steps. First, they searched through published scientific research and international food composition databases to find measurements of heme and non-heme iron in different foods. Second, they assigned values to the most common foods (called core foods) based on what they found. Third, for less common foods, they used a special computer program to calculate the values based on similar foods. Fourth, they checked all their work to make sure the values made sense and were consistent across different food groups.
This approach is important because heme iron and non-heme iron behave very differently in your body. Heme iron comes from the blood and muscle of animals, while non-heme iron comes from plants and is also found in animal products. Your body can absorb heme iron much more efficiently, sometimes up to three times better than non-heme iron.
Having accurate information about both types of iron in foods is crucial for nutrition science and health. Previous databases often only measured total iron, which doesn’t tell you how much of that iron your body can actually use. By separating heme and non-heme iron, researchers and health professionals can now give better advice about iron intake. This is especially important for people at risk of anemia, vegetarians and vegans who rely on non-heme iron sources, and athletes who need optimal iron levels for performance.
This research is a methodology paper, which means it describes a process rather than testing a hypothesis. The strength of this work lies in its systematic approach and completeness. The researchers achieved 100% data coverage, meaning every food in the database now has iron values assigned. However, for some meats and seafood (24% of these foods), they had to use imputation, which means they estimated values based on similar foods rather than direct measurements. This is a reasonable approach but introduces some uncertainty for those specific foods. The work was published in the Journal of the Academy of Nutrition and Dietetics, a peer-reviewed publication that focuses on nutrition science.
What the Results Show
The research successfully assigned heme and non-heme iron values to all 19,500 foods in the database with no missing data. This is a significant achievement because it means nutrition apps and professionals now have complete information. The team found that foods fell into three main categories based on their iron composition.
The first category included foods with no iron at all. About 14% of the core foods (the most commonly eaten foods) had zero total iron and were assigned 0 mg for both heme and non-heme iron. These included foods like oils, sugar, and some beverages.
The second category included eggs, dairy products, and plant-based foods that contain iron. For these foods, 100% of the iron was classified as non-heme iron, which makes sense because these foods don’t contain the heme iron found in animal blood and muscle. This category represented 68% of core foods and includes items like beans, leafy greens, fortified cereals, milk, and cheese.
The third category included meats and seafood, which contain both types of iron. For these foods, the researchers calculated heme iron based on scientific literature showing the typical ratio of heme to total iron in different meats and fish. Then they subtracted the heme iron from the total iron to get the non-heme iron amount. This category represented 18% of core foods. For some meats and seafood (24% of this group), the researchers had to estimate values using their imputation rules because direct measurements weren’t available in the literature.
The quality assurance process revealed important patterns in how iron is distributed across food groups. The systematic review of all assigned values ensured consistency, meaning that similar foods had similar iron profiles. This consistency check is important because it helps catch errors and makes sure the database is reliable for nutrition professionals and app developers.
Previous food databases typically only measured total iron content, without distinguishing between heme and non-heme iron. This new approach builds on decades of nutrition research showing that these two forms of iron have very different absorption rates in the human body. The methodology aligns with international standards for food composition databases and incorporates the latest scientific understanding of iron bioavailability, which is the amount of iron your body can actually absorb and use.
The main limitation is that some values, particularly for meats and seafood, are based on imputation rather than direct measurement. This means about 24% of meat and seafood values were estimated using rules and similar foods rather than actual laboratory analysis. Additionally, this research describes a methodology for one specific database. The results may not apply exactly the same way to other food databases that use different sources or calculation methods. The research also doesn’t test whether using this more detailed iron information actually changes health outcomes for people using nutrition apps or working with dietitians, though that would be an important follow-up study.
The Bottom Line
If you use nutrition apps or work with a registered dietitian, you can now trust that they have more accurate information about the iron in your food. This is particularly helpful if you’re managing anemia, pregnant, vegetarian, vegan, or an athlete. The recommendation is to use this improved data to make informed choices about iron-rich foods. If you’re concerned about iron intake, focus on heme iron sources (meat, poultry, seafood) when possible, as your body absorbs these much more efficiently. If you eat plant-based foods, pair them with vitamin C sources (like citrus or tomatoes) to improve non-heme iron absorption. Confidence level: High for the accuracy of the database itself; moderate for practical health outcomes, since this is a methodology study rather than a clinical trial.
This research matters most for registered dietitians, nutritionists, and app developers who help people track their nutrition. It’s also relevant for people managing iron deficiency anemia, pregnant women, vegetarians and vegans, endurance athletes, and anyone whose doctor has recommended monitoring iron intake. People eating a typical mixed diet with adequate meat consumption may see less practical benefit, though the information is still useful for understanding their nutrition.
If you’re using this improved data to manage iron intake, you won’t see immediate changes. Iron deficiency develops and improves slowly over weeks and months. If you’re anemic and increase your heme iron intake based on this better information, you might expect to see improvements in energy levels and blood work within 6 to 12 weeks, depending on the severity of your deficiency and your overall diet.
Frequently Asked Questions
What is the difference between heme iron and non-heme iron and why does it matter?
Heme iron comes from animal blood and muscle (meat, poultry, seafood) and your body absorbs it much more efficiently, sometimes up to three times better than non-heme iron. Non-heme iron comes from plants and dairy. Your body absorbs only 2 to 20% of non-heme iron but 15 to 35% of heme iron, making heme sources more effective for preventing anemia.
How accurate is the new iron data in nutrition apps and databases?
The new database has 100% data coverage with no missing values. However, about 24% of meat and seafood values were estimated using imputation rules rather than direct laboratory measurements. For the remaining 76% of foods, values come from scientific literature and international databases, making them highly reliable.
Can vegetarians and vegans get enough iron without eating meat?
Yes, but it requires more planning. Plant-based iron (non-heme iron) is absorbed less efficiently, so vegetarians and vegans need to eat more iron-rich foods and pair them with vitamin C sources like citrus, tomatoes, or peppers to improve absorption. The new database helps identify which plant foods are highest in iron.
Should I use this information to change my diet if I don’t have anemia?
If you eat a mixed diet with regular meat consumption and have normal energy levels, you’re likely getting adequate iron. However, understanding heme versus non-heme iron helps you make informed choices. If you’re vegetarian, pregnant, or an athlete, this information is more directly useful for optimizing your iron intake.
How long does it take to see health improvements from better iron intake?
Iron deficiency develops and improves slowly. If you’re anemic and increase heme iron intake, expect 6 to 12 weeks to see improvements in energy levels and blood work, depending on how severe your deficiency is and your overall diet quality.
Want to Apply This Research?
- Track your heme iron intake separately from non-heme iron intake. Set a daily target for heme iron (aim for at least 1 to 2 mg per day from meat, poultry, or seafood) and monitor whether you’re meeting it. Log which meals included heme iron sources and note your energy levels to see if there’s a correlation.
- Add one heme iron source to your diet each day. This could be a small portion of chicken, fish, beef, or pork at lunch or dinner. If you’re vegetarian or vegan, pair your plant-based iron sources with vitamin C-rich foods at the same meal to improve absorption. Use the app to identify which plant foods are highest in iron and which vitamin C sources you enjoy.
- Over 8 to 12 weeks, track your energy levels, mood, and any symptoms of anemia (like fatigue or shortness of breath) alongside your iron intake data. If you have a blood test scheduled, compare your iron levels before and after making dietary changes based on this improved database information. Share this data with your doctor or dietitian to see if the changes are working for you.
This research describes a methodology for measuring iron in foods and does not constitute medical advice. If you have symptoms of anemia, iron deficiency, or concerns about your iron intake, consult with your doctor or a registered dietitian before making significant dietary changes. This information is especially important for pregnant women, people with diagnosed iron deficiency, and those with medical conditions affecting iron absorption. Do not use this information to self-diagnose or self-treat iron deficiency without professional medical guidance.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.