A 2026 cross-sectional analysis of 9,208 American adults found no association between folate intake or blood folate levels and kidney stone disease. According to Gram Research analysis, after adjusting for other health factors, people with the highest folate intake had similar kidney stone rates to those with the lowest intake (odds ratio 0.94). This suggests that folate is not a major driver of kidney stone formation in the general US population, and there’s no evidence-based reason to avoid folate-rich foods for kidney stone prevention.
Researchers analyzed data from over 9,000 American adults to see if folate—a B vitamin found in leafy greens and fortified foods—affects kidney stone risk. According to Gram Research analysis, they measured both how much folate people ate and the levels of folate in their blood. Surprisingly, after accounting for other health factors, the study found no meaningful connection between folate intake or blood folate levels and kidney stone disease. This challenges earlier concerns and suggests that folate may not be a major driver of stone formation in the general population.
Key Statistics
A 2026 cross-sectional study of 9,208 American adults from the National Health and Nutrition Examination Survey found no significant association between dietary folate intake and kidney stone disease after adjusting for sociodemographic, lifestyle, and clinical factors.
According to research reviewed by Gram, the overall weighted prevalence of kidney stones in the study population was 9.4%, but this rate showed no meaningful difference across folate intake levels or any of four circulating folate biomarkers tested.
A 2026 analysis of 9,208 US adults found that people consuming the highest folate (top quarter) had an odds ratio of 0.94 for kidney stones compared to those consuming the least, indicating no increased risk from higher folate intake.
The Quick Take
- What they studied: Whether eating more folate or having higher folate levels in your blood increases your risk of developing kidney stones
- Who participated: 9,208 American adults from a national health survey conducted between 2017 and 2020, representing a diverse cross-section of the US population
- Key finding: After adjusting for other health factors, there was no significant link between folate intake or blood folate levels and kidney stone disease. About 9.4% of participants had kidney stones, but folate status didn’t explain the difference
- What it means for you: If you’ve been avoiding folate-rich foods like spinach or broccoli due to kidney stone concerns, this research suggests that’s probably unnecessary. However, if you have a personal history of kidney stones, consult your doctor about your specific situation
The Research Details
Researchers used data from the National Health and Nutrition Examination Survey (NHANES), a large government study that tracks the health of Americans. They looked at information collected from 2017 to 2020 on 9,208 adults. To measure folate intake, participants reported everything they ate in a single 24-hour period. The researchers also measured four different types of folate in participants’ blood: total serum folate, a specific form called 5-methyltetrahydrofolate, another form called tetrahydrofolate (THF), and folate stored in red blood cells.
The team used statistical methods to compare kidney stone rates across groups with different folate levels. They started with simple comparisons, then gradually added adjustments for other factors that might affect kidney stone risk—things like age, sex, income, exercise habits, diet quality, and existing health conditions like diabetes and high blood pressure. This approach helps isolate whether folate itself matters or if other factors are really responsible.
The researchers divided folate measurements into four groups (quartiles) to see if higher folate was associated with more kidney stones. They looked for both straight-line relationships (more folate = more stones) and curved relationships (where very high or very low folate might be problematic).
This careful approach is important because kidney stone formation is complex and involves many factors. Early studies suggested folate might matter because it’s involved in chemical pathways that affect stone formation. However, previous research gave mixed results. By using a large, nationally representative sample and adjusting for many confounding factors, this study provides stronger evidence about whether folate is actually a concern for the general population
This study has several strengths: it’s large (over 9,000 people), nationally representative (meaning results likely apply to all US adults), and uses rigorous statistical methods. The researchers measured folate multiple ways rather than relying on just one measure. However, because it’s a cross-sectional study (a snapshot in time rather than following people over years), it can’t prove that folate causes or prevents kidney stones—only whether they’re associated. The study also relied on people’s memory of what they ate, which can be imperfect
What the Results Show
When researchers first looked at the data without adjusting for other factors, they found that people with higher RBC folate and THF levels had slightly higher odds of kidney stones. This initial finding might have seemed concerning. However, when the team adjusted for sociodemographic factors (age, sex, race, income), lifestyle factors (exercise, smoking, alcohol use), and clinical factors (diabetes, high blood pressure, kidney disease), these associations disappeared completely.
For dietary folate intake specifically, people eating the most folate (top quarter) had an odds ratio of 0.94 compared to those eating the least (bottom quarter). An odds ratio near 1.0 means no difference. The confidence interval (0.57-1.55) was wide and crossed 1.0, indicating no meaningful association. Similar null findings appeared for all four circulating folate biomarkers tested.
The researchers also tested whether there was a dose-response relationship—meaning whether more folate consistently led to more stones at any level. They found no significant linear or curved dose-response trends. This strengthens the conclusion that folate status isn’t driving kidney stone formation in this population.
The study found that approximately 9.4% of the weighted sample had a history of kidney stones, which aligns with other estimates of kidney stone prevalence in the US. The fact that this prevalence was consistent across folate levels further supports the main finding. The researchers’ careful adjustment for multiple confounders (sociodemographic, lifestyle, and clinical factors) revealed that the initial associations were likely due to these other factors rather than folate itself
Previous research on folate and kidney stones has been limited and inconsistent. Some studies suggested folate metabolism might influence stone formation through its role in one-carbon metabolism, a biochemical pathway involved in various disease processes. Other research found conflicting results. This study is notable for being the first large, nationally representative analysis in the US population using multiple folate biomarkers. It provides stronger evidence than previous smaller studies and suggests that earlier concerns about folate may have been overstated
As a cross-sectional study, this research shows associations at one point in time but cannot prove cause-and-effect. Dietary folate was measured from a single 24-hour recall, which may not represent typical eating patterns. The study couldn’t account for all possible factors affecting kidney stone risk, such as hydration status or family history. Additionally, people with kidney stones might have changed their diet after diagnosis, which could affect the results. The study also couldn’t distinguish between people with a single kidney stone episode and those with recurrent stones
The Bottom Line
Based on this research, there is no evidence-based reason to restrict folate intake to prevent kidney stones in the general population. Folate-rich foods like spinach, broccoli, asparagus, and fortified grains are nutritious and should be part of a healthy diet. If you have a personal or family history of kidney stones, discuss your individual risk factors and dietary needs with your doctor rather than avoiding folate
This finding is relevant to anyone concerned about kidney stone prevention, particularly those who’ve heard that folate might increase risk. It’s especially important for people with folate deficiency or those taking folate supplements for other health reasons—they can feel reassured that folate intake isn’t a kidney stone risk factor. However, people with a personal history of kidney stones should still follow their doctor’s specific recommendations, as individual risk factors vary
This research provides a snapshot of associations rather than tracking changes over time. If you’re concerned about kidney stone prevention, focus on established protective measures like staying well-hydrated, limiting sodium intake, and maintaining a balanced diet. Changes in kidney stone risk from dietary modifications typically take weeks to months to become apparent
Frequently Asked Questions
Does eating folate-rich foods like spinach increase kidney stone risk?
No. A 2026 study of over 9,000 Americans found no link between folate intake and kidney stones after accounting for other health factors. Folate-rich foods like spinach, broccoli, and legumes are nutritious and safe to eat for kidney stone prevention.
Should I avoid folate supplements if I’m worried about kidney stones?
This research suggests folate supplements don’t increase kidney stone risk in the general population. However, if you have a personal history of kidney stones, discuss supplement use with your doctor, as individual risk factors vary and other dietary modifications may be more important.
What’s the best way to prevent kidney stones if folate isn’t the issue?
Research shows staying well-hydrated, limiting sodium intake, and maintaining adequate calcium intake are the most effective kidney stone prevention strategies. Discuss your individual risk factors with your doctor, especially if you have a family history of kidney stones.
Can high folate levels in my blood cause kidney stones?
According to a 2026 analysis of 9,208 adults, no. Even people with the highest blood folate levels showed no increased kidney stone risk after adjusting for other health factors. Multiple types of blood folate were tested with the same result.
Is this study definitive proof that folate doesn’t cause kidney stones?
This large, nationally representative study provides strong evidence that folate isn’t a major kidney stone risk factor in the general US population. However, individual cases may differ, so consult your doctor about your personal risk factors and medical history.
Want to Apply This Research?
- Track daily folate intake (measured in micrograms) alongside kidney stone risk factors like hydration status, sodium consumption, and calcium intake. Log servings of folate-rich foods like leafy greens, legumes, and fortified grains to ensure adequate intake without concern
- Use the app to set a daily folate goal (400 mcg for adults) and log folate-containing foods. Create reminders to eat folate-rich vegetables and track hydration separately, as proper hydration is the most evidence-based kidney stone prevention strategy
- Monitor overall diet quality and hydration patterns rather than focusing on folate restriction. Track any kidney stone symptoms and correlate them with dietary patterns, hydration, sodium intake, and other known risk factors to identify personal triggers
This research applies to the general US adult population and should not replace personalized medical advice. If you have a personal or family history of kidney stones, have been diagnosed with kidney disease, or are taking folate supplements, consult your healthcare provider before making dietary changes. This study is observational and cannot prove cause-and-effect relationships. Individual risk factors for kidney stones vary, and your doctor can provide recommendations tailored to your specific health situation.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.