What happens when you take green tea with folate?
Green tea polyphenols, especially epigallocatechin-3-gallate (EGCG), interfere with folate biology at three different levels. First, they competitively inhibit the proton-coupled folate transporter (PCFT) in the upper small intestine, which is the main carrier responsible for absorbing dietary folate and folic acid from supplements. Second, EGCG inhibits dihydrofolate reductase (DHFR), the enzyme needed to convert synthetic folic acid into the metabolically active tetrahydrofolate forms that cells can use. Third, in solution and in serum EGCG can generate hydrogen peroxide that oxidatively degrades active folate, an effect that vitamin C can reverse.
The net clinical effect was measured in a human pharmacokinetic study published in 2008. When healthy volunteers took 400 micrograms of folic acid with green tea, the peak blood concentration (Cmax) dropped by about 58% and total exposure (AUC) dropped by about 44% compared with folic acid taken with water. Black tea produced a similar but somewhat smaller reduction. In other words, more than half of the folic acid dose effectively never reached the bloodstream when it was taken at the same time as tea.
Why is this important?
Folate (vitamin B9) is essential for DNA synthesis, red blood cell formation, and neural tube closure in early embryonic development. Adequate folate status before conception and during the first trimester of pregnancy reduces the risk of neural tube defects such as spina bifida and anencephaly by 50-70%. National health bodies, including the NIH and CDC, recommend that all women who could become pregnant take 400-800 micrograms of folic acid daily.
If a woman trying to conceive, or in early pregnancy, takes her prenatal vitamin with a cup of green tea, she may be absorbing only about half of the labelled folic acid dose. Over weeks and months this can leave folate status meaningfully lower than the supplement label would suggest. The concern is greatest for women with genetic variations in folate metabolism (such as MTHFR polymorphisms), women on antifolate medications like methotrexate (where the interaction goes in a more complex direction), and women using high-dose green tea extract supplements for weight loss.
Folate is also important outside pregnancy: deficiency causes megaloblastic anaemia, raises homocysteine levels, and may contribute to cognitive decline, depression, and cardiovascular risk. Anyone supplementing folic acid for these reasons should be aware that timing relative to green tea matters.
What should you do?
Take folic acid (or a prenatal/multivitamin containing folic acid) with plain water, well separated from green tea. A gap of at least 30-60 minutes between the two is the practical minimum, and longer is better. Many clinicians recommend taking the prenatal first thing in the morning with water and saving green tea for later in the day.
Vitamin C (ascorbic acid) partially protects folate from oxidative degradation by EGCG. Taking your folate with a glass of orange juice, or with a vitamin C supplement, is sensible, especially if green tea is a regular part of your diet. Choosing methylfolate (5-MTHF, the active form) instead of synthetic folic acid bypasses the DHFR-inhibition step but does not bypass the transporter-inhibition step, so timing separation is still wise.
If you use a concentrated green tea extract supplement (often standardised to 50-90% EGCG), separate it from folate by at least 2 hours. Women actively planning a pregnancy or in the first trimester may want to avoid high-dose green tea extracts altogether, both because of the folate interaction and because of separate concerns about hepatotoxicity at high catechin doses.
Which specific products are affected?
On the folate side, the interaction applies to synthetic folic acid in prenatal vitamins, standalone folic acid tablets, B-complex supplements, and folic-acid-fortified foods (breakfast cereals, enriched bread and pasta in countries with mandatory fortification). It also affects the active form L-methylfolate (5-MTHF) because both share the PCFT for intestinal absorption.
Dietary folate from leafy greens, legumes, and citrus is also affected by the transporter-inhibition mechanism, although the lower folate doses involved mean the clinical impact is harder to detect.
On the green tea side, all forms are implicated: brewed green tea (sencha, matcha, gyokuro, dragon well, jasmine green), bottled green tea drinks, and especially green tea extract supplements with concentrated EGCG. Decaffeinated green tea retains the catechin content and still interacts.
The bottom line
Green tea, through its catechins, can cut absorption of folic acid roughly in half and interferes with the conversion of folic acid to its active form. For most healthy adults this is a minor issue, but for women planning pregnancy, women in early pregnancy, and anyone treating folate deficiency, the interaction is clinically significant. Take folate supplements with water at least 30-60 minutes away from green tea, pair them with vitamin C when you can, and avoid concentrated EGCG supplements close to your folate dose.