Arguably, no conventional nutrient has undergone as much of a research renaissance in recent years as folate. Many people are familiar with the name of this B complex vitamin, and it has long been recognized as a key nutrient in human health. Low intakes of folate can have devastating effects, ranging from birth defects to blood diseases and possibly even cancers.
Much more recent in our understanding of this critical B vitamin is its many different forms in food, and its influence far beyond birth defects, blood diseases, and cancers. In our Role in Health Support section, we will be giving you many more details on exciting new folate research.
If the word folate sounds like foliage to you, this is not an accident. The words share a common root (the Latin word folium, meaning "leaf"), which helps remind us that green plant foods can be among the richest sources of folate. However, as the chart and table in this article show, there are outstanding sources of folate in other food groups as well (especially legumes). .
Because of the promising role of folate in disease risk reduction, U.S. public health organizations have taken many steps to help increase intake of folate in the U.S. population. These public health programs have helped decrease the occurrence of neural tube defects associated with folate deficiency by as much as 30% over time. (Although enrichment of processed wheat flour with vitamins B1, B2, and B3 was practiced in the U.S. as early as the 1940's, it wasn't until 1998 that the U.S. Food and Drug Administration established guidelines for enrichment of processed wheat flour with folate.)
The adult Dietary Reference Intake (DRI) level for folate—and our WHFoods recommended daily intake level—is 400 micrograms DFE, where "DFE" stands for "Dietary Folate Equivalents." In the 2009-2010 National Health and Nutrition Examination Survey (NHANES), both male and female adults in the U.S. averaged well over this amount, with approximately 475 mcg DFE for adult women and 625 mcg DFE for adult men. However, a significant amount of this folate came in the form of fortified foods, enriched foods, or folate supplements rather than whole, natural foods. From a health standpoint, our WHFoods recommendations always focus on whole, natural foods, and if you regularly enjoy our recipes, you will be likely to do just as well as the average U.S. adult in your food-based intake of folate, without resorting to fortification or enrichment. Dozens of our recipes contain more than half of the recommended daily intake level for this B vitamin.
Our profiled foods include 10 excellent sources of folate, 17 very good sources, and 24 good sources. Included in these ranked sources of folate are foods from various food groups, including vegetables, fruits, and legumes. Given this wide variety of choices, we are confident about your ability to develop a whole foods meal plan that will provide you with plenty of folate.
As mentioned earlier, the past decade of folate research has taught us much more about the nature of this vitamin and its critical role in support of our health. However, we would also point out that, in general, folate has been a complicated vitamin for researchers to understand, and research on folate has produced some confusion when scientific findings need to get translated into practical steps that we can take in the grocery store and in the kitchen. Our goal in these next paragraphs is provide you with a framework for simplifying key aspects of recent research on this B vitamin.
Let's start off with the name of the vitamin itself. "Folate" is a very general name for a complicated family of nutrients found in both plant and animal foods. (At WHFoods, we use this very general term as our name for this B vitamin, and when we use it, we are not trying to specify any particular form of the vitamin. We just want to refer to this B vitamin in a consistent way.) To give you an idea of many different folate forms in food, consider the following list: methylfolates, dihydrofolates, monoglutamyl folates, and polyglutamyl folates. All of these vitamin forms can be found in varying amounts in whole, natural foods. By contrast, fortified and enriched foods are typically boosted in content with a single form of this vitamin, namely, folic acid. While you can find not only folic acid but many different forms of folate available in the form of dietary supplements, this vitamin gets added to food almost exclusively in the form of folic acid.
This complicated situation involving fortified foods led the National Academy of Sciences (NAS) to establish a new category for measuring dietary folate, called Dietary Folate Equivalents, or DFEs. If you consume 1 microgram of folate from a whole natural food, the NAS considers you to have consumed 1 microgram DFE. However, if you consume 1 microgram of folate from a food that has been fortified with folic acid, the NAS considers you to have consumed 1.6 micrograms DFE. Finally, if you take a folic acid supplement on an empty stomach in which no foods are simultaneously being consumed, the NAS considers you to have consumed 2 micrograms DFE. These differences in DFE calculation are based on studies measuring blood folate levels following intake of folate in various forms. The higher DFEs reflect higher blood levels associated with intake of supplemental folic acid versus natural food folate.
However, in order to more fully understand the health benefits of this vitamin, it would be a mistake to stop our discussion with consideration of supplemental folic acid, food folate, and DFEs. During the time that has passed since the NAS establishment of folate DFEs in 1998, there have been numerous advances in research on this vitamin. In comparison to the original DFE research, which showed about 50-60% bioavailability of food folate versus 85% bioavailability of supplemental folic acid, we now know that "bioavailable" can have many meanings and blood levels of folate are not always the best way to measure bioavailability. For example, we now know that polyglutamated folate found in vegetables and citrus fruits can be absorbed in the 60-98% range. We also know that a methylated form of folate (5-methyl-tetrahydrofolate) is the major form of folate in most plant cells, and that methylfolate appears to be the only form of this vitamin that crosses over the blood brain barrier and into the brain. This research has greatly increased interest in whole foods and the extent to which they naturally contain methylfolates.
Taken as a whole, these more recent research studies suggest that folate DFEs do not tell the whole story of this vitamin with respect to health benefits, and that whole, natural foods providing folate in a variety of forms are likely to be your best bet for obtaining health benefits related to this B vitamin. With this general guideline in mind, we would like to highlight specific areas in which folate health benefits have been most consistently documented in research studies.
Folate has long been known to help support production of nervous system function, and in particular, production of messaging molecules that are used by nerves to send signals throughout out body. More recently, however, research has broadened our understanding in this area of folate benefits.
In what has come to be named the BH4 Cycle (where is an abbreviation for tetrahydrobiopterin), researchers have verified a close connection between production of multiple neurotransmitters (with special emphasis on serotonin and dopamine) and availability of folate. In fact, part of the molecule for which this BH4 Cycle is named (dihydrobiopterin, or BH2) can itself be readily converted into a form of folate (dihydrofolate). In addition, researchers now know that BH4 cross over the blood brain barrier using the same transport mechanism as folate.
Interest in these nervous system messaging molecules and folate has been fascinating and widespread. Since much of the dopamine produced in our nerve cells begins with conversion of one amino acid (phenylalanine) into another amino acid (tyrosine), folate availability has been shown to be closely connected with this neurotransmitter pathway since BH4 is required for conversion of phenylalanine into tyrosine. Yet broader still are possible connections between two additional neurotransmitters—glutamic acid and GABA—and folate metabolism.
Glutamine is the preeminent amino acid in our central nervous system, and it is the starting point for production of both glutamic acid and GABA. While glutamic acid is widely known as an "excitatory" neurotransmitter that can stimulate and speed up nerve cell activity, it actually plays a much wider role in nervous system health that includes proper brain development, differentiation of nerve cells, and survival of nerve cells. By contrast, GABA (gamma-aminobutyric acid) is widely regarded as a primary inhibitory neurotransmitter that can decrease nerve activity in certain areas and help initiate nervous system balance needed to pave the way for activities like sleep. Researchers do not yet know exactly how folate metabolism is related to metabolism of either glutamic aid or GABA. But what researchers do know is that folate is a B vitamin that contains a "tail" comprised of glutamic acid molecules. In fact, this glutamic acid vitamin "tail" controls absorption of folate from our intestines up into our body.
During the past 10 years, research on the role of folate in nervous system support has greatly overlapped with folate research as it relates to support of the cardiovascular system. In fact, it might be hard to find an area of metabolic research that has generated more excitement that this overlapping area of folated-related events critical for health of our cardiovascular and nervous systems.
The overlap begins with the ability of adequate dietary folate to help keep blood levels of homocysteine in check. Homocysteine (Hcy) is a well-documented marker for cardiovascular disease that when excessive, represents a clearly increased risk for a variety of cardiovascular problems. (Hyperhomocysteinemia is the name of the condition for high Hcy in the blood.) Optimal levels of blood folate in one particular form (5-methyltetrahydrofolate, or 5-MTHF) can directly help lower Hcy levels. By helping to keep Hcy levels in check, healthy intake of folate can help lower risk of cardiovascular disease.
The benefits of folate for lowered cardiovascular risk do not stop with Hcy, however. Balanced levels of nitric oxide (NO) in the blood are equally well-established as being important for cardiovascular health. NO helps to regulate many cardiovascular functions, and appropriate levels of NO are considered protective again high blood pressure, excessive clumping of platelet cells, and other key aspects of blood flow.
Several different forms of an enzyme called nitric oxide synthase (NOS) are responsible for helping keep NO at appropriate levels in our blood. However, NOS enzymes cannot actually generate NO unless certain molecules are present to help the NOS enzymes function properly. One such molecule is BH4 (tetrahydrobiopterin). Without enough BH4 around, the NOS enzymes not only fail to produce enough NO, but they can actually worsen our cardiovascular health by producing too much of an oxygen free radical called superoxide. How is it that our bodies keep enough BH4 around? Our bodies accomplish this task with the help of an enzyme called dihydrofolate reductase (DHFR). Of course, you can easily recognize the word "folate" in the name of this enzyme, because it is the same enzyme that converts folate into its most central bioactive form in the body, called tetrahydrofolate, or THF. In other words, the same enzyme that makes sure we have enough BH4 around to keep up our nitric oxide levels also makes sure that we have the most centrally active form of folate. So you can see how our folate metabolism and our cardiovascular health are so closely connected on a metabolic level.
The key role of folate in our cardiovascular health does not stop here, however. It turns out that the overall cycle used by our body to regenerate active forms of folate—called the folate cycle—is directly tied to a central cycle in cardiovascular health called the methylation cycle. The methylation cycle is our primary way of understanding blood homocysteine levels, since this cycle continually interconverts the amino acid methionine (MET) and its fellow amino acid, homocysteine (Hcy). When our folate cycle breaks down, our methylation cycle breaks down. However, the way in which our methylation cycle breaks down is important because a breakdown in our folate cycle means a breakdown in our conversion of Hcy back into MET. In other words, a breakdown in our folate cycle means excessive accumulation of Hcy and increased risk of heart disease.
As complicated as these metabolic pathways might seem, the bottom line here is straightforward: folate is a central nutrient for cardiovascular health, and its role in cardio support is wide-ranging.
It would be wrong to leave the topic of folate and cardiovascular health without making a special note about red blood cell production. Folate is one of many nutrients necessary for the production of red blood cells. These cells carry oxygen from the lungs to other parts of the body. Along with iron, copper, vitamin B12, and vitamin B6, a deficiency of folate can impair blood cell production.
Still, the deficiency of folate must be fairly severe to impair the production of red blood cells. Although this can occur, it is rare in the United States, where adults average more than the recommended daily intake level.
When women deficient in dietary folate become pregnant, the developing fetus is at increased risk for neural tube defects, a developmental condition that adversely affects nervous system development in the fetus. These neural tube defects are potentially devastating and can often cause loss of pregnancy.
Adverse effects on nervous system development in the fetus can occur very early in pregnancy, even before a woman is aware that she is pregnant. Because this very early occurrence of problems can be "invisible," it is important for women to consume enough of this nutrient before they become pregnant. From a practical standpoint, this scenario means special attention to folate intake by any woman who is considering pregnancy. As noted earlier, current evidence supports a conclusion that better folate intake by women prior to pregnancy can directly reduce risk of neural tube defects in a significant way.
Some studies show lower risk of breast cancer in women with higher dietary intakes of folate, as well as decreased cancer risk at other sites in both men and women. However, the overall research on folate and cancer risk is both controversial and on the surface, sometimes contradictory, since some studies find an association between high folate intake and increased cancer risk. However, this important area of research is often confounded by the failure of studies fail to distinguish between supplemental folic acid and natural food folate.
Prevention and treatment of mental health problems—especially depression—are topics of special interest in relationship to folate intake, and we have seen some preliminary studies linking folate deficiency to increased risk of depression.
As the name implies, green leafy vegetables (or foliage) are among the best sources of folate. Spinach, turnip greens, bok choy, parsley, and romaine lettuce are all rated by our system as excellent sources of folate. Other vegetables can be strong sources as well, and we see asparagus, cauliflower, broccoli and beets join the excellent group.
We also see a number of the legumes do very well for this nutrient. At the top of the list here are lentils, which achieve a rating of "excellent" for folate. In fact, among all WHFoods, lentils rank as our best source of folate! Rating "very good" as sources of folate are garbanzo beans, navy beans, kidney beans, and pinto beans.
Some, but definitely not all, fruits are important sources of folate. Papayas and strawberries are very good sources of this nutrient, while oranges, pineapple, raspberries, kiwifruit, cantaloupe, lemons and limes all rate as "good" sources of this B vitamin.
To design a whole foods diet that contains enough folate, you'll want to make sure to include plenty of minimally processed plant-based foods. If you are eating 5 cups' worth of vegetables, a couple of fresh fruits, and a legume-based meal during an average day, you are quite likely to be meeting your folate needs.
|World's Healthiest Foods ranked as quality sources of|
|Turnip Greens||1 cup||28.8||169.92||42||26.5||excellent|
|Romaine Lettuce||2 cups||16.0||127.84||32||36.0||excellent|
|Bok Choy||1 cup||20.4||69.70||17||15.4||excellent|
|Pinto Beans||1 cup||244.5||294.12||74||5.4||very good|
|Garbanzo Beans||1 cup||269.0||282.08||71||4.7||very good|
|Black Beans||1 cup||227.0||256.28||64||5.1||very good|
|Navy Beans||1 cup||254.8||254.80||64||4.5||very good|
|Kidney Beans||1 cup||224.8||230.10||58||4.6||very good|
|Papaya||1 medium||118.7||102.12||26||3.9||very good|
|Brussels Sprouts||1 cup||56.2||93.60||23||7.5||very good|
|Green Peas||1 cup||115.7||86.78||22||3.4||very good|
|Bell Peppers||1 cup||28.5||42.32||11||6.7||very good|
|Green Beans||1 cup||43.8||41.25||10||4.2||very good|
|Celery||1 cup||16.2||36.36||9||10.1||very good|
|Cabbage||1 cup||43.5||36.00||9||3.7||very good|
|Summer Squash||1 cup||36.0||36.00||9||4.5||very good|
|Strawberries||1 cup||46.1||34.56||9||3.4||very good|
|Tomatoes||1 cup||32.4||27.00||7||3.8||very good|
|Leeks||1 cup||32.2||24.96||6||3.5||very good|
|Fennel||1 cup||27.0||23.49||6||3.9||very good|
|Lima Beans||1 cup||216.2||156.04||39||3.2||good|
|Dried Peas||1 cup||231.3||127.40||32||2.5||good|
|Sunflower Seeds||0.25 cup||204.4||79.45||20||1.7||good|
|Winter Squash||1 cup||75.8||41.00||10||2.4||good|
|Collard Greens||1 cup||62.7||30.40||8||2.2||good|
|Beet Greens||1 cup||38.9||20.16||5||2.3||good|
|Mushrooms, Crimini||1 cup||15.8||18.00||5||5.1||good|
|Kiwifruit||1 2 inches||42.1||17.25||4||1.8||good|
|Swiss Chard||1 cup||35.0||15.75||4||2.0||good|
|Mushrooms, Shiitake||0.50 cup||40.6||15.22||4||1.7||good|
|Mustard Greens||1 cup||36.4||12.60||3||1.6||good|
|Lemons and Limes||0.25 cup||13.4||12.20||3||4.1||good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
Like most water-soluble vitamins, folate can frequently be removed from foods during processing. You should expect there to be a substantial loss of folate in the manufacture of canned foods. The exact amount of folate lost depends on the food in question and the processing method used, but here are some practical examples. One cup of cooked garbanzo beans (prepared from dried beans) can provide you with over 275 micrograms of folate, while the same amount of canned garbanzo beans (by weight) is likely to provide you with about 75 micrograms. Or to use a folate-rich vegetable example, like asparagus: one cup of cooked asparagus (prepared from fresh form) can provide over 265 micrograms of folate, with the same amount of canned asparagus (by weight) providing about 170 micrograms. So as you can see, there is substantial loss of folate in both of these examples. The difference between canned and non-canned legumes is one you will want to keep in mind when enjoying the convenience of canned legumes. You can help maintain strong folate intake when using canned legumes by combining them with non-canned folate-rich foods like green leafy vegetables.
Our basic approach to food selection and preparation at WHFoods is to avoid processing as much as possible and rely instead on fresh and minimally cooked foods. Loss of folate during processing is one of the many reasons we have adopted this approach.
Occasionally, a method of food preparation can increase the level of a nutrient, and we are aware of one such example involving folate. This particular example involves conventional preparation of tofu and tempeh using microorganisms and fermentation. While folate is typically lost during the early stages of the tofu/tempeh preparation due to soaking of soybeans in water, fermentation of the soaked beans can ultimately replenish the lost folate. While neither tofu nor tempeh emerge as ranked sources of folate at WHFoods, both contain measurable amounts of folate in the 25-30 microgram per serving range.
One final note about fermentation here: we've seen studies show that fermentation of cow's milk—as would occur in production of yogurt, and especially with live cultures remaining in the final product—can also somewhat increase the milk's folate content.
Folate should be fairly stable to cold, at least over short periods of time. For example, one study found that Chinese cabbage did not lose a significant amount of folate over three weeks of refrigeration. Of course, we generally recommend enjoyment of fresh cabbage stored for a week or so at most in the crisper bin of the refrigerator.
As mentioned earlier, both male and female adults in the U.S. averaged well over the recommended intake level for folate in the 2009-2010 National Health and Nutrition Examination Survey (NHANES). From our perspective, however, this adequate intake of folate in terms of amount was actually inadequate in terms of food quality, since a significant amount of this folate came in the form of fortified foods, enriched foods, or folate supplements instead of whole, natural foods. We believe that your health is always better served if you are able to get the nutrients you need from whole, natural foods. If U.S. adults did not currently consume folate-fortified and folate-enriched foods, in combination with folic acid-containing supplements, they would not average adequate intake for folate! However, if you regularly enjoy our recipes, you will personally be likely to do just as well as the average U.S. adult in your food-based intake of folate, without resorting to fortification, enrichment, or supplements.
For many of our nutrients, we can design a sample daily diet to feature multiple strong sources of the nutrient and ensure good continuity over days and weeks of eating. With respect to folate, this task is especially easy. To approximate our DV of 400 mcg, you just need to have a large serving of greens . If you'd prefer, you could get within 15% of the DV by having a legume-rich meal (such as our Black Bean Chili). We have 25 recipes that rate as excellent sources of folate, most of which contain over half your DV for folate.
Folate is more difficult to absorb and utilize than most of the other water-soluble vitamins. As such, people with bowel disease or other conditions that interfere with absorption may need to pay extra attention to folate nutrition.
Certain conditions and life stages can increase your need for folate, even when dietary supply is consistent. The most important is pregnancy. If you plan to and/or are able to become pregnant, make sure and have a look at the public health recommendations below. Breastfeeding is also a time when the need for folate increases, and it is therefore also a time of greater deficiency risk.
Many medications, including seizure medications and drugs used to treat inflammation, interfere with folate metabolism. If you are on one of these medications, you may need to work with your doctor to ensure you get enough folate.
Folate is a member of the B complex vitamins, and like the others in this group, it will rely on the presence of the entire group to do its job effectively. Luckily, most of the B complex vitamins are found in the same plant foods that are rich in folate, so a diet rich in one is often rich in the others.
The most important exception to this rule is also the B vitamin whose role is most entwined with folate. Vitamin B12, which can only be made by microorganisms and which typically only accumulates in animal foods, fermented plant foods, and mushrooms works closely with folate in many of its different roles. Because folate is provided by a much larger variety of foods than B12, and because a wider variety of foods are typically fortified with folate and not B12, it is sometimes possible to get very large amounts of folate in comparison to B12. This type of imbalanced intake can be problematic since excessive amounts of folate can make deficiency of B12 more difficult to detect through standard lab tests. If left undetected, longstanding B12 deficiency can lead to sometimes irreversible health problems.
Luckily, the amounts of folate needed to create this type of problem is large and would be virtually impossible to obtain from whole, natural foods. You could, however, create this type of folate-to-B12 imbalance from a routine combination of fortified foods and supplemental folic acid. As you'll see below in the Risk of Dietary Toxicity section, this safety factor provided by whole foods versus fortified foods and supplements is the reason that an upper limit was set by the National Academy of Sciences for intake of folate from fortified foods and supplements, but not for intake of folate found in natural, non-fortified foods.
The pathways that utilize folate and vitamin B12 are also dependent on vitamin B6 and riboflavin for proper functioning. Compared to folate and vitamin B12, however, these additional two B vitamins are less likely to be deficient to the point of creating a problem.
There is no known risk of toxicity from excessive naturally occurring folate from foods. This is good news, since the diets highest in folate tend to be those highest in vegtables, legumes, and other highly desirable foods that belong in most healthy meal plans.
It would, however, be very easy to go above the Tolerable Upper Intake Limit (UL) of 1000 mcg of added or supplemental folic acid on a regular basis. (Note: this UL is set for all individuals 19 years and older, with the exception of women under 19 years of age who are pregnant or breastfeeding. For women in that category, the UL is 800 mcg.) For example, if you take a multiple vitamin supplement that contains 400 mcg of folic acid, and on top of that you add an energy bar that contains 15 micrograms, and a breakfast cereal fortified with 30 micrograms, you'll have 445 micrograms of folate or 45% of the UL before you start counting your primary list of foods for the day. One cup of lentils, one cup of broccoli, and 2 tablespoons of peanuts would put you over the UL at 1,059 micrograms.
The level of folate intake describe above is unlikely to cause problems on an occasional basis. However, if you plan to routinely consume folate-fortified foods and take supplements providing large amounts of folic acid, you may want to talk with a nutritionist and/or healthcare provider to help avoid possible problems with B vitamin balance given regular high intake of this B vitamin.
One additional note about the upper limits set for folate intake: for children 1-3 years of age, the UL is 300 micrograms; for children 4-8, the UL is 400 micrograms; for 9-13 year olds, it is 600 micrograms; and for 14-18 year olds, it is 800 micrograms.
In 1998, the National Academy of Sciences (NAS) published Dietary Reference Intake (DRI) guidelines for folate. These guidelines included Recommended Dietary Allowances (RDAs) for all persons one year and older. The folate recommendations were established in terms of micrograms of Dietary Folate Equivalents (or micrograms DFE) in order to adjust for intake of folate from fortified foods and supplements. For infants under one year of age, the DRIs were established as Adequate Intake (AI) levels rather than RDAs. A summary of these recommendations appears below:
The National Academy of Sciences also recommended that any woman who could become pregnant consume 400 mcg of folic acid daily from either a supplement or from fortified foods in addition to the naturally occurring folate in the diet. In 1991, the Centers for Disease Control (CDC) recommended women who have previously had a child with a neural tube defect should take 4000 mcg of supplemental folic acid when starting pregnancy planning.
Tolerable Upper Limits, or ULs for folate were also established by the NAS. The ULs do not apply to naturally occurring folate in food. (In other words, there was no limit set on the amount of natural food folate found to be safe.) Instead, the ULs only apply to folate obtained from fortified foods or supplements. Below is a summary of the ULs:
The Daily Value (DV) recommendation for folate is 400 mcg per 2000 calories. This is the value we use to calculate food rankings in all of our food and nutrient charts.