Are You Getting Too Much Folic Acid? Why It Matters


B vitamins are essential for good health. In fact, there are eight different B vitamins, each with a slightly different function in your body. One of their many activities that B vitamins take part in is energy metabolism.


In other words, B-vitamins play an ancillary, but still mandatory role, in chemical reactions that your body uses to make energy and sustain life.


Because of the importance of B vitamins, the idea has been perpetuated, mostly by vitamin companies, that more B vitamins are better. As you’ll soon see, that’s not always the case. One of the B vitamins, folic acid, may be particularly problematic if you take it in supplement form.


First, let’s look at what folic acid does and then we’ll look more closely at why too much folic acid is a problem.


What Does Folic Acid Do?


Folic acid (not the same as folate as you’ll soon see) plays a critical role in keeping you healthy. As mentioned, you need it for energy and for cells to divide and reproduce. It also participates in the production of red blood cells.


To divide, cells have to replicate their DNA and without enough folate, they can’t easily do that. What happens if you don’t get enough?


If you had a significant deficiency of folate, also called vitamin B9, you would likely develop an anemia marked by large red blood cells. The red blood cells are substantial in size but immature.


The reason is the red blood cell can’t replicate their DNA well enough to become mature red blood cells. So, yes, you need a certain amount of folate for cellular health and for the production of healthy, mature red blood cells. No argument there. 


Folic Acid vs. Folate: What’s the Difference?


How do folic acid and folate differ? Folate is the natural version of vitamin B9, the form your body actively uses to do all the good things folate does – make red blood cells and ensure that cells divide without a hitch and without doing something you don’t want, like forming a malignant cell.


Folate is a vitamin with clout. It has the power to turn genes on and off through a process called methylation. So, folate helps determine things like when genes that control cell division and maturation are turned on or whether they’re turned on at all. That gives folate a great deal of control and power!


Where does this high-profile vitamin hide out in food?


You find substantial amounts of natural folate in vegetables, particularly green, leafy ones as well as whole grains. Also, many packaged foods are fortified with it.


Here’s where it gets tricky. Folate, the natural form found in healthy foods like vegetables, is NOT the same thing as folic acid, the kind in multivitamins, B-complex supplements, and in fortified foods.


Folic acid is a cheap, synthetic version of folate and one that your body can’t easily recognize. To use  this synthetic form  of vitamin B9, your body has to convert it to the natural form, folate. To do this, it needs a specific enzyme called dihydrofolate reductase.


The problem is up to 30% of the population doesn’t produce enough of this enzyme and can’t easily convert folic acid to folate, the form your body needs. So, when you take a folic acid supplement, you won’t get the full benefits unless you can easily make the conversion from folic acid to folate.


So, what happens to all the folic acid you got from the supplement? It stays in your bloodstream and in your tissues where too much folic acid can cause more harm than good.


Here’s an interesting video on the topic:


What Kind of Harm Can Folic Acid Cause?


Some evidence suggests that supplementing with folic acid spurs the growth of cancer cells and pre-cancerous cells. We know that fruits, vegetables, and whole grains are an abundant source of folate and these foods are linked with a lower risk of many types of cancer.


Yet, folic acid in its supplemental form seems to promote the growth of cells that haven’t already undergone a cancerous transformation.


How many of us have pre-malignant cells hiding in our body? Most of us. As we get older, the number of such cells increases. Cancer cells and pre-cancerous cells form all the time but a healthy immune system keeps them in check.


These cells may be relatively quiet and not cause problems until you stimulate their growth and proliferation by taking folic acid.


In fact, some cancer treatment drugs stop cancer growth by blocking the effects of folic acid. In one study, when patients with leukemia ate a diet deficient in folic acid, it reduced the growth of leukemia cancer cells.


Too much folic acid is harmful if you have a malignant or pre-malignant condition.


What about healthy people? Several studies show that supplementing with folic acid is linked to a higher risk of some cancers. For example, folic acid supplementation is associated with a higher risk of breast cancer whereas dietary folate seems to lower the risk of breast malignancies.


When a Folic Acid Supplement IS Necessary


While taking a folic acid supplement isn’t a good idea for the average person, you should take 400-600 micrograms daily of folic acid if you’re trying to become pregnant.


Research clearly shows that taking a folic acid supplement, in this case, lowers the risk of neural tube defects, severe birth defects that affect a baby’s brain, spinal cord, or both. The sooner you begin taking folic acid the lower your risk.


In fact, you should start taking it even BEFORE you try to get pregnant. Neural tube defects happen very early during pregnancy. When we say you shouldn’t take a folic acid supplement, we assume you’re not pregnant. 


Too Much Folic Acid: Summing Things Up


Most people get enough folate by eating a healthy diet. Flour, cereals, and many packaged foods have added folic acid. In fact, the amount of synthetic folic acid in packaged foods may actually be harmful. That’s because the quantity of folic acid in some packaged foods is higher than the amount recommended for health.


If you eat packaged foods and also take a multi-vitamin, almost all of which contain folic acid, you get a substantial amount of synthetic folic acid. Research shows that when you get more than the recommended amount, 400 micrograms per day, unmetabolized folic acid can build up in your blood.


Of note, the incidence of some cancers, especially colorectal cancer rose after the addition of folic acid to packaged foods started. Also keep in mind, that many drugs used to treat cancer block the effects of folic acid. That’s how they destroy cancer cells.


If you are being treated for cancer, there’s even more reason to avoid folic acid in supplement form and multivitamins that contain it.


If you do need to take a folate supplement, because your level is low, take one that has the active form of folate. This avoids the problem of the build-up of unmetabolized folic acid.


One example of a supplement with active folate is this one.  There’s also a multivitamin with active folate.  Keep in mind, if you eat a whole food, balanced diet, you probably don’t need a multivitamin. 


Take-Home Points


  • Folic acid is a synthetic form of folate, the natural form of vitamin B9. It’s abundant in vegetables, fruits, and whole grains.
  • Your body needs a special enzyme to convert folic acid to folate. If you don’t have enough of this enzyme, folic acid can build up in your tissues.
  • Packaged foods often contain substantial quantities of folic acid. If you eat these foods regularly, especially if you take a multi-vitamin, you may have unmetabolized folic acid in your bloodstream.
  • Unmetabolized folic acid may stimulate the growth of pre-malignant cells that you don’t know you have.
  • Unless you have a known folate deficiency, are planning to become pregnant or are currently pregnant, you shouldn’t take a folic acid supplement.
  • Folate found naturally in foods does not seem to have the same drawbacks as synthetic folic acid. In fact, folate-rich vegetables are linked with a lower risk of some types of cancer.


The Bottom Line


You definitely need a certain amount of folate in your diet. A lack of folate likely also increases the risk of cancer and is linked with other health problems as well.


For example, people who are deficient in folate have higher levels of a marker for inflammation called homocysteine. High homocysteine is linked to heart attack and stroke. Folate deficiency also causes anemia.


What you DON’T need, unless you’re pregnant, is supplemental folic acid or the excessive amounts of folic acid in packaged foods. The folic acid in multivitamins is another reason to reconsider taking one.


Use this information to skip the supplements and add more vegetables and whole grains to your diet. Don’t settle for the cheap synthetic folic acid in processed foods and your multivitamin. 



WebMD. “Folate (Folic Acid)”
Science Based Medicine “The benefits and risks of folic acid supplementation” “Folic Acid vs. Folate”

Kristie Leong M.D.

Dr. Kristie Leong and Dr. Apollo Leong are physicians helping you to lead a healthy lifestyle by sharing nutrition and fitness tips and keeping you abreast of the latest health news.

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