Why you should avoid folic acid supplements and folic acid fortified food?

Difference between folic acid and folate

The reason I decided to write this post is because of my recent attempt to buy ready made smoothie in M&S. When I buy food I always check labels. My main checks are for sugar content, type of oils used and forms of vitamins & minerals (if they have been added). What put me off when I was trying to get this smoothie was folic acid. I know that folic acid is quite often added to breakfast cereal and flour but I didn’t know about smoothies! So let me explain why I didn’t like this ingredient.

Difference between folic acid and folate

Folic acid is synthetic form of folate. Folic acid and folate are forms of vitamin B9. They are often used interchangeably but they are not the same thing.  Folate is found in food in form of folinic acid and methylfolate. Active form of vitamin B9 is called ‘reduced folate or ‘methylfolate’. Both folic acid and folate need to be converted to active form (through methylation process) to be used by the body. MTHFR is a gene that produces enzymes required for the conversion. It’s also quite common that many people have MTHFR gene mutation however you would need to do blood test to find out.

I can imagine that now you may want to say – if both have to be converted to active form why folic acid is bad and folate is good?


Folate from food already contains other co-factors required for conversion to active form. Moreover, folate in food is usually a combination of inactive form folinic acid and active form -methylfolate. It means, that even if you have MTHFR gene mutation responsible for conversion, you probably would be still able to get some active folate from food. If you are able to get enough of it, it’s another thing that should be considered. Folate is not only important for pregnancy, cell growth and red blood formation, is also a key vitamin for homocysteine breakdown which is one of the major risk factors for cardiovascular diseases.

  • Synthetic folic acid impairs 5-MTHFR enzyme activity which is required for conversion to active form. In other words, long term exposure to folic acid can reduce our body’s ability to use and convert folate from food
  • Folic acid needs to be metabolised by the liver which puts extra stress on this organ.
  • Large amount of unmetabolized folic acid can lead to toxicity.

Industrialization and processing of grains caused increase in birth defects linked to vitamin B9 deficiency. In 1998 US introduced mandatory fortification of food with folic acid to prevent birth defects. Other countries followed it, including UK. However, there is more and more evidence emerging indicating the harmful effect of the synthetic form of folic acid. You may also wonder so why the government decided to ‘improve’ food with harmful substance? That time, the studies indicting benefits of folic acid were conducted on rats which have significantly higher ability to convert folic acid to active form. Unfortunately it’s not the same case with humans.

  • Vitamin B9 in active form together with B6 and B12 are essential for homocysteine breakdown. As mentioned earlier, homocysteine is amino acid that is considered as a risk factor for cardiovascular disease. High levels of homocysteine can be due to high stress, high meat diet, smoking, high alcohol and coffee intake
  • Excess unmetabolized folic acid can mask vitamin B12 deficiency.
  • Excess vitamin B9 (in supplemental form) can accelerate cancer cell growth. Vitamin B9 is responsible for DNA replication, if the cancer cells are present, then supplementation of folic acid may be harmful.
  • Avoid vitamin B9 in form of folic acid no matter if it’s from fortified food or supplement
  • Vitamin B9 is needed for various processes in the body and the best is to get if from food. There are no known adverse effects of too much of vitamin B from food.
  • If you decide to supplement vitamin B9, consider if you may have MTHFR gene mutation, the form and dosage.

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