Folic acid reduces blood pressure and counteracts blood clots

Folic acid (vitamin B9) reduces blood pressure, but such a large amount is required that you need to take it as a supplement. At the same time, the vitamin protects the heart and brain from thrombosis.

Since long, it has been documented that the B-vitamin folic acid (B9) prevents congenital neural tube defects. In Canada, all kinds of flour have been enriched with folic acid during the past 8 years, and 80% of the congenital neural tube defects have thus been prevented. In the USA, enrichment is also obligatory, but in Britain, expectant mothers are left to themselves. They have to figure out for themselves to take a supplement - before they become pregnant!

The main source of folic acid is leafy green vegetables (the latin "folium" means "leaf"). Many people do not like these leafy greens and folic acid deficiency is therefore more common than any other vitamin deficiency. Unfortunately, the deficiency probably does not only harm the unborn baby but does also increase the mortality of coronary thrombosis and cerebral apoplexy in adults. But this is not all: Folic acid deficiency probably also increases the risk of hypertension.

The connection between folic acid deficiency and hypertension that has been unknown till now was discovered when an eight-year study was concluded involving 156,000 American nurses *1). The risk of the nurses having hypertension while being 27 - 44 years of age was only half as great when they took 1 mg (1000 mcg.) of folic acid a day compared to when they took 0.2 mg. In both the US and Britain, 0.2 mg. is just below the average daily folic acid intake which is 0.25 mg. It is almost impossible to get 1 mg. of folic acid a day - which is four times as much - without taking a supplement.

With regard to apoplexy and coronary thrombosis, much interesting knowledge has been produced during recent years:

In the US, where enrichment of flour with folic acid began in 1996, the mortality rate following apoplexy has droppped dramatically - in all groups of society, that is, and for both men and women - so the results are rather regardless of lifestyle, etc.

Before 1996, the annual drop in mortality as a result of apoplexy was about 1%. This drop was the result of improved treatment and prophylaxis. However, in the succeeding three years, mortality rates dropped three times as fast, i.e. with a total of 10 - 15%! Statistically, this has been explained by the fact that the average American now has twice as much folic acid in his/her blood as before *2).

Moreover, apoplexy is far more dangerous if you are deficient in folic acid. This was recently demonstrated on mice. They were given an artificial apoplexy in that their cerebral artery was simply clamped. It turned out that the cerebral damage was only half as great in the mice that had been given enough folic acid *3).

Folic acid seems to be able to protect the heart as well. This appeared most recently when Italian doctors studied 900 patients hospitalized with or without coronary thrombosis. The patients were divided into three groups according to their estimated daily intake of folic acid. Among the patients admitted to the cardiology department, most of them belonged to the group that got the least folic acid!

The third of the patients that got the least folic acid had twice as great a risk compared to the third of the patients that got the most folic acid. When vitamin B6 intake was also taken into account (vitamin B6 collaborates with folic acid), the ones who got the most folic acid only had a relative risk of 29% *4).

It is not the folic acid itself that protects the heart and the brain. However, folic acid reduces the blood content of the harmful amino acid homocysteine which attacks the blood vessels.

About 10% of the population are unaware that they have a hereditarily increased homocysteine level in their blood (and therefore need more folic acid). Recently, it was discovered that these 10% suffer apoplexy significantly more often than others *5, 6). It was already known that these people already have an increased risk of suffering coronary thrombosis *7).

Nobody has yet performed a blinded study in which supplements have been used to efficiently lower the blood contents of homocysteine. However, this kind of research is now being encouraged *8). Yet, with our existing knowledge, it seems wise to take a folic acid supplement.

The ideal dosage may be around 0.8 mg. (800 mcg.) a day.



  1. Forman JP, Rimm EB, Stampfer MJ, Curhan GC. Folate intake and the risk of incident hypertension among US women. JAMA. 2005 Jan 19;293(3):320-9.

  2. American Heart Association's 44th annual Conference on Cardiovascular Disease Epidemiology and Prevention.carole.bullock(at)

  3. Endres M, Ahmadi M, Kruman I, Biniszkiewicz D, Meisel A, Gertz K. Folate deficiency increases postischemic brain injury. Stroke. 2005 Feb;36(2):321-5.

  4. Taivani A et al. Folate and vitamin B6 intake and risk of acute myocardial infarct in Italy. Eur J Clin Nutr 2004;58:1266-72

  5. Al-Delaimy WK, Rexrode KM, Hu FB, Albert CM, Stampfer MJ, Willett WC, Manson JE. Folate intake and risk of stroke among women. Stroke. 2004 Jun;35(6):1259-63.

  6. Casas JP et al. Homocysteine and stroke: Evidence on a causal link from mendelian randomisation. The Lancet 2005;365: 224-32

  7. Klerk M, Verhoef P, Clarke R, Blom HJ, Kok FJ, Schouten EG; MTHFR Studies Collaboration Group. MTHFR 677C-->T polymorphism and risk of coronary heart disease: a meta-analysis. JAMA. 2002 Oct 23-30; 288(16):2023-31.

  8. S Schwammenthal et al. Homocysteine, B-vitamin supplementation, and stroke prevention. From observational to interventional trials. Lancet Neurol. 2004;3(8):493-5.