Three B vitamins, folate, vitamin B12 and vitamin B6, are also needed to lower levels of homocysteine, a harmful amino acid which, if allowed to accumulate, can damage the circulation.
What is folic acid?
Folate is a water-soluble vitamin naturally found in green leafy vegetables such as spinach, broccoli and kale, as well as wholegrains, beans and citrus fruit. The form known as folic acid is better absorbed than the natural form which is why it is used in supplements and fortified foods. As the body stores very little folic acid, it is one of the most widespread vitamin deficiencies. The UK government are therefore considering the fortification of flour with folic acid.
Folic acid is especially needed by cells that are rapidly dividing, such as during early pregnancy to prevent developmental abnormalities known as neural tube defects (eg spina bifida). In other situations, lack of folic acid can lead to a form of anaemia known as macrocytic (large cell) anaemia. One of its most important roles for a healthy heart and circulation, however, is the ability of folate to convert the harmful amino acid, homocysteine, to a safer form that does not damage artery walls.
What is homocysteine?
Homocysteine is a toxic amino acid formed in the body from the breakdown of the dietary amino acid, methionine. If levels are allowed to rise, homocysteine damages artery walls to hasten hardening and furring up of the arteries (atherosclerosis).
Normally, homocysteine levels are tightly controlled by three enzymes that convert homocysteine back to safe amino acids, either back to methionine or on to cysteine, which is used by cells for growth. Two of these enzymes rely on the presence of folate to work properly.1 Vitamin B12 and, to a lesser extent, vitamin B6, also aid this process. The main nutritional cause of raised plasma homocysteine is therefore folate deficiency.2
People with a raised homocysteine level have an increased risk of atherosclerosis, coronary heart disease, stroke, peripheral vascular disease, dementia and other conditions associated with abnormal blood clotting, which is why obtaining sufficient folic acid is important. The results from 12 studies, involving 23,623 people, showed that people with the highest homocysteine level were 68% more likely to die from cardiovascular disease than those with the lowest level, and overall risk of death from all medical causes increased by 93%.3
The EU RDA/NRV for folic acid is 200mcg per day. Women of fertile age who could become pregnant are advised to take supplements providing 400mcg.
What is vitamin B12?
Vitamin B12 is found mainly in liver, meat, oily fish, eggs and dairy products. Low vitamin B12 levels are common in the elderly both because of reduced dietary intake and reduced absorption from the gut (malabsorption) linked with reduced production of hydrochloric acid in the stomach. As the quality of your stomach lining reduces with age (a process known as atrophic gastritis), lack of acid becomes increasingly common, affecting as many as 19% of people in their 50s, 24% in their 60s, 32% of those in their 70s and 40% of those aged 80 plus, resulting in reduced absorption of B vitamins.
Absorption of B12 requires a special substance called 'intrinsic factor' which is secreted in the stomach by the same cells that make stomach acid, so as acid production falls, so does intrinsic factor. Without this, B12 from either food or supplements will not be absorbed, and lack of B12 can lead to pernicious anaemia as well as contributing to raised blood levels of homocysteine. Data from 25 trials show that taking 400mcg per day vitamin B12 can reduce homocysteine levels by 7%, in addition to the effects of folic acid supplements.4
The EU RDA/NRV for vitamin B12 is 2.5 mcg per day.
What is vitamin B6?
Vitamin B6 is the collective term for a group of water-soluble substances that are all converted into the most active form, pyridoxine, in the body. These are mainly obtained from meat, oily fish, eggs, wholegrains, beans, green leaves and yeast extract. Vitamin B6 is essential for red blood cell formation, energy metabolism. Homocysteine can also be converted to cysteine when sufficient vitamin B6 is present.5
The EU RDA/NRV for vitamin B6 is 1.4 mg per day.
Diet versus supplements
Diet should always come first, and a healthy diet providing plenty of green leaves, wholegrains, oily fish and some animal products should supply your needs. If you follow a plant-based diet, however, it can be difficult to obtain enough vitamin B12.
With increasing age, and falling stomach acid levels, absorption of B vitamins reduces. Because of this, multivitamins designed for people aged fifty plus usually contain higher amounts. High dose vitamin B complex blends are also popular for both heart and health benefits.
The Nurses' Health Study looked at dietary intakes of folic acid and vitamin B6 in over 80,000 women who were followed for 14 years. After adjusting for other cardiovascular risk factors (such as smoking, high blood pressure and intakes of alcohol and saturated fat), they found that those with the highest dietary intakes of folate (696 mcg/day) and vitamin B6 (6.6 mg/day) were 45% less likely to have coronary heart disease than those with the lowest intakes (158 mcg folate and 1.1mg vitamin B6 per day). Interestingly, the relative risk of coronary heart disease was 24% lower among women who regularly used multivitamins compared with those who did not.6
It is unclear whether taking folic acid supplements might reduce the risk of a heart attack in those with a previous history of cardiovascular disease, however.7
For more information on how to keep your heart healthy, see our heart health hub.
1Selhub J (1999). Homocysteine metabolism, Annu Rev Nutr
2Strain JJ et al. (2004). B-vitamins, homocysteine metabolism and CVD, Proc Nutr Soc
3Peng HY et al. (2015). Elevated homocysteine levels and risk of cardiovascular and all-cause mortality: a meta-analysis of prospective studies, J Zhejiang Univ Sci B
4Homocysteine lowering trialists’ collaboration. (2005). Dose-dependent effects of folic acid on blood concentrations of homocysteine: a meta-analysis of the randomized trials, Am J Clin Nutr
5Selhub J (1999). Homocysteine metabolism, Annu Rev Nutr
6Rimm EB et al (1998). Folate and vitamin B6 from diet and supplements in relation to risk of coronary heart disease among women, JAMA
7Bazzano LA et al. (2006). Effect of folic acid supplementation on risk of cardiovascular diseases: a meta-analysis of randomized controlled trials, JAMA