Folic Acid - how important is it?
How Important is Folic Acid?
Folic acid, also referred to as folate, is an essential vitamin required for a wide spectrum of biochemical reactions; however, unlike bacteria and plants, mammals cannot make folate endogenously and so must obtain the vitamin through external sources. We need folate, sometimes known as vitamin B9, for:
· the production of red blood cells
· to reduce the risk of neural tube defects such as spina bifida in unborn babies
· synthesis of DNA and RNA. An impairment of this reaction initiates a process that can lead to megaloblastic anaemia, one of the hallmarks of folate deficiency (National Institutes of Health, 2021).
· Regulation of homocysteine, elevation of which is an independent risk factor in cardiovascular disease (Vidmar et al. 2019)
· the methylation of deoxyuridylate to thymidylate in the formation of DNA, for proper cell division (Smith et al. 2008).
Folate is especially abundant in foods of plant origin. The name ‘folate’ pertains to foliage and indeed, leafy green vegetables such as asparagus, kale, spinach and broccoli are among the richest sources of this vitamin. Other rich sources include legumes, citrus fruit and liver (National Health Service, 2020).
Heat and oxidation during cooking and storage can destroy up to 50% of the folate in foods. It can even be lost from foods when stored at room temperature for long periods. Folate containing foods should therefore be consumed as fresh as possible and with minimal cooking in order to retain the nutritional benefit (Haas & Levin, 2006).
Folic acid refers to the synthetic form, a monoglutamate, found only in fortified foods and supplements but readily converted to the natural co-factor forms after ingestion. Folic acid is fully oxidised; natural food folates in comparison are inherently less stable and show incomplete bioavailability (McNulty et al. 2012). Bioavailability refers to the amount of folate that is absorbed in the gut and that becomes available for metabolic processes (Winkels et al. 2007).
Food folates are usually reduced, often methylated, typically polyglutamated and eventually protein-bound, and their absorption efficiency has been estimated to be no more than 50% (European Food Safety Authority, 2006). It is thought that this figure may underestimate the bioavailability of food folates, however, with Winkels et al. 2007 estimating that folate from food is approximately 80% of that obtained from supplements.
How much do we need?
The official RDA of folate for an adult is 330µg DFE/day. The unit of measurement: DFE (Dietary Folate Equivalents) accounts for the difference between in bioavailability between folate and folic acid (European Food Safety Authority, 2014).
The NHS advises pregnant women and those trying to get pregnant, to take 400mcg folic acid per day. For those not trying to get pregnant, the RDA of folate can be obtained from food providing a healthy, wholefood diet is followed. Taking doses of folic acid higher than 1mg can mask the symptoms of vitamin B12 deficiency, which can eventually damage the nervous system if not recognised and treated. This is of particular concern for the elderly as it becomes more difficult to absorb vitamin B12 with age (National Health Service, 2021).
Folic acid and the thyroid
A common symptom of Hashimoto’s thyroiditis is acid reflux. This is often treated with a PPI (proton pump inhibitor) such as Omeprazole. These medications are nutrient depleting and one of those nutrients at risk is folic acid (National Health Service, 2019). By getting to the root cause of the acid reflux, often a lack of hydrochloric acid rather than an excess, we can eliminate symptoms as well as ensure the body is receiving adequate nutrients.
Processed foods
When food is processed, many of the nutrients are stripped away. For example, what starts out as a wheat kernel made from starch, bran and germ ends up as a starchy “flour” as the nutrient-rich bran and germ are removed. This flour is bleached to make it more aesthetically pleasing to the public and then synthetic nutrients including folic acid, as well as iron and other B vitamins, are added via fortification (Scientific Advisory Committee on Nutrition, 2017). The fortification of flour was introduced to help us reach our recommended daily allowance of essential nutrients.
Genetic Causes of Nutrient Depletions
Some individuals with Hashimoto’s thyroiditis may have a gene variation that prevents them from properly activating folic acid. This gene variation is present in up to 55% of the population and appears more commonly in those with hypothyroidism. This gene is MTHFR and provides instructions for making the enzyme, methyl-tetrahydrofolate reductase, which converts the amino acid homocysteine to methionine, a building block for proteins. Nutrient deficiencies in folate, vitamin B6 and vitamin B12 have been associated with elevated homocysteine, an independent risk factor for cardiovascular disease. The folic acid added to processed foods, as well as that present in cheap supplements, is difficult for individuals with this gene variation to process so folate should be obtained from food rather than in synthetic supplement form where possible (Cheng L. et al. 2010).
Toxins
Among the many chemical contaminants, halogenated organochlorines and pesticides variably affect efficacy of the thyroid. PCBs and their metabolites as well as polybrominated diethyl ethers, bind to thyroid transport proteins, such as transthyretin, displace thyroxine and disrupt thyroid function. Furthermore, folic acid is needed in phase 1 and phase 2 liver detoxification. The cytochrome P450 enzymes require folic acid to turn toxins into intermediary metabolites before these are conjugated for release from the body by methylation as part of phase 2 detoxification. Methionine is synthesised from choline, Vitamin B12 and folic acid to produce SAMe required in oestrogen detoxification. We all encounter more toxins on a daily basis than ever before. Some of us are unable to detoxify these toxins efficiently which can lead to the onset of autoimmunity, including Hashimoto’s thyroiditis (Cheng L. et al. 2010).
Conclusion
Folic acid is essential for optimal health and our aim should be to obtain it from wholefoods in its folate form where possible, particularly if thyroid disease is present.
References
Cheng, L. Prasad, A. Rieder, M. (2010). ‘Relationship between antiepileptic drugs and biological markers affecting long-term cardiovascular function in children and adolescents’, Canadian Journal Clinical Pharmacology, 17(1) e5-e46
EFSA Panel on Dietetic Products, Nutrition and Allergies (2014). ‘Scientific opinion on dietary reference values for folate’, EFSA Journal [Online]. Available at: https://www.efsa.europa.eu/ (Accessed 13 September 2021).
Ferrari, S. Fallahi, P. Antonelli, A. et al. (2017). ‘Environmental issues in thyroid diseases’, Front Endocrinol (Lausanne), 20(8) pp.50.
Field, M. & Stover, P. (2018). ‘Safety of folic acid’, Annals of New York Academy of Science, 1414(1) pp.59–71.
Haas, E. & Levin, B. (2006). Staying healthy with nutrition. 21st century edn. Berkeley: Celestial Arts, pp131-2.
McNulty, H. Pentieva, K. Hoey, L. et al. (2012). ‘Nutrition throughout life: folate article’, International Journal for Vitamin and Nutrition Research, 82(5) pp.348-354.
National Health Service (2019). ‘Vitamin B12 or folate deficiency anaemia’, [Online]. Available at: https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/ (Accessed 12 September 2020).
National Health Service (2020). ‘B vitamins and folic acid’, [Online]. Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitaamin-b/ (Accessed 7 September 2020).
National Institutes of Health (2021). ‘Folate’, [Online]. Available at http://ods.od.nih.gov/factsheets/Folate-HealthProfessional (Accessed 7 September 2021).
Scientific Advisory Committee on Nutrition (2017). ‘Update on folic acid’, Membership of Scientific Advisory Committee on Nutrition. [Online]. Available at: https://www.gov.uk/government/publications/folic-acid-updated-sacn-recommendations (Accessed 7 September 2012).
Smith, A. Kim Y. & Refsum, H. (2008). ‘Is folic acid good for everyone?’, American Journal Clinical Nutrition, 87, pp.517–533.
Vidmar, M. Grželj, J. Mlinarič-Raščan, I. et al. (2019). ‘Medicines associated with folate–homocysteine–methionine pathway disruption’, Arch Toxicol. 93, pp.227–251.
Winkels, R. Brouwer, I. Siebelink, E. et al. (2007). ‘Bioavailability of food folates is 80% of that of folic acid’, American Journal Clinical Nutrition, 85, pp.465–73. [Online] Available at: http://ajcn.nutrition.org/ (Accessed 8 September 2021).
