Folate Above or Below Normal: Causes in Athletes and What to Do
A folate deviation from the norm is not always about nutrition. A high result sometimes signals a vitamin B12 deficiency, and a low one may be a consequence of medications or alcohol. The editorial team examines the causes of deviations in athletes and explains how to respond to them correctly.
What counts as a deviation
Laboratories use their own reference intervals, but to assess deficiency they most often rely on the thresholds of the World Health Organization: serum folate below 10 nmol/L (4 ng/mL) and red blood cell folate below 340 nmol/L (151 ng/mL). These values are linked to the level at which homocysteine begins to rise.
No single upper limit indicating toxicity has been established for folate. A "high" result usually means a value above the upper limit of the laboratory interval or above the analyzer's measurement limit. This happens mainly against a background of supplements.
Remember the different time windows of the indicators. Low serum folate with a normal red-cell value often indicates a recent worsening of nutrition, whereas low red-cell folate indicates a prolonged deficiency.
Any folate deviation is assessed only in conjunction with vitamin B12. This is the main rule that all hematological guidelines repeat.
Causes of a low folate level in athletes
The body has relatively small folate reserves — much smaller than the reserves of B12. Therefore a deficiency can develop within a few months of inadequate nutrition.
- A diet with little vegetables, greens and legumes.A typical "sports" diet of chicken, rice and protein may be poor in folate.
- Low energy availability.With a chronic calorie deficit, the intake of all micronutrients suffers.
- Alcohol.It reduces absorption, disrupts metabolism and increases the excretion of folate.
- Intestinal diseases:celiac disease, inflammatory diseases.
- Folate-antagonist medications:methotrexate, some anticonvulsants, trimethoprim, sulfasalazine.
- Increased need:pregnancy and lactation, hemolytic conditions with increased red blood cell formation.
Heat treatment destroys a significant portion of natural folate, so prolonged boiling of vegetables reduces their value. Raw or briefly cooked vegetables and legumes retain more of the vitamin.
Intense training in itself is not a proven cause of deficiency, but it increases cell renewal, and against a background of a poor diet this can accelerate the appearance of a problem.
A practical marker for the doctor is an increased volume of red blood cells (MCV) in the complete blood count. In that case both folate and B12 are checked.
Causes of a high level
The most common cause is the intake of folic acid as part of multivitamins, individual supplements, fortified drinks and bars. If the test is taken shortly after intake, serum folate will be inflated.
The second important cause is B12 deficiency. Because of the "folate trap", folate cannot pass into working forms and accumulates in the plasma. In such a situation, high serum folate combines with low B12, high homocysteine and, possibly, macrocytosis.
The third is laboratory-related: hemolysis of the sample. Red blood cells contain much more folate than plasma, and their destruction in the tube falsely raises the result.
The US Institute of Medicine has set for adults an upper tolerable intake limit for synthetic folic acid from supplements and fortified products of 1000 µg per day. The restriction is related primarily to the risk of masking B12 deficiency: folic acid can correct anemia, while the neurological damage continues to progress.
The possible long-term effects of high intake of synthetic folic acid are being studied, but there are no unambiguous conclusions. The editorial team considers it reasonable not to exceed the upper limit without medical indications.
What to do in case of a deviation
Actions depend on the direction of the deviation, the B12 results and the complete blood count. Let us summarize the strategy in a table.
| Result | Possible explanation | Next step |
|---|---|---|
| Low folate, normal B12 | Diet, alcohol, medications, absorption | Diet analysis, consultation with a doctor about correction |
| Low folate and low B12 | Mixed deficiency, absorption problem | GI examination, treatment of both deficiencies |
| High folate, low B12 | Folate trap or supplements | Priority — diagnosis and treatment of B12 deficiency |
| High folate, normal B12 | Supplements, non-fasting test, hemolysis | Review of supplements, retake fasting |
In case of a deficiency related to nutrition, the first step is diet: leafy greens, legumes, broccoli, citrus fruits, liver. Folic acid as a supplement is prescribed by the doctor, only after checking B12.
A repeat test should be done no earlier than a few weeks later for serum folate and in 2–3 months for red-cell folate, in order to see the real changes in reserves.
For athletes who take several vitamin-containing products at once, the editorial team advises compiling a list of all supplements and calculating the total dose of folic acid.
Editorial conclusions
Low folate in athletes is most often explained by a monotonous diet, a calorie deficit, alcohol or medications. High folate is explained by supplements, incorrect test-taking or the "folate trap" in B12 deficiency.
Folate is always interpreted together with B12, homocysteine and the complete blood count.
Correction is carried out through nutrition and, if necessary, supplements under a doctor's supervision, without exceeding the upper limit without indications.
We also recommend reading our materials on what the folate test shows, on vitamin B12 deviations from the norm and on preparing for the homocysteine test.
References
- World Health Organization. Serum and red blood cell folate concentrations for assessing folate status in populations. Vitamin and Mineral Nutrition Information System. Geneva: WHO; 2015.
- Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
- Devalia V, Hamilton MS, Molloy AM; British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol. 2014;166(4):496–513.
- Bailey LB, Stover PJ, McNulty H, et al. Biomarkers of Nutrition for Development — Folate Review. J Nutr. 2015;145(7):1636S–1680S.
- Stabler SP. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149–160.
- Mountjoy M, Sundgot-Borgen JK, Burke LM, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. Br J Sports Med. 2018;52(11):687–697.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
