Folate

Folic acid is the name of the B vitamin in tablets and fortified food; folate is the natural form in green leafy vegetables, legumes, whole grains, fruit and liver. The word comes from folium, leaf. In your body it is a helper in making the building blocks of DNA and in converting homocysteine, and with that indispensable for every cell that divides. The cells that divide fastest, in your bone marrow, the wall of your gut and a growing embryo, notice a deficiency first. Your body does not make folate itself and stores only a few months' supply, in the liver. The number in your blood therefore follows what you ate in recent weeks, and it responds quickly: a meal with a lot of vegetables or a supplement shortly before the draw lifts it straight away. With a deficiency the red blood cells become too large and too few, an anaemia recognisable by a high MCV, and homocysteine rises. Your report prints folate in nmol/L. Normal is roughly 12.2 to 38.5 nmol/L, where the labs overlap; below 10 nmol/L the World Health Organization speaks of a deficiency. Above the band nothing is wrong, because a surplus leaves the body through the urine.

Folate is the vitamin that runs out first in anyone who eats few vegetables, drinks a lot or eats one-sidedly, and the deficiency shows in the blood count: large red blood cells, a rising RDW and eventually anaemia with tiredness. Homocysteine rises with it, and that is one of the reasons a deficiency is linked to cardiovascular disease. The second reason is pregnancy. In the first weeks, when the neural tube of the embryo closes, often before a woman knows she is pregnant, enough folate greatly reduces the chance of spina bifida and other birth defects. That is why the advice is to take 400 micrograms every day from the moment you want to become pregnant up to and including the tenth week, beside what you eat. The honest limitation is that the number in the blood is a snapshot of recent days, not of the store in your cells. A vegetable-rich meal or a tablet the morning before can mask a deficiency. And folate and vitamin B12 work together: a lot of folate can hide the anaemia of a B12 deficiency while the nerve damage continues, so always read the two together.

A low folate means too little came in or too much was used in recent weeks. Usually it is the first and rarely the last: too few vegetables, legumes and whole grains in the diet, the most common reason in anyone who eats one-sidedly or mainly processed food; a pregnancy or breastfeeding, in which the embryo and the child use a lot; alcohol, which inhibits absorption and drains the store in the liver; medication, such as methotrexate, some epilepsy medicines and the pill; and a bowel disease such as coeliac disease or Crohn's disease, in which the gut does not absorb it. A high folate is harmless and almost always comes from supplements or fortified food, such as breakfast cereals and some breads; a surplus leaves the body through the urine. The one thing to watch: a lot of folate with a B12 deficiency hides the anaemia while the nerve damage continues, so with a high value from supplements have your B12 measured too. Folate belongs beside vitamin B12, because the two work together and a lot of folate can hide a B12 deficiency, beside MCV and RDW, which rise with a deficiency, beside haemoglobin, which says whether there is already anaemia, and beside homocysteine, which reflects the store in your cells more honestly than the number in the blood.