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Nutrition and Metabolism


What is folate?

Folate is vitamin B9, a vitamin primarily comes from leafy vegetables. It is also known as folic acid, the synthetic version of folate that present in fortified food. Insufficient dietary folate intake in pregnant women may lead to child birth defects. Folate deficiency may also lead to hyperhomocysteinemia, a condition exists in about 5% of the general population and associates with increased risk for cardiovascular and neurodegenerative diseases, auto immune disorders, diabetes, renal disease, osteoporosis, neuropsychiatric disorders, anemia and cancer.

How is folate used in human body?

Folate is the precursor for several nucleotides and amino acids.  Nucleotides and amino acids are the building blocks for DNA and proteins respectively.  Folate is also the primary one carbon (methyl) group donor for the epigenetic modification of DNA and proteins, which controls the turn on and turn off of genes in human cells.

What is the normal folate level in human body?

Folate concentrations are normally measured at two levels: plasma folate and the RBC (red blood cells) folate. Plasma (or serum) folate reflects short-term while RBC folate measures long-term folate intake.  The normal ranges are shown in Table 1.

Table 1. The normal ranges of folate level in human body.

  Children Adults
Plasma 5-21 ng/ml 3-13 ng/ml
RBC >160 ng/ml 140-628 ng/ml

A folate deficiency for adults is defined as plasma folate <3.0 ng/ml AND RBC folate <140 ng/ml. Folate deficiency could be caused by insufficient dietary intake as well as certain underlying diseases or genetic impairments. When your plasma and RBC folate levels do not agree with each other, your may have certain medical conditions and should seek advice from your doctor.

High levels of folate are normally OK as long as your vitamin B12 level is also normal. Your cells need vitamin B12 to use folic acid. When vitamin B12 level is too low, folic acid cannot be used and will build up in the blood. You would need to seek help from your health provider to determine if the high folate level is a concern or not.

How much folate do I need in my diet?

The Institute of Medicine of the National Academies recommends DFE (Dietary Folate Equivalent) and UL (Upper Intake Levels) for different human population based on age and gender (Table 2). Since the regulation by FDA to added folic to all enriched cereal-rain products (including bread, flour, cornmeal, rice, pasta, and other grain products) in 1998, most Americans have sufficient folate intake. However, certain populations such as pregnant women or people with certain genetic variants are still at the risk of insufficient folate intake. The UL is set for people who take folic acids supplements because it is impossible to reach UL by dietary folate and folic acid from fortified foods. The risk of too much folic supplement is its masking effect on vitamin B12 deficiency, which may cause neuronal damage to your body.

Table 2. DFE and UL of folate recommended by the Institute of Medicine of the National Academy of Sciences. Since folic acid is easier to be absorbed by human body, the amount of folic acid should be reduced accordingly to the equation: 1 DFE folate = 0.6 μg folic acid.

Age (years)  DFE (μg/day) UL (μg/day)
1–3 150 300
4–8 200 400
9–13 300 600
14–18 (general population) 400 800
14–18 (pregnant women) 600 800
14–18 (lactating women) 500 800
19+ (general population) 400 1000
19+ (pregnant women) 600 1000
19+ (lactating women) 500 1000

Should I take folic acid supplement?

It is generally safe to take folic acid supplement, provided you don’t get enough from foods. Folic acid is a soluble vitamin, so any excess intake is usually lost in the urine. Beside the risk for masking the vitamin B12 deficiency, the risk of toxicity from folic acid supplements intake is low. There are reports that high levels of folic acid can cause seizures in patients taking anticonvulsant medications. So if you are taking anticonvulsant medicines or you are not sure about your vitamin B12 level, it is your best interest to consult with a medical doctor before taking a folic acid supplement.

Why folate is more important for people carrying certain gene variants?

Two genetic variants of the MTHFR gene, ranging from 13 to 57% in different ethnic groups, have reduced capacity to carry on the conversion of folate from one to another. People carrying these two variants are more sensitive to folate deficiency, therefore need take extra precaution to make sure sufficient daily folate intake.

Which foods contain high level of folate?

Green leafy vegetables, beans and animal livers represent the three groups of natural foods that contain high levels of folate (Table 3).  Many fortified cereals and grain products (not listed in Table 3) also contain folic acids ranging from 10% - 100% daily value per serving.

Table 3. Common folate-rich foods.

Fortified Cereals
Per 100 g (DFE) 2253
Per Serving (DFE) 676
Serving Size 1 NLEA serving (31 g)
Per 100 g (DFE) 2180
Per Serving (DFE) 676
Serving Size 1 NLEA serving (31 g)
Animal Livers
Goose liver pate
Per 100 g (DFE) 738
Per Serving (DFE) 630
Serving Size 3 oz
Beans, Mung beans
Per 100 g (DFE) 625
Per Serving (DFE) 81
Serving Size 1 tablespoon
Beans, Lentils
Per 100 g (DFE) 479
Per Serving (DFE) 57
Serving Size 1 tablespoon
Beans, Black
Per 100 g (DFE) 444
Per Serving (DFE) 54
Serving Size 1 tablespoon
Beans, Lima beans
Per 100 g (DFE) 395
Per Serving (DFE) 44
Serving Size 1 tablespoon
Beans, Kidney
Per 100 g (DFE) 394
Per Serving (DFE) 47
Serving Size 1 tablespoon
Dark Green Vegetables
Turnip greens
Per 100 g (DFE) 194
Per Serving (DFE) 107
Serving Size 1 cup (55g)
Per 100 g (DFE) 194
Per Serving (DFE) 58
Serving Size 1 cup (30g)
Mustard greens
Per 100 g (DFE) 187
Per Serving (DFE) 105
Serving Size 1 cup (56g)
Collard greens
Per 100 g (DFE) 166
Per Serving (DFE) 60
Serving Size 1 cup (36g)
Brussels sprouts
Per 100 g (DFE) 61
Per Serving (DFE) 54
Serving Size 1 cup (88g)

How to get sufficient dietary folate intake?

First you are recommended to use the GB Food Calorie and Nutrition Calculator to get the most accurate estimate of your current folate intake.

To get sufficient dietary folate intake, the best way is to eat folate-rich foods as those shown in Table 3.

Many fortified cereal and grain products (enriched flour for example) have high amount of added folic acid.  However, you need to read the Nutrition Facts label carefully.  Folic acids level in fortified foods can vary greatly from 10% daily value (40 DFE) to 100% (400 DFE).

For high risk populations such as pregnant women and those carrying the MTHFR gene variants, folic acid supplement is recommended. 

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