Author: Li Jiewen
Master of Nutrition from Columbia University, Registered Dietitian in the United States, Contracted Dietitian of China Clinical Nutrition Network, Member of Chinese Nutrition Society.
He has many years of experience in nutrition consulting in medical institutions such as hospitals, nursing homes, and rehabilitation centers.
Specialty: nutrition intervention, weight management, and nutritional therapy for chronic diseases such as diabetes, triple high, fatty liver, kidney disease, etc.
Article first published on: Physician Online
Reprinted by China Clinical Nutrition Network
Folic acid, also known as vitamin B9, is one of the most important nutrients for women trying to conceive and during pregnancy, because the lack of folic acid during pregnancy increases the risk of fetal neural tube defects, affects the nervous system and some basic physiological functions, and may also be associated with low newborn weight, premature birth, fetal growth retardation and neonatal congenital heart disease.
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Folic acid requirements and intake
The recommended daily intake of folic acid for pregnant women is 600 mcg of folic acid equivalent (600 μg DFE). 1 μg DFE = 1 μg natural folic acid from food sources = 0.6 μg Dietary supplement synthetic folic acid taken during meals = 0.5 μg Dietary supplement synthetic folic acid taken on an empty stomach.
For healthy women with no risk factors, folic acid supplementation of 400 μg daily through dietary supplements and the consumption of folic acid-rich foods during pregnancy and pregnancy should be consumed.
For women with diabetes, obesity, epilepsy, gastrointestinal malabsorption diseases, congenital hydrocephalus, congenital heart disease, cleft lip and palate, limb defects, urinary system defects, or a family history of the above defects, or a history of neural tube defects in the first and second degree of immediate family, folic acid supplementation of 800 to 1000 μg per day is recommended.
If women who are trying to conceive and are taking drugs that increase the risk of fetal neural tube defects, such as carbamazepine, valproic acid, phenytoin, primidone, phenobarbital, metformin, methotrexate, sulfasalazine, trimethoprim, trimethoprim, triamterene, and cholestyramine, it is also recommended to supplement folic acid 800 to 1000 μg daily.
Folic acid supplementation is usually recommended to start 3 months before pregnancy until the end of pregnancy, preferably until the end of pregnancy, and in special cases, the doctor's advice shall prevail. There are 3 reasons why folic acid supplementation is needed in advance:
First, the blood folate concentration after 1 to 3 months of folic acid supplementation can prevent fetal neural tube defects;
Second, the intake of folic acid in the diet is generally low, and most women of childbearing age do not even reach 1/3 or even 1/4 of the recommended daily intake;
Third, the fetal neural tube will be completely closed 21 to 28 days after conception, but some women do not know that they are pregnant at this time, resulting in folic acid supplementation being delayed to achieve the purpose of early prevention.
For healthy women 19 years of age and older with no risk factors, the maximum daily intake is 1000 μg (equivalent to 1667 μg DFE), beyond which this dose may pose a risk. One study noted that folic acid supplementation of more than 1000 micrograms per day was associated with lower cognitive abilities in children aged 4 to 5 years compared with daily folic acid supplementation of 400 to 999 micrograms per week of pregnancy.
Of course, women with a special medical history may take more than the maximum dose of folic acid under medical advice. For example, when one of the spouses has a neural tube defect or a previous history of neural tube defects, it is recommended to supplement folic acid with 4000 μg of folic acid daily starting at least 1 month before pregnancy.
Different forms and sources of folic acid
During pregnancy, you should consume more foods rich in folic acid, such as dark green vegetables (asparagus, spinach, etc.), fruits, animal liver, beans, etc. Natural folic acid in food is mostly in the form of tetrahydrofolate (THF), which is unstable after light and heat, and only about 50% of folic acid can be absorbed and utilized by the human body, while pregnant women can consume about 200μg of folic acid from food.
Synthetic folic acid in dietary supplements has a higher stability and absorption rate. When taken with a meal, about 85% of folic acid in health supplements can be absorbed. Some of the synthetic folic acid in some new health supplements is 5-methyltetrahydrofolate (5-MTHF), which is also the active form of folic acid in the blood, and this form of folic acid supplementation may be better for women who are taking drugs that can affect the metabolic response of folate, and for people who have been tested to have genetic mutations related to the metabolic response of folate.
Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that plays a key role in folate metabolism and is involved in the synthesis of biologically active 5-methyltetrahydrofolate in vivo. When there is a related gene mutation (e.g., from a normal C677C mutation to C677T), this metabolic response rate may decrease by 17% to 75%. Studies have shown that for people with this type of genetic mutation, direct supplementation with 5-methyltetrahydrofolate (800 μg per day) may benefit more significantly, while avoiding the intake of traditional synthetic forms of folic acid leading to an increase in the concentration of inactive folate in the body, which in turn affects immune system function.
Other considerations
When guiding women who are trying to conceive and women during pregnancy to choose specific folic acid dietary supplements, they should remind them to pay attention to the ingredient list in the product, especially when choosing a pregnancy multivitamin, to ensure that the daily required folic acid dose is fully replenished, and at the same time, avoid the presence of other nutrients in the selected supplement to avoid corresponding side effects. For example, there are some pregnancy multivitamins with excessive iron content, which can easily cause gastrointestinal discomfort, nausea, constipation during pregnancy, and increase the risk of gestational diabetes.
In addition, it is recommended that the man also supplement folic acid during pregnancy preparation until the woman confirms the pregnancy result. For healthy men with no risk factors, 400 μg of folic acid supplementation is recommended daily.
Clinical attention should also be paid to personalized supplementation. For example, when the pregnancy preparation time is short, the amount of folic acid supplementation can be appropriately increased according to the specific situation to increase the concentration of blood folic acid faster and achieve the purpose of preventing fetal neural tube defects.
The daily requirement for folic acid in women in the middle and third trimester of pregnancy remains 600 μg. Folic acid is beneficial for the prevention of megaloblastic anemia. Considering that the natural folic acid in food is unstable and sensitive to heat, light and acid, up to 50% to 90% of folic acid will be lost after cooking. Therefore, for healthy women without risk factors, it is recommended to continue to supplement folic acid 400 μg daily in the second and third trimesters.