Author: Li Chun, Registered Dietitian in China
Review: Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center
Rumors
A few days ago, a #Does folic acid really cause cancer if you eat too much# topic rushed to the hot search, which made many unknown netizens worried. Especially my pregnant friends, I even asked if I still want to take folic acid. What is the cause of folic acid causing cancer? Should we eat less foods with more folic acid in our daily diet? Today, we will take a detailed look at it.
Image source: Weibo screenshot
analysis
Let's start with the conclusion:
Moderate folic acid intake can prevent cancer, and a lack or excess intake may increase cancer risk.
Folic acid is a type of B vitamin found in animal liver, kidneys, eggs, legumes, yeast, green leafy vegetables, fruits and nuts. The average healthy adult usually does not need additional supplementation as long as they eat a balanced diet. Only in the pregnant and trying to conceive people, due to the significant increase in the demand for folic acid, it is recommended to supplement additionally.
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The tolerable maximum intake of folic acid per day is 1000 μg. For healthy adults, as long as the daily intake is less than 1000 μg, it is generally safe.
Folic acid has a two-way effect on cancer
But more research is needed
1. Hot searches that have been distorted and interpreted
The claim that folic acid causes cancer is not groundless, and the "eating too much folic acid will cause cancer" that rushed to the hot search originated from a study published by the Fudan University research team in the sub-journal Nature in 2022.
In the experiment, the researchers divided mice with liver cancer into 3 groups and were given a high-fat diet of 20mg/kg, 2mg/kg, and 0mg/kg folic acid. It was found that mice in the high-dose folic acid group developed liver cancer faster.
The study made it clear that cancer in mice with cancer developed rapidly under a diet of high doses of folic acid. What does this have to do with carcinogenicity?
Carcinogenesis is the process from not having cancer to getting cancer. The above experiment is the process from cancer to cancer aggravation.
In addition, in the study, high-dose folic acid supplementation was performed based on the body weight of the mice. If you switch to 60kg, it is equivalent to 1200mg of folic acid a day. In fact, according to the 2010~2012 study on the dietary vitamin intake of Chinese residents, the average daily intake of folic acid for mainland residents is 180.9μg (less than 0.2mg). It is impossible to achieve such an extreme situation with a normal diet or folic acid supplementation.
Image source: Dietary Vitamin Intake of Chinese Residents in 2010~2012
So, this distorted interpretation, there is no need to panic.
2. Folic acid is a double-edged sword against cancer
Although the above hot search is misinterpreted, there is evidence that folic acid plays a dual role in the occurrence and progression of cancer.
The Office of Dietary Supplements (ODS) of the National Institutes of Health describes folic acid and cancer in its folic acid section as follows:
Folic acid, which is naturally found in food, can help reduce the risk of many types of cancer, but folic acid supplements are not the same depending on how much we eat and for how long. Moderate amounts of folic acid can help reduce the risk of cancer before cancer develops, but if cancer has already occurred, especially if it is like colorectal cancer, high doses of folic acid may make it progress faster.
However, due to a series of problems in the current experimental studies, such as population differences and differences in experimental methods, the conclusion is affected by the limitations of the literature, and more research is needed to understand the role of dietary folic acid and folic acid supplementation in cancer risk.
In conclusion, a moderate intake of folic acid can prevent cancer, and a deficiency or excess may increase the risk of cancer.
In addition to its effects on cancer, folic acid is actually an undervalued nutrient, so let's take a look at what other little-known effects folic acid has.
Folic acid has many benefits, but don't supplement it indiscriminately
Folic acid, in fact, is a type of B vitamin, which is a water-soluble vitamin.
When it comes to folic acid, many people think of folic acid supplementation during pregnancy to prevent fetal malformations. In fact, in addition to playing an important role during pregnancy, folic acid is also essential for most people with normal physiological conditions.
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1. What are the benefits of folic acid for ordinary people?
1. Prevent pernicious anemia
The reason why folic acid can prevent anemia is because it is involved in the synthesis of red blood cells and is one of the raw materials for hematopoiesis.
If there is a lack of folic acid, it affects the synthesis of DNA, causing red blood cells to become larger and develop megaloblastic anemia. Common manifestations are: weakness, fatigue, difficulty concentrating, irritability, headache, etc.
2. Involved in the synthesis of neurotransmitters
Folic acid promotes the synthesis of important neurotransmitters in the brain and maintains the metabolic response of vitamin B12, acetylcholine, etc. in the brain.
3. Boosts immunity
Animal experiments and in vitro studies on human lymphocytes have found that folic acid helps maintain the normal function of the immune system. It promotes the normal functioning of lymphocytes and also helps the body to synthesize antibodies.
4. Prevention of hyperhomocysteinemia
Homocysteine is a protein metabolite in the human body that is normally metabolized in the body. However, when the body is deficient in folic acid, homocysteine metabolism is affected, causing it to accumulate in the body and form hyperhomocysteinemia.
Hyperhomocysteinemia is closely related to the occurrence and development of coronary arteriosclerotic heart disease, hypertension, type 2 diabetes, congenital malformations, senile dementia, cerebrovascular diseases, depression and other diseases.
After reading the benefits of folic acid, are you tempted? Do you want to replenish it immediately? But you can't eat folic acid indiscriminately.
Second, indiscriminate supplementation of folic acid is harmful to many people
In addition to the risk of cancer caused by regular and large supplementation, folic acid can interact with a variety of drugs, reduce drug efficacy, increase toxic side effects and even aggravate the severity of the disease.
If you have been taking medication recently and are supplementing or planning to supplement folic acid, be sure to see if there is anything you are taking in the "Chinese Multidisciplinary Expert Consensus on Reasonable Clinical Folic Acid Supplementation". This table summarizes the interactions between folic acid and medications, and if you are taking a medication, consult your doctor as soon as possible.
Image source: "Multidisciplinary Expert Consensus on Rational Clinical Folic Acid Supplementation in China"
Not only that, but excess folic acid can also affect zinc absorption. Supplementation with high daily doses of folic acid during pregnancy may lead to zinc deficiency and increase the risk of fetal malformations and developmental delay.
In addition, too much folic acid can mask the early manifestations of vitamin B12 deficiency. Excessive intake of folic acid in patients with megaloblastic anemia can interfere with the early diagnosis of vitamin B12 deficiency and may lead to irreversible neurological damage.
Therefore, in the latest edition of the "Nutrient Reference Intakes for Chinese Residents" released in 2023, it is mentioned that for adults, the tolerable maximum daily intake (UL) of folic acid is 1000 μg. That is, consuming more than 1000 μg of folic acid per day increases the safety risk.
In this way, folic acid has the greatest health benefits
Folic acid has many health benefits, but the consequences of missing or supplementing too much are quite serious, how to make up the most scientific?
1. How much folic acid do I need per day?
The Dietary Reference Intakes for Chinese Residents (2023 Edition) recommends:
General adults: 400 micrograms of folic acid per day;
Pregnancy: Due to the neurodevelopment of the fetus, the expectant mother has a greater need for folic acid, requiring 600 μg of folic acid per day throughout pregnancy;
Lactation: Since the folic acid in breast milk also has an impact on the growth and development of the baby, the requirement for lactation is also higher than that of the general population, requiring 550 μg of folic acid per day.
2. How to get folic acid?
For adults, folic acid is safest to obtain through diet. Foods rich in folic acid include animal liver and kidney, eggs, legumes, yeast, green leafy vegetables, fruits and nuts.
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In your diet, think about whether you can do it:
Ensure to eat 1 egg, 300~500g of vegetables (half of which are dark vegetables), 200~350g of fruits every day, eat 50~70g of nuts and soybeans or their products equivalent to 105~175g of soybeans every week, and eat animal offal 2~3 times a month.
The above dietary recommendations in the "Dietary Guidelines for Chinese Residents" have met the standards, and folic acid is naturally about the same.
However, the loss of folic acid in food is affected by cooking. In addition, 3/4 of the folic acid in food will bind to multiple glutamic acids, and in order to be absorbed, it needs to be enzymatically hydrolyzed first, resulting in a discount to the overall absorption rate of only 70%. The folic acid in the supplement is a stable, well-absorbed oxidized monoglutamate folate that can be 100% absorbed by the small intestine.
Therefore, if the need for folic acid is large and diet alone cannot meet all the folic acid needs, additional folic acid supplementation is required.
3. Who needs additional folic acid supplements?
If you have any of the following, please supplement under the guidance of your doctor.
1. Trying to get pregnant, pregnancy. 600 micrograms of folic acid per day during pregnancy, 200 micrograms more than before pregnancy. The Dietary Guidelines for Chinese Residents (2022 Edition) recommends that 200 micrograms be obtained in the diet, and the remaining 400 micrograms should be obtained through supplements.
Supplementation of 400 μg of folic acid per day for 3 months before pregnancy can bring the concentration of folic acid in red blood cells to a level that is effective in preventing the occurrence of neural tube defects in offspring, and 400 μg of folic acid supplementation per day during pregnancy can meet the body's needs.
2. Patients with cardiovascular disease. Currently, folic acid is not recommended for the prevention of cardiovascular disease. However, folic acid supplementation is suggested as an effective way to reduce high homocysteine levels for those at high cardiovascular risk or in patients with hypertension who also have hyperhomocysteinemia.
3. It should be noted that people who regularly drink alcohol, smoke, drink strong tea, coffee and take certain drugs are not conducive to the absorption and metabolism of folic acid, so they should pay attention to it when supplementing.
conclusion
Dose determines toxicity, and folic acid supplementation below 1000 μg per day is safe. For most people, we should pay more attention to increasing the intake of folic acid from the diet to reduce the diseases caused by folic acid deficiency.
Source: Science Refutes Rumors New Media
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