In the 1920s, Lucy Willis, who was one of the first British women to become a medical doctor, started studying a particularly severe and often fatal form of anemia that often occurred in pregnant poor women in India. As in cases of “pernicious anemia,” the women didn’t have enough red blood cells, but the red blood cells they had were often abnormally large.
Dr. Willis suspected that this “pernicious anemia of pregnancy” was due to a dietary deficiency. In 1931, she found that a cheap yeast extract called Marmite quickly cured the problem. Later on, the substance that was responsible for curing the anemia was isolated from spinach. It was named “folate,” after the Latin word folium, which means leaf. Folate is also called vitamin B9.
Folate is a perfect example of why it is better to get your nutrients from food than from pills. The form of vitamin B9 that is found in foods is called folate. Unfortunately, this form tends to be unstable. The form of vitamin B9 that is used in processed foods and in vitamin supplements is called folic acid. It’s much more stable, and if you take a reasonable dose of it, it’s a good source of vitamin B9. Yet some food scientists and public health authorities are concerned about the effects of taking too much folic acid, from fortified foods or from vitamin supplements.
The body has a complicated system for controlling how much folate gets absorbed from the food into the bloodstream. As a result, people don't get too much folate from eating too many leaves. On the other hand, if they take too much folic acid, the extra folic acid could bypass the systems that the body usually uses to control folate levels. The extra folic acid in the bloodstream could be dangerous in someone who has a deficiency of vitamin B12. It could correct the anemia that is an important warning sign of vitamin B12 deficiency, perhaps allowing the problem to progress to the point that the person suffers permanent damage to the nervous system. This is a serious concern, considering that so many elderly people are at risk for vitamin B12 malabsorption. The have also been some reports that taking too much folic acid could increase the risk of cancer.
Women who have a folate deficiency are more likely to give birth to babies with severe birth defects, called neural tube defects. Examples include anencephaly (absence of the brain) and spina bifida (open spine). In these cases, the damage is done at a very early stage of development, usually before the woman even knows that she is pregnant. That’s why it’s important to make sure that women who might become pregnant have good folate status.
To help prevent neural tube defects, the U.S. Food and Drug Administration started requiring food manufacturers to add folic acid to several different kinds of food, including ready-to-eat cereals and the enriched flour used to make baked goods. The food fortification program led to a significant drop in the risk of neural tube defects. Some researchers argue that this has been balanced by a rise in the risk of colorectal cancer. However, it’s unclear whether that increase was real or simply the result of an increased number of patients receiving colonoscopies.
People who eat a health-optimizing diet will automatically get plenty of folate and are at low risk of getting too much folic acid in their food. That’s because they eat lots of fruit and vegetables, including plenty of leafy green vegetables. They also eat whole-grain products, rather than the “enriched” white flour products that have had folic acid added to them.
- Quinlivan EP, Gregory JF, III. Effect of food fortification on folic acid intake in the United States. Am J Clin Nutr. 2003;77(1):221-225.