Scientists Get the Facts on Folic Acid in Red Beets

November 21, 1997

Red beets may not be the most popular vegetables, but they are a good source of folic acid, an essential nutrient that prevents certain types of birth defects and cancer and can protect against heart attacks. Scientists at UW–Madison have found that the amount of folic acid in beets can be increased through breeding, and that beets harvested later in the growing season contain the highest amount of the nutrient.

More than 4,000 acres of beets are grown in Wisconsin, which is half of all U.S. production and worth more than $2.5 million to the Wisconsin beet canning industry.

“Beets are among the highest vegetable contributors of folic acid,” said Irwin Goldman, a horticulturist at the College of Agricultural and Life Sciences, who studied folic acid in beets with graduate student Min Wang. “One average size beet contributes 25 percent of the U.S. Food and Drug Administration’s recommendation for adults.”

The FDA recently increased its folic acid recommendation from 180 micrograms to 400 micrograms for adults and from 400 micrograms to 800 micrograms for pregnant women. Folic acid is important in early pregnancy to prevent defects in the embryo’s neural tube, which will develop into the baby’s brain and spinal cord. Neural tube defects can result in debilitating conditions that last a lifetime, such as spina bifida.

Also, because of the importance of folic acid in the diet, the FDA has mandated that folic acid be added to foods such as flour beginning in 1998. According to Goldman, as more is learned about folic acid in beets, they may be used as a natural source of folic acid for vitamin supplements. An average beet can contribute 100 to 150 micrograms of folic acid.

Until Goldman and Wang’s research, very little was known about the nutrient in beets. The researchers studied the variation in folic acid levels among beet varieties, the inheritance of folic acid content in beets, and the folic acid levels in beet root versus greens throughout the growing season.

For their first investigation they compared 18 beet varieties during two growing seasons and found that the amount of folic acid varied greatly among varieties. They also found that the amount of folic acid within a beet variety varied between the two years. Therefore folic acid production in beets is dependent on genetic traits within a variety as well as on weather during the growing season.

Goldman and Wang next investigated how inheritance of folic acid content occurs. They crossed two different beet varieties. First they crossed a male flower part from one beet with the female flower part from the other beet. Then they used the same two varieties but switched the variety that contributed the male flower parts and the variety that contributed the female flower parts.

Although the direction of the cross was important, in both cases the cross resulted in much higher folic acid content than was found in either of the parent varieties, Goldman said. The researchers concluded from the two investigations that beets with high levels of folic acid could be developed through breeding.

Lastly the researchers compared folic acid in the leaves and roots 60, 80 and 100 days after planting. They found that the amount of folic acid in the leaves peaked at 80 days after planting while folic acid in the roots continued to increase and was highest at 100 days after planting. The results indicate that for higher levels of folic acid in the root, beets should be harvested later in the growing season.

“Interestingly, in all of the cases folic acid in the leaves was much higher than in the roots, suggesting that beet greens, if people would eat them, would be an even better source of folic acid,” Goldman said.

The results from the last experiment also raise some interesting biological questions about how folic acid is accumulated in roots, which may help researchers develop better beet varieties. The researchers proposed that there may be different physiological functions and synthetic ability of folic acid in leaves and roots. Also, rapidly developing root tissue may result in more folic acid being moved to the roots from the leaves. However, further research in this area is needed.

The researchers used a common method for determining the amount of folic acid in beets. “We quantified the amount of folic acid in the beet plant extract by measuring the consumption of folic acid by a bacterium, Lactobacillus casei,” Goldman said. In this method, the amount of free folic acid that the bacteria consume equals the amount that the human body can absorb directly from the diet.

More than 4,000 acres of beets are grown in Wisconsin, which is half of all U.S. production and worth more than $2.5 million to the Wisconsin beet canning industry. In the future, Goldman would like to conduct breeding experiments to increase the amount of folic acid in beets and study the nutritional differences between eating beets and taking folic acid supplements.

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