A newly released report by the American Cancer Society highlights a promising statistic—cancer mortality is on the decline and has been for decades. A few exceptions, however, include a particularly perplexing and alarming one: Colon cancer has been on the rise in young adults since the 1990s.
According to the report, the disease has taken the lead this year as the top cause of cancer deaths in adults under the age of 50. This begs the question: What is causing this uptick in the under-50 age group?
Research suggests that poor diet may be the top culprit. There is existing evidence linking pro-inflammatory foods, such as alcohol and processed meats, to colon cancer. A new study published in Cancer Research Communications provides further data to strengthen the diet connection. The study found that dietary folic acid supplementation enhances the risk of colorectal cancer in mice. In 1996, the U.S. Food and Drug Administration (FDA) began requiring that all enriched grain products be fortified with folic acid by 1998 to help prevent serious birth defects; this was at about the same time that colon cancer began to rise in younger adults. That mandate was effective for its intended purpose, but did it come with a cost?
The Link Between Folic Acid and Colon Cancer
Folate and folic acid are often used interchangeably, but there is a notable difference between the two. Folate is a B vitamin found naturally in certain foods, including fruits, vegetables, and legumes. During the digestive process, your body converts folate into its active form before entering the blood.
Folic acid is simply a synthetic form of folate used in enriched food products. Your body isn’t able to metabolize folic acid as easily as naturally occurring folate. The process of converting folic acid to its active form takes longer than it does with folate. This can lead to a buildup of folic acid in the blood, and eating fortified food products may contribute to that surplus.
A team of researchers at Baylor College of Medicine examining dietary factors and colon cancer risk uncovered a pathway between folic acid and tumor growth in the colons of mice. The lab developed the first animal model that mirrors the stages of colon cancer development in humans. Using this model, they fed mice a supplemented diet that mimicked the folic acid food fortification program.
The folic acid given to the mice was equivalent to FDA-mandated fortification levels in enriched grain products. Researchers fed it to female mice before conception, during pregnancy, and to the offspring throughout their lives. The mice on the supplemented diet had significantly more tumors that were larger in size in both their small intestines and colons compared to the control group.
The strongest risk factor for colon cancer is aging. As we grow older, an important gene that suppresses tumor growth is silenced. The study showed a substantial increase in alterations of this gene in the mice that consumed the folic acid-supplemented diet.
“These findings illuminate a direct link between dietary folate and accelerated tumor development in the colon,” Dr. Lanlan Shen, a professor of pediatrics and nutrition and author of the study, told Baylor College of Medicine.
Past evidence has hinted at a link between folic acid and colon cancer, but more research was needed. It’s here now.
What Is an Enriched Grain Product?
Food enrichment and fortification are intended to prevent and correct deficiencies in micronutrients in the population. An enriched grain has added B vitamins—thiamin, riboflavin, and niacin. These nutrients are removed during the refinement process and often added back in as enrichment. A whole grain has all parts of the grain intact, whereas a refined grain has the germ and bran removed during the milling process. Any grain that is labeled enriched is refined and has had these nutrients added back to the FDA-specified levels required to bear the enriched label. Fortified grains have added nutrients that may not have been there in the first place naturally, including folic acid and iron.
Since 1941, the FDA has regulated the enrichment and fortification of grains with B vitamins and iron. In 1998, the FDA mandated all enriched grains also be fortified with folic acid in an effort to prevent neural tube defects in pregnant women. Grain enrichment and fortification are not mandatory, but encouraged, and the FDA has strict standards to meet for any product seeking to qualify to use the enriched label.
The Diet and Colon Cancer Connection
A review of 45 meta-analyses published in JAMA in 2021 found that a higher intake of fiber, calcium, and yogurt, and limited consumption of red meat and alcohol can help to prevent colon cancer. Another study published in 2019 in the International Journal of Epidemiology also concluded that red and processed meats and alcohol were associated with an increased risk of developing colon cancer, while fiber, particularly from bread and cereal, was associated with reduced risk.
In 2018, a prospective cohort study found that stage three colon cancer patients who consumed a diet rich in fruits, vegetables, and whole grains had increased their survival rate. The American Cancer Society and Academy of Nutrition and Dietetics recommend refraining from alcohol, limiting red and processed meats, and upping intake of vegetables, fruits, and whole grains to help to reduce one’s risk of colon cancer.
Foods Labeled Whole Grain May Be Enriched
The only label that meets the strict FDA standard for whole grain is “100 percent whole wheat.” Anything labeled as simply “whole grain,” “made with whole wheat,” or “contains whole grain” is not deemed a whole grain by the FDA. The U.S. Department of Agriculture (USDA) requires whole grain foods to consist of greater than 50 percent whole grain ingredients by weight, and the remaining 50 percent of the grains in the food to be either enriched grains or other intact whole grains. Products labeled as 100 percent whole wheat often also contain enriched grains that are fortified with folic acid.
The 2020–2025 USDA Dietary Guidelines for Americans recommend that at least half of your intake of total grains be 100 percent whole grains and that those who consume refined grains should opt for enriched grains. Further, they suggest that those who eat only whole grains also incorporate grains that have been fortified with folic acid into their diet.
According to the guidelines, Americans are not meeting the USDA’s guidance—98 percent fall below the recommended amount of whole grains, and 74 percent exceed the upper limit for refined grains. While the USDA differentiates between 100 percent whole grain and refined and enriched grains, and the required labeling reflects those facts, many consumers are probably not reading ingredient lists to examine what the product consists of or even understand the differences.
Foods that contain folate naturally (not in the synthetic form of folic acid) pose no known health risks, nor is there an upper limit for a daily intake. Natural sources of folate include fruits and vegetables (notably asparagus, Brussels sprouts, and dark leafy greens such as spinach), meats (especially liver), nuts, beans, peas, seafood, eggs, poultry, and whole grains.