A large international study that was published on Thursday indicates that people with higher levels of vitamin D in their blood are at a lower risk for colorectal cancer, the third most common cancer in the U.S. Results from prior studies were inconclusive, but that's not the case with this one.
The study was conducted by over 20 medical centers and organizations across the globe, including the National Cancer Institute, the American Cancer Society, and the Harvard T. H. Chan School of Public Health. The amount of vitamin D that must be consumed in order to provide protection against colorectal cancer is far greater than what is currently recommended by the National Academies of Sciences, Engineering and Medicine.
Their recommendations are based on bone health, according to the Washington Post. Researchers also found that the opposite is true. People with a level of vitamin D in their bodies that is lower than what's recommended for bone health have a 31 percent higher chance of developing colorectal cancer based on a follow-up period of five years that was part of the study. Those with higher levels reduced their chances by 22 percent.
JoAnn Manson, chief of the division of preventive medicine at Brigham and Women's Hospital in Boston, was not involved in the study, but was on the team that developed the current vitamin D recommendation. She doesn't believe that the results of this study prove a cause-and-effect relationship between vitamin D consumption and colorectal cancer risk. While the latest research is based on observation, what's needed to establish cause and effect is a study that is large in scale and random. She is currently conducting such a study and notes that many other factors, including outdoor activity and obesity, can affect the amount of vitamin D in a person's body.