Many people take nutritional supplements such as fish oil and Vitamin D to prevent deadly diseases such as cancer and heart disease.
Findings of a government-funded study, however, have provided evidence that these supplements may not actually help in staving off these diseases.
The new study, which was presented at the American Heart Association Scientific Sessions in Chicago and published in the New England Journal of Medicine involved nearly 26,000 adults who were at least 50-years-old without any history of cancer, heart attack, stroke, and other forms of heart disease.
Chief of the Division of Preventive Medicine at the Brigham and Women's Hospital JoAnn Manson and colleagues randomly assigned the participants to take a daily dose of vitamin D, fish oil containing omega-3, or placebo.
After more than five years, they found that there was no significant difference in rates of heart disease and cancer between those who take supplements and those who take a placebo.
"Both trials were negative," Lawrence Fine, chief of the clinical application and prevention branch of the National Heart, Lung, and Blood Institute said, according to NPR.
"Overall, they showed that neither fish oil nor vitamin D actually lowered the incidence of heart disease or cancer.
Doctors are interested to know the value of these supplements because of their popularity with patients.
Citing a 2017 study, USA Today said that 26 percent of Americans age 60 and older take vitamin D supplements. Twenty-two percent also take supplements that contain omega-3 fatty acids, a key ingredient found in fish oil.
Despite the disappointing results of the new study, experts said that the findings do not necessarily mean that people should ignore the importance of vitamin D and fish oil.
Vitamin D and omega-3 acids are important nutrients. The best way to get them is through a balanced diet. Fatty fish such as sardines, salmon, and tuna, as well as vitamin D-fortified cereals, orange juice, and milk are good sources of these nutrients.
"Diet is more important than supplementation. If you have a good diet, you won't need supplements," Nathan Davies, lead for the Clinical Nutrition and Public Health program at University College London told CNN.
Davies, who is not involved in the study, nonetheless acknowledged that getting the nutrients from diet is not always practical as there are other factors such as availability and income that can affect people's food intake.
Fine said that those who think about taking supplements should talk about their physician or healthcare provider.