By Alan Safdi, M.D., FACG
In November 2018, an article in the New England Journal of Medicine made headlines at CNN and other mainstream news outlets. A randomized sample of 25,000 patients seemed to show that vitamin D and omega-3 supplements do not prevent cancer or heart disease.
The VITAL Study enrolled 25,871 individuals, a large enough group to answer several research questions in one trial. For the omega-3 study, 12,933 individuals were assigned to the fish oil supplements and 12,938 to placebo. For the vitamin D part, 12,927 individuals were assigned to receive the study supplement and 12,944 people were given placebo. The dose of Vitamin D was 2,000 IU per day and the omega 3 intake was 1,000 mg (1 gram) per day. Unfortunately, the vitamin D dosage was not adjusted for blood levels, which is common in medical practice.
1,617 participants were diagnosed with cancer (793 taking vitamin D; 824 on placebo) during 5.3 years of follow-up. A major cardiovascular event occurred in 386 people taking marine n-3 (omega-3 fish oil) fatty acids versus 419 participants on placebo during 5.3 years of follow-up.
Now, let’s explore beyond the headlines. First, 5.3 years is a short time to look for cancer prevention. I typically do not recommend supplements, but other studies have shown benefits to vitamin D.
Previous research has suggested a link between high vitamin D levels and better survival rates in people going through breast cancer treatment. So, what about a possible decrease in the development of breast cancer? Prior researchers analyzed data from two randomized clinical trials with a total of 3,325 participants between them. They found that people with higher blood concentrations of the vitamin D biomarker were exposed to a significantly lower risk of breast cancer. They found that participants with blood levels of vitamin D (25(OH)D) that were above 60 nanograms per milliliter (ng/ml) had one-fifth the risk of breast cancer compared to those with less than 20 ng/ml.
Another prior study, the largest of its kind, showed that low levels of vitamin D are linked with a significant increase in colorectal cancer risk. Conversely, higher levels appear to offer protection.
The results of subgroup analyses in the VITAL study raised the possibility of differential effects on cancer incidence according to body mass index, with normal-weight participants who received vitamin D having a lower incidence of cancer than those who received placebo. Another very important factor is that omega-3s did happen to reduce total myocardial infarction [heart attacks] by 28%, with the greatest reductions in those with low dietary fish intake and in African Americans.
Omega-3s may be of some benefit to vegetarians or people who do not like fish. In people who don’t eat the recommended one or two servings of omega rich fish a week, the supplements were linked to a 40% reduction in heart attacks. But for people who followed the recommendation, there was no such association.
In regard to cancer prevention, the study could have benefited significantly by a much longer duration. Having adequate blood (serum) vitamin D levels may be of benefit for colon and breast cancer prevention. Even this study may have shown some benefit in regard to cancer development with vitamin D in normal-weight individuals. If the vitamin D dose had been adjusted by blood levels, could we have seen more benefits? In my opinion, vitamin D supplements should be guided by blood tests.
There is no better supplement than a well-balanced Mediterranean-style diet and that should get you all the nutrients that you need to help protect against heart disease. Some of the key common characteristics of populations that live longest are predominantly plant-based diet, eat legumes and/or nuts and very little red meat. No smoking and live a very active lifestyle with vigorous social engagement (especially among other healthy people and empowered women), and maintain low stress levels.
Dr. Alan Safdi is past chairman of the Section of Gastroenterology at Deaconess Hospital and served as co-founder and president of the Ohio Gastroenterology and Liver Institute. Dr. Safdi is board certified in internal medicine and gastroenterology, and is a Fellow of the American College of Gastroenterology. He is former chairman of the Crohn’s and Colitis Medical Advisory Board in Cincinnati and still serves as president of Consultants for Clinical Research. He was also co-founder of eMerge Health Solutions, Consultants for Clinical Research, and outpatient GI and anesthesia programs.
The information included in my posts are for educational purposes only. It is not intended nor implied to be a substitute for professional medical advice. The reader should always consult his or her healthcare provider to determine the appropriateness of the information for their own situation or if they have any questions regarding a medical condition or treatment plan. Reading the information in my posts does not create a physician-patient relationship.
Alan V. Safdi MD, FACG