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New Evidence That Vitamin D and Fish Oil Supplements May Lower Chances of Cancer Death and Heart Attack

Whether or not their patients should take supplements has long been a question healthcare providers wished they had a firm answer for. Researchers now appear to have a better idea how vitamin D and fish oil supplements may benefit people.

In September, scientists presented new meta-analyses at the North American Menopause Society (NAMS) Annual Meeting in Chicago showing that vitamin D supplements were found to cut the risk of death from cancer, and omega-3 fatty acid supplements significantly reduced the odds of heart attack. The meta-analysis of 13 studies that examined the effects of omega-3 supplements on heart-related outcomes was published September 30 in the Journal of the American Heart Association (JAHA).

The results back up a large-scale investigation of nearly 26,000 participants that was published in January in the New England Journal of Medicine (NEJM) and that had reached the same conclusions as the meta-analyses.

“It does appear that these dietary supplements have benefits: for vitamin D, reducing cancer deaths; and for omega-3s, reducing heart attacks,” says the lead author of the NEJM study, JoAnn Manson, MD, a professor of medicine at Harvard Medical School and the chief of the division of preventive medicine at Brigham and Women’s Hospital in Boston.

But in terms of the supplements’ relationships to other heart- and cancer outcomes, there did not necessarily appear to be a benefit, she says.

How a Daily Dose of D and Fish Oil May Help

The data published earlier this year in NEJM revealed that taking a one gram supplement daily of fish oil (which is rich in omega-3 fatty acids) was associated with a 28 percent reduction in heart attacks overall and a 50 percent lower risk of fatal heart attacks compared with those taking a placebo over the course of the more than five years in which the individuals took the supplements and were followed for the study. Fish oil did not lower the risk of stroke or cancer, however.

The study participants who took daily vitamin D (a dose of 2,000 IU) had a 25 percent drop in the risk of dying from cancer during the five-year study period compared with those in the trial who did not take any vitamin D; though taking vitamin D supplements did not appear to significantly affect the number of study participants diagnosed with cancer. (No one in the trial had cancer or had had a history of cancer when they joined. And for this analysis, the researchers excluded any cancer deaths that happened within the first two years to help ensure they were recording cancer death rates that could have been influenced by regular vitamin D supplementation.)

For the large VITamin D and OmegA-3 TriaL (VITAL), which took place over the course of 5.3 years, Dr. Manson and her collaborators followed 25,871 individuals who had no history of cancer, heart attack, stroke, or other forms of cardiovascular disease when they joined the trial. Trial participants were predominantly white (73 percent) and at least 50 years old at time of enrollment (the average age was 67), and included 13,085 women and 12,786 men.

The study population was separated into four groups — one that took a daily dose of both vitamin D and omega-3 fish oil (6,463), one that took vitamin D and a placebo stand-in for fish oil (6,464), one that took a fish oil supplement and a placebo of vitamin D (6,470), and one that took placebos for both fish oil and vitamin D (6,474).

Meta-Analyses Support Some Potential Benefits of Fish Oil and Vitamin D

Since the data from the VITAL study were published, researchers conducted a meta-analysis of five trials looking at cancer deaths among people taking vitamin D (representing about 80,000 people total), as well as the meta-analysis published this week examining cardiovascular outcomes among those taking fish oil (representing more than 127,000 people). Both of the meta-analyses were published at NAMS in Chicago last month.

“The meta-analyses of all randomized trials of omega-3s documented that there are small reductions in heart attacks and coronary events from supplements, but no reduction in stroke,” says Manson.

“And when you look at all the trials that have been done on vitamin D that were large enough to include the endpoint of cancer death, overall there is a significant reduction of cancer death, so it looks like a promising association,” she adds.

Sarah Samaan, MD, a cardiologist with Baylor Scott & White Legacy Heart Center in Plano, Texas, who was not involved in the research, says the results of meta-analyses should be approached with caution.

“They combine studies with different types of individuals with a variety of medical conditions, different approaches, and even different forms of the supplement,” she says. “Nevertheless, the report points to a potential benefit of an inexpensive and widely available supplement that has relatively little downside.”

A Big Heart Attack Reduction Benefit Was Found in African Americans

An interesting finding from the VITAL trial was that, among this study population, the 5,106 African Americans appeared to have the most dramatic results when it came to lower heart attack risk after taking omega-3 supplements. They had a 77 percent lower incidence of heart attack compared with the control group of individuals not taking any supplements.

African Americans overall experience high death rates due to heart disease compared with whites and other ethnic groups, according to the Heart Foundation. About 48 percent of African American women and 44 percent of African American men have some form of heart disease.

More research is needed, Manson says. But if other studies show that African Americans can benefit from omega-3 supplements, this approach may be a potential way to help reduce heart attacks in this population. “It may be a way to reduce health disparities [in terms of this endpoint], as far as cardiovascular disease is concerned,” Manson says.

The researchers note in the JAHA study published this week that the previous trials that had looked at omega-3 supplements and heart health for that meta-analysis did not include enough African American participants to make conclusions about that specific population.

Dr. Samaan says, “There appeared to be a benefit to African American participants, but it is important to note that this is one study, and the results would need to be confirmed in other larger trials in order to be more certain.”

Another possibility driving the high rate of heart attack risk reduction in the VITAL trial among African Americans may be that incidence of type 2 diabetes and hypertension are much higher for African Americans than for others, meaning comparably this subgroup is having more heart attacks to begin with, explains Benjamin Hirsh, MD, the director of preventive cardiology at Northwell Health’s Sandra Atlas Bass Heart Hospital in Manhasset, New York. “Whether that is the case needs to be teased out.”

Manson speculates that the outcomes with African Americans may relate to metabolism and gene variants that differ among races and ethnicities.

Findings Highlight That There Is No One-Size-Fits-All Prescription When It Comes to Supplements

Another key finding was that those who ate less fish benefited more from taking the omega-3 supplements. Those who ate fewer than one and a half servings of fish per week (which was the average fish in this study) had a 19 percent reduction of major cardiovascular events, such as stroke and heart attack, and a 40 percent reduction in heart attack specifically, compared with those who took no supplements.

“We found it surprising with the omega-3s that there was such a strong signal for heart attack reduction, and the results varied so much with fish consumption,” says Manson. “If you’re already getting two servings of fish per week, you’re not going to see any clear benefit from the dietary supplement.”

In a similar fashion, closer analysis of the finding that vitamin D reduced risk of dying from cancer also revealed that certain subgroups benefited more than others. When looking at those who were obese or overweight, there appeared to be no benefit in terms of preventing cancer deaths. “The pattern of findings suggests a complex balance of benefits and risks for each intervention,” the researchers note in the study abstract.

Other research has called into question the value of these supplements, however. A meta-analysis published in July this year in the Annals of Internal Medicine of 277 trials found that few nutritional supplements offered protective effects against heart disease. It noted that there was some evidence that in high-risk populations omega-3 fatty acid supplements did help protect against heart attack.

A comprehensive look at the findings (and at other existing evidence) shows there’s no one-size-fits-all answer when it comes to taking supplements, Manson says. The data suggests that who benefits from taking either vitamin D or fish oil supplements, what the benefits are, and what the risks are, is different for different subgroups of people.

“The research points to the need for additional research to determine which individuals may be most likely to derive a net benefit from these supplements,” Manson says.

So, to Supplement or Not? There Are Possible Benefits, but Don’t Overdo It

Does the research suggest you should change your habits when it comes to taking supplements or not? Manson advises that when it comes to dietary supplements, more is not necessarily better, and often it is worse. “We saw no adverse [side effects], but mega-dosing on these supplements can have risks,” she says.

The National Cancer Institute warns that excessive intake of any nutrient can be toxic. Too much vitamin D can be harmful because it increases calcium levels, which can lead to calcinosis (deposits of calcium salts in the kidneys, heart, or lungs) and hypercalcemia (high blood levels of calcium).

“In general vitamin D or fish oil is not too harmful,” Dr. Hirsh explains. “But I don’t want people to be blinded with an idea that vitamin D and fish oil are going to save the day.”

For those taking vitamin D or fish oil supplements in moderate doses, the study suggests that they may want to continue doing so, according to Manson.

Hirsh points out that the benefits of vitamin D are not as clear in this investigation. (Note that the current data did not find a reduction in cancer incidence among those taking vitamin D supplements; the data found a reduction in cancer deaths among those in the study taking vitamin D who were subsequently diagnosed with cancer compared with those not taking supplements.)

But taking omega-3 supplements may improve heart health, especially among African Americans, who had such dramatic results in this study, Hirsh says.

“For African Americans who are healthy overall, increasing omega-3 supplement intake may be worthwhile and protective,” says Hirsh. “There’s no harm and possibly some great benefit.”

It’s important to remember when you’re talking about what steps you can take to reduce unwanted health outcomes, like heart attack and cancer death, to focus on the steps that have already been proved to make a big difference, Hirsh says.

“Before people get hung up on taking supplements as a way to demonstrate that they are doing well, they really have to just focus on lifestyle improvements, such as exercising regularly and eating healthy. Otherwise, they’re missing the big picture,” Hirsh says.

Manson and her collaborators expect to continue with a longer-term follow-up of the study population and to look further into genetic factors and biomarkers that might predict health outcomes so they may better identify those who are likely to benefit from supplements.

Fuente: Everyday Health