A mammoth medical study that may answer that question is underway.
Vitamin D and omega-3s are the supplements and millions of Americans are popping them.
Now one of the largest studies of its kind aims to find out just how powerful these pills are.
There's a call for volunteers and there's no need to go anywhere.
The pills are delivered right to participants' doors.
Found in sunshine, it's known for strengthening bones.
Without enough vitamin D you could be at higher risk for fractures.
In salmon, nuts, and seeds, omega-3s could keep your heart healthy and your mind sharp. Two-time U.S.A memory champ Nelson Dellis says they were key in his back-to-back wins.
"I eat a lot of antioxidants and omeg-3," he said.
Now, researchers want to know what happens when vitamin D and omega-3 dietary supplements are combined.
Rush neurologist Dr. Raj Shah says some studies show vitamin D and/or omega-3s may help prevent heart attack, stroke, or cancer.
"We don't know whether these treatments, omega-3 or vitamin D, really do help prevent these conditions," he said.
These pills will help experts figure out.
"Are the benefits there? Do they outweigh risks?" Dr. Shah asks.
And people like Chicago South Sider Samuel Strachan will also help answer those questions.
The 79-year-old minister gets a good amount of exercise and tries to eat healthy.
"Whole grain and less fat in the diet and so forth," he said.
Now part of his daily diet is these pills, which he's volunteering to take for a long time.
It's all part of the vital study. Researchers are looking for 20,000 people nationwide to take these supplements every day for five years.
Participants get packets once a month in the mail.
They don't know if they're taking is the real deal or pretend pills.
"I'm hoping that I'm getting the real thing, not placebo," Strachan said.
Study directors are targeting men aged 50 and up and women 55 and older, and are putting a strong emphasis on African Americans.
"Because there are some thoughts in the African American community that they're at more risk for developing things like heart attack, stroke, or cancer, and they tend to have lower vitamin D levels," Dr. Shah said.
Strachan has been taking the pills since April. He's not sure if anything is happening, but...
"I feel good," he said.
The vital study will look at the effects of vitamin D and omega-3s on other health issues, including diabetes, high blood pressure memory loss depression and macular degeneration.
Rush University Medical Center
About the Vital Study: www.vitalstudy.org