Below are some of the major studies done to test the efficacy of vitamin pills over many years, with hundreds of thousands of people.

There were no positive effects of vitamin pills seen in any study.  And in some, there were negative effects.

Offit, Paul. 19 July 2013. The Vitamin Myth: Why We Think We Need Supplements. The Atlantic.

Wang, Shirley, 25 Oct, 2011. Is This the End of Popping Vitamins? The case for dietary supplements is collapsing.  Wall Street Journal.

Dooren, Jennifer C. 11 Oct 2011. Supplements Offer Risks, Little Benefit, Study Says. Wall Street Journal.

Cenicola, Tony. Nov 20, 2008.  News Keeps Getting Worse for Vitamins. New York Times.

Rabin,Roni. Nov 18, 2008. Vitamins E and C Fail to Prevent Cancer in Men. New York Times.

Bakalar, Nicholas. Nov 17, 2008. Vitamins Seen as No Help in Heart Disease. New York Times.

Parker-Pope, Tara. Oct 1, 2008.  Vitamin C May Interfere With Cancer Treatment. New York Times.

Dooren, Jennifer C. 11 Oct 2011. Supplements Offer Risks, Little Benefit, Study Says. Wall Street Journal.  “Researchers tracked nearly 39,000 women for an average of 19 years. Multivitamins and many other dietary supplements provide little benefit for most people and may be harmful, according to researchers behind a large new study”.

May 2007.  The largest study yet on multivitamins (Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women’s Health Initiative Cohorts) looked at 161,808 post-menopausal women over 8 years and found no benefit for heart disease, cancer risk, premature death, or overall survival.  Consumer Reports On Health.

A Johns Hopkins School of Medicine review of 19 vitamin E clinical trials of more than 135,000 people showed high doses of vitamin E (greater than 400 IUs) increased a person’s risk for dying during the study period by 4 percent. Taking vitamin E with other vitamins and minerals resulted in a 6 percent higher risk of dying.

A later study of daily vitamin E showed vitamin E takers had a 13 percent higher risk for heart failure.

The Journal of Clinical Oncology published a study of 540 patients with head and neck cancer who were being treated with radiation therapy. Vitamin E reduced side effects, but cancer recurrence rates among the vitamin users were higher, although the increase didn’t reach statistical ignificance.

A 1994 Finland study of smokers taking 20 milligrams a day of beta carotene showed an 18 percent higher incidence of lung cancer among beta carotene users. In 1996, a study called Caret looked at beta carotene and vitamin A use among smokers and workers exposed to asbestos, but the study was stopped when the participants taking the combined therapy showed a 28 percent higher risk for lung cancer and a 26 percent higher risk of dying from heart disease.

Vitamin A intake and hip fractures among postmenopausal women. A Harvard study of more than 72,000 nurses who took a high amounts of vitamin A (in food, multivitamins, and supplements) had a 48 percent greater risk of hip fractures than nurses with the lowest vitamin A.

Antioxidant users of Vitamins A, C, and E (singly or combined), beta carotene, and selenium had a 6% higher death rate than placebo users in a 2004 study of esophageal, gastric, colorectal, pancreatic, and liver cancers.

Two studies presented to the American College of Cardiology in 2006 showed that vitamin B doesn’t prevent heart attacks, leading The New England Journal of Medicine to say that the consistency of the results “leads to the unequivocal conclusion” that the vitamins don’t help patients with established vascular disease.

The British Medical Journal looked at multivitamin use among elderly people for a year
but found no difference in infection rates or visits to doctors.

Novella, Steven. Feb 11, 2009. Another Negative Study of Vitamins. sciencebasedmedicine.org

Clearly there are exceptions, some vitamins are worthwhile, i.e., folate, vitamin D, B2 for migraine sufferers, and B12 for vegetarians.

And don’t get me started on supplements — QUACK QUACK QUACK!  If they’re toxic or harmful, we’ll never know, since they’re not tested or regulated.

Nestle, Marion.  May 10, 2009. Dietary supplements’ regulations hard to digest. San Francisco Chronicle

Sorry, but you can’t take your white bread with a multi-vitamin pill and keep the doctor away. Sure, you can get the missing nutrition from other food, but white flour is mostly empty calories, leading to weight gain and diabetes, and white flour doesn’t help protect you from many diseases.

Below are some excerpts from Wang, Shirley, 25 Oct, 2011. Is
This the End of Popping Vitamins? Wall Street Journal.

A succession of large-scale human studies, including two published earlier this month in leading medical journals, suggests that multivitamins and many other dietary supplements often don’t have health benefits—and in some cases may even cause harm.

After decades of research on the possible benefits of nutritional supplements, the handwriting is on the wall: Vitamins look to be a bust for the majority of people, many leading scientists are concluding.

The data have prompted some nutrition researchers to say taking vitamins is a waste of money for those without a specific nutrient deficiency or chronic illness. Such findings have also fueled a debate about whether the field should continue conducting expensive human trials to figure out whether particular supplements affect health.

“The better the quality of the research, the less benefit [supplements] showed,” says Marion Nestle, professor of nutrition, food studies, and public health at New York University. “It’s fair to say from the research that supplements don’t make healthy people healthier.”

For instance, vitamins B-6 and B-12 are often touted as being good for the heart, but several studies have failed to find that they lower risk of cardiovascular disease, according the Office of Dietary Supplements, part of the National Institutes of Health.

“We have an enormous body of data telling us that plant-rich diets are very healthy,” says Josephine Briggs, head of the National Center for Complementary and Alternative Medicine, another NIH center. “As soon as we take these various antioxidants?[and other nutrients] out and put them in a pill, we’re not consistently getting a benefit.”

Micronutrients, which include antioxidants like vitamin C, hormones like vitamin D and metals like iron, are essential to the body in small amounts because they help facilitate important reactions in and between cells. Too much of them, however, can cause problems.

The effectiveness of many dietary supplements remains untested and makers aren’t required to do tests before selling a product.

The supplement industry brought in $28 billion in sales in 2010, up 4.4% from 2009, according to Nutrition Business Journal, an industry trade publication.

Vitamin users may derive a benefit from the placebo effect, experts say. And they often are convinced the supplements make them feel better, regardless of what studies show.

“The thing you do with [reports of studies] is just ride them out, and literally we see no impact on our business,” said Joseph Fortunato, chief executive of supplement retailer GNC Corp.

Of growing concern to many scientists are the increasing hints of harm from vitamins.

Excerpt from Offit, Paul. 19 July 2013. The Vitamin Myth: Why We Think We Need Supplements. The Atlantic.

In 1994, the National Cancer Institute, in collaboration with Finland’s National Public Health Institute, studied 29,000 Finnish men, all long-term smokers more than fifty years old. This group was chosen because they were at high risk for cancer and heart disease. Subjects were given vitamin E, beta-carotene, both, or neither. The results were clear: those taking vitamins and supplements were more likely to die from lung cancer or heart disease than those who didn’t take them — the opposite of what researchers had anticipated.

In 1996, investigators from the Fred Hutchinson Cancer Research Center, in Seattle, studied 18,000 people who, because they had been exposed to asbestos, were at increased risk of lung cancer. Again, subjects received vitamin A, beta-carotene, both, or neither. Investigators ended the study abruptly when they realized that those who took vitamins and supplements were dying from cancer and heart disease at rates 28 and 17 percent higher, respectively, than those who didn’t.

In 2004, researchers from the University of Copenhagen reviewed fourteen randomized trials involving more than 170,000 people who took vitamins A, C, E, and beta-carotene to see whether antioxidants could prevent intestinal cancers. Again, antioxidants didn’t live up to the hype. The authors concluded, “We could not find evidence that antioxidant supplements can prevent gastrointestinal cancers; on the contrary, they seem to increase overall mortality.” When these same researchers evaluated the seven best studies, they found that death rates were 6 percent higher in those taking vitamins.

In 2005, researchers from Johns Hopkins School of Medicine evaluated nineteen studies involving more than 136,000people and found an increased risk of death associated with supplemental vitamin E. Dr. Benjamin Caballero, director of the Center for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health, said, “This reaffirms what others have said. The evidence for supplementing with any vitamin, particularly vitamin E, is just not there. This idea that people have that [vitamins] will not hurt them may not be that simple.” That same year, a study published in the Journal of theAmerican Medical Association evaluated more than 9,000 people who took high-dose vitamin E to prevent cancer; those who took vitamin E were more likely to develop heart failure than those who didn’t.

In 2007, researchers from the National Cancer Institute examined 11,000 men who did or didn’t take multivitamins. Those who took multivitamins were twice as likely to die from advanced prostate cancer.

In 2008, a review of all existing studies involving more than 230,000 people who did or did not receive supplemental antioxidants found that vitamins increased the risk of cancer and heart disease.

On October 10, 2011, researchers from the University of Minnesota evaluated 39,000 older women and found that those who took supplemental multivitamins, magnesium, zinc, copper, and iron died at rates higher than those who didn’t. They concluded, “Based on existing evidence, we see little justification for the general and widespread use of dietary supplements.”

Two days later, on October 12, researchers from the Cleveland Clinic published the results of a study of 36,000 men who took vitamin E, selenium, both, or neither. They found that those receiving vitamin E had a 17 percent greater risk of prostate cancer. In response to the study, Steven Nissen, chairman of cardiology at the Cleveland Clinic, said, “The concept of multivitamins was sold to Americans by an eager nutraceutical industry to generate profits. There was never any scientific data supporting their usage.” On October 25, a headline in the Wall Street Journal asked, “Is This the End of Popping Vitamins?” Studies haven’t hurt sales. In 2010, the vitamin industry grossed $28 billion, up 4.4 percent from the year before. “The thing to do with [these reports] is just ride them out,” said Joseph Fortunato, chief executive of General Nutrition Centers. “We see no impact on our business.”