We should never have told people to start taking vitamins, and new research linking one type to cancer shows why

They're colorful, chewable, and more affordable than a doctor's visit. And if you believe some of their claims, supplements can do everything from giving you an energy boost to helping you lose weight. At the very worst, your daily tablet can't do any harm - right?

Not so fast. A growing body of research - including a study published August 22 in the Journal of Clinical Oncology - suggests that some supplements can carry real health risks. These risks range from vomiting and nausea to an increased risk of cancer and death.

Epidemiologists at two American cancer research institutes and the National Taiwan University found evidence to suggest that long-term, high-dose supplementation with vitamins B6 and B12 - two supplements that allegedly increase energy - was linked with an increased risk of developing lung cancer in men who regularly smoked.

For their research, they looked at data from more than 77,000 men aged 50-76 who had signed up for a long-term observational study designed to look at potential connections between supplements and cancer risk. After observing them for 10 years, the researchers found that the men who took more than 20 mg of B6 or 55 micrograms of B12 every day were three times more likely to develop lung cancer than those who didn't take the supplement.

The study has key limitations. First, the men in it all smoked regularly, were older, and were already predisposed to develop the disease. Still, it was large and done over a long period, which suggests that its findings should be taken seriously. The study is also the first of its kind to look at the link between the two supplements, which had been believed to reduce cancer risk, and lung cancer.

"This is certainly a concern worthy of further evaluation," Theodore Brasky, one of the study authors and a cancer researcher at Ohio State, said in a statement.

Most importantly, the work jibes with other research which increasingly hints that supplements are far from the panacea that they have long been made out to be.

Should we have started taking supplements in the first place?

When supplements were introduced in the 1930s and 1940s, they were presented as a way to address nutrient deficiencies that caused illnesses like rickets and scurvy. They were also seen as a way to avoid expensive and difficult-to-access medical treatment.

In recent years, however, a new generation of supplements that targets primarily middle-class and affluent women has emerged . These formulas ooze with the lifestyle trends of 2017: minimalism ("Everything you need and nothing you don't!"), bright colors, "clean eating," and personalization.

The actress Gwyneth Paltrow's new lineup of $90 monthly vitamin packs - released through her controversial wellness company, Goop - have appealing names like "Why Am I So Effing Tired" and "High School Genes." They claim to deliver health benefits like energy boosts and metabolism jump-starts.

"What is different about what Goop offers is that the combinations, the protocols put together, were done by doctors in Goop's team," Alejandro Junger, a cardiologist who helped design several of Goop's multivitamin packs, told Business Insider.

But a look at the ingredients in "Why Am I So Effing Tired," which Junger helped design, suggests the formula is not based on rigorous science. The vitamin packets include 12.5 milligrams of vitamin B6 - about 960% of the recommended daily allowance (although on Goop's label it is listed as 625%) - and ingredients like rosemary extract and Chinese yam, whose effects have never been studied in humans and for which no standard daily allowance exists.

According to the Mayo Clinic, vitamin B6 - one of the supplements involved in the latest study - is "likely safe" in the recommended daily intake amount: 1.3 milligrams for people ages 19-50. But taking too much of the supplement has been linked with abnormal heart rhythms, decreased muscle tone, and worsened asthma. High doses of B6 can also cause drops in blood pressure, the Mayo Clinic notes, and can interact with drugs prescribed for anxiety and Alzheimer's, as well as Advil and Motrin.

"People using any medications should check the package insert and speak with a qualified healthcare professional, including a pharmacist, about possible interactions," the Mayo Clinic's website says.

Junger declined to comment on specific ingredients in the formula but said that many of them were added to "address the most common nutrient-mineral deficiencies of today: B, C, D, and E vitamins, iodine, magnesium, molybdenum, among others."

Another new supplement product that has materialized in recent months is called Ritual, and it arrives at your doorstep in a white-and-yellow box emblazoned with the words "The future of vitamins is clear."

A month's supply of the glass-like capsules - filled with tiny white beads suspended in oil - costs $30. But the pills don't differ much from a standard, cheap multivitamin - they have similar amounts of magnesium, vitamin K, folate, vitamin B12, iron, boron, vitamin E, and vitamin D.

VitaMe, another new supplement manufacturer, ships personalized daily packets with names like "Good Hair Day" and "Bridal Boost" in a box resembling a tea-bag dispenser each month for $40.

Supplements and disease

Researchers have been studying potential links between supplements and disease for decades. The idea is that if supplements are doing any substantive good, we might see evidence of this in long-term studies. Yet the existing research has not supported that idea. In fact, it's mainly found the opposite.

A large recent review published in the Annals of Internal Medicine looked at 27 trials of vitamins involving more than 400,000 people. The researchers concluded that people who took vitamins did not live longer or have fewer cases of heart disease or cancer than people who did not take them.

Another long-term study published in the Journal of the American Medical Association in May divided nearly 6,000 men into groups and gave them either a placebo or one of four supplements touted for their brain-protecting abilities. The results showed no decreased prevalence of dementia among any of the supplement-taking groups.

Scientists have also turned a particular focus to smokers to see if supplements could help decrease the risk of developing diseases like lung cancer (which smokers are already at an elevated risk of developing).

Again, however, the existing studies suggest certain supplements are not providing benefits and may in fact be linked with harm.

A large, long-term study of male smokers found that those who regularly took vitamin A were more likely to get lung cancer than those who didn't. And a 2007 review of trials of several types of antioxidant supplements put it this way: "Treatment with beta carotene, vitamin A, and vitamin E may increase mortality."

With all of this in mind, experts say it's wiser to hold off on taking supplements and instead look to food to get the nutrients we need.

"Consumers should expect nothing from [supplements] because we don't have any clear evidence that they're beneficial," S. Bryn Austin, a professor of behavioral sciences at the Harvard T.H. Chan School of Public Health, told Business Insider. "And they should be leery that they could be putting themselves at risk."