This week, federal regulators announced they'll be taking a more active role in policing the more than $40 billion supplement industry.

From vitamins to specialized supplements for improved focus and weight loss, some formulations have been tied to serious health risks.

The vast majority of supplements and vitamins have little to no strong science behind them, but the space is booming for startups — especially in Los Angeles and Silicon Valley.

Vitamins are supposed to be good for you. But if recent research is any indication, the pricey pills and powders may offer more of a health risk than a nutritional boost.

From vitamins to specialized supplements for improved focus and weight loss, several formulations have been tied abnormal heart rhythms, worsened asthma symptoms, and even death.

So as of this week, federal regulators will be taking a more proactive role in policing the more than $40 billion industry, which has continued to blossom in recent months with the entrance of new startups.

On Monday, Scott Gottlieb, the head of the Food and Drug Administration (FDA), announced a series of steps his agency would take in coming months to crack down on manufacturers that tout the ability of their formulas to do everything from increase energy to cure cancer. Of particular concern, he said in a statement, are pills that claim to treat Alzheimer’s, a serious brain disease that hinders memory and has no cure.

Dietary supplements "cannot claim to prevent, treat, or cure diseases like Alzheimer’s," Gottlieb wrote. "Such claims can harm patients."

On Monday, the FDA said it sent warnings or advisory letters to 17 companies for illegally selling products that claim to treat Alzheimer's disease.

Other, less niche supplements may be equally risky, according to a recent Business Insider review of dozens of "wellness" formulations that include multivitamins, weight-loss pills, and energy formulas.

Read more: The $37 billion supplement industry is barely regulated — and it's allowing dangerous products to slip through the cracks

The vast majority of supplements and vitamins have little to no strong science behind them, the review found. Yet a new startup peddling the pills seems to emerge every few months.

A new generation of supplements is emerging in Los Angeles and Silicon Valley

When supplements were introduced in the 1930s, they were presented as a way to address serious nutritional deficiencies that caused illnesses such as rickets and scurvy.

But in recent years, a new generation of supplements has emerged. Most of them are being pioneered by a handful of California startups in areas including Los Angeles and Silicon Valley. The companies' advertisements ooze with recent lifestyle buzzwords such as minimalism ("Everything you need and nothing you don't!"), bright colors, "clean eating," and personalization. They often target specific demographics, such as people who consider themselves overweight, and sometimes vulnerable populations, such as older people at risk for Alzheimer's and other forms of dementia.

There's little to no evidence that any of these pills or gummies actually improve your health. Last month, the authors of a new paper published in the Journal of the American Medical Association concluded that most of the supplements that claim to help prevent Alzheimer's or improve memory actually do nothing of the sort.

Read more: New evidence suggests that most vitamins are useless. Here are the only ones you should take.

"No known dietary supplement prevents cognitive decline or dementia, yet supplements advertised as such are widely available and appear to gain legitimacy when sold by major US retailers," they wrote.

The authors of a recent study published in the New England Journal of Medicine found that supplements — especially those advertised for weight loss — may send some 23,000 people to emergency rooms every year. And between 2000 and 2012, the annual rate of negative reactions to supplements rose 166%, they found.

The researchers behind another recent supplement study found that over the same 12-year period, 34 people died after using pills and powders for weight loss and sexual performance. Six of the deaths resulted from the banned weight-loss supplement ephedra, and one person died after using yohimbe, an herbal supplement used for weight loss and erectile dysfunction.

How the FDA is cracking down

Dietary supplements "cannot claim to prevent, treat, or cure diseases like Alzheimer's," FDA commissioner Scott Gottlieb wrote. "Such claims can harm patients." Flickr/Steve Depolo With any multivitamin or supplement, experts advise caution because none of these products has been approved as medications by the FDA. Their risks can include allergic reactions, changes to normal heart rhythms, and even a heightened risk of serious diseases, such as cancer. Their potential benefits, such as increased energy and improved digestion, may not be worth it.

This week, the FDA said it sent a series of warning letters to companies that are illegally selling nearly 60 products. Many of them are sold as unapproved or misbranded drugs that claim to treat or cure diseases.

"These products, which are often sold on websites and social media platforms, have not been reviewed by the FDA and are not proven safe and effective to treat the diseases and health conditions they claim to treat," Gottlieb wrote in a separate statement on Monday.

The items include tablets, capsules, and oils, and are made by companies such as Pure Nootropics, DK Vitamins, and TEK Naturals, according to letters posted on the FDA's website.

Pure Nootropics said it is developing a plan to fix the issues raised by the FDA.

"We will act swiftly to update our website to be in compliance with all applicable rules & regulations," the company said in an email.

TEK Naturals said it's in touch with the FDA and "committed to compliance with all legal requirements."

The companies must respond to the FDA within 15 days by outlining their plans to address the issues cited in the letters. If they don't, the products can be seized, Gottlieb said.

"Health fraud scams prey on vulnerable populations, waste money, and often delay proper medical care — and we will continue to take action to protect patients and caregivers from misleading, unproven products," Gottlieb said.