Madeline Papineau, like many girls her age, wanted to drop a few pounds to look good in her prom dress.

So in mid-April, the 17-year-old picked up an "all-natural" green tea weight-loss supplement at a big-box retailer; the product promised to "increase your CALORIE BURNING capacity today!"

Madeline took two liquid capsules a day, as per the instructions, for six days. But on the seventh day, she woke up vomiting violently.

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She figured that it was gastroenteritis and would pass, but when the vomiting continued for days, she went to Cornwall Hospital, where, dehydrated, she was given three litres of fluids intravenously. The same routine was repeated a couple of days later. But the teen was getting sicker, so her mother decided to take her to the Children's Hospital of Eastern Ontario in Ottawa.

There, doctors were immediately alarmed by the yellowish tinge of Madeline's skin and blood tests that set off alarm bells: Her alanine aminotransferase (ALT) level – a measure of liver damage – was 2,575 units a litre, whereas normal is in the 7-to-35 range. (It was only then that they learned about the herbal supplement.) The girl's liver and kidneys were shutting down, and the build-up of fluids in her body was starting to cause heart trouble. She was immediately placed on dialysis (a machine that does the work of the kidneys) and spent 10 days in intensive care and almost a month since at home recovering.

"I can't believe a teenager can just walk into a store and buy stuff like this," her mother, Julie Papineau, says. "Madeline was critically ill."

The list of ingredients on the product's label looks pretty innocuous: green tea extract, black tea extract, white tea extract, vitamin B6, vitamin B12, vitamin C, vitamin E, niacinamide, folic acid, caffeine and bitter orange. But the reality is that drugs are drugs, whether they are "natural" or not. And when a drug has a desired effect, it invariably also has an undesired side effect.

There are more than 60 case reports in medical literature of green tea extract being associated with liver failure, sometimes leading to transplant and death. In addition, bitter orange is one of the "dirty dozen" ingredients in herbal supplements that Consumer Reports magazine identified as "linked to serious adverse events." There are also numerous reports of supplements being tainted with unlisted ingredients and synthetic chemicals. Almost all of these problems occur with weight-loss and sports supplements.

One reason for these problems is that testing and approval standards for natural health products – from weight-loss supplements through to homeopathic "vaccines" – are much more lax than for prescription and non-prescription drugs.

The Natural and Non-prescription Health Products Directorate (NNHPD) of Health Canada regulates natural health products (NHPs), as well as all other non-prescription drugs and disinfectants.

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The regulator's role is to ensure that the natural health products contain the ingredients listed on the label, and that they are safe. But it does not verify that the products actually do what they purport (such as "burn fat") and has limited recall power. Adverse events such as Madeline's don't have to be reported, as they do for prescription drugs. (However, Health Canada is investigating after the family and Madeline's treating physician filed a formal complaint.)

The United States has similarly industry-friendly laws. Under the terms of the Dietary Supplement Health and Education Act (DSHEA), the U.S. Food and Drug Administration has far less power to regulate and recall natural health products than prescription and non-prescription drugs.

As a result, the NNHPD and the FDA have an almost impossible task. There are 54,000 products listed in the Natural Medicines Comprehensive Database, and that number is growing every day. Currently, 3,774 products contain green tea extract, including 384 licensed in Canada.

Some supplements are useful, many are innocuous but some can be harmful and dangerous. The same is true of prescription and non-prescription drugs, but again, the regulations are far stricter.

The result of this double standard is a need for consumers to embrace the admonition caveat emptor while, at the same time, giving credence to the flawed notion that natural equals safe. As Ms. Papineau says: "I'm never going to look at the word 'natural' the same way again."