John Doherty says scientific studies need an “endpoint” – something to measure a therapy against. In the most recent studies, that meant asking if people who took multivitamins lived longer, had less heart disease or fewer cancers. (The authors said those endpoints were chosen because if multivitamins made people healthier, there should be an impact on the two main causes of death.)
“We’re not claiming the products will ... prevent death or prevent cancer or prevent cardiovascular disease. But they will improve your quality of life,” Doherty says of multivitamins.
In augmenting nutrition, multivitamins make people feel better, he says, but he notes that capturing that effect in a clinical study is hard to do. “The problem is those kinds of studies aren’t really conducive to clinical trials. How do you measure that?”
Dr. Gordon Guyatt, a pioneer in the field of evidence-based medicine, says research into antioxidant nutrients – once thought to cut one’s risk of cancer and heart disease – has also led to disappointment.
“What it turns out is that people who take antioxidant vitamins do in fact have lower cardiovascular and cancer risks. Unfortunately it has nothing to do with the antioxidant vitamins,” says Guyatt, a professor of medicine at McMaster University in Hamilton.
He suggests this is a case of what’s known as the “healthy user” effect in action. People who take antioxidants are typically folks who work to maintain good health.
Even vitamin D hasn’t lived up to the fevered hopes that surrounded it just a few years ago. Vitamin D deficiency was suspected as contributing to the development of some cancers, multiple sclerosis and other ailments, and researchers hurried to study if supplementing vitamin D stores could protect against those diseases.
Late last week the journal Lancet Diabetes and Endocrinology published a review of more than 40 randomized controlled trials which suggested vitamin D supplements don’t prevent heart attack, stroke, cancer, or bone fractures to a significant degree and probably provide little if any benefit. The study concludes that vitamin D deficiency probably isn’t the cause of disease, but a consequence of it.
Repeated studies have also called into question the merits of many over-the-counter cough medicines. A 2012 review of cough remedies by the influential Cochrane Collaboration concluded there is no evidence for or against the efficacy of the popular products. (The Cochrane Collaboration is an organization which publishes studies that draw together all available high quality research findings on particular topics to create a picture of the state of the science.)
Dr. Susan Smith of Ireland’s Health Research Board Centre for Primary Care Research was the lead author of that 2012 review. In an email exchange, she explains what “no evidence for or against” means.
“The lack of evidence does not mean we can say for sure that they don’t work. However, this Cochrane review had 26 randomized controlled trials that covered a variety of products in children and adults and if these medicines were effective one would expect such an effect to become apparent.”
“What I say to my patients is that there is no evidence that buying over-the-counter cough medicines is any better than using honey and lemon or other remedies that you make at home yourself,” Smith says.
While some suggest cough syrup may deliver a placebo effect, others warn its use isn’t necessarily benign, especially in young children. In the United States, more than 7,000 children a year end up in hospital emergency rooms requiring treatment for inadvertent drug overdoses caused by excess use of cough and cold remedies, Mamdani notes.
Health Canada advises against giving cough and cold medications containing anti-histamines, anti-tussives, decongestants and expectorants to children under the age of six.
Antibacterial soaps are another product about which questions are being raised, at least in terms of their use in normal household settings, says Dr. Susan Poutanen, a microbiologist at Toronto’s Mount Sinai Hospital.
Poutanen says there is good evidence that people can reduce their risk of contracting some illnesses by frequent hand washing. But ordinary soap and water does the trick.