The Science of Health
Trusted Information Sources Lead to Better Choices
Fifty or so years ago cigarette smoking was considered fashionable and cool! The science today tells us otherwise. It has proven that cigarette smoking is one of the most toxic lifestyle habits that kills thousands of people every year. It took a cycle of fourty years and two generations to get the tobacco industry to install warnings on packaging and to educate the public about the dangers of smoking.
Today, we are witnessing similar cycles of the rejection of solid, reputable and validated science showing harmful effects of overly processed foods, meat products and dairy and its evidence based scientific connection to lifestyle illnesses. Educating the public can be a daunting task but because of the way information is dispersed these days, the general public is beginning to question the motives of the corporate food industries with their constant and insidious marketing of processed foods as "healthy". Just like tobacco giants, the meat, dairy and processed food industries hire powerful lobbyists to sway politician's votes away from what would be a vote in the best interest of the people they serve. My mission is to encourage you to do your own research and here is how...
Vetting your sources
The media cover all types of intriguing studies, but reporters sometimes fail to put a study in context by explaining the type of research reported and what kind of questions it can honestly answer. Exciting new findings make headlines, often creating a misleading impression that the results are definitive. Also, studies often make the news precisely because they contradict a larger body of evidence, which may remain more convincing despite a single clashing new finding.
So, the bottom line is to read reports of health & nutrition news skeptically, and consider whether the weight of evidence from a series of solid studies warrants making any changes in your lifestyle habits. It’s also important to consider whether the possible benefits to your health outweigh potential risks.
Before making a change, do your own research to get more information. Many studies may have personal or funding biases to support an outcome they are looking for. Reputable sources of health information put key studies in perspective for you.
GET TO KNOW YOUR SOURCE
Besides the quantity of studies, consider the type of study being reported. Gaining an understanding of the different types of research and which types are most trustworthy can help you decide how much weight to give reports of studies on food and health.
GIVE THE LIGHTEST WEIGHT TO LABORATORY STUDIES
Experiments done in test tubes or laboratory trials involving animals can suggest how and why the underlying biochemistry might work, but the findings may not automatically translate to people.
GIVE MODERATE WEIGHT TO OBSERVATIONAL STUDIES OF PEOPLE
Observational studies of people, in which researchers follow large groups, often for decades, command a moderate amount of weight. Examples include the Women’s Health Initiative, the Nurses’ Health Study, and the Health Professionals. Follow-up Study. Using questionnaires and other methods, scientists collect data at regular intervals as thousands of participants simply live their lives. Most risk factors cannot be tested directly in people, but by comparing those who stay healthy with those who fall ill, scientists try to identify factors that could account for the difference. This category includes the types of epidemiological studies called cohort, longitudinal, prospective, and case-control studies.
GIVE THE MOST WEIGHT TO EXPERIMENTAL STUDIES IN PEOPLE
In these, the researchers control what happens. In the case of nutrition and health studies, that usually means testing a diet or behavior change. Often called clinical trials, experimental studies start small and, if successful, are repeated with more and different groups of people. Within this category are randomized controlled trials. If conducted properly, these are considered the gold standard—the most credible studies of all. Volunteers participating in these trials are randomly assigned either to a group that tests an experimental drug, a food, a dietary supplement, or another treatment, or to a control group whose members receive a placebo or standard treatment or diet for comparison.If possible, both the volunteers and the researchers are “blinded,” meaning they don’t know who is in which group until the end of the study.
One helpful analysis growing more popular in nutrition studies is called a systematic review. In these, researchers conduct comprehensive searches of previous studies, evaluate the best-quality evidence, and summarize large amounts of information. They are published in journals and available from other sources, such as the Cochrane Library and the U.S. Agency for Healthcare Research and Quality. If the studies are similar enough, researchers may conduct a meta-analysis, which combines and reanalyzes the data from several studies. Even when you do know how much relevance a study commands, news articles may include little about the quality of the research.
THE "GOLD" STANDARD
The “gold standard” is randomized clinical trials of dietary interventions on hard endpoints such as cancer and heart disease. However, such trials are often infeasible due to high cost, low long-term compliance, and potential ethical issues. In the absence of evidence from such trials, the strongest study design would be well-designed prospective cohort studies, in which a large number of healthy participants are followed for years or decades for disease outcomes. Cohort studies are usually superior to retrospective case-control or cross-sectional studies, which are prone to biases due to recall of dietary factors and selection of control participants. Animal studies can help understand disease mechanisms but the results may not apply to humans. Smaller human dietary intervention trials on intermediate biomarkers such as blood glucose or cholesterol can also help to illuminate biological mechanisms, and evidence from such trials is complementary to that from large cohort studies. In the end, combined evidence from several types of studies—prospective cohort studies and human intervention trials in particular—can be used to inform dietary guidelines and policies. Summarizing evidence using meta-analyses or systematic reviews can be helpful, but meta-analyses should be conducted with caution and interpreted in light of the totality of the evidence.
Whenever reading or watching a news story on nutrition and health, keep these questions in mind:
Is the story simply reporting the results of a single study? Only very rarely would a single study be influential enough for people to change their behaviors based on the results. So it is important to see how that study fits in with other studies on the topic. Some articles provide this background; other times, you may need to do more digging on your own.
How large is the study? Large studies often provide more reliable results than small studies.
Was the study done in animals or humans? Mice, rats, and monkeys are not people. To best understand how food (or some other factor) affects human health, it must almost always be studied in humans.
Did the study look at real disease endpoints, like heart disease or osteoporosis? Chronic diseases, like heart disease and osteoporosis, often take many decades to develop. To get around waiting that long, researchers will sometimes look at markers for these diseases, like narrowing of the arteries or bone density. These markers, though, don’t always develop into the disease.
How was diet assessed? Some methods of dietary assessment are better than others. Good studies will have evidence that the methods have validity.
Partially adapted from: http://www.hsph.harvard.edu/nutritionsource/media/