Turmeric seems to be everywhere these days. This signature spice that lends curries and mustards their distinct colour is now popping up in unlikely foods and beverages like golden spice lattes, hot chocolate, and even sodas.
And you can count on more foods adopting turmeric’s characteristic yellow-orange hue, as the turmeric food trend is a strong one. A recent Google food trend analysis ranks turmeric as the number 1 rising star, as interest in turmeric has grown significantly in a short period.
The Internet is a go-to source for information about food and health. But teasing out the evidence-based information from the hype is becoming increasingly more difficult. Is the turmeric trend supported by the body of scientific evidence?
What Is Turmeric?
Turmeric comes from the thick root of the turmeric plant: it looks a bit like a small ginger root, and cooks prepare it in a similar way to add a subtle earthy flavour and bright colour to dishes. If you are new to cooking with turmeric, be aware that turmeric can stain hands, clothes, and even cooking utensils bright yellow orange (historically turmeric was a popular dye, and some use it as a dye today). Most people are more familiar with turmeric ground to a golden powder, which is available in the spice isle of most grocery stores.
Recognized as an ancient home remedy in Asia, and commonplace in Ayurvedic and Chinese medicine, many believe that turmeric has medicinal properties. A quick search reveals turmeric as a “cure-all.” The claims for turmeric’s healing properties are wide ranging — from improving cognitive function, cardiovascular function, and weight loss to fighting cancer, Alzheimer’s disease, diabetes, arthritis, headaches, depression, digestive diseases, the common cold, and many more health conditions. No wonder people are sprinkling turmeric on everything. . . (whether it tastes good or not). Does this sound too good to be true?
A large body of research has looked into turmeric and health, focusing on curcumin, a polyphenol compound thought to be responsible for turmeric’s potential therapeutic effects. Curcumin makes up only about 3-5% of turmeric.
Preclinical studies suggested that curcumin’s anti-inflammatory action might help prevent or treat various chronic diseases. Though promising, it is important to categorize this research as preliminary or hypothesis generating, as much of it is “in vitro” (conducted in test tubes) or in animals. Researchers have studied curcumin in humans, but results have been inconclusive. Also, best to interpret this research with caution as most studies had a small number of participants, short durations, and many did not compare curcumin to a placebo. Though we shouldn’t generalize conclusions from these small-scale studies, their findings can inform larger scale trials.
Another issue with research in humans is that the body doesn’t absorb regular curcumin very well: you can consume a lot of it, but very little reaches the blood or tissues where it can have a clinical effect. Research shows that rodents absorb little (<1%) of the curcumin they consume. However, one line of research is investigating ways to improve absorption: for example, some studies suggest that black pepper boosts the bioavailability of curcumin.
So, turmeric contains <5% of curcumin, and most of this tiny amount isn’t bioavailable . . . why are so many stretching the culinary uses of this standard curry spice to desserts and convincing themselves that turmeric flavoured smoothies “taste good,” or are even “good for you?”
It’s too easy to be persuaded of turmeric’s potential healing powers. Those championing turmeric’s benefits are citing individual studies without proper scientific context. Critically evaluating the available research is a challenge and requires substantial expertise. Luckily, a new comprehensive review published in January 2017 has done just that. Investigators at the University of Minnesota reviewed the evidence for curcumin, which included thousands of studies and over 120 clinical trials. The authors raise important questions about the research and comment that curcumin’s health benefits are “much ado about nothing.”
There is no rigorous human study (double-blinded, placebo controlled clinical trial) showing benefit to turmeric. Another serious problem overlooked by many is that curcumin’s chemical structure is unstable and can produce “false hits” in studies – i.e., showing that it is acting on a disease-causing protein, when it really isn’t.
Although many studies have investigated turmeric/curcumin, and some have shown promise, at this point these findings aren’t good enough evidence to suggest that consuming turmeric improves any health condition. It’s important to consider the preliminary nature of the research and recent review questioning of curcumin’s biological activity. Turmeric is certainly not a cure-all panacea as some have touted. More research may help uncover specific benefits to curcumin or other compounds in turmeric.
But cooking with spices like turmeric is a great idea. These plant-based seasonings can flavour food deliciously without the need for excess salt or fat. And looking for recipes featuring turmeric may help you cook more and inspire you to prepare healthful dishes. But even if effective, turmeric is a small-player for promoting health and preventing disease: better to focus efforts on eating a good diet, maintaining a healthy weight, and getting enough physical activity, measures that have proven benefits for health and well-being.
The media has a tremendous influence on our health decisions, and unfortunately good health and science reporting is often overshadowed by attention-grabbing headlines. Nutrition and health studies are quite popular in the news media, and often poorly reported.
The general public does not have a good understanding of the scientific process, research design, or nutrition epidemiology. So it is critical for health reporters to help readers understand what the research means to them. They can do this by interviewing the right experts in the field, putting the research in context, and considering the cumulative scientific knowledge in the area.
Here is a hilariously funny and well-researched piece on John Oliver’s Last Week Tonight. Oliver explains how the media misinterprets the findings of scientific studies, providing real examples. His clever delivery informs, educates, and will certainly make you laugh.
A consequence of poor reporting is confusion. How many times have we heard
“researchers keep changing their minds”
about what to eat for good health. Because expert consensus is important to foster trust in science, poor reporting can fuel this distrust. And this is worrying because such distrust can have serious consequences; for example, distrust or poor understanding of science is the reason some people question the efficacy or safety of vaccines, putting the health of many at risk.
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Are you confused about how much fat you should eat? You have good reason! Many journalists and “internet experts” skillfully weave convincing stories about a large body of research. We are often told to ignore academic experts and decades of nutrition research. What’s going on here?
A recent example is journalist Ian Leslie’s “The Sugar Conspiracy.” This was indeed a good story and quite persuasive. Leslie provides a historical account of the research on the role of fat intake and heart disease. He states that the current recommendations of nutrition experts are wrong, and explains that nutrition researchers are biased and discount studies that don’t fit with their thinking.
Leslie has many convincing arguments, relying heavily on work of popular journalists Gary Taubes (Good Calories Bad Calories; Why We Get Fat) and Nina Teicholz (Big Fat Surprise), but he ignores a large body of evidence that would support any counter-arguments. Is he, and other sugar conspiracy proponents, guilty of the biased thinking for which they accuse nutrition researchers?
I’ll will examine Leslie’s arguments below, and summarize the following topics to help you understand the current nutrition debates.
John Yudkin vs. Ancel Key’s: Does Fat or Sugar Cause Heart Disease?
Leslie provides a fascinating account of how in the 1970’s, prominent nutrition researchers ridiculed the work and destroyed the reputation of a scientist (John Yudkin) who proposed that sugar was responsible for heart disease, diabetes, and obesity. Good story material for sure – bad guys, a good guy, and a conspiracy.
Did this really happen? A nutrition scientist has scrutinized Leslie’s account of the story and provides an evidenced-based interpretation of Ancel Key’s research here. (Spoiler alert: Not really). Have a look! You’ll also figure out how to interpret the graph below:
Does the research of good guy John Yudkin stand up to scrutiny? Kevin Klatt has reviewed his research here, and concludes that “there were significant limitations of Yudkin’s work and of the hypotheses surrounding sugar at the time.”
Did Americans Get Fat Because of Dietary Guidelines?
“Scientists have to reckon with the fact that the obesity epidemic basically began with the first dietary guidelines. You can’t look at that and not think we’ve done something terribly wrong” – Nina Teicholz
O.K., the first set of guidelines weren’t perfect. But, did they cause the obesity epidemic? Maintaining an ideal weight is critical to good health, and featured prominently in Guideline #2. Only 2/7 guidelines relate to Teicholz’s concerns (#3 and #4 to limit fat and eat adequate starch), but even then they emphasized whole foods. And don’t miss guideline #5 (I think Nina may have) – Avoid Too Much Sugar.
Contrary to stories of Leslie, Taubes, and others, these guidelines show there has been longstanding and prominent advice to limit sugar and refined carbohydrates. And, as I wrote in this article, contrary to what Teicholz, Leslie, and others allude most people did not follow the guidelines.
BIG Food = BIG Bodies
Did Americans Follow the Guidelines? While the 1980 Guidelines discouraged too much sugar and refined carbohydrates, Americans increased their intake of these foods: importantly, they also increased total calories and did not follow the low-fat recommendations, and they got fatter. Was eating this way an unintended consequence of the Guidelines to reduce fat intake? Doubtful.
Although nutrition experts emphasized vegetables, fruits, beans, and fiber-rich grains, the food industry latched onto “low fat,” and replaced fat in junk food with less healthful ingredients (more sugar/refined carbohydrates). Food giants like Pepsico and Nabisco (Snackwell’s) produced low-fat cookies, chips, and other snacks and cleverly marketed it as healthy, because it was low in fat. And this was quite profitable.
The food industry has large budgets, powerful marketing, and their bottom line is money, not public health. Consumer confusion and distrust in nutrition experts and evidence-based guidelines can actually be good for their bottom line. The food industry’s influence is far-reaching: consider also that they have a big say in Dietary Guidelines. James Hamblin’s How Agriculture Controls Nutrition Guidelines is a good example of the industry sowing distrust in science.
So, clever food marketing and not nutrition experts convinced people that anything labeled “low fat” was healthy (even cookies . . . so why not eat two?). And it worked! Research now confirms that simply seeing the words “low fat” on a label encourages consumers to eat more.
Beyond the food industry, sedentary behavior, our obesogenic environment, and other influences have contributed to rising rates of obesity and preventable diseases. It is deceptive to blame these conditions on nutrition recommendations.
Making dietary recommendations requires considerable expertise to interpret research from various fields, put it in context, and consider the cumulative scientific knowledge in the area. Many have criticized Teicholz’ ability to objectively critique research. According to Teicholz
“Americans have been the subjects of a vast, uncontrolled diet experiment with disastrous consequences.”
But how much weight should you give to individual studies? Just because a study was conducted in mice, or because a human study was “observational” doesn’t mean it should be discounted. And even the results of long-term well-designed clinical trials need to be carefully interpreted. (If you’re curious about how to weight various evidence, here’s a good primer). Nutrition researchers do recognize the limitations of dietary data and implications for making evidence-based recommendations. Importantly, experts often have strict methodologies for examining the scientific literature (see examples below). Unfortunately, the same can’t be said for many popular books and news articles, as is evident in a critical review of the Big Fat Surprise.
Even Experts Disagree. . . But That’s O.K.! People complain that findings of research studies contradict each other. But, as explains epidemiologist Michael Marmot, who chaired the WHO World Cancer Research Fund’s examination of the evidence of diet and lifestyle influences on cancer, “That is the nature of science and a source of its strength.” For example, the World Cancer Research Fund review has a panel of expert scientists who examine and debate the scientific evidence to come up with recommendations to guide new research, prevention guidelines, and policy. They categorize the evidence as (1) convincing; (2) probable, or (3) substantial effect on risk unlikely. For example, this graphic shows how they categorized lifestyle risks on colorectal cancers.
The Scientific Committee for the Dietary Guidelines reports also follow a detailed protocol to interpret the literature, as explained here.
Do you think authors of newspaper articles and popular books or “internet experts” have such rigorous protocols or methodologies when they interpret the scientific literature? It’s something to think about before you trust their stories.
Fats or Carbs?
What’s All the Fuss About FATS?
The 1980’s Guidelines advised avoiding too much fat or saturated fat. Now more evidence shows that certain fats are beneficial and should be part of a healthy eating pattern. These “healthy’ fats include monounsaturated and polyunsaturated fats found in nuts, seeds, fatty fish, and some vegetable oils. Trans fats – found primarily in processed foods – are considered unhealthy and should be avoided.
The role of saturated fat in health is a topic of much debate (and confusion!). Years of research have associated saturated fat with heart disease, some cancers, and diabetes. But more recent studies suggest that some types of fats may not be as harmful to some conditions as once thought. However, the evidence isn’t strong enough to disregard research showing saturated fat intake is harmful.
Are Meat and Butter Good for You? Many headlines interpret the emerging research on saturated fats as meaning that certain foods are good for us. While the role of saturated fat in heart disease needs more study, saturated fat intake is linked to other diseases. In terms of cancer, there is still considerable evidence linking high consumption of meat and/or processed meat with an increased risk of cancer mortality and an increased risk of incident cancers, particularly colorectal cancer. Just because something is not as bad as once thought, doesn’t mean it’s beneficial, especially in copious amounts. Replacing cookies with cheese might be a good swap, but replacing cookies with nuts is likely better.
CARBOHYDRATES Can Be Confusing, but That Doesn’t Make Them Bad
The type of carbohydrate you eat is likely more important than the amount. Carbohydrate critics tend to lump all carbohydrates into one category (somewhat like equating candy to broccoli). Vegetables, fruits, whole grains, and legumes are carbohydrate-rich foods, and affect the body differently than the refined and processed carbohydrates found in many popular foods.
Certain people may be more susceptible to the influences of carbohydrates on insulin (but again, eating lentils will influence the body differently than cake . . .). And how we metabolize carbohydrates has a lot to do with how active we are: though some studies do account for physical activity, even those participants categorized as “active” do not move much.
The world’s fastest distance runners have very high carbohydrate diets (about 75% carbs for Kenyans and 65% carbs for Ethiopians): and good evidence shows carbs are the preferred fuel for endurance athletes. New research recommends tailoring carbohydrate consumption to activity intensity and duration. Some athletes seem keen to try High Fat Low Carb (HFLC) diets, despite the fact that carb restriction compromises the effectiveness of high intensity interval training and no evidence shows performance benefits. The research is quite limited: an expert in this area, Louise Burke, provides a good evidence-based summary of the state of research on HFLC diets for athletes here.
Dietary Patterns Matter More than Nutrients
Experts agree that it’s critical to consider the overall dietary pattern: eating less saturated fat won’t be helpful if the rest of your diet is full of highly processed foods. Though there are many healthy ways to eat (low carb and low fat), a large body of research shows that the most disease-protective dietary patterns are Mediterranean, DASH (Dietary Approaches to Stop Hypertension), or patterns assigned by studies as “Prudent” “High Quality” or “Healthy Eating” – they all contain healthful carbohydrates.
Examining the Credibility of Two Popular Anti-Carb Crusaders
Nina Teicholz and Gary Taubes are journalists with a disturbing degree of influence. Should we be trusting them to interpret nutrition research?
Big Fat Surprise “Painstakingly Researched?” While Leslie calls Teicholz’s book “painstakingly researched,” most evidence-based reviews show that Teicholz lacks the appropriate nutrition expertise to critique studies and put decades of research in context. Many experts question her credibility and you should too.
Here is a detailed scientific critique that fact checks Teicholz’s text that outlines the many errors and biases (see The Big Fat Surprise: A Critical Review (Part 1; Part 2). Here are a few examples:
Gary Taubes argues that the main cause of obesity is eating too many carbohydrates. Many talk about the insulin-carbohydrate hypothesis of obesity as if it is fact. In reality, numerous studies don’t support this hypothesis. Obesity researcher Stephan Guyenet does a nice job explaining the insulin-carbohydrate hypothesis and outlines why you should question this reasoning.
The latest study to refute this hypothesis, published in Cell Metabolism, showed that for the same number of calories, a low-fat diet was better than a low-carb diet to lose body fat. This was a “feeding study” – one of the most rigorous forms of studies that I summarize below:
Study participants received two diets in random order (a low-carb diet and low-fat diet) and spent part of the study in a “metabolic chamber” that captured all the air they inhaled and exhaled. Urine and body gases collected allowed researchers to determine the number of calories participants were burning and whether those calories came from carbohydrates, fat, or protein. Calories were restricted, so, as expected, participants lost weight and body fat on both diets. The low-fat diet seemed to have a metabolic advantage, and the low-carb diet slowed metabolism. A low-fat diet didn’t slow metabolism, and had increased fat burning and fat loss compared to the low-carb diet.
Do these results mean that “low-fat diets are best to lose fat” or “low-carb diets don’t work”? No, although this type of interpretation is common. The study authors caution that they conducted the research to better understand metabolism and energy balance, and not to form the basis of dietary recommendations. Here’s a good interview with the lead author explaining the study results, and if you’re interested in how this study relates to the carbohydrate-insulin hypothesis of obesity, obesity researcher Stephan Guyenet explains that here.
The insulin-carbohydrate hypothesis is an important theme in Taube’s anti-carb campaign and his books “Good Calories/Bad Calories” (you’ll find an excellent critical review here) and “Why We Get Fat.” Obesity expert Yoni Freedhoff provides an excellent and detailed review of the book. Among many other criticisms . . .
“Taubes seems to have decided to abandon journalistic and scientific integrity in place of observational data, straw men and logical fallacy.”
“Taubes doesn’t just rely on non-scientific argument, he also appears to be comfortable in ascribing his beliefs to other people and to omitting facts when it’s convenient.”
Should we trust the work of nutrition scientists? Critics claim that their diet recommendations led us to eat more sugar and refined carbohydrates, but this is not true. On the contrary, the first recommendations issued in 1980 recommended limiting sugar and refined carbohydrates. Obesity is a complex problem and it does not have a single cause. Put simply, people eat too much, likely due to a variety of influences, including the food industry, sedentary behavior, and our obesogenic society. Understanding the multiple factors that influence obesity and preventable chronic diseases is critical, and undermining the public trust in nutrition research is not helping progress.
Some Key Points:
Nutrition science is difficult to conduct and interpretation can be complicated. Experts in the field are the best ones to interpret this research, not clearly biased journalists
Conspiracies make for a good story, but typically don’t represent good science
Nutrition experts never recommended increasing sugar intake or intake of refined carbohydrates, and it is doubtful that this was a direct consequence of nutrition guidelines
Food industry marketing is more persuasive than the advice of nutrition scientists
Photo of Kenyan runners in Berlin Marathon By Dirk Ingo Franke (Own work) CC BY 3.0 via Wikimedia Commons