The Shortcomings of Nutritional Science

It seems we cannot go a week without scientific and medical institutions (or even the wider public) flip-flopping on the healthiness or unhealthiness of particular foods. Slate explores what this often chaotic and confusing state of affairs says about nutrition science and its present limitations.

The takeaway from the potato controversy is not that lobbyists sometimes base their campaigns on real science. Rather it’s that the David-and-Goliath narrative of science versus Big Ag may be blinding us to another, even bigger problem: the fact that there is often very little solid science backing recommendations about what we eat.

Most of our devout beliefs about nutrition have not been subjected to a robust, experimental, controlled clinical trial, the type of study that shows cause and effect, which may be why Americans are pummeled with contradictory and confounding nutritional advice. Nutritional bad guys that have fallen from grace in the national consciousness—white potatoes, eggs, nuts, iceberg lettuce—have been redeemed years later. Onetime good guys, like margarine and pasta, have been recast as villains. Cholesterol is back in the probably-won’t-kill-you column after being shunned for 40 years, as of the latest nutritional advice from the Dietary Guidelines Advisory Committee in February. (That advice was still too timid, according to Cleveland Clinic cardiologist Steve Nissen, who also wants the nutritional guidelines to admit our best evidence suggests fat isn’t bad for you either). And then there’s salt—don’t eat too little, says the newest research. You could die…

…Many nutritional studies are observational studies, including massive ones like the Nurses’ Health Study. Researchers like Willett try to suss out how changes in diet affect health by looking at associations between what people report they eat and how long they live. When many observational studies reach the same conclusions, Willett says, there is enough evidence to support dietary recommendations. Even though they only show correlation, not cause and effect, observational studies direct what we eat.

Apart from their inability to determine cause and effect, there’s another problem with observational studies: The data they’re based on—surveys where people report what they ate the day (or week) before—are notoriously unreliable. Researchers have long known that people (even nurses) misreport, intentionally and unintentionally, what they eat. Scientists politely call this “recall bias”.

The coupling of observational studies and self-reported data leads some observers to the conclusion that we know neither how Americans do eat nor how they should eat. A recent PLOS One article even suggests that several national studies use data that is so wildly off base that the self-reported caloric intake is “incompatible with survival”. If people had eaten as little as they reported, in other words, they would be starving.

Peter Attia, a medical researcher and doctor, started questioning the basis of dietary guidelines when he saw that following them didn’t work for his patients. They didn’t lose weight, even when they virtuously stuck with their diets. When he took a look at the research supporting the advice he was giving to his patients, he saw shoddy science. Attia estimates that 16,000 nutritional studies are published each year, but the majority of them are deeply flawed: either poorly controlled clinical trials, observational studies, or animal studies. “Those studies wouldn’t pass muster in another field”, he told me.

It is little wonder that quackery, ignorance, and deceit are increasingly taking hold of people’s health decisions. Not only does all this contradictory or ambiguous evidence make room for all sorts of unverified or dangerous claims, but they erode public trust in science and medicine — even if specialists finally get something right with certainty, they will likely be met with incredulity or apathy.

It is not unlike how the inefficiencies of the U.S. health care system, combined with the predations of big pharmaceutical companies, taints evidence-backed medicine as a whole and sends people into the arms of frauds and scammers. With distrust of institutions and authoritative bodies — political, academic, and religious — at an all time high, it seems health and lifestyle choice will be increasingly determined by individual fiat, errors in reasoning, anecdote, or other unreliable bases.

Of course, this is not to condemn all scientific bodies or the scientific approach as a whole. The article makes clear that while a lot of the misconceptions around nutrition and health are attributed to “shoddy” research, various psychological biases, as well as the sheer complexity of measuring all the variables involved with health, make the endeavor a difficult one to pursue in itself.

Ultimately, nutrition science is still a new and burgeoning field of study, and I trust that it will be self-correcting in time, especially now that both the public and establishment are scrutinizing these problems. But while we try to work out better and more reliable ways to learn about what is good for our bodies, there are going to be a lot of mistakes — and outright fakery — made.

Moreover, let us not overstate the problem: while the minutiae and other details are an open questions, there are still general rules that seem to hold true: smoking cigarettes is broadly unhealthy, a plant-centered diet is generally the healthiest, regular physical activity is beneficial, and so on. Of course, we will have to see what more can be said about such conventional health wisdom.

Carnivores of the World

It turns out that one country has famously carnivorous America beat: the small European nation of Luxembourg (which hosts a lot of transients and expatriate workers from around the world, thus possibly driving consumption higher).

The following graph,courtesy of The Economist, lists the countries where meat is most popular.

Carnivores of the World

It is interesting to see how some types of meat prevail in certain countries: Argentina, perhaps unsurprisingly, leads the way in beef consumption; people in Kuwait, Israel, and the Caribbean nation of St. Lucia love poultry; and Austrians, Danes, and Spaniards favor pork. While developing countries like China, India, and Brazil are driving the overall demand for meat, people in the developed world eat far more per person.

Here is how meat consumption has changed over the years, according to The Economist:

Cow (beef and veal) was top of the menu in the early 1960s, accounting for 40% of meat consumption, but by 2007 its share had fallen to 23%. Pig is now the animal of choice, with around 99m tonnes consumed. Meanwhile advances in battery farming and health-related changes in Western diets have helped propel poultry from 12% to 31% of the global total.

One wonders how much longer we can sustain such increasingly meat-dominated diets. Raising livestock is a drain on finite resources like land, water, and grain (which could all be put to better, human-centered use). It also produces a lot of pollution, including the kind that contributes to climate change. While China and other rising countries are routinely blamed for driving up demand — which is indeed the case — it is still the richer world that consumes far more resources per person.

Coffee vs. Smoothie: Which is Healthier?

Two of the world’s most popular drinks are head-to-head in the battle for which is healthiest. As the BBC reports, the conclusion may surprise you, and perhaps be met with much skepticism and discord.

Let’s start with coffee, which has long been regarded as unhealthy except in the most moderate amounts. As the articles notes, the widespread misconception that coffee leads to many health problems stems from methodological flaws in past studies on coffee drinkers:

These claims have been largely based on case control studies, where you take a group of people who drink coffee and compare them with another matched group who don’t.

The problem with this approach is that coffee drinkers are more likely than non-coffee drinkers to have other “bad” habits, like drinking alcohol or smoking, so it is hard to tease apart what is really doing the harm.

A more reliable way to get at the truth is to do what is called a prospective cohort study. You take a group of disease-free individuals, collect data about them, then follow them for a large number of years to see what happens.

So what did those more reliable studies reveal?

When scientists collected data on the coffee drinking habits of 130,000 men and women and then followed them for over 20 years they found that coffee is rather a good thing (The Relationship of Coffee Consumption with Mortality, Annals of Internal Medicine, June 2008).

They crunched the numbers and concluded that “regular coffee consumption was not associated with an increased mortality rate in either men or women”.

In fact, data from this study suggests that moderate coffee consumption is mildly protective, leading to slightly lower all-cause mortality in coffee drinkers than non-coffee drinkers. Based on this and other studies the most effective “dose” is two to five cups a day. More than that and any benefits drop off. There are hundreds of different substances in coffee, including many different flavonoids (compounds widely found in plants that have antioxidant effects). Which of these ingredients is beneficial, we simply don’t know.

But wait, there’s more! Coffee even confers some psychological benefits, if you could believe it:

In research recently published in the World Journal of Biological Psychiatry (July 2013) they found that people who drank two to four cups of caffeinated coffee a day were half as likely to commit suicide as those who either drank decaff or fewer than two cups a day. This research pulled together data from three studies that had followed more than 200,000 people for more than 14 years, so it’s pretty reliable. It is also supported by a number of other studies, which makes this claim even more plausible.

One reason why caffeine may be a mild anti-depressant is that as well as making you more alert, it increases levels of neurotransmitters in the brain, like dopamine and serotonin, that are known to improve mood.

As anyone who’s ever needed to get through a rough workday can attest, coffee does indeed do wonders to one’s mood. As a recent nine-to-fiver myself, I’ve been won over by coffee out of sheer necessity. Few other things help get me going, except tea (and even then, coffee is the secret weapon for when even tea won’t suffice).

Of course, like any good study (or like most things in life in general for that matter), there are important caveats to keep in mind:

The researchers don’t recommend going overboard, noting that “there is little further benefit for consumption above two to three cups”.

One note of caution is that these trials began many years ago so the sort of coffee consumption being tested is almost certainly good, old-fashioned coffee.

A simple mug of coffee delivers somewhere between zero and 60 calories, depending on whether it is black, white or white with one sugar. Cappuccinos, lattes and mochas contain coffee but they also contain a lot of calories — anything between 100 and 600 — so when it comes to fancy coffees I limit myself to the occasional tall, skinny cappuccino (70 calories).

In short, like most dietary guidelines, stay in moderation and be wary of what kind of coffee you’re drinking. It seems simple enough, especially when the benefits are vast.

So what about that other popular trend, smoothies?

In a study published in August 2013 in the British Medical Journal (Fruit Consumption and risk of type 2 diabetes) they found that while eating fruit cuts your risk of developing diabetes, drinking it appears to increase the risk.

This was another big study involving lots of people followed for many years. An interesting finding was that different fruits gave different levels of benefit. Three servings of blueberries, for example, cut the risk of diabetes by 26%, while eating apples, pears, bananas and grapefruits also had a positive, albeit much smaller, effect.

Overall those who ate fruit cut their risk of developing diabetes by 2%, while those who drank it (more than three glasses of fruit juice a week) increased their risk by 8%.

More bad news for fruit juice drinkers comes from a case-controlled study done in Western Australia that examined the daily diets of more than 2,000 people. They found that eating some types of fruit and vegetables (cabbage, broccoli, cauliflower and apples) cuts your risk of colorectal cancer, while drinking fruit juice was associated with an increased risk of rectal cancer. Sugary drinks lead to raised levels of the hormone insulin and persistently high levels of insulin are associated with increased risk of some cancers. The researchers point out that many things that protect against bowel cancer, such as antioxidants and fibre, are lost or diminished during the juicing process.

In other words, not only do juices and smoothies diminish the palpable health benefits of fruits and veggies, but they may worsen your health due to additives such as sugar. But again, here’s the caveat:

None of these studies specifically looked at the health benefits or otherwise of fruit smoothies, which are a relatively recent phenomenon, nor did they look at the impact of different types of juice – for instance, whether it was freshly squeezed or from concentrate, homemade or shop-bought. I would assume, for example, that drinking a homemade vegetable smoothie is going to be a lot better for you than a commercial fruit smoothie.

And I very much doubt that the occasional fruit juice or fruit smoothie is going to do any harm.

There you have it folks. Just watch your intake and source. Coffee, fruits, and veggies are fine so long as you’re not adding too much sugar, milk, processing, and the like. It seems like a reasonable enough result. What say you all?

Nutrition, Health, and Gender

Sadly, I don’t have as much time to get into this topic as I’d like (hence my recent lull in posting). But I believe it merits being brought up.

Has anyone else noticed how commercials and ads for healthy food or weight loss products tend to generally target women, whereas those for fast food or processed goods seem to explicitly appeal to men? Anecdotally, I’ve observed people openly regard eating healthy as “feminine” and I’ve had my masculinity challenged because of it. I can’t even so much as eat a salad without getting, at best, some amused inquiries. What does that say about the nature of gender identity and health?  If you want to be masculine, you shouldn’t care about your health, whereas woman should strive more in that regard?

It’s “manly” to eat lots of meat and processed food with no regard for your health? It’s “womanly” to concern yourself about your weight and nutritional intact? The demarcation of health based on one’s sex is completely absurd. It should be in every human’s interest to be eat well and be healthy. What’s interesting is that it’s perfectly acceptable for men to get healthy through exercise, but less so if it’s by dieting (as if that made any sense, considering that the latter matters far more than the former). Women often have the burden of needing to do it both ways, based on their own high standards.

Indeed, I’ve noticed that it’s usually my female cohorts and companions that are more keen on at least discussing their health problems, if not trying to work on them. In contrast, I know few men that I can relate with when it comes to eating and living better. Obviously, I’m not saying women are necessarily healthier than men; rather, it seems that our culture and society frown down upon men worrying about their health. Eating well and exercising is always viewed in the context of body image, rather than the more practical and crucial objective of living a long and happy life. Since men aren’t supposed to be concerned with body image, it’s not properly masculine for them to care about what they eat or how they live (hence the male proclivity for engaging in other risky behavior, such as gambling, bing drinking, and reckless driving – though all that is largely hormonal in nature).

What’s interesting is how men and women alike mutually enforce such codes on one another. Perhaps it is just a confirmation bias, but I’ve personally experienced several women remark on the feminineness of men dieting or eating well; at the same time, men often seem to hold women to a higher standard of being healthy, with women who eat a lot or are overweight being viewed as unattractive. It’s interesting that nutrition has taken such a context.

I would love to spend more time exploring this issue, but as I noted before, time is short. I suppose I’ll leave it to you all to muse on about this. Am I wrong about my perceptions? Are my experiences merely anecdotal and not part of a wider socio-cultural trend? I look forward to some comments on the matter.