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Planetary health, Lesson 1: What does evolving evidence on saturated fat say about the state of our species and our planet?

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I grew up quite sure about what was the greatest food threat to my health: fat. Not at first – I remember in elementary school the snacks my mother would prepare when my brother and I got home from school, with plenty of grapes, apples, peanut butter – and cheese. We had whole milk in the house. 

But then began the age of evil fat, of fat free ice cream and delicious sugary yet fat free Entenmann’s cakes (did I say sugar)? Sugar was an issue, of course – brush well, not good for your teeth – but otherwise, well, glucose was the brain nourishment. We switched to something called Skim Plus milk – you can still find it in some supermarkets. Peach yogurt was a favorite snack. Who gave a thought to the sugar content?  It was calcium, protein, low-fat, and tasted so good, too. My favorite snack food, cereal, was safe. And years later, when work took me abroad, there was always safety and comfort for my vegetarian and culinary conservative self in bread roll upon bread roll.

Mainstream messages evolved. Some fats, in particular monosaturated fats, like those that largely comprised olive oil, were not bad for you at all, and were in fact an important part of a healthy diet. There was a good reason that peanut butter (high-fat but low-saturated fat, low sugar) is an old staple. But at least one thing remained certain (I thought): saturated fat was to be avoided.

I reflect on this in light of a widely publicized review of evidence on the health risks of saturated fat on cardiovascular health. There had already been strong hints that the simple picture of saturated fats as bad for you was oversimplified – for example, some evidence suggested that moderate consumption of eggs (cage-free, please) were not associated with poor heart health, cholesterol and saturated fat (though not too much) notwithstanding. And other studies questioned that saturated-fat-is-bad-for-you mantra.

The new meta-analysis found no significant association between overall saturated fat consumption and heart health, leading to the headlines questioning whether saturated fats are in fact bad for you. The study itself was a bit more nuanced, finding that some fatty acids in saturated and other fats were associated with higher risk of poor heart health, while others – including one found in dairy  – were associated with better heart health.

The study is not without controversy. One critic asks the quite reasonable question of, in lieu of what? Replacing saturated fats with lots of refined carbohydrates might not help your heart health. But replacing them with polyunsaturated fats could be a heart healthy choice. The American Heart Association has not changed its recommendations on a heart healthy (and low saturated fat) diet, and responded to the new study by re-iterating its current recommendations. The American Heart Association continues to recommend a diet low in saturated fat (indeed, recently revised guidelines lowered its recommended daily limit of saturated fat from 20 grams to 16 grams for a 2,000 calorie diet).

Perhaps all of this has been foreshadowed by the latest studies and commentary on what has been dubbed the whole food movement, focused on avoiding chemicals and other modified foods. Advice from Michael Pollan on healthy eating, which seems ever more sensible, is : “Eat food. Not too much. Mostly plants.” Vegetables and fruits, whole grains, legumes, nuts, these are among the foods that were and remain foundations of a healthy diet.

There is a lesson for our planet’s health here. If you will permit what may seem like a digression, a short trip to the experimental and temporal edges of the universe:

Last year, scientists reported that when colliding protons together at tremendous energy, they had detected the postulated – but never before experimentally verified – Higgs particle. This discovery appears to confirm the existence of the Higgs field, which explains the existence of mass. In a tunnel below Geneva, with particles racing around near the speed of life, scientists have buttressed the current model of our universe.

And just last month, scientists peering back to the earliest moments of our universe detected gravitational waves, very strong evidence for inflation, another fundamental yet heretofore not yet experimentally verified aspect of our universe. This meant that we have peered back to a mere one trillion of a trillionth of a trillionth of a second after the Big Bang.

All this is to say, our species has quite phenomenal scientific prowess. Yet back here on the surface of planet Earth, even as our basic understanding remains solid, questions of the healthiest diet — much less the protective role of particular nutrients and how they interact —  persist. The recent analysis of the evidence on saturated fats at coronary health might not lead to changes in recommendations of what we eat. But it does highlight how complex we are, how complex human health is. It is one example upon many of this complexity, from why a cancer medicine might be a miracle cure for one person but have no effect on another, to why some people can do everything right from a medical point of view and still suffer a heart attack, while another person can do everything wrong yet maintain cardiac health.

And this is just human health. How much more complicated the health of millions of species interwoven in the complex web of life, the complex interplay of life forces that sustain us, that give us a chance to be here and to be healthy?

Juxtapose the current limits of science with the disconcerting level of distrust in our society of science, exemplified by climate change deniers (or as evidence mounts and mounts, now more likely to be dubbed climate skeptics). Dire warnings of climate change, the loss of biodiversity, and the other harms we are beating down upon our planet are overblown, they say. The jury is still out. Or if they are (reluctantly) convinced of the problem, they are still more convinced of the power of human ingenuity and technology to manage whatever challenges these planetary risks might pose. We don’t need to make any major changes that might shake up our economy, or current patterns of development, our sources of energy. Where we do need to change, we do not need to move at an urgent clip.

Au contraire. The real lessons of scientific progress are at least two, with the opposite implication.

Lesson one: First, yes science is tremendously powerful. Think Higgs particle and gravitational waves.

Lesson two: Science is not all powerful. Think dietary advice, and multiply this by the immense degree of complexity of health of not a single human being or even our entire species, but of the entire collection of life on Earth – and non-living features that interact with life – and you see what science is up against.

Implication for planetary health: Humbleness. The study on saturated fat is a window into how, at least a sense, as measured by scientific progress, the nature of nature, the life and life-supporting systems of Earth, is even more complex than the fundamental properties of the universe.

We must be very, very cautious about pushing the boundaries of nature. Even leaving aside harms that climate change is already causing or the tragedy of species destruction and the epoch of the Sixth Extinction that we have created, the mark that seven-plus million people are putting on our planet, we need to acknowledge the limits of our knowledge. We are already pushing planetary boundaries in historic ways. It is a time when we must be very, very careful in minimizing how much further we test these boundaries, lest we put ourselves and future generations in the situation of learning whether the more dire scenarios are borne out. We need to be similarly cautious about our ability to manage ongoing changes through technology. Maybe we would be able to. But maybe we would not.

Yet the reality is that writ large, we move only tepidly to respond to these problems. Much as one message on the study on saturated fat and heart health might be taken to be one of balance – such fats are neither an absolute evil nor something to be eaten with abandon – we need balance with our environment, one sustainable in the long run. With the manifold ways in which animals as a source of our food contributes to climate change, Michael Pollan’s “[eat] mostly plants” will need to be part of that balance.

Right now, we are severely out of balance. We need to invest more in understanding planetary health, to see whether we can begin to match our knowledge of the universe with our knowledge of our home. But there is no time to lose in dramatically curtailing greenhouse gas emissions and the many other measures required to ease our earthly footprint. Such is one lesson, it seems to me, of our nutritional knowledge, questions, and the state of science.

Look to this space tomorrow for a second posting on planetary health, a short posting about the connection between the Malaysia Airlines plane that disappeared and an ill-fate boat of refugees in Uganda. Today’s lesson I posed with an eye towards the future. Tomorrow’s looks us squarely in the face today.

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