This is Everyday Science with Clare Wilson, a subscriber-only newsletter from The i Paper. If you’d like to receive this content directly in your inbox every week, you can sign up here.
Hello and welcome back to Everyday Science. Most of us are familiar with the official guidelines for healthy eating—limit red meat, salt, and saturated fats, while increasing our intake of fruits, vegetables, and whole grains. But what is the actual impact of following such dietary advice? A recent study, touted as the largest to date exploring lifestyle factors in relation to healthy aging and mortality risk, may yield surprising insights, especially for those who believe diet is the ultimate determinant of health.
This research set out to elucidate the roles of lifestyle choices versus genetic predispositions in influencing mortality risk. It leveraged data from the UK Biobank, a comprehensive project initiated two decades ago that enlisted half a million middle-aged individuals across Britain to participate in regular health assessments and questionnaires. This extensive dataset has fueled numerous scientific inquiries worldwide.
In their latest analysis, researchers from the University of Oxford sought to quantify various environmental factors that could potentially impact health—collectively termed the “exposome.” They examined 164 variables, spanning everything from smoking habits and dietary choices to the conditions of participants’ homes, street noise levels, and even their attendance at religious services. Additionally, the researchers scrutinized the DNA sequences of participants to assess their genetic susceptibility to 22 prevalent medical conditions linked to mortality, such as cancer and cardiovascular diseases.
The outcomes of this ambitious study included tracking mortality rates and the causes of death among participants. For those still living, levels of 25 specific proteins in their blood—previously associated with healthy aging—were also measured. It’s important to note that while these aging “biomarkers” are commonly used in research, their reliability as indicators of health status remains debatable. Different researchers often select varying protein groups, leading to questions about which, if any, are definitive. Although aging biomarkers appear to reflect some aspects of health, labeling them as such lends undue credibility to the “biological age” tests marketed by dubious entities. For now, we will refer to them as aging biomarkers for the sake of discussion.
Nature or Nurture
So, what did the findings reveal? Published in the journal Nature Medicine, the study highlights that lifestyle factors play a significantly larger role in mortality risk and aging biomarkers than genetic factors. Specifically, lifestyle choices account for 17% of the variation in risk, whereas genetics contribute a mere 2%. In essence, if you subscribe to the notion that our DNA dictates our fate, these statistics should prompt a reconsideration. Just because your parents faced health challenges does not guarantee you’ll follow the same path.
However, I find even more intriguing conclusions within the study. The relatively small percentage of our disease susceptibility attributable to lifestyle choices is striking. With the constant emphasis on the importance of healthy eating, sufficient sleep, and regular physical activity, a mere 17% seems quite low. The most substantial factors influencing mortality risk were age and gender—elements entirely beyond one’s control. When combining these contributions with lifestyle and genetic factors, they collectively account for only 68% of variance in risk.
Que Será, Será
The remaining 32%—more than double the impact of lifestyle factors—appears to stem from chance events, such as accidents, or other uncontrollable elements. This finding could lend support to a “Que será, será” philosophy regarding life.
Another fascinating aspect of the study involves identifying the specific lifestyle factors that contribute to health outcomes. Many findings align with widely accepted beliefs. The primary lifestyle factor affecting health is the decision to smoke, often made during teenage years. Physical activity levels also play a critical role in influencing mortality rates, as one might expect.
However, the surprising revelation is that diet, in general, did not emerge as a significant correlate of healthy aging. With the exception of one food group—which I will discuss shortly—none of the usual dietary suspects, such as red meat, processed meat, fiber, or vegetables, were linked to health outcomes in this study. This could be attributed to the researchers’ criteria for associating food groups with health, requiring both a link to mortality risk and aging biomarkers. For example, while vegetable intake was associated with reduced mortality risk, it also correlated with poorer aging biomarkers, which raises questions about the validity of such findings. Alternatively, this could reinforce my skepticism regarding the reliability of aging biomarkers.
Weak Evidence
Moreover, a significant caveat of this study—typical of much nutritional research—is that it relies on “observational” studies, a weaker form of medical evidence. In contrast, the most reliable nutritional research derives from randomized trials, which directly manipulate dietary factors to observe health effects. Thus, if a dietary change leads to a health improvement, one can confidently assert that the new diet caused the effect.
In observational studies, researchers merely observe dietary habits and health outcomes, identifying correlations that do not imply causation. For instance, individuals with higher wealth often exhibit healthier lifestyles, making it difficult to determine if diet is the true cause of better health outcomes.
Consequently, observational studies should not dictate our lifestyle choices. As Professor Kevin McConway, a statistician at the Open University, aptly put it, “If you change a factor that is correlated with ill health but doesn’t cause it, you won’t change the level of ill health.” These challenges contribute to the contradictory nature of dietary research, where one week may herald the dangers of full-fat milk, only for the next to celebrate its benefits.
As Professor Cornelia van Duijn at the University of Oxford noted, “We don’t see consistency of findings even in our study, let alone over multiple studies.” Her colleague, Dr. Austin Argentieri, emphasized that their study does not categorically dismiss the impact of diet. It could simply be that the UK Biobank study lacked sufficiently reliable assessments of dietary habits. Given that UK Biobank is widely regarded as one of the most extensive and reputable health studies globally, the inability to conclusively determine the relationship between diet and health raises significant questions.
If you lean towards skepticism (as I do), you may conclude that the entirety of nutritional observational research is unreliable, allowing individuals to cherry-pick studies that support their dietary ideologies. Advocates of various diets can find evidence to justify their beliefs, whether it’s vilifying red meat, demonizing carbohydrates, or criticizing ultra-processed foods.
As for the latest findings, I might just place my faith in the one dietary conclusion that emerged as significant: cheese. While the NHS recommends limiting cheese intake due to its high saturated fat and salt content, this study found that individuals consuming more cheese had a reduced risk of death and more favorable aging biomarkers. Perhaps it’s time to reconsider the narrative surrounding cheese.
What Else I’ve Written Recently
As winter draws to a close, it appears the anticipated “quad-demic” did not materialize. What strategies will health officials devise for next year to elevate the threat level—will we look forward to a “quin-demic”?
I’m Reading
A Gentleman in Moscow by Amor Towles. If you think it might be challenging to empathize with a Russian aristocrat residing in a luxurious hotel, think again. I find myself staying up far too late each night, captivated by this book and eager to discover what unfolds next.
