Is Food Medicine? The Role of Food in Prevention, Precision, and Healthspan
“Imagine a world in which medicine was oriented toward healing rather than disease, where doctors believed in the natural healing capacity of human beings and emphasized prevention above treatment. In such a world, doctors and patients would be partners working toward the same ends.” -Dr. Andrew Weil
It is often said that an ounce of prevention is worth a pound of cure, but modern Medicine has been driven by the Diagnostics and Therapeutics industries with very little investment in preventive care. This, of course, is because of where the business incentives are and where scientific knowledge is most readily established. After all, it’s much easier to prove the accuracy of a test or benefit of a treatment in a relatively short period of time. Just imagine how one might prove the long term benefit of a single preventive act. The number of participants and time required to do so would be cost prohibitive, and the design of most such studies would be riddled with flaws, rendering them inconclusive speculation at best and a waste of valuable resources at worst.
Most nutrition studies, for example, are severely limited by a healthy user bias (patients who eat a certain way are more likely to pursue other health-seeking behaviors), recall bias (inaccurate memory of what one ate in the past), and a lack of adequate controls for such known and unknown confounders alike. Not only is the science of prevention extremely difficult with respect to methods, but our minds are not primed for the results. We’re asked to overcome the emotional weight given to more striking, immediate, and concrete outcomes over those that never occur or are significantly delayed — a form of salience or availability bias.
Admittedly, however, this portrayal is incomplete. There are current examples of preventive interventions that work and are mainstays of healthcare. Such successes include hand-washing, vaccines, seat-belts, PrEP for reducing the risk of HIV transmission, smoking cessation, hypertension screening and treatment, and age-appropriate cancer screening, to name several. And regular exercise is one of the most important of them all. What all of these have in common as effective measures for the primary prevention of harm is that actual illness rates are reduced at the population level while risk of illness is reduced in the individual. The question becomes, how do we build on public health wins of the 20th Century, which saw a near 30-year increase in life expectancy, and create a more targeted approach to further reduce the risk of disease and disability? This shift in focus to extending healthy life is what many aging researchers and clinicians are calling the transition from “Lifespan to Healthspan.”
Figure 1: The red zone represents a period in life when the risk of frailty and disability begins to increase rapidly. The goal of aging science is to delay and compress the red zone, which may extend healthy life.
Source: Olshansky S. JAMA. 2018 Oct 2;320(13):1323–1324
As I see it, there are two major movements in Western Medicine today, mostly operating in parallel and at opposite ends of the care spectrum. One is the evolution of the traditional R&D, diagnose and treat, “reactive care” paradigm. The other is a renaissance of preventive health, which emphasizes a proactive lifestyle, wellness, and active monitoring. I believe these movements can coalesce and mutually reinforce each other in several areas, especially with respect to what and how we eat.
Movement 1: The Right Treatment for the Right Patient at the Right Time
The era of Personalized Medicine was ushered in with the completion of the Human Genome Project in the early 2000s. The goal and promise was that medical treatments would be tailored to individual characteristics including the genetic profile of the patient, a cancerous tumor, or both, for instance. The term “Precision Medicine” has more recently been adopted as largely a replacement yet more expansive term. It continues to emphasize a customized approach to medical care based on unique patient factors (genes, environment, lifestyle, preferences), and even predictive technology. Since President Obama launched the Precision Medicine Initiative in 2016, more and more healthcare technologies and concepts have gone mainstream in a seemingly endless “hope-or-hype” cycle. According to a recent research report, “the global precision medicine market was estimated at $78.85 billion in 2018 and is expected to grow over $216.75 billion by 2028.” What does this mean for the average patient and consumer?
It means that we are still likely several years to decades away from seeing meaningful and lasting changes to the way the majority of patients are diagnosed and treated for even the most common acute and chronic ailments. And even with such large, important investments to bring together insights from genetics and genomics, bioinformatics, the microbiome, and smart monitoring technologies, among others, I worry that this is largely a continuation of the more reactive and singularly focused, “War on Disease X” approach. I am hopeful, however, that more preventive efforts will gain traction with insights from long term studies such as Alphabet/Verily’s Project Baseline, which seeks to define and map human health over time using a data-driven, large-scale approach.
But by continuing our current “sick care” model, addressing one specific diagnosis or acute illness episode at a time, we won’t make much of a dent in life expectancy, unfortunately. The phenomenon of “competing risks” makes it clear that if we reduce the risk of death from one cause (e.g. cancer), the risk of death from other causes (e.g. stroke, heart disease, Alzheimer’s, etc.) increases and becomes more debilitating with advancing age. It’s an unintended consequence of our current model, which is why many researchers are highlighting the need to focus on the upstream, underlying mechanisms common to age-related disease, thereby shifting priority to healthspan.
Figure 2: “The graph shows an exponential increase in disease as each year passes after the age of 20. It’s hard to appreciate exponential graphs. If I were to draw this graph with a linear Y-axis, it would be two stories tall. What this means is your chance of developing a lethal disease increases by a thousandfold between the ages of 20 and 70, so preventing one disease makes little difference to lifespan.”
Source of graph: Adapted from A. Zenin, Y. Tsepilov, S. Sharapov, et al., “Identification of 12 Genetic Loci Associated with Human Healthspan,” Communications Biology (2 January 2019).
Source of description: Sinclair, David, Matthew D. LaPlante, and Catherine Delphia. 2019. Lifespan: why we age — and why we don’t have to. PDF of supplemental material via Audible.
Movement 2: Healthspan and Food
Lifestyle modification always has and continues to be the top and earliest priority for disease prevention and management. We’re taught this in medical school, guidelines support it, and it ought to be discussed early and often in medical visits. Yet we’ve seen a resurgence in interest in “Lifestyle Medicine” (a vague term we continue to use) as both age and the consequences of modern convenience fuel the growing burden of chronic disease. Whether it’s Obesity, cardiovascular disease, Type 2 Diabetes, frailty, cognitive decline, or cancer, food is back in vogue with increasing optimism, building upon the Farm-to-Table movement which commenced in the 1970s. There is also a particular urgency now that poor diet is the leading risk factor for premature death. When I counsel patients about nutrition and their dietary habits, I tell them to actually think in terms of three components: Quality, Quantity, and Timing of eating (or What, How Much, and When). Each of these can affect our health in important ways, both as prevention and treatment. (*To be sure, there are several pillars of Lifestyle Medicine of which food is one, and a good diet cannot overcome poor exercise and sleep habits and high levels of chronic stress.)
Quality/What to Eat
Nutrition is what our bodies need to function. There are macronutrients like carbohydrates, fats, and protein, which are our main energy sources (water and fiber are macronutrients that do not provide energy). There are micronutrients such as vitamins and minerals, which are essential for cellular processes. Although these work together, it’s important to remember that people don’t eat macro and micronutrients; they eat food. And the easiest example of “food as medicine” is when a particular nutrient is low (often causing symptoms), adding or increasing its food-based source in the diet is the easiest and most sensible thing to do.
Diet, on the other hand, is what someone actually eats. And to put recommendations in context, we must understand the typical baseline, or starting point, in most Western countries: The Standard American Diet (SAD). This generally consists of highly processed and packaged foods with low quality sources, ingredients, and preparation. The SAD tends to be high in refined grains, added sugars, artificial sweeteners, salt, processed meats, and unhealthy fats. It’s low in whole grains, whole fruits, non-starchy vegetables, fish, and legumes. What we’re left with are calorie-rich and nutrient-poor meals, all day, everyday.
What should you eat? To that, most clinicians and researchers will say, “it depends.” First, anything tends to be better than the SAD. Do the opposite and you’re off to a great start. Second, it’s helpful to know if you have any medical conditions that would warrant consideration. Despite the challenges in nutrition research for prevention of major health outcomes, we actually do have significant amounts of research in terms of condition-specific needs and clinical improvement studies. Some of these conditions include pregnancy, Celiac disease, Hypertension, Type 2 Diabetes, Irritable Bowel Syndrome, Heart Failure, Fatty Liver Disease, Gastroesophageal/Acid Reflux, Obesity, and Polycystic Ovary Syndrome. We can also make other evidence-based recommendations due to various allergies, intolerances, states of inflammation, malabsorption, or a necessary medication. Third, I try to understand any additional health goals and say “the diet for you is the diet that works.” There is no one-size-fits- all diet. However, we can offer general guidance, and the best advice supported by the existing medical literature I give to healthy individuals is to follow something that resembles a Mediterranean-style diet. This does not mean any particular food is required or proven to be the exact diet to follow at each and every meal, especially since there is broad diversity among the countries and cultures which surround the Mediterranean Sea. It simply illustrates a vast improvement in contrast to the SAD based on the following dietary pattern:
- Vegetables (non-starchy and fibrous)
- Legumes (beans, peas, chickpeas, peanuts, lentils, etc.)
- Nuts and Whole Fruit (not juice)
- Whole Grains (as opposed to refined/milled)
- Fish (cold water, fatty fish: salmon, mackerel, anchovies, sardines, herring, tuna)
- Fats (unsaturated over saturated, and high in omega-3 polyunsaturated fatty acids found in the fish above)
- Dairy (fermented)
- Meat (white meat over red meat, and less overall is probably better but the evidence is low quality)
- Alcohol (moderate/1–2 drinks per day)
Keeping in mind the limitations to nutrition research, some of the best evidence we have on the Mediterranean diet comes mostly from studies suggesting improvements in cardiovascular disease (e.g. Diet and Reinfarction Trial, LYON Heart, PREDI-MED, REGARDS), and improvements in blood pressure (a top risk factor for cardiovascular disease) for patients with hypertension following a DASH diet, which was adapted from the Mediterranean.
Another thing to consider in terms of quality is food sourcing and preparation. Such topics are outside of the present scope, but they include terms like Organic, Genetically Modified, Wild Caught, Farm Raised, Free Range, Pasture Raised, Grass Fed/Finished, among others. Culinary Medicine, a strong interest of mine, encompasses all of this, from diet for your diagnosis to various cooking techniques with an emphasis on building flavor with healthy ingredients, minimizing waste, and eating mindfully.
Quantity/How Much to Eat
How much food you choose to eat in a single sitting is a portion. A serving, on the other hand, is a standardized amount set by the USDA and FDA to meet certain nutritional standards (you can find this on the label). Portion control is very important when it comes to meals and snacking, especially since our food is much more calorie dense and easier to scarf down than it ever has been. With high amounts of processing and refinement, we tend to eat much less fiber thereby absorbing our food more quickly leading to blood sugar spikes and crashes while taking longer to feel full. So, I tell patients a couple things: 1) Slow down, savor your food, and try not to eat with distractions. Eating more mindfully gives more time for your brain to catch up to your stomach as satiety hormones like leptin increase and hunger hormones like ghrelin decrease. This takes time, and your grandmother was right: wait 15–20 minutes after eating what’s on your plate and you won’t feel hungry anymore. 2) Choose whole food snacks that are around 100 calories, with less than 10 g of sugar (ideally none), 5 or more grams of fiber, 1 gram or less of saturated fat, and no trans-fats. Whole fruits, nuts, and whole grains tend to be good choices. And, rarely drink your sugar, if ever.
Traditional dieting advice has focused on how much food to eat as research on macronutrient quality (e.g. low carb vs. low fat) generally favors neither for weight loss. “A calorie is a calorie,” and “calories in must be less than calories out,” so the advice goes (although I do not completely agree with this since quality matters as well). Extending this logic has led to the calculation that in order to lose weight, one should aim for a 500–1,000 calorie deficit per day. This will add up to at least 3,500 calories per week, which equals a pound. I often use this calculator to give patients an idea of how many calories they burn per day, depending on how active they are. This helps them set an intake target depending if they are trying to lose, maintain, or gain weight. Sound easy? Tracking calories tends to be quite difficult, although some can do it with the help of apps like LoseIt! and MyFitnessPal, but I generally give patients a visual idea of how much to eat and encourage them to focus on slowing down. The Okinawans of Japan have a phrase, “Hara hachi bu,” which is a Confucian teaching they say before meals, and roughly translates to “eat until you’re eight tenths full.” This is a great rule of thumb.
Timing/When to Eat
While research and diet debates have confused us with ever-changing advice on what to eat and how much, a third aspect of eating, timing, appears to matter just as much and maybe more. Thanks to the cyclical nature of hormones and circadian rhythms in more than just our brain cells, a growing body of research is looking at “Time Restricted Eating” (or Time Restricted Feeding) as a tool for improving metabolic health. It’s been popularized under the term “Intermittent Fasting,” which is a broader term referring to any form of alternating periods of eating and fasting (although some argue that a true fast is at least 48 hours long). Regardless of the semantic differences, the key idea is to shorten the window in which you eat and prolong the time between eating windows. The average American eats for 15+ hours per day (first bite to last), and each time calories are consumed, the body’s nutrient sensors flip us from energy burning mode to energy storage mode. Eating all day means we’re spending much more time than our ancestors did storing energy to prepare for the famine that never comes anymore. We also know that our cells and tissues undergo complex maintenance and rejuvenation processes while in a prolonged fasted state. For example, you may hear terms such as “autophagy” (self-eating) referring to the way in which our bodies take out the trash, replace the old with the new, and keep inflammatory cells at bay.
So, in order to improve metabolic balance as well as cellular maintenance and repair, it may be important to shrink the eating window down to somewhere between 6–12 hours while fasting the other 12–18 hours per day, or doing this a few days per week. There are studies showing that time restricted eating/intermittent fasting can be effective for short-term weight loss and this recent pilot study showing improvements in metabolic markers possibly due to these mechanisms, but we cannot yet say which method is optimal or sustainable and who the best candidates are. There is also this comprehensive, recent review article summarizing the existing research and promise for intermittent fasting’s impact on health, aging, and disease. I do recommend for those who are interested and low risk, to try one of the methods described here. I would discourage this, however, for individuals who are required to eat meals at regular intervals such as those with type 1 diabetes, pregnant and breastfeeding women, the frail elderly, individuals with eating disorders, and those in need of regular food intake to take medications.
Looking ahead, I think we see a future where Movement 1 (precise yet reactive treatment) and Movement 2 (prevention through lifestyle optimization) find synergy in our dietary habits. This will likely happen as various tracking tools in and around our bodies capture more and more data from our gene expression, gut bacteria, metabolic markers, and how these change over time. We’re still in the early stages of gleaning clinical insights from the human genome and what our genes mean for our health risks and response to potential treatments. We have even learned that many diseases, especially those related to aging, are influenced more by our epigenome, or the dynamic way genes are switched on and off, than by our static DNA sequences themselves. We’re at the dawn of understanding the microbiome, which encompasses all of the bacteria that live in and on our bodies, and its impact on both health and disease as we explore what foods and hygienic behaviors promote or spoil this symbiotic relationship.
Finally, the laboratory tests used by doctors to screen for and monitor metabolic diseases are becoming cheaper and more accessible to the general public at any preferred time interval. From ordering a panel of blood markers to track levels of inflammation, bad cholesterol, various hormones and organ function (think liver, kidney, bone marrow, thyroid, etc.), to wearing a continuous glucose monitor to see precisely how your diet, activity, sleep, and mood affect your blood sugar levels 24/7, the future means a ton of data. As artificial intelligence and machine learning technologies mature to try to make meaningful sense of it all, the hope is that the term “Precision Medicine” will further evolve to include a kind of “Precision Prevention” as well. That is, as long as we’re careful not to let the emotional hype get the best of our evidence-based, reasonable sense.