According to scientists Davy and Davy (2019), “The amount and composition of the diet has a profound influence on disease risk.” Scientists at Tufts agree. According to the Tufts Food is Medicine Initiative, the food system in the U.S. plays a major role in development of chronic illness.
What we eat—and don’t eat—has a complex interplay with metabolic processes and the functioning of body systems. Some foods have known deleterious effects on health (e.g., trans fats), and every food choice displaces something else in the diet. When consuming too much of foods that may damage health, we also may eat too little of foods that benefit health.
A wealth of scientific evidence points to a growing role of nutrition in mitigating the risk of illness and achieving wellness. Rather than focusing on individual nutrients or foods, Davy and Davy emphasize understanding “the impact of dietary patterns and/or overall diet quality on chronic disease risk.” Healthy dietary patterns that have received considerable investigation include the Mediterranean Diet and the Dietary Approaches to Stop Hypertension (DASH) diet.
In this course, you’ll learn about the Western diet and its impact on disease risk. You’ll learn what components of foods, beyond nutrients, appear to impact health. You’ll learn more about the role of the gut microbiome, as well as specific findings related to chronic diseases. You’ll also learn about nutrigenomics and future directions for continuing research on diet and wellness. These topics have taken center stage in discussions about nutrition, and the Academy of Nutrition and Dietetics now has a professional practice group devoted to these ideas called Dietitians in Integrative and Functional Medicine.
Nutrition scientists, healthcare leaders, and legislators alike are seeking to apply what we know to advance the health of our population. Congress created a Food Is Medicine working group in 2018. Dr. Dariush Mozaffarian of Tufts University was quoted in TIME (Park, 2019) saying, “The idea of food as medicine is not only an idea whose time has come. It’s an idea that’s absolutely essential to our healthcare system.”
Upon completing this course, you’ll be able to:
Many terms are tossed around in the discussion about food as medicine. While there is not solid agreement in the professional community, here are some terms and their common definitions.
Lifestyle choices, including dietary patterns, have a major impact on illness, according to Veselkov and colleagues (2019). They say, “With rapidly aging populations, the world is experiencing an unsustainable healthcare and economic burden from chronic diseases such as cancer, cardiovascular, metabolic, and neurodegenerative disorders.” They note that 30-40% of cancers can be prevented by dietary and lifestyle measures.
The National Conference of State Legislators (2019) reports that nearly half of adult Americans suffer from at least one chronic condition, such as heart disease, hypertension, cancer, arthritis, chronic respiratory disease, asthma, or diabetes. They explain that 75% of healthcare spending in the U.S. is devoted to care of chronic conditions. In addition, they say, chronic illness has an economic cost in lost productivity, equaling $1 trillion annually.
Tufts University, in its Food Is Medicine Initiative, states, “10 foods are estimated to cause nearly half of all U.S. deaths from heart disease, stroke, and diabetes each year.” More specifically, they say we have deaths from eating too much: sodium, processed meat, sugary beverages, and unprocessed red meat. In addition, deaths come from eating too little of: nuts/seeds, seafood omega-3s, vegetables, fruits, whole grains, and polyunsaturated fats. Tufts also concludes that “diet-related disease is a leading driver of skyrocketing healthcare costs.” For example, cardiovascular disease incurs $316 billion per year in healthcare costs, while diabetes incurs $327 billion.
They say that advances in nutrition science provides a “road-map” for improving our health and suggest that “the number-one cause of poor health [diet] should be the priority of the healthcare system.” For example, they estimate that providing free fresh food as a treatment for diabetes can reduce the risk of serious complications by 40%.
HealthDay News (2019), reporting on research from Tufts and Brigham and Women's Hospital, said, “Healthier eating could save the United States more than $50 billion a year in health care costs associated with heart disease, stroke, type 2 diabetes, and related illnesses.”
Consumption of ultra-processed foods has been on an upswing, representing almost 58% of caloric intake in the U.S., according to Martinez Steele et al. (2016). In addition, people who rely heavily on ultra-processed foods also have higher sugar intakes. Many researchers associate this dietary pattern with poor diet quality and poor health outcomes (Davy and Davy, 2019; Martinez Steel et al., 2016). For example, Canadian research (Nardocci et al., 2019) indicates that adults consuming the highest amounts of ultra-processed foods as a proportion of their energy intake had 31% higher odds of obesity, 37% higher odds of diabetes, and 60% higher odds of hypertension.
Ultra-processed foods defined
NOVA, an internationally accepted classification system, places foods in four groups based on level of processing. Ultra-processed foods are defined as industrial formulations which, besides salt, sugar, oils and fats, include substances not used in culinary preparations. These may be additives used to make food look, feel, or taste like from-scratch preparations. Examples are frozen prepared dishes, prepared sauces, dried mixes, soft drinks, chips, packaged cookies, candy, breakfast cereals, and more. “Ultra-processed” is different from “processed” foods, which are packaged, whole-food ingredients like canned beans or cheese (Rosenbloom, 2018).
Zinocker and Lindseth (2018), researchers in Norway, say that “the dietary pattern that characterizes the Western diet is strongly associated with obesity and related metabolic diseases, but biological mechanisms supporting these associations remain largely unknown.” They examine a number of findings that may shed light. For example:
Zinocker and Lindseth observe that research supports the idea that the Western diet causes changes to the gut microbiota associated with obesity and metabolic disease such as diabetes. Dietary fiber and other complex carbohydrates are important substrates for favorable microbes in the gut, according to Ludwig and others (2018). Conversely, added sugars in the diet alter the microbiota and also raise blood triglycerides, total cholesterol, and blood pressure. Ludwig and associates conclude that quality—rather than total amount—of carbohydrate has a major impact on the development of disease.
Valdes explains that the gut microbiota influences many aspects of human health, “from innate immunity to appetite and energy metabolism.” An unfavorable complement of gut flora is called dysbiosis and is associated with many chronic illnesses.
“The human diet contains thousands of bioactive molecules which modulate a variety of metabolic and signaling processes, drug actions, and interactions with the gut microbiota in health and disease,” according to Veselkov and colleagues (2019). As mentioned earlier, functional foods contain biologically active compounds that can impact metabolic processes and offer physiologic benefits. Here is an overview of some of these compounds.
Prebiotics, probiotics: Dietary fiber and resistant starches, which are indigestible to humans, are called prebiotics because they serve as food for health-promoting gut flora. These proliferate in vegetables, fruits, and whole grains. Probiotics added to food or taken as supplements are live bacteria and yeasts that are considered beneficial to human health. Examples of food sources are fermented foods, kombucha, yogurt, and kefir. Synbiotics are mixtures of prebiotics and probiotics.
Common examples of probiotic bacteria are Lactobacillus and Bifidobacterium. Valdes and colleagues state that bacteria ferment dietary fiber and produce health-promoting short chain fatty acids and gases in the colon. Dietary patterns, food additives, drugs, and lifestyle factors all can affect gut microbiota. Research reviewed by the Valdes group concludes that probiotics can have positive effects on preventing eczema, Crohn’s disease, ulcerative colitis, type 2 diabetes, cardiovascular risk, depression, periodontitis, and other conditions.
Antioxidants: A term applied to many groups of functional food ingredients is antioxidants. This broad group of compounds neutralizes free radicals in body cells. Free radicals are byproducts of metabolism that can have a toxic effect on the body, damaging cells and potentially leading to illness. Examples of compounds with antioxidant activity are carotenoids, polyphenols, phytosterols, and glucosinates.
Carotenoids: Carotenoids are naturally occurring pigments found in most fruits and vegetables (Eggersdorfer, 2018). Carotenoids may have a positive impact on cognitive function, cardiovascular health, eye health, and cancer prevention (Eggersdorfer, 2018).
Examples of carotenoids are beta-carotene, the vitamin A precursor found in carrots, other orange vegetables, and dark green vegetables like spinach; and lycopene, which gives tomatoes their red color. Among its many benefits as an antioxidant, Coronel (2019) suggest that beta-carotene could have a favorable effect on fat metabolism and decrease obesity. In turn, this could reduce the risk for many chronic diseases. Lycopene, which has highest concentrations in cooked tomato products, has a protective effect against cardiovascular diseases, neurodegenerative diseases, hypertension, osteoporosis, diabetes, and cancer (Ranjan et al., 2019).
The pigments lutein and zeaxanthin are crucial to eye health; these pigments actually accumulate in the retina. Dietary intake of lutein and zeaxanthin is believed to reduce the risk of macular degeneration. Dietary sources of lutein and zeaxanthin include leafy greens, egg yolks, orange peppers, asparagus, peas, broccoli, and pumpkin. (Eisenhauer, 2017).
Carotenoids may become more bioavailable in combination with other foods. For example, Iowa State University (2017) reported that oil in salad dressing increases absorption of carotenoids from the salad vegetables. Similarly, Purdue University (2015) noted that eggs make a difference, saying, “Absorption of carotenoids was 3.8-fold higher when the salad included three eggs compared to no eggs.”
Polyphenols: This is a large group of compounds that includes flavonoids, ellagitannins, lignans, resveratrol, and isoflavones. According to Fraga and colleagues (2019), polyphenols have a positive impact on the gut microbiota, which in turn confers health benefits. For example, they say, polyphenols in green and black tea inhibit growth of pathogenic bacteria. They also explain that flavonoids in cocoa increase production of butyrate by beneficial gut microbes. Butyrate is a metabolic byproduct of gut microbes, one of the short-chain fatty acids thought to have health benefits. Flavonoids in tea and cocoa reduce the risk for cardiovascular disease, reduce blood pressure and reduce fasting blood sugar levels, according to the Fraga group. In addition, they note that polyphenols appear to improve cognitive functioning. Food sources of flavonols (a type of polyphenol) include tea, cocoa, nuts, grapes, apples with skin, and legumes.
One type of flavonoids, isoflavones, found in soybeans and other legumes, have estrogen-like effects and have been promoted for relief of menopause symptoms. Isoflavones are a type of phytoestrogen, meaning a plant-based compound that has effect similar to estrogen. In a review of the research, though, Chen and colleagues (2019) state, “There is still no consensus on the effects of isoflavones despite over two decades of vigorous research.” They say, however, that isoflavones do reduce incidence of hot flashes and reduce bone loss during menopause. They add that isoflavones are safe and appear to benefit “overall health”.
Lignans, found in flax, nuts, whole grains, legumes, broccoli, and many other plant foods, are also considered phytoestrogens. Dietary intake of lignans can reduce the risk of heart disease, alleviate menopausal symptoms, and help prevent osteoporosis and breast cancer, according to Rodriguez-Garcia and colleagues (2019). They note that lignin consumption is also associated with reduced C-reactive protein levels. They conclude, “Dietary intake of lignan-rich foods could be a useful way to bolster the prevention of chronic illness.”
Anthocyanins, which are pigments responsible for red, purple, and blue colors in plant foods, are an important group. They have antioxidant and antimicrobial activities, according to Khoo and colleagues (2017). They also provide preventive benefits for diabetes, cancer, and cardiovascular disease, according to the researchers. Examples of foods that contain anthocyanins are blueberries, raspberries, red grapes, cherries, black beans, eggplant, and other red or purple colored vegetables.
Resveratrol has been the subject of extensive research. Found in grapes, red wine, and berries, resveratrol can reduce blood cholesterol levels, fasting glucose, blood pressure, and a marker of inflammation called C-reactive protein (Fraga et al., 2019).
Glucosinolates are sulfur-containing compounds in cruciferous vegetables, such as broccoli, cauliflower, cabbage, Brussels sprouts, and kale. These help reduce the risk of cardiovascular disease and stroke (Blekkenhorst et al. 2018).Intake of cruciferous vegetables may also lower the risk of prostate cancer, colon cancer, lung cancer, and breast cancer, according to the NIH (2019).
“Among the multiple risk factors underlying the incidence and progression of type 2 diabetes mellitus, diet is the main modifiable factor,” according to Nimesh and Ashwlayan (2018). For example, Ludwig and colleagues (2018) explain that optimizing the gut microbiota by eating fiber and resistant starch leads to production of beneficial short-chain fatty acids and increased insulin sensitivity.
In a broader view, Alkhatib and colleagues (2017) state that many functional food components, such as polyphenols, terpenoids, flavonoids, alkaloids, sterols, and pigments, play a role in preventing and managing type 2 diabetes. All of these categories, according to the researchers, offer antioxidant, anti-cholesterol, and anti-inflammatory properties. Each component may have a specific mechanism. Thus, a composite diet rich in olive oil, fruits, vegetables, legumes, nuts, and whole grains helps in many different ways. “Exercise and an active lifestyle appear to increase the benefits through their positive effects on metabolism,” they add.
The same authors state that green tea consumption (3 cups per day) reduces waist-hip ratio and reduces fasting glucose levels. Certain herbal teas, such as yerba mate, may also provide protective benefits. They sum up their advice with an integrated model for diabetes management that includes components of a Mediterranean diet, ingestion of herbal components, and physical activity.
“According to Battson et al. (2018), gut dysbiosis is linked to cardiovascular disease. As noted earlier in this course, prebiotics and probiotics can play a role in maintaining a healthy gut microbiome. In a similar vein, Panchal and Brown (2019) suggest that chronic inflammation (rather than dietary intake of fat and/or cholesterol) may be a critical factor in atherosclerosis. Reducing ,markers of inflammation, such as C-reactive protein, may be important for reducing the cardiovascular risk, according to the authors. In fact, they suggest that high blood cholesterol levels may be “a biomarker rather than a cause for the development of atherosclerosis,” and that treatment of inflammation is “a key therapeutic aim.”
They suggest that chronic inflammation can be managed through dietary modifications and lifestyle. Their review of research points out that several dietary patterns have shown positive results in managing the cardiovascular risk and/or reducing inflammation, including the Mediterranean diet, the Okinawan diet, the Nordic diet, and the DASH diet. All of these eating plans are high in vegetables, which means they are also high in fiber, polyphenols, and many other plant-based functional food components. Fraga et al. (2019) links polyphenols to reduced cardiovascular risks as well.
Lopez-Jarmillo et al. (2018) conducted statistical analysis of dietary intake patterns and cardiovascular risk. They found that the more fruits, vegetables, and legumes consumed, the lower the risk of cardiovascular disease and associated deaths.
“Plant-based foods are particularly rich in cancer-beating molecules,” according to Veselkov (2019). These include fiber and resistant starch, polyphenols, terpenoids, and flavonoids. They suggest that these food components provide “an unprecedented opportunity to reduce healthcare costs and potentially enhance health outcomes for chronic disease such as cancer.”
Oxidation, inflammation, and other processes are thought to play a role in cancer. Antioxidants in foods “reduce free radical damage to DNA, which is believed to be the root cause of most cancers,” according to Aghajanpour et al. (2017). They cite the antioxidant activity of carotenoids, for example. They mention that isothiocyanates found in cruciferous vegetables lower the risk of lung, breast, liver, esophagus, stomach, small intestine, and colon cancers. Lutein and zeaxanthin have been shown to reduce the risk of breast cancer by 52%, according to the authors. They cite many more examples and also explain that probiotics and gut health play a role in cancer prevention.
After analyzing a database of 7,962 food components, Veselkov et al. (2019) identified 110 that had anti-cancer potential. They note that one that seems to have the strongest anti-cancer properties is 3-indole-carbinol, found in cruciferous vegetables. They also mention apigenin, found in coriander, parsley, and dill, as well as dydamin, found in citrus fruits. Additional findings:
Findings such as these help fuel research into nutraceuticals for prevention and treatment of cancer. At the same time, they equip everyone to promote health by including a variety of fruits, vegetables, and whole grains in the diet.
Polyphenols, including chocolate, have been shown to improve cognitive functioning and reduce the risk of cognitive decline (Fraga et al., 2019). Green and black tea specifically are also linked to a lower incidence of cognitive disorders, according to the authors.
Research with elderly subjects indicated that those taking a flavonol drink had improved attention and executive functioning (Fraga et al., 2019). Intake of nuts helps protect against cognitive decline (Nutraceuticals World, 2019).
Zhao et al. (2018) suggest that decreasing inflammation and optimizing cardiovascular health are among the important factors for preventing Alzheimer’s. They state that in general, “Western-type meat-based diets have been associated with greater inflammation, while vegetable and fruit-based diets have been associated with decreased inflammation.” They also say that gut dysbiosis seems to be connected to inflammation and degeneration in the nervous system.
Sun et al. (2019) say that aging is associated with dysbiosis. This dysbiosis may explain a decline in cognitive function. They conclude that exercise and high fiber diets are among the strategies that hold promise.
Both DASH and Mediterranean diets have been linked to a slowdown in cognitive decline, according to Dominguez and Barbagallo (2018).
Extensive research connects functional foods and dietary patterns with many other conditions. Schulze and colleagues (2018) sum up a review of dietary patterns and chronic disease prevention with this guidance, “Food based prevention of chronic disease should prioritize fruits, vegetables, whole grains, and fish and lower consumption of red and processed meats and sugar-sweetened drinks. Higher consumption of nuts, legumes, fermented dairy products, and coffee are further likely to confer benefit.”
They recommend the Mediterranean Diet as guidance to reduce the risk of disease because it is the most strongly backed by clinical research. The DASH diet is also frequently cited by nutrition researchers as excellent advice. Both limit meat and encourage intake of cereals, vegetables, fruits, nuts, legumes, and fish. Key differences, according to Schulze and colleagues (2018) are:
Alkhatib and colleagues (2017) cite the Mediterranean diet as a “model for functional foods” based on its “natural content of nutraceuticals.”
In addition, many researchers agree that dietary patterns that provide prebiotics and advance gut health are central to disease prevention. Sandefur and colleagues (2019) sum it up this way, “A plant-based diet appears to be beneficial for human health by promoting the development of more diverse microbial systems. Higher fiber intake also encourages growth of species that ferment fiber into metabolites as short-chain fatty acids, including acetate, propionate, and butyrate.”
It’s clear there is more to research in the area of food as medicine. The role of the gut microbiota may turn out to provide deeper insights into how foods affect health. Zinocker and Lindseth (2018) suggest that some of the conflicting findings of nutrition research may be explained by ignoring the gut microbiome in study design. They advocate for reinvestigating the impact of dietary fats, comparing diets high in ultra-processed foods with whole diets, and looking at the microbiome. They also advocate “thorough testing of every food additive on the gut microbiota before approval.”
Nutrigenomics is a science in its infancy today. Cary Kreutzer at the University of Southern California (Sommer, 2019) says that through a deeper understanding of nutrition and genetics, we will be able to “help people take control of their health” and “decrease the prevalence of chronic disease that plagues our nation.”
Nutrigenomics is built on the idea that there is no one-size-fits-all advice. It’s based on using dietary modifications to influence gene expression. Based on what is known about an individual’s genetic profile, health professionals will be able to offer guidance to combat potential health risks evident in the genes.
How can nutrition and foodservice professionals apply the science? Tufts Food is Medicine Initiative identifies roles among multiple sectors, including farmers, supermarkets, food manufacturers, food service, healthcare, insurance, schools, universities, media, and others.
A nonprofit in Boston, Community Servings, is based on the idea that food as an intervention can improve health outcomes and decrease hospital readmissions (Padilla, 2019). The organization serves clients with chronic illnesses such as HIV, diabetes, and heart disease. The program offers medically tailored meals and home delivery. They emphasize from-scratch cooking using local produce and fresh ingredients, tailored to both the medical needs of clients and their cultural food preferences. They state that they have been able to document a 16% healthcare cost savings for patients that they've fed.
The nonprofit is part of the Food is Medicine Coalition, “an association of nonprofit medically tailored food and nutrition service providers.” The coalition defines medically tailored meals as: “meals approved by a RDN that reflect appropriate dietary therapy based on evidence-based practice guidelines.” They have advocates, including healthcare groups and nonprofits, operating programs throughout the country (Food is Medicine Coalition, 2019).
At Geisinger Health System, a program called Fresh Food Farmacy “provides healthy foods—heavy on fruits, vegetables, lean meats and low-sodium options” to patients (Park, 2019). Park writes, “Food is becoming a particular focus of doctors, hospitals, insurers, and even employers who are frustrated by the slow progress of drug treatments in reducing diet-related diseases like type 2 diabetes, heart disease, hypertension, and even cancer.”
Other approaches to using food as medicine include food prescription programs, such as Veggie Rx in Central Oregon (Spurr, 2019). This program provides fresh produce to individuals who have diet-related diseases and lack access to fresh food. Clients may be referred by a physician or can sign up on their own. Vouchers allow them to obtain fresh produce at local farmers markets or get free meals at a mobile food truck.
The South Side Diabetes Project in Chicago has partnered with Walgreens to give patients a food prescription, redeemable for healthy foods at Walgreens or a local farmers market (Washington, 2019).
A program called Fresh Foods Rx in Virginia targets patients of the Carilion Clinic who are overweight or obese; diagnosed with diabetes; and live in medically underserved areas. The program provides fresh food through a mobile farmers market (American Hospital Association, 2017). The program reports that 70% of patients achieved a reduction in hemoglobin A1C, indicating improved management of diabetes.
Swartz (2018) summarizes a number of food prescription programs operating around the country and delves into what makes the model work. It uses “a partnership model of care whereby an authority figure (i.e., the referring physician) rewards and positively reinforces repeated health-seeking behaviors.” The majority of programs reviewed target individuals with low socioeconomic status. Some target individuals with diet-related health conditions. Some target both criteria. The programs remove barriers to obtaining healthy food and give clients more choice. The author notes that these programs are not yet linked to government assistance, but could be.
We’ve already examined how heat denatures protein. Did you know that other factors can denature protein, too? Here’s a quick overview.
Dietary patterns have an impact on development and management of chronic diseases. Focus on improving dietary patterns offers significant benefits to health and reduction of healthcare costs.
Influence of diet on the community of microbes in the gut is an important factor in health. Consuming foods that are high in fiber and resistant starch may have positive effects on the microflora. Beyond nutrients, many components of foods are biologically active and can confer health benefits.
Each person’s genetic make-up can play a role in how the body responds to foods. Thus, individualized approaches to nutrition informed by genetics may become more commonplace as research advances. Healthy eating and access to plant-based foods are central policy ideas in healthcare today.
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