Diet Book Critique
In Defense of Food
It has long since been recognized that the Western diet has caused a dramatic increase in obesity rates in the United States. With processed and fast foods becoming the standard in this country, Michael Pollan argues in his documentary, In Defense of Food, that getting to the bottom of eating in a more healthful way is actually more simple than people realize. His guidelines for eating comes in three parts: eat food, not too much, mostly plants. Pollan goes in depth in each part of his claim and provides examples from society as to how each part of his claim has helped people to lower their risk of non-communicable diseases, such as heart disease, type 2 diabetes and obesity. This in depth explanation of each claim largely mirrors the United States Department of Agriculture’s Dietary Guidelines for Americans. Pollan also defines what he considers to be food, and what he calls “food-like products”. In this literature review, the validity of Pollan’s three-part claim will be investigated using scientific evidence. In doing so, this review will support Pollan’s claim that eating by his guidelines will help to lower these risk of non-communicable diseases, when compared with the traditional Western diet.
Claim 1: Eat Food.
The first claim of Pollan’s guidelines is to eat food. Pollan defines food as what are traditionally considered whole foods, such as meat, fish, vegetables, fruits and grains. These are foods that will eventually rot and have been cooked by humans, rather than produced in a factory (Pollan, M., 2015). What Pollan considers “food-like products” are processed foods that have long ingredient lists, a long shelf life, and health claims presented on the packaging. It also includes junk foods and fast food. Pollan explains that the health claims on the packaging of foods can lead to confusion for consumers, as it breaks down the food itself into its nutrient components. Over the years, various nutrients have been labelled as “evil”, while others have been glorified. It can be difficult for consumers to keep up with the latest denominations, causing confusion and allowing companies to manipulate consumers’ decisions. They may believe that they are purchasing something healthy based on a health claim on the package, without knowing that the product may have added sugar that is not advertised on the front of the box.
A comprehensive review performed by Dariush Mozaffarian, MD DrPH examines the effect of dietary patterns on the risk of cardiovascular disease, diabetes, and obesity. Mozaffarian explains that focusing on specific nutrients, rather than the food and makeup of the diet as a whole, can lead to an increased cardiometabolic risk. The study goes on to explain that a food-based approach, rather than nutrient-based, can help consumers to make better choices when shopping, and lessen the manipulation by food companies (Mozaffarian, D., 2016). Additionally, the study provides evidence that cardiometabolic diseases are influenced more by foods and diet as a whole, rather than by specific nutrients. This type of approach can also help consumers better understand and adhere to the recommendations from health professionals, as well as tailor their diet to their own preferences. It puts nutrition in terms of food, rather than nutrients they cannot see that can be difficult to understand and calculate. Mozaffarian also explains the potential harms of processed foods. When foods are processed as heavily as has become the standard, nutrients such as fiber, fatty acids, phenolics and various vitamins and minerals can be lost, while sugars, sodium, and trans fats have been added (Mozaffarian, D., 2016). These additions, compounded with the removal of essential nutrients, lowers the nutritional value of the product. A prime example of this is white bread, which has the bran and germ parts of the grain removed. The bran and germ are the components of the grain which contain the most vitamins and minerals, but they are removed because they reduce the shelf life of the bread. Overall this study was unlikely to have any bias, it was representative of the population discussed, and its conclusions were supported by results with limitations taken into consideration.
A study done by Yoona Kim, Jennifer Keogh and Peter Clifton discussed the effects of a red/processed meat and refined grain meal versus a meal consisting of dairy, chicken, nuts and whole grains on glucose, insulin and triglyceride levels (Kim, Y., Keogh, J. B., & Clifton, P. M., 2016). In this randomized crossover study, fifty-one participants completed two meal tests. They were over the age of eighteen and without type 2 diabetes. They had not gained or lost and a significant amount of weight over the previous three months, and were asked not to change their lifestyle and to maintain their body weight for the duration of the study. Participants were instructed specifically what to eat for four weeks, specific to their body mass index (BMI) and gender. Intakes were periodically collected throughout the study to ensure adherence to their respective diets. Researchers who carried out data analysis and measurements of blood samples were blinded as to which group the participants were a part of. After an overnight fast following the four week diet period, each group crossed over for a meal from the other group for a meal tolerance test (MTT). This was done twice, with a three week washout period of the participants usual diets before switching the groups’ respective instructed meal plans. The results from each round of dieting and MTT were consistent with the authors’ hypothesis. A meal of red meat and refined grains after a four week period of a diet similar to this resulted in elevated insulin and incremental glucose responses when compared with the dairy, chicken, nuts and whole grain meal (Kim, Y., Keogh, J. B., & Clifton, P. M., 2016). This is consistent with the increased insulin resistance observed in adults with pre-diabetes. In conclusion, these researchers found that a diet consisting of red/processed meat and refined grains lead to increased insulin resistance and blood glucose levels, similar to those of a pre-diabetic state. This article explained all withdrawals from the study, as well as the limitations of the study. Their conclusion was supported by their results, was unlikely to hold any bias, and appropriately blinded their data collection. This study supports Pollan’s claim of a diet consisting of processed foods, such as red meat and refined grains, leading to an increased risk of non-communicable diseases, specifically type 2 diabetes.
Claim 2: Not Too Much.
Pollan’s second claim of not eating too much is intuitive in that overeating can be detrimental to one’s health. Increased calorie consumption can lead to weight gain, and eventually obesity. The study performed by King Sun Leong BMedSci, MRCP and John Wilding DM, MRCP, showed the correlation between obesity and diabetes and cardiovascular disease (Leong, K. S., & Wilding, J. P., 1999). These researchers found that plasma leptin, tumor necrosis factor-α and non-esterified fatty acids are elevated as a result of obesity, and are influential to developing insulin resistance. Additionally, they found that with a reduction of obesity, diabetic glycemic control and insulin resistance improve (Leong, K. S., & Wilding, J. P. 1999). Generally, this study supports Pollan’s claim by depicting a significant increase in risk of type 2 diabetes and cardiovascular disease when a patient is obese.
Pollan advises his viewers to “eat more like the French do”, in the way that they eat their meals more slowly, in order to avoid overeating. He explains that not eating too much does not have to necessarily be restrictive, but instead can be achieved by changing the manner in which food is eaten. Essentially, Pollan is saying that not eating too much can be achieved if the meal is simply eaten at a slower rate. A study performed in 2015 by Danielle Ferriday, et al, found that the rate at which a meal is consumed does have an effect on satiation levels. Forty participants, with an equal distribution of men and women, were recruited and were blinded as to the true purpose of the study. They were divided into groups to follow a fast or slow eating rate condition. The participants were given tomato soup through a tube that was connected to a pump that administered the soup to them at a specific rate dependent on which group they were in. They were unable to see the pump, or the reservoir in which the soup was contained. The tube feeding was explained to participants in a way that would not reveal the intention of the study. Each participant consumed 400 mL of tomato soup. For those in the group following a fast eating condition, the pump switched between two seconds of soup administration and four seconds of inactivity. For the group following the slow eating condition, the pump alternated between one second of soup administration and ten seconds of inactivity. Three hours following this procedure, participants were offered biscuits and chocolate chip cookies, and were free to consume as much as they desired to assess ad libitum snack food intake. After ten minutes, the cookies and biscuits were removed and analyzed for calorie consumption by each participant. Participants were asked to complete a survey before the session, immediately after consumption of the soup, two hours after the consumption of the soup, and following the consumption of the biscuits and cookies. As part of the survey, the participants rated their hunger and thirst levels (Ferriday, D., et al, 2015) .
At the start of the experiment, the two groups had no significant difference in the time since their last meal, or feeling of fullness, as well as other factors that were polled as part of the survey. The average recorded meal time for the fast eating group was 203 seconds, where the average meal time for the slow eating group was 800 seconds. Immediately following soup consumption, the group that ate at a slower rate reported a significantly higher change in fullness from the start of the experiment, when compared to the group that ate at a faster rate. This was true for each of the next two times the survey was completed as well, which was both before the snack administration and after the snack administration. Overall, the group that ate more slowly reported feeling more satiated both immediately after the meal, and two hours after the meal was consumed (Ferriday, D., et al, 2015). The study properly blinded its participants to avoid bias, their outcomes were clearly defined and measurements were valid and reliable. The intervention factors were clear and there were no withdrawals from the study. This study therefore supports Pollan’s claim that eating more slowly can help to promote satiety both immediately following the meal and throughout the day, leading to lower calorie consumption on a daily basis.
Claim 3: Mostly Plants.
Pollan’s third and final guideline to eating in such a way that will lower one’s risk of non-communicable diseases is to consume mostly plants at each meal. He suggests eating a variety of plants, varying in color to achieve maximal range of vitamins and minerals. The image that he provides for his guidelines directly mirrors that of MyPlate, which is administered by the USDA, as shown below (USDA, 2015). MyPlate is a tool used by the USDA to provide consumers with a comprehensive visual of what each meal should be comprised of, based on the Dietary Guidelines for Americans 2015-2020. These guidelines were created through evidence based research done by the USDA.
A study done in support of the USDA’s Dietary Guidelines for Americans explored the various health benefits associated with fruits, vegetables and legumes in a review of various epidemiologic studies. Overall they found that dietary fiber from this food group lowers the risk of cardiovascular disease and obesity. Additionally, they found that other nutrients in fruits and vegetables, such as vitamins, minerals, and phytochemicals all support health and reduce the risk of the aforementioned non-communicable diseases (Slavin, J. L., & Lloyd, B., 2012). This study depicted its inclusion and exclusion factors for studies they reviewed, as well as supported their conclusions with results from each study. It is therefore in support of Pollan’s claim that eating mostly plants can help to improve health and lower risk of cardiovascular disease and obesity.
A prospective cohort study was performed by Earl Ford, MD, MPH and Ali Mokdad, PhD, to examine the association between type 2 diabetes incidence and fruit and vegetable consumption. They followed a sample of 9,665 participants, aged 25-74 for twenty years. Of the 9,665 participants, 1,018 developed type 2 diabetes. After adjusting for age, race/ethnicity, smoking status, systolic blood pressure, use of antihypertensive medication, serum cholesterol concentration, BMI, recreational and non-recreational exercise, and alcohol consumption, the researchers found that the percentage of participants who consumed five or more fruits and vegetables in a day was significantly lower in the participants who developed type 2 diabetes (Ford, E. S., & Mokdad, A. H., 2001). This article concludes that the consumption of fruits and vegetables was inversely associated with incidence of type 2 diabetes. All lifestyle variables were accounted for, and there is little evidence as to any bias due to funding. The conclusions of this article are supported by their results, and their study groups were representative of the population. All statistical analyses were appropriate for the experiment, and outcomes were clearly defined, valid and reliable. This study is therefore of good quality, and helps to support Pollan’s claim of eating mostly plants at each meal having an impact on lowering risk of type 2 diabetes.
Throughout this literature review, many studies have been brought to light that support each part of Pollan’s guidelines to healthy eating: Eat Food, Not Too Much, Mostly Plants.They have shown that eating whole foods, rather than processed foods, can lead to a decreased risk of non-communicable diseases such as obesity, type 2 diabetes and cardiovascular disease. This is done through a better understanding from consumers of what a healthy diet is comprised of in terms of food groups, rather than specific nutrients, as well as showing the harmful effects of eating processed foods. Additionally, these studies have shown that lowering calorie consumption can help to lower risk of the previously mentioned non-communicable diseases, and provided evidence for increased levels of satiation due to a slower rate of eating. Finally, these studies supported the claim that a diet of mostly plants can increase intake of vitamins, minerals and fiber in order to maintain health and, again, lower the risk of type 2 diabetes, obesity and cardiovascular disease. It can therefore be concluded that Pollan’s guidelines are valid in their claim of improving overall health and reducing the risk of these non-communicable diseases.
- Ferriday, D., Bosworth, M. L., Lai, S., Godinot, N., Martin, N., Martin, A. A., … Brunstrom, J. M. (2015). Effects of eating rate on satiety: A role for episodic memory? Physiology & Behavior, 152(Pt B), 389–396. https://doi.org/10.1016/j.physbeh.2015.06.038
- Ford, E. S., & Mokdad, A. H. (2001). Fruit and Vegetable Consumption and Diabetes Mellitus Incidence among U.S. Adults. Preventive Medicine, 32(1), 33–39. https://doi.org/10.1006/pmed.2000.0772
- Kim, Y., Keogh, J. B., & Clifton, P. M. (2016). Differential Effects of Red Meat/Refined Grain Diet and Dairy/Chicken/Nuts/Whole Grain Diet on Glucose, Insulin and Triglyceride in a Randomized Crossover Study. Nutrients, 8(11). https://doi.org/10.3390/nu8110687
- Leong, K. S., & Wilding, J. P. (1999). Obesity and diabetes. Best Practice & Research Clinical Endocrinology & Metabolism, 13(2), 221–237. https://doi.org/10.1053/beem.1999.0017
- Mozaffarian, D. (2016). Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity – A Comprehensive Review. Circulation, 133(2), 187–225. https://doi.org/10.1161/CIRCULATIONAHA.115.018585
- Pollan, M. (2015). In Defense of Food. Netflix. Retrieved from https://www.netflix.com/watch/80097071?tctx=0%2C0%2C3c5c14f0-cf73-4cb4-8826-a37c79723f2a-79675857%2C%2C
- Slavin, J. L., & Lloyd, B. (2012). Health Benefits of Fruits and Vegetables. Advances in Nutrition, 3(4), 506–516. https://doi.org/10.3945/an.112.002154
- USDA. 2015. “Dietary Guidelines for Americans 2015-2020.” 8. https://health.gov/dietaryguidelines/2015/resources/2015-2020_Dietary_Guidelines.pdf.