Key points

Introduction

For the vast majority of human evolution, our ancestors had been hunter-gatherers, migrating to take advantage of seasonal food availability from wild plants and animals. With the advent of agriculture approximately 10,000 to 12,000 years ago, humans began to take active roles in food production, which paved the way for major societal changes, such as the establishment of complex social organizations and the development of science, technology, and medicine. Since the dawn of agriculture, humans have been breeding plants and animals, actively selecting for particular, desirable traits of their food. However, recent major technological advances in food production—from agricultural practices, food harvesting, processing, preservation, and distribution—have inadvertently led to the modern world’s greatest threat to human health: obesity.

In the United States, greater than two-thirds of adults are classified as overweight (body mass index [BMI] of 25.0–29.9 kg/m ² ), and more than one-third are classified as obese (BMI of 30 kg/m ² and greater). In 2010, the annual medical costs associated with obesity in the United States were estimated at 160 billion dollars, with indirect costs associated with obesity estimated at another 450 billion dollars. The obesity epidemic correlates closely with major changes in food production practices and consumption patterns. Currently, less than 20% of Americans consume what would be considered a healthful diet, which should include multiple daily servings of vegetables and fruits along with lean protein sources. Most Americans now consume most of their daily calories from processed foods, which includes the preponderance of prepared foods purchased from restaurants or grocery stores.

Physicians are witnessing a significant change in another chronic disease that may also be related to alterations in dietary habits. Celiac disease is an immune-mediated enteropathy that manifests in some genetically susceptible individuals (HLA-DQ2 and/or HLA-DQ8) on exposure to dietary gluten: protein complexes found in wheat, rye, and barley. The prevalence rate of celiac disease in the 1950s was approximately 0.02%, and today is closer to 1% or greater. Historically, celiac disease was diagnosed in childhood; however, now diagnosis is becoming more common at nearly any age. The explanation for this dramatic increase in prevalence remains unclear. There does not appear to have been an increase in overall wheat consumption during this period of time; however, major changes to the way in which cereal grains are processed for modern foods have led some to speculate that modifications associated with processing may be responsible for the increased prevalence of celiac disease. It is certain that changes in human population genetics cannot account for the increased prevalence, because celiac disease susceptibility genes remain at stable frequencies (∼30%) within the US population.

Functional gastrointestinal disorders (FGIDs), which are defined as symptoms arising from the gastrointestinal tract without an identifiable structural or biochemical cause, represent other processes that may also be related to diet. Irritable bowel syndrome (IBS) is the most common FGID, affecting an estimated 15% of the general population in Western countries and 11% worldwide. The vast majority of afflicted individuals report at least one food trigger. Women with IBS report more food items as potential triggers for their symptoms than men. Furthermore, individuals that report more food triggers have lower quality-of-life scores and more severe IBS symptoms. An intriguing recent study by Fritscher-Ravens and colleagues demonstrated real-time mucosal changes after exposure to certain food antigens using confocal laser endomicroscopy in IBS patients. In the group of individuals that experienced mucosal changes with food antigen application, dietary elimination of this specific food antigen led to dramatic improvement or complete resolution of their IBS symptoms that was durable at 1 year of follow-up. This work strongly suggests that food is playing a major role in the cause of IBS symptoms and provides a potential method to identify specific food triggers that could allow physicians to make better dietary recommendations for their patients.

Many patients seek guidance for dietary changes they can implement in an effort to alleviate their symptoms, but often lack the knowledge or motivation to implement these recommendations. Furthermore, because of the complexity of diet and food choices, getting people to embrace and adhere to major dietary changes is difficult. As a society, we seem to have lost sight of the fact that our diet is a major determinant of our health, health expectancy, life expectancy, and overall quality of life and can be a powerful tool in preventing disease and ameliorating symptoms of disease.

A review of the literature did not produce a consensus regarding the effects of gender on the response to specific dietary interventions or dietary adherence. However, for most households within the United States, food choices are primarily dictated by women, and women with greater food knowledge are better able to appropriately implement healthful dietary interventions. Therefore, targeting women with dietary advice and nutrition-focused education has the potential to have far greater effects that could benefit the entire household.

In this article, the complex relationship of food and diet is discussed in the context of women’s health. The authors encourage the reader to simplify the dietary recommendations suggested to patients in an effort to develop consistent messages about food and diet choices and increase compliance.

Food consumption patterns

Food consumption patterns in the United States have changed dramatically over the past few decades for multiple reasons. During this time period, there have been major advancements in food-processing and preservation technologies that have allowed for longer-term storage of prepared processed foods. This, combined with more women entering the out-of-home workforce, has created an environment in which food preparation within the home has significantly declined. Within most households, women traditionally have been responsible for food procurement and preparation, a pattern that has not changed significantly despite more women entering the out-of-home workforce. As women entered the out-of-home workforce, this led to a decrease in time allotted for food preparation–related activities, and therefore, to greater demands for prepared or partially prepared processed foods that require less preparation time. With these changes, there has also been a concomitant increase in consumption of higher calorie, lower nutrient-dense foods to the detriment of the consumption of fresh vegetables and fruits.

For many people, there is a lack of understanding of the important contribution food makes to overall health. Individuals no longer view food consumption as a necessary part of a healthy lifestyle and therefore are failing to see the direct consequences of poor food choices on their health and the development of disease.

Current diet trends

The clinical definition of diet is simply the total food intake by an individual over a given time period. However, for many people, diet is defined as a short-term intervention to accomplish an objective such as weight loss. These types of diets are often associated with unsustainable or unhealthy food restrictions, which can reduce the long-term effectiveness of these interventions. For others, diet is a necessary medical therapy, such as those with celiac disease, who must commit to life-long avoidance of foods containing gluten in order to maintain health and minimize adverse outcomes from untreated disease. Some individuals consume certain diets because of a belief they represent a “healthier” way of eating, while other individuals avoid certain foods, such as meat, dairy, or eggs, due to religious restrictions or concerns for animal welfare and the environment.

Physicians encounter individuals that are interested in treating their ailments or preventing the development of disease with diet modification, yet most people in the United States do not consume a healthy diet. The reason for this contradiction is complicated. Physicians often fail to provide consistent messages about what constitutes a healthful diet, especially given the seemingly contradictory recommendations for patients with certain medical conditions. This problem is also confounded by the fact that an individual’s motivation, level of knowledge, time, and finances all vary, as do their baseline nutritional state and medical comorbidities. Here, some of the more common dietary trends are reviewed, and it is argued that for most people simplified dietary recommendations can be made both to achieve overall better health and to treat a wide range of underlying medical conditions ( Table 1 ).

Over the past few years, physicians have been recommending diets for several different conditions, such as weight loss, diabetes, cardiovascular disease, hypertension, or symptoms related to IBS. Examples include the low-carbohydrate diet for management of weight loss or diabetes, the low-fat diet for management of cardiovascular disease, the low-salt diet for management of hypertension, and the low-Fermentable Oligo-, Di-, Mono-Saccharides and Polyols (FODMAP) diet or the Mediterranean diet for management of IBS. Many physicians recommend these dietary interventions with little knowledge of what these diets entail or what burden this type of diet may place on their patients. Furthermore, when individuals are left to decipher the nuances of these particular diets themselves, they often become confused and frustrated with the conflicting information available to them.

For many physicians, time is also a factor in counseling patients regarding healthful food choices. The physician often refers the patient to nutritionists or dieticians and has little knowledge of the quality or validity of their recommendations or follow-up care. In this article, it is argued that simplification of nutritional recommendations will make physician counseling easier, less time-consuming, and less cumbersome for patients to implement.

In the following paragraphs, some of the more common diets that are encountered in clinical practice are reviewed. The basic nutritional principles that form the foundation of these diets are discussed, and some common pitfalls associated with them are described, providing the reader with the information required to educate their patients, empowering them to make healthful food choices.

Low-carbohydrate diet

The basic principle of the low-carbohydrate diet is to restrict the total daily calories from carbohydrate intake. The Institute of Medicine, Dietary Reference Index defines the consumption of between 45% and 65% of total daily calories from carbohydrates as normal. Therefore, less than 45% of daily calories from carbohydrates can be considered a low-carbohydrate diet. When coupled with overall calorie restriction, these diets typically result in weight loss and beneficial metabolic changes. However, some often interpret the focus of this diet solely on the carbohydrate restriction, without calorie restriction, and end up replacing the calorie reduction achieved from carbohydrate restriction with those from fat or protein consumption, which in turn can reduce or negate the positive health effects of this dietary intervention. The major pitfall of this diet is that, without concomitant calorie restriction, the health benefits of carbohydrate restriction are lost. Another pitfall of this diet is that it does not differentiate between carbohydrates from vegetables, fruits, and whole grains with those from processed foods, which have been shown to have differing effects on cardiometabolic parameters.

Low-fat diet

The basic principle of the low-fat diet is the restriction of total daily calories from fat intake. The Daily Reference Intakes from the Institutes of Medicine recommends that 20% to 35% of total daily calories should be from fat. Therefore, a low-fat diet would constitute a diet of less than 20% of total calories. Fats from the diet are a necessary energy source and aid in the absorption of fat-soluble food components, such as vitamins, A, D, E, and K. A diet too low in fat can lead to fat-soluble vitamin and other micronutrient deficiencies. The intention of this diet is to reduce total daily calorie consumption from fat and replace those calories with the consumption of vegetables, fruits, and lean protein sources, while also implementing overall daily calorie restriction. However, the major pitfall of this diet is that the calories avoided by fat consumption are often replaced by consumption of refined sugars and processed foods.

Low-Fermentable Oligo-, Di-, Mono-Saccharides and Polyols diet

The low-FODMAP diet aims to limit foods containing Fermentable Oligo-, Di-, and Mono-saccharides And Polyols in an effort to treat IBS. Saccharides are simply sugars and can be either naturally occurring in food (intrinsic) or added during food processing or preparation (extrinsic). Glucose and fructose are examples of monosaccharides. Sucrose and lactose are examples of disaccharides. Sucrose comprises the monosaccharides, glucose and fructose, and when extracted and refined from cane, becomes common table sugar. Lactose comprises the monosaccharides, galactose and glucose, and is found primarily in mammalian milk sources. Lactose is broken down to its constituent monosaccharides by intestinal lactase. The persistence of intestinal lactase production into adulthood dates back approximately 4000 years to our European ancestors and correlates with increased consumption of dairy products into adulthood. The terms, fructans, galactans, and inulins, refer to differing length oligosaccharides. Polyols are sugar alcohols, such as sorbitol and mannitol, intrinsic to fruits, such as apples, pears, and nectarines, and vegetables, such as cauliflower and mushrooms. Polyols can also be extrinsically added to processed foods as low-calorie sweeteners.

In several studies, the low-FODMAP diet has demonstrated significant improvement in the symptomatic treatment of IBS patients. However, long-term adherence to a strict low-FODMAP diet is not recommended. The diet is complicated and can severely restrict food choices, especially when combined with other restrictive diets, such as a gluten-free diet. The goal of the low-FODMAP diet is to adhere to the diet in an effort to reduce symptoms. In individuals that respond to the strict low-FODMAP diet, a stepwise reintroduction of certain foods is undertaken, in an effort to identify their particular food triggers. Only the foods associated with trigger symptoms will need to be avoided long term. This diet typically requires the oversight from a nutritionist familiar with the diet and its nuances. In addition, a recent small study evaluating the efficacy of dietary FODMAP restriction against standard dietary advice demonstrated similar rates of symptom reduction without the complexities of the low-FODMAP diet.