Ch 1 - The Science and Scope of Nutrition

Nutrients

- A nutrient is a chemical substance that is required for growth and to maintain proper body functioning. - The body can produce many of its own nutrients, but other essential nutrients (such as vitamins) must be supplied through what we eat and drink because the body cannot produce them or enough of them on its own.

Where do most people obtain nutrition information?

- According to the Academy of Nutrition and Dietetics, most people obtain nutrition information from the Internet, from television, or from magazines. - The most trustworthy sources provide evidence that stems from multiple peer-reviewed publications and has the support of a group of experts in the field, described sometimes as "scientific consensus." - Be wary of ".com" websites (which might be selling a product related to the nutrition "advice"), and turn mostly to sites that are managed or reviewed by qualified health professionals

Robert Waterland and the Nutrition Research Study on Pregnant Mice

- After working in Stunkard's lab, Waterland entered graduate school to continue studying the multigenerational effects of nutrition. - During that time, another study on the subject was published that deepened his interest even further. - This study showed that the diet of pregnant mice appeared to affect the coat colors of their young. - Normally, when this strain of mice gives birth, the litter contains babies with coats in a range of colors—some yellow, some brown, and all shades in between. - The babies with yellow fur were more likely to eventually become obese and develop diseases, such as cancer, than their brown brothers and sisters. - But when scientists fed pregnant mice supplements that contained a mix of folic acid, vitamin B12, and other nutrients, mothers gave birth to fewer babies with yellow fur. - "That caught my attention," recalls Waterland. - To him, this study result was even more compelling evidence that what mothers eat during pregnancy can have lifelong effects on their children. - And interestingly, recent studies find that what fathers eat prior to conception can also have lifelong effects on their children.

The Influence of Waterland's Experiment

- Although Waterland is quick to emphasize that the results of his experiment only apply to mice, it is now clear that epigenetic modifications are critical factors affecting the development of many human diseases. - The mouse coat color experiment, along with the Dutch famine research, have "absolutely affected the way we think about nutrition," says Patrick Stover, PhD, director of the division of nutritional sciences at Cornell University. - "Some people seem to eat whatever they want and never gain weight. This has always been the case in nutrition—people sometimes respond differently to the same foods. That cliché—we are what we eat—has never really applied," says Stover. - "We are just now beginning to understand how genetic differences among individuals are shaped by historical exposures, including food."

America's Nutrition Shortfall

- Although the U.S. food supply is abundant, we are experiencing major shortfalls in certain essential nutrients and excesses in others. - Approximately half of Americans don't get enough of the mineral magnesium, another 40% have low vitamin A intake, and another 35% are not getting enough vitamin C. Approximately 75% of Americans fail to consume enough fruit, and 85% or more people consume inadequate amounts of red, orange, and deep-green vegetables, and legumes. - Snacks provide one-quarter of all daily calories, and many snack foods are high in empty calories (calories with few nutrients)—namely, solid fats (butter, shortening, fat in meat), added sugars (syrups and other caloric sweeteners), and refined starches. - For adults and children older than two years, nutrition surveys reveal that approximately 85% of Americans significantly exceed recommended limits for these empty calorie foods. - Desserts and sweet snacks (such as cake, cookies, candy, and ice cream) account for the second-highest source of total calorie consumption among all food group subcategories.

Hypothesis in Waterland Experiment

- Based on the previous findings, Waterland hypothesized that supplementing the diet in pregnant mice affected an epigenetic mechanism called DNA methylation at the agouti gene, which controls coat color, so his hypothesis maintained that supplementing the diet of pregnant mice with specific nutrients would increase the frequency of DNA methylation at agouti and therefore of the healthier brown-coated offspring. (Waterland and others have found that the high intake of the nutrients used in this study can also have additional affects that are potentially harmful.)

Tolerable Upper Intake Levels (ULs)

- Because store shelves are overflowing with food and supplements that supply extra amounts of nutrients, the DRI also sets safe limits of nutrients with its set of values known as Tolerable Upper Intake Levels (ULs). - These represent the highest amount of a specific nutrient that most people can consume daily without causing any harm. - As research evolves, existing DRI values are modified, and new ones for additional nutrients are created. - DRI values have been set for macronutrients, micronutrients, and water

Robert Waterland and the Infant Nutrition Research Study

- During his time in Stunkard's lab, Waterland helped set up a research study of infants born to mothers who were either of healthy weight or obese. - The mothers brought their babies into the laboratory, where Waterland and his team spent the day measuring how much food the babies consumed, checking their body composition, and even observing how they ate—their sucking style while breastfeeding or bottle feeding, for instance. - The purpose, he says, was to see if any of these variables measured in infancy would predict a baby's likelihood of becoming obese later in life.

Results of the Waterland Experiment

- He repeated the mouse experiment, feeding some pregnant mice a supplemented diet, and obtained the same results. - Mothers who ate the extra nutrients had more babies with brown fur, which previous research had found were at lower risk of obesity and other diseases than those mice with yellow fur. - After performing analyses of DNA methylation, he found that these epigenetic changes completely explained the effect of diet on coat color. - "When I first saw those results that was when I felt just, 'Wow, we really have something here.'" - As a final step in the scientific method, Waterland published his findings in a scientific journal. - His findings became another core source of evidence supporting the effect of food on genes—a field known as nutritional genomics, or nutrigenomics.

Observation in Waterland Experiment

- He started with an observation and then identified a question or problem to investigate further. - In his case, the observation that diet in pregnancy changed mouse babies' coat color and overall health led him to wonder how that occurred. - So he talked to his boss at the time, Randy Jirtle at Duke University in North Carolina, and said he wanted to repeat the mouse study and try to understand the mechanism by which a mother's nutrition before and during pregnancy could change the coat color of her offspring.

The "Healthy People" Initiative

- Healthy People 2020, a government-sponsored initiative, identifies measurable health improvement objectives and goals for Americans. - Every decade the Healthy People initiative develops a new set of science-based, 10-year national objectives with the goal of improving the health of all Americans. - The nutrition-related objectives recommend that we should consume a variety of nutrient-dense foods within and across different food groups, emphasizing whole grains, fruits, vegetables, low-fat dairy products, and lean meats and other sources of protein. - Americans should eat only as many calories as they need and limit their intake of saturated fats, trans fats, cholesterol, added sugars, sodium (salt), and alcohol.

Placebos in Experiments

- In other studies, such as those that look at the effect of medications, people in the control group receive a placebo drug, a substance that contains no active properties. - The purpose of the placebo is to eliminate the placebo effect, a psychological phenomenon in which people feel better after receiving a treatment simply because they have an expectation that they will feel better, not necessarily because the treatment worked. - Therefore, their account of the actual effectiveness or ineffectiveness of a treatment is unreliable. - To eliminate the placebo effect, it is critical that people do not know whether they are receiving the active treatment or the non-active placebo—in other words, they are blind to what they are receiving. - By comparing people receiving a treatment with the possibility of effect with those taking a placebo that has no possibility of effect, researchers can determine whether the treatment is actually effective, outside of people's expectations. - Often, placebos are a key element of randomized controlled trials (RCTs), which rigorously compare experimental interventions (such as a treatment) with controls (such as no treatment or administration of a placebo), and randomly assign people to each category to offset any potential bias. - In addition to RCTs, epidemiological and animal studies also help us explore and evaluate the role of diet and dietary components in health and disease.

Other than RDNs, who else is a reliable source for credible nutrition information?

- Individuals who may not be RDNs but possess an advanced degree in nutrition, nutritional biochemistry, or other related disciplines from accredited universities can also be reliable sources of nutrition information. - These individuals may work in universities as faculty (often teaching the courses that future RDNs take), government agencies, or research institutions, and they carry out the research that informs our understanding of the impact of nutrition on health and disease

Role of Nutrients in Homeostasis

- Nutrients play a critical role in maintaining homeostasis, the process by which the body maintains a stable internal environment in the face of external variability. - For instance, nutrients in the foods we eat participate in processes that regulate the balance of fluids in the body, our pH, and our body temperature. - As long as cells get the nutrients they require, all is well; when cells receive either inadequate or excess nutrients, however, problems arise.

National Health and Nutrition Examination Survey (NHANES)

- Over the years, the U.S. government has monitored the health of Americans through the National Health and Nutrition Examination Survey (NHANES), a program that collects data from individuals about their food and nutrient consumption and conducts physical examinations

Chronic Disease and Overconsumption

- Overconsumption is often associated with chronic disease of slow progression, such as heart disease and type 2 diabetes. - Chronic diseases are now, by far, the leading causes of mortality worldwide, and diet plays a specific role in the risk, progression, and treatment of nearly every chronic disease. - In addition to providing many calories, the highly processed foods common in our "Westernized" diet are generally low in nutrients such as fiber, potassium, calcium, and vitamin D that reduce the risk of chronic diseases.

How do DRI values vary?

- The DRI values vary depending on the specific nutritional needs of different groups of people—children, adults, men, women, the elderly, and women who are pregnant or nursing. - It is this last group that is often most concerned with getting all of the nutrition they need.

Dietary Reference Intakes (DRIs)

- The Health and Medicine Division issues Dietary Reference Intake (DRI) values, which are quantitative estimates of nutrient intakes to be used to plan and assess diets for healthy people. - These values not only help us avoid nutrient deficiency but also are intended to help individuals optimize their health, prevent disease, and avoid consuming too much of any one nutrient.

Epigenetics

- The fascinating area of study that looks at the cross-generational effects of exposure to nutrients, toxins, and behaviors is called epigenetics. - Waterland was interested in epigenetics; he simply had to understand more about why a mother's diet during pregnancy could affect the future health of her children

Genetics

- The field of genetics describes how genes encoded in DNA are passed on between generations (from parents to child), but sometimes the DNA in our genes can become modified after it's inherited, which can change traits in the current generation (as well as in subsequent ones). - This explains why identical twins—who have the exact same genes—actually have slight differences in their appearance and risk of disease.

Waterland on the American Nutrition Crisis

- These nationwide data are very concerning to nutrition scientists, including Waterland, now an associate professor at the USDA/ARS Children's Nutrition Research Center at Baylor College of Medicine. - Although Waterland studies how a mother's nutrition before and during pregnancy affects the lifelong health of her child, he urges us to eat in a way that promotes our own health and well-being. - Waterland explains: "The more variety of things you eat, the better, because there's still so much that we don't understand about nutrition. The safest bet is to eat a wide variety of foods, so you're exposing your body to all the potential benefits. Not just the epigenetic benefits, but others that we know about, and still others we haven't discovered yet."

Recommended Dietary Allowances (RDA)

- To create the RDA for a nutrient, a safety margin is added to the EAR so that the RDA represents the average daily amount of a particular nutrient that meets or exceeds the requirements of nearly all (97-98%) healthy individuals. - It is important to recognize that we do not need to meet the RDAs each day and that it is normal for our nutrient intake to be highly variable from one day to the next. - Consuming an adequate, balanced, and varied diet each day will allow our average daily intake to meet the RDAs over the course of several days. - During brief periods of inadequate intake, our bodies will tap into nutrient stores to meet immediate needs. - In some cases, we will respond to longer periods of low nutrient intake by increasing nutrient absorption and/or decreasing their excretion to help maintain an adequate supply of essential nutrients. - When there is insufficient evidence to generate an EAR for a nutrient, the RDA for that nutrient cannot be set and the committee establishes yet another set of values: the Adequate Intake (AI) value.

Estimated Average Requirements (EARs)

- Used to capture the average amount of a nutrient needed by people, grouped by sex and age, in general. - As such, this is an intake that meets the nutritional requirements of 50% of individuals within a group. - Therefore, EARs are not recommendations for individuals, as half of the population would be eating less than they need at this level of intake. - Rather, the EARs are used to assess the nutrient adequacy of populations and are the first step in setting another set of values, the Recommended Dietary Allowances (RDA).

What groups were involved in Waterland's study?

- Waterland's study contained many of the important elements of the scientific process. - It had a control group, a group of pregnant mice that received a healthy diet that did not contain any extra supplementation. - Waterland then compared the results from the control group with those from mice in the experimental or treatment group, which received the supplemented diet, and he determined that the supplemented diet did produce important epigenetic changes.

Calories on Food Labels

- When we see calories listed on food labels, these are actually kilocalories (kcal) that reference the amount of energy in food. - A kilocalorie is equal to 1000 calories. - By convention, when Calorie is spelled with a capital C, it also refers to a kilocalorie.

Macronutrients

- we need in relatively large quantities to stay healthy—these are carbohydrates, proteins, lipids (fats, a common term for triglycerides, are a subclass of the diverse group of compounds called lipids), and water. - With the exception of water, macronutrients primarily supply energy and/or a large portion of the structural components in our body.

The 4 DRI values

Recommended Daily Allowances (RDA) Adequate Intakes (AI) Tolerable upper intake levels (UL) Estimated average requirements (EAR)

How are macronutrients, micronutrients, and Phytochemicals extracted from food?

Through the process of digestion and then absorbed and used by the body.

Obesity

a condition characterized by excess body fat and often associated with other health problems, is a classic example of overnutrition. - It's a relatively new public health concern. - Historically, nutrition policy and research focused on making sure people had enough to eat so that they could meet their nutrient and energy needs. - But over the past few decades, policymakers have focused more on the role of diet and nutrition in diseases caused by overconsumption—primarily too many calories along with too much solid fat (such as animal fats), sugar, and sodium.

malnutrition

a state of inadequate or unbalanced nutrition. - Both undernutrition and overnutrition are forms of malnutrition ** Sometimes undernutrition does not stem from a lack of food overall, but from a lack of specific essential nutrients, known as nutrient deficiency.

Nutrition

an interdisciplinary science that studies factors that affect our food choices, the chemical and physiological processes involved in processing and delivering the chemical components of those foods to cells throughout our body, and ultimately how those chemicals affect our health every day.

Phytochemicals

are chemicals in plants that are beneficial to human health. - Commonly found in vegetables, fruits, and whole grains, these compounds—which number in the thousands—give plants key properties such as color, aroma, and flavor. - The phytochemical lycopene, for example, gives tomatoes and watermelon their red color and may reduce the risk of cancer in humans. - Some phytochemicals promote health because they have hormonelike actions or they repair or prevent damage to cells. - Anthocyanins, for instance, are phytochemicals that give berries their blue or purple color and act as antioxidants.

Micronutrients

are needed in much smaller amounts—these are vitamins and minerals. - Micronutrients do not supply energy or calories but even in tiny amounts are crucial to normal growth and development

Adequate Intake (AI)

based on research or observations of the amount of the nutrient healthy individuals typically consume. F - or example, the B vitamin called folate has an established RDA, but the recommended intake for biotin, another B vitamin, is currently provided as an AI.

6 classes of nutrients

carbohydrates, fats, proteins, vitamins, minerals, water - All six classes of nutrients regulate numerous body processes, and most supply the building blocks of key body structures such as cell membranes, muscles, and bones. - They are required for normal growth, development, reproduction, maintenance, repair of cells, and other vital body processes.

Estimated Energy Requirement (EER)

is similar to the EAR in that it represents the average amount of calories a healthy person of a particular age, sex, weight, height, and level of physical activity needs in order to maintain his or her weight. - This value meets the energy requirements of 50% of the population and actually exceeds the needs of nearly 50% of individuals.

2 Major Categories of Nutrients

macronutrients and micronutrients

Acceptable Macronutrient Distribution Ranges (AMDRs)

provide a healthy range of intakes for carbohydrates, protein, and total fat (as well as some specific types of fat) expressed as a percentage of total calories. - Adults can obtain adequate amounts of macronutrients when their carbohydrate intake falls between 45% and 65% of total calories, their protein intake falls between 10% and 35% of total calories, and their fat intake is within 20% and 35% of total calories. - Individuals who regularly eat below or above these ranges put themselves at risk of getting too few essential nutrients or of developing chronic diseases.

Registered Dietitian Nutritionist (RDN)

relies on the research and recommendations of scientists in nutrition, biochemistry, medicine, and the behavioral sciences to provide scientifically valid nutrition information and guidance to individuals and groups. - Most RDNs work in hospitals and other health care facilities, perform research, have private practices, or have jobs in public health to help prevent and treat disease. - They belong to the Academy of Nutrition and Dietetics, the professional organization of Registered Dietitian Nutritionists