Chapter 1 - Nutrition: Linking Food and Health

What are food, nutrition, and the main areas studied in nutrition?

Food refers to the plants and animals we consume and provides chemical compounds that maintain and support health. Nutrition is the science that studies food, including how food influences health and how food nourishes the body. Nutrition studies food consumption, digestion, absorption, storage, factors influencing eating patterns, recommended amounts of types of food, food safety, and the global food supply.

How did nutrition develop as a science, and how did its focus change over time?

Nutrition is a relatively new discipline of science. Over the last 400 years, early research linked dietary deficiencies with illnesses and focused on identifying and preventing deficiency diseases. After World War II, the American diet improved. Modern nutrition research focuses on supporting health and preventing and/or treating chronic diseases. Nutrition research has answered many questions but also raised many new ones.

What are scurvy and pellagra, and what do they illustrate about nutrition?

Scurvy causes hemorrhaging of tissues and often bleeding gums. It was common in sailors because of a lack of citrus fruits; frequent consumption can prevent it. It was discovered in the mid 1700s and is caused by lack of vitamin C. Pellagra causes skin rash, diarrhea, and mental impairment; its four Ds are dermatitis, diarrhea, dementia, and eventually death. In the early 20th century it afflicted more than 50,000 people each year and 10% of cases resulted in death. It was originally thought to be infectious, but was effectively treated by changing from a corn-based diet to a nutritious diet and is caused by vitamin B deficiency involving niacin.

How does nutrition contribute to chronic disease prevention and overall health?

Chronic diseases come on slowly and last a long time despite treatment. Nutrition research has particular interest in obesity, cardiovascular disease, type 2 diabetes, and various cancers. Nutrition guidelines and an abundant food supply have almost completely wiped out nutritional deficiency diseases in developed countries, but poor nutrition can subtly influence osteoporosis and progression of some cancers. Heart disease, stroke, and diabetes are among the top ten causes of death in the United States. Good nutrition strengthens the immune system, and gut health can influence mental health. Common goals of a healthy diet are to prevent deficiency diseases and lower the risks of chronic disease. Other health factors include increasing physical activity, reducing toxin exposure, adequate sleep, and proper stress management.

What is wellness, and how does nutrition fit into it?

Wellness is a multidimensional, active process by which people make choices to enhance their lives. It includes physical, emotional, social, occupational, and spiritual health. Nutrition and physical activity are components of wellness.

What is Healthy People 2020, and what are its goals?

Healthy People is a health-promotion initiative revised every decade that identifies goals and objectives to reach. Its goals are to attain high-quality, longer lives free of preventable disease, disability, injury, and premature death; achieve health equity, eliminate disparities, and improve the health of all groups; create social and physical environments that promote good health for all; and promote quality of life, healthy development, and healthy behaviors across all life stages.

What are nutrients and the six essential nutrient classes?

Nutrients are chemicals in foods that are critical to human growth and function. The six essential nutrient groups are carbohydrates, fats/oils, proteins, vitamins, minerals, and water.

What are macronutrients and micronutrients, and how do they differ?

Macronutrients are nutrients required in relatively large amounts: carbohydrates, fats, and proteins. They provide energy/calories. Micronutrients are nutrients required in smaller amounts: vitamins and minerals. Neither vitamins nor minerals yields energy.

What is a kilocalorie, and why are individual energy needs different?

A kilocalorie (kcal) is the amount of energy required to raise the temperature of 1 kg of water by 1°C. On food labels, “Calorie” refers to kilocalories. Bodies are uncontrolled environments, so how people use calories and their energy needs are unique to individuals.

What are carbohydrates, and what are their major characteristics?

Carbohydrates are organic compounds and the primary source of fuel for the body, especially the brain. They provide 4 kcal per gram and contain carbon, hydrogen, and oxygen. They are found in grains, vegetables, fruits, legumes, dairy, nuts, and seeds.

What are fats, and what are their major characteristics?

Fats are organic compounds composed of lipids, molecules insoluble in water. They provide energy for the body when at rest or during low-intensity exercise and provide 9 kcal per gram. They contain carbon, hydrogen, and oxygen (fatty acids). Having less oxygen and water than carbohydrates allows fats to pack more tightly and yield almost twice the energy of carbohydrates and proteins. Sources include butter, margarine, and vegetable oils such as canola, olive, and sunflower oil. Adipose tissue is stored fat that can be broken down for energy.

What are proteins, and what are their major characteristics and functions?

Proteins are organic compounds that are chains of amino acids. Dietary proteins are broken down into amino acids and reassembled to build body proteins. Protein can supply energy per gram but is not usually a primary energy source. Proteins contain carbon, hydrogen, oxygen, and nitrogen; nitrogen sets them apart from carbohydrates and fats. Proteins are found in muscles and blood and are involved in building new cells and tissues, maintaining bone structure and strength, repairing damaged tissues, regulating metabolism, assisting in the breakdown of foods, and fluid balance. It is important to get energy from carbohydrates and fats so protein can perform these functions.

What are vitamins, and what are their roles and categories?

Vitamins are organic molecules that assist in regulating body processes such as energy metabolism. They are classified by how they are absorbed, transported, and stored: fat-soluble and water-soluble. Both are essential for health and found in a variety of foods. Vitamins assist in releasing macronutrients, building and maintaining bone, muscles, and blood, and supporting immune function and vision. They do not contain energy or kilocalories; they assist in using and releasing energy from other sources.

How do fat-soluble and water-soluble vitamins differ?

Fat-soluble vitamins are A, D, E, and K. They are soluble in fat, require fat for absorption, and are stored in the body, so excess amounts can accumulate and cause toxicity. Water-soluble vitamins are vitamin C and the B vitamins: thiamin, riboflavin, niacin, vitamin B6, vitamin B12, pantothenic acid, biotin, and folate. They are soluble in water, are not stored to any extent, and excess is excreted in urine; toxicity generally occurs as a result of supplementation.

What are minerals, and how are they classified?

Minerals are inorganic substances required for body processes. They do not contain carbon and hydrogen or other substances; they are single elements. Examples include sodium, calcium, iron, potassium, and magnesium. They have functions including fluid regulation and energy production, are essential to bones and blood, and help eliminate harmful by-products of metabolism. Minerals cannot be destroyed by heat or light and remain in the same form. They are classified by the amount needed in the diet and how much is found in the body.

What distinguishes major minerals from trace minerals?

Major minerals include calcium, phosphorus, sodium, potassium, chloride, magnesium, and sulfur. They are needed in amounts greater than 100 mg/day and are present in the body in amounts greater than 5 g (5,000 mg). Trace minerals are needed in amounts less than 100 mg/day and are present in the body in amounts less than 5 g (5,000 mg).

What is water's role as an essential nutrient?

Water is an inorganic nutrient vital for health and survival. It is involved in fluid balance inside and outside cells, nutrient transport, nerve impulses, removal of wastes, muscle contractions, and body temperature.

How do you calculate calories from macronutrients and alcohol?

Multiply grams by kcal per gram: carbohydrates = 4 kcal/g, protein = 4 kcal/g, fat = 9 kcal/g, and alcohol = 7 kcal/g. In the chapter example, 10 g carbohydrate = 40 kcal, 5 g protein = 20 kcal, 5 g fat = 45 kcal, and 14 g alcohol = 98 kcal, for a total of 203 kcal. The example gives approximately 20% from carbohydrate, 10% from protein, 22% from fat, and 48% from alcohol, totaling 100%.

What are functional foods, probiotics, prebiotics, and phytochemicals?

Functional foods have biologically active ingredients that provide health benefits beyond basic nutrition. Probiotics contain live microorganisms that improve intestinal microbial balance. Prebiotics are non-digestible food ingredients that stimulate the growth and/or activity of probiotic bacteria. Phytochemicals are naturally occurring plant compounds believed to have health-promoting effects in humans.

What is the human microbiome and why is it important?

The human microbiome is the set of genes belonging to microorganisms that inhabit the human body. Health is affected by how these microorganisms interact with human cells and genes required for digestion. GI flora are helpful bacteria in the gastrointestinal (GI) tract.

What are Dietary Reference Intakes (DRIs), and what do they address?

DRIs identify the amount of a nutrient needed to prevent deficiency disease in healthy people in a particular life stage and gender group, an amount that may reduce the risk of chronic disease, and the upper level of safety for nutrient intake. For most nutrients, the four values are Estimated Average Requirement (EAR), Recommended Dietary Allowance (RDA), Adequate Intake (AI), and Tolerable Upper Intake Level (UL). Together they identify quantities needed to optimize health, prevent deficiency diseases, and avoid consuming too much of a nutrient.

What are EAR, RDA, AI, and UL, and how do they differ?

EAR is the average daily intake level that meets the needs of half of healthy people in a particular life stage and gender group and is used to determine the RDA. RDA is the average daily intake level required to meet the needs of 97–98% of healthy people in a particular life stage and gender group. AI is a recommended average daily intake level assumed to be adequate, used when an RDA is not established, and based on observations and estimates from experiments; examples include vitamin D, vitamin K, fluoride, and chromium. UL is the highest average daily intake level not likely to have adverse effects on the health of most people; intake above the UL is not considered safe.

Which DRIs apply to energy and macronutrients, and what do they mean?

The two DRIs specifically related to energy and macronutrients are Estimated Energy Requirement (EER) and Acceptable Macronutrient Distribution Range (AMDR). EER is the average dietary energy intake to maintain energy balance and is based on age, gender, weight, height, and physical activity. AMDR is the range of energy intake from carbohydrate, fat, and protein associated with reduced risk of chronic disease and the range of macronutrient intake that provides adequate essential nutrients.

What are the AMDR ranges for carbohydrates, protein, and lipids?

Carbohydrates: 45% to 65% of total calories. Proteins: 10% to 35% of calories. Lipids: 20% to 35% of calories.

What is the Mifflin St Jeor equation?

For women: 10 × weight (kg) + 6.25 × height (cm) – 5 × age (y) – 161. For men: 10 × weight (kg) + 6.25 × height (cm) – 5 × age (y) + 5.

What are the steps of the scientific method in nutrition research?

1) Observe and describe a phenomenon. 2) Propose a hypothesis, or educated guess, explaining why it occurs. 3) Develop an experimental design to test the hypothesis. 4) Collect and analyze data to support or reject the hypothesis. 5) If data do not support the original hypothesis, propose and test an alternative hypothesis. 6) If data support the original hypothesis, draw a conclusion. 7) Make the experiment repeatable so other researchers can obtain similar results. 8) Propose a theory based on repeated experiments that repeatedly support the hypothesis.

What is the difference between a hypothesis, conclusion, and theory?

A hypothesis is an educated guess proposed to explain why a phenomenon occurs. A conclusion is drawn when the data support the original hypothesis. A theory is a conclusion drawn from repeated experiments that have supported the hypothesis time and time again, offering an explanation for why a phenomenon occurs. Theories can still be challenged as scientific knowledge evolves.

What are animal studies, and what are their main purpose and drawbacks?

Animal studies conduct preliminary research that assists in designing human studies. Their drawbacks include ethical concerns and the possibility that results may not apply to humans.

What are epidemiological, observational, and case-control studies?

Epidemiological studies report disease prevalence and incidence and use large populations. Observational studies determine relationships between factors that may influence a phenomenon and examine patterns of health and disease, but do not suggest cause and effect. Case-control studies are more complex; they compare a group with a condition to a similar group without the condition and identify factors that differ between the groups besides the condition.

What are clinical trials, and what are randomization, blinding, and placebo?

Clinical trials test an intervention's effect on a disease or health condition using an experimental group and a control group. They can use randomized trials and single- or double-blind experiments. A placebo is an imitation treatment that has no effect, given to the control group in placebo-controlled double-blind randomized clinical trials.

How should Dr. Rivas's vitamin Z study be classified?

It is a single-blind randomized clinical trial with a placebo control. Students are randomly assigned by drawing names from a hat. The experimental group receives vitamin Z, while the control group receives an identical-looking and tasting sugar pill. Dr. Rivas knows which participants receive each treatment, but the participants do not.

How can you evaluate the scientific validity of a nutrition-related claim?

Ask who is reporting the information and what their credentials are; who conducted the research and who paid for it; whether there is a conflict of interest; whether the report is based on reputable research; whether there were control and experimental groups; whether the sample size was large enough to rule out chance variation; whether a placebo was effectively administered; whether the study was double-blind; whether the report relies on testimonials; and whether the claims are too good to be true.

How can you determine whether a nutrition website is reliable?

Look at the website sponsors' credentials, whether the website date is recent, and the Internet address (.gov, .edu, and .org are generally considered reliable). Check whether the highlighted message is consistent with other credible sources, whether it contradicts common knowledge, and whether it includes conspiracy theories designed to breed distrust.

Whom can you trust for nutrition information?

Trustworthy experts are educated and credentialed, including Registered Dietitians (RDs), Licensed Dietitian Nutritionists, nutritionists with credentials and experience, professionals with advanced nutrition degrees (MS, MA, or PhD), and physicians with appropriate nutrition expertise. Government agencies are usually trustworthy. Professional organizations publish cutting-edge nutrition research and information.

Which government agencies and professional organizations are listed as trustworthy nutrition sources?

The CDC supports two large national surveys: the National Health and Nutrition Examination Survey (NHANES) and the Behavioral Risk Factor Surveillance System (BRFSS). The NIH focuses on research areas including cancer; heart, lung, and blood diseases; diabetes; and alternative medicine. Professional organizations listed are the Academy of Nutrition and Dietetics (AND), American Society for Nutrition (ASN), American College of Sports Medicine (ACSM), and The Obesity Society (TOS).