Nutrition Basics and Scientific Method

Overview of Nutrition

This section is an overview of nutrition, focusing on food and dietary selection. At the end of this section, you will be able to discuss food in the nutrients contained therein, identify six classes of essential nutrients, and explain the link between nutrient density and health.

What is Food?

• Food is defined as a plant or animal product that is ingested, digested, and absorbed by the body.

• According to Merriam Webster, food consists essentially of protein, carbohydrates, and fat, used to sustain growth, repair, and furnish energy.

Nutrients

• All foods contain nutrients, which are substances that provide energy and support structure, regulation of bodily processes like metabolism.

• Essential Nutrients: There are six essential nutrients divided into two groups:

  • Macronutrients (energy-yielding): carbohydrates, proteins, and fats.

  • Micronutrients (not energy-yielding): vitamins and minerals.

  • Water is also considered a macronutrient, although it doesn't provide energy, it is a medium for chemical reactions.

Nutrient Density

• Nutrient density is a measure of the nutrients provided by food relative to its caloric content.

• Healthy diets emphasize foods with high nutrient density to reduce chronic disease risks.

• Example: Low-fat milk vs. sweetened iced tea - low-fat milk has more nutrients per calorie.

Studies on Nutrient Density

1. A study showed liver is highly nutrient-dense compared to eggs and refined grains.

2. Nutrient-dense diets are associated with reduced risks of type 2 diabetes, cancer, and cardiovascular disease (from studies like the Healthy Eating Index, DASH diet).

Nutrient Sources

• Nutrients can be obtained from:

  • Fortified Foods: Foods with added nutrients to eliminate deficiencies (e.g., vitamin D in milk).

  • Phytochemicals and Zoo Chemicals: Compounds in plants (e.g., polyphenols) and animals that provide health benefits beyond essential nutrients.

• Examples of functional foods include oatmeal, nuts, and salmon, which have benefits beyond their nutrient content.

Supplements

• Supplements can fill nutrient gaps but do not provide all the benefits of whole foods.

• It's better to prioritize whole food intake for optimal nutrient profiles and phytochemical benefits.

Food Selection Factors

• Food choices are influenced by biological drives (hunger, hormones) and personal preference (cultural, social factors).

• Health considerations can also guide food selection to prevent diseases like diabetes or heart disease.

Essential Nutrients Overview

• Classes of Essential Nutrients

  1. Macronutrients: Carbohydrates, proteins, fats

  2. Micronutrients: Vitamins, minerals

  3. Water: Does not provide energy but is vital for health

• Importance of Essential Nutrients

  • Required for optimal health and well-being

  • Cannot make sufficient amounts of many nutrients (e.g., certain amino acids)

Functions of Nutrients

• Energy Production:

  • Macronutrients provide energy (calories)

  • Breakdown of nutrients releases energy

• Structural Role:

  • Carbohydrates, proteins, and minerals build muscles, tendons, and bones

• Regulatory Functions:

  • Water regulates blood pressure, body temperature

  • Micronutrients regulate metabolic processes

Nutritional Composition

• Body Composition:

  • ~62% water

  • ~16% protein (structural proteins)

  • ~16% fat (cell membranes)

  • ~6% other compounds (minerals, carbohydrates)

• Macronutrient Needs:

  • Macronutrients needed in large quantities (measured in grams)

  • Micronutrients needed in smaller quantities (measured in milligrams or micrograms)

Nutritional Quality

• Organic vs. Inorganic:

  • Organic: Contains carbon (carbs, proteins, fats)

  • Inorganic: Does not contain carbon (e.g., minerals, water)

• Caloric Density:

  • Macronutrients have distinct caloric values:

    • Carbs & Proteins: 4 calories/gram

    • Lipids: 9 calories/gram

Malnutrition

• Definition:

  • Condition caused by excess or deficient nutrient intake

• Consequences:

  • Increased risks of chronic diseases (cardiovascular, diabetes, etc.)

Genetic Influences on Nutrition

• Diet-Gene Interactions:

  • Genetic factors influence nutrient needs and health outcomes

  • Food intake can change gene expression

Guidelines for Healthy Eating

• Key Concepts:

  • Variety: Consume from all food groups and diverse foods

  • Balance: Combine healthy and less healthy choices

  • Moderation: Control portions and avoid excess

• Focus on Nutrient-Dense Foods:

  • Fruits, vegetables, whole grains for health and chronic disease risk reduction

  • Limit refined sugars, sodium, saturated fat, and trans fat.

• Hydration:

  • Importance of adequate water intake for physiological functions

Scientific Method in Nutrition Research

Learning Objectives

• Explain the process of the scientific method.

• Define good vs. bad components and types of scientific studies.

• Identify the difference between scientific publications and media stories.

Evolution of Nutrition Science

• Nutrition science is constantly evolving based on new information, technology, and scientific measurements.

• The use of butter vs. margarine illustrates how scientific findings change over time (e.g., the discovery of trans fatty acids in margarine).

• The scientific method is vital for developing nutrient recommendations, understanding nutrient functions, and promoting health.

Key Steps of the Scientific Method

1. Observation: Notice a phenomenon in nature.

2. Question: Formulate a question based on the observation.

3. Hypothesis: Develop a testable hypothesis.

4. Experiment: Conduct experiments to test the hypothesis.

5. Analyze Data: Collect and analyze data from experiments.

6. Conclusion: Draw conclusions based on data analysis.

7. Publish Results: Submit findings for peer review and publication.

Peer Review Process

• Critical for ensuring the study's methods, data collection, analyses, and conclusions are sound and unbiased.

• It involves submitting the research to experts for review before publication.

The Importance of Repeatability

• Data from single studies should not be fully trusted; repeatability and reproducibility increase credibility.

• The accumulation of many studies leads to theory development.

Hypotheses vs. Theories

• Hypothesis: Proposed explanation based on observation, which can be tested.

• Theory: Supported by extensive experimentation and data; formal explanation of an observed phenomenon.

Example of Applying the Scientific Method

• The author's lab study using mice to understand dietary effects provides an example of research methodology from hypothesis to publication.

• The study's findings can inform real-world nutrition recommendations, but the journey from basic research to application is complex.

Media Portrayal of Scientific Research

• Media may misrepresent research findings, which can lead to sensationalized claims that do not accurately reflect the study’s conclusions.

• Evaluating the credibility of media portrayals is essential for understanding genuine research findings.

Types of Nutrition Studies

1. Epidemiological Studies: Observational studies examining the relationship between diet and health.

2. Experimental Studies: Studies with controlled conditions testing specific nutritional hypotheses.

3. Meta-Analysis: Pooling of data from multiple studies to draw stronger conclusions.

4. Case Control Studies: Observations based on individual cases that may spark hypotheses.

5. Human Studies: Inclusive of case studies, clinical trials, and observational research.

Components of Good Studies

• Clearly stated problem and rationale.

• Defined study team with transparent funding information.

• Clearly defined treatment groups and rigorous data collection methods (e.g. blinding).

Role of Registered Dietitians

• Registered Dietitians (RDs) are the primary authorities on nutrition and undergo extensive training compared to less formal nutrition educators.