2 Chapter 2: Identifying Valid Claims and Nutritional Research

The Scientific Method in Nutrition Research

Researchers employ the scientific method, which is a systematic and standardized methodology, to test hypotheses, develop new knowledge, and improve our current understanding of nutrition, health, and disease. In nutritional and scientific research, it encourages objectivity, critical thinking, and consistency. Perhaps most importantly, it minimizes the impact of philosophical, political, or personal biases on study findings.

There are six key steps in the traditional scientific method:

1. Ask a Question – Identify a specific problem or area of inquiry.
2. Conduct Background Research – Understand existing knowledge and gaps.
3. Formulate a Hypothesis – Develop a testable statement or prediction.
4. Test the Hypothesis – Use experiments or observations to gather data.
5. Analyze Data and Draw Conclusions – Interpret the results objectively.
6. Communicate Results – Share findings in peer-reviewed journals or professional conferences.

This standardized style makes it possible for researchers worldwide to assess and replicate studies, guaranteeing that knowledge is founded on factual data and analysis rather than anecdotes or beliefs.

Why the Scientific Method Matters

Every new discovery in science generates more queries and calls for increasingly complex techniques. The scientific method has the advantage of being able to challenge anecdotal evidence or outdated beliefs. For example, in the not-so-distant past, many dietary guidelines indiscriminately recommended low-fat, high-carbohydrate foods simply because of the reduced caloric content of low-fat foods. Dietary fat was then demonized, and many consumers wrongly steered clear of it, even healthy fatty acids.

Dietary requirements differ depending on lifestyle, genetics, medical history, and health goals. We know that certain dietary requirements aid particular populations through years of consistent, highly controlled studies. Our confidence in the findings increases when several studies employing the same methodology yield comparable results. Having a standardized approach for each of these studies is paramount to producing results that we can trust.

Types of Research in Nutrition

Experimental Research

When conducting experimental research, the researcher manipulates one or more variables (independent variables) with the objective of observing the effect on another variable ( dependent variable). Usually carried out in controlled environments, this kind of research is ideal for determining cause-and-effect relationships.

Another example would be a study that splits participants into three groups to assess the effect of routinely consumed beetroot juice on hypertension. The first group receives a high dose of daily beetroot juice, the second group receives a low dose of daily beetroot juice, and the third group is the control group and does not receive any beetroot juice. Then, researchers analyze participants’ blood pressure after 8 weeks of the specified protocol. The beetroot juice would be the independent variable in this scenario because it is being manipulated. In contrast, the blood pressure results would be the dependent variable because it is the effect of the manipulation. In experimental research, it is easier to link variations in outcomes to the intervention since the intervention is manipulated and regulated, and all other factors are kept constant.

Key characteristics:

• Researcher sets forth criteria for the independent variable before the trial
• Randomizing participants increases reliability
• Blinding researchers and participants during random assignment minimizes bias and further increases reliability
• Common in clinical trials (e.g., testing supplements or specific diet patterns)

Non-Experimental Research

Observational, or non-experimental, research is employed when variables cannot be changed because of practical, logistical, or ethical limitations. Researchers observe and measure naturally occurring behaviors, biological markers, or dietary patterns.

Common types include:

• Descriptive research – Characterizes a population or phenomenon (e.g., “Why prompted a population of vegans to first adopt a plant-based diet?”)
• Case studies – Detailed examination of one individual or a small group
• Correlational studies – Explore relationships between variables (e.g., fruit and vegetable intake and depression, as exemplified above, or dietary sugar intake and BMI)
• Cross-sectional and cohort studies – Evaluate groups at one time or over a long period

While these studies are unable to establish causality, they are essential in identifying patterns and forming a hypothesis for future experimental research.

Identifying High-Quality Studies and Journals

How do people identify the best journals and studies?

When conducting academic research or writing evidence-based papers, it’s important to differentiate high-quality sources from generic or untrustworthy ones. People should consider key guidelines to help them identify a high-quality study:

• Peer-review status – Is the article “peer-reviewed”?
• Impact factor – Does the journal have a notable scientific reputation?
• Publication Date – Is the research published within the last 10 years? If older, does the evidence still hold up?
• Type of article – Is the article a review or original research? If it is a review, is it a general review with no methodology, or is it a systematic review with a standardized methodology?
• Level of evidence – How strong is the evidence? Is it toward the top or bottom of the levels of evidence pyramid?

 What is the highest level of evidence among individual articles?

A randomized controlled trial (RCT) is considered the gold standard in scientific research because participants are only selected if they meet the rigid and uniform selection criteria for the study. Participants are only selected if they possess similar characteristics that align with the study’s methodology and are then randomly assigned to groups, thereby minimizing bias. Neither researchers nor participants have a say in the random assignment process. This allows researchers to isolate the effect of a single variable (independent variable) and establish a cause-and-effect relationship that is strong, as the results are likely due to the intervention rather than outside variables.

If neither researchers nor participants are aware of the group assignment and who is receiving the treatment or placebo, it is referred to as a double-blind trial, widely considered the strongest and most reliable form of evidence among studies. These methods reduce the risk of placebo effects and researcher influence.

RCT components generally include:

• Abstract – A brief summary of the study, typically less than 300 words
• Introduction – Background and rationale, typically expands on the purpose
• Methods – Contains participant selection criteria with detailed procedures and variables
• Results – Raw data and findings, states any statistical significance
• Discussion – Interpretation of results and their significance with a comparison to other relevant literature
• References – Supporting sources, typically numbered in chronological form as they appeared in the article

What about cohort studies?

RCTs are the most powerful type of individual study, and systematic reviews are the most powerful collection of studies. Nevertheless, cohort studies also play a crucial role in nutrition research. These studies follow large groups of people over lengthy periods of time, often decades, to observe the relationship between dietary behaviors and long-term health outcomes.

Two main types of cohort studies exist:

• Prospective cohort studies – follow participants forward in time
• Retrospective cohort studies – examine existing data from the past

Cohort studies are far less stringent than RCTs, but they require much more time. There is no randomization with cohort studies, and due to the more lax requirements, confounding variables exist, which researchers cannot control. This is why cohort studies cannot prove causation, though they are excellent at detecting associations. For example, the Nurses’ Health Study is a well-known cohort study initiated in 1976 that is still ongoing, and it linked trans fat consumption to an increased risk of heart disease long before the FDA banned trans fats.

Avoiding Unverified Claims and Pseudoscience

Not all nutritional information is produced with rigorous scientific methodology. The rise of social media influencers, grifting websites, and wellness marketing has led to a flood of unsubstantiated statements and advice. Some influencers or pseudoscientists don’t cite any peer-reviewed evidence or use one flawed or isolated piece of evidence to exaggerate a claim that suits their agenda.

As you can see, any influencer or pseudoscientist can make a claim that looks scary on the surface but requires more nuance and empirical context.

Red flags to watch for include:

• Does not cite research
• Fear-based or sensational language
• Claims based on a single study or non-human data
• Content that sells a product or supplement

What about supplements?

The supplement market in the United States is also one that can fall victim to sensational or false claims. It is not the duty of U.S. Food and Drug Administration (FDA) to approve dietary supplements for safety or effectiveness before they reach the market. This means that some products may be mislabeled or contain contaminants. When buying supplements, consumers should look for:

• Third-party testing
• Reputable history
• Transparent ingredient lists
• No exaggerated health claims