Podcast Summary: The Dr. Gabrielle Lyon Show
Episode: The Truth About Nutrition: How You Can Take a Science-Based Approach | Bradley Johnston PhD
Release Date: February 25, 2025

Introduction

In this enlightening episode of The Dr. Gabrielle Lyon Show, host Dr. Gabrielle Lyon engages in a profound conversation with Dr. Bradley Johnston, a distinguished expert in nutrition science. With nearly 200 peer-reviewed publications, Dr. Johnston brings a wealth of knowledge on evidence-based practices in nutrition, systematic reviews, and the complexities of nutritional research. The episode delves deep into how individuals and clinicians can navigate the often conflicting landscape of nutritional advice to make informed, science-based decisions.

Background of Dr. Bradley Johnston

Dr. Johnston introduces his academic journey, highlighting his undergraduate degree in kinesiology and doctoral training in experimental medicine at the University of Alberta. He further advanced his expertise with postdoctoral training in evidence-based healthcare at the University of Oxford and McMaster University, specializing in clinical epidemiology and biostatistics.

"My understanding and passion for evidence-based practice and health research methodology really kind of was inspired at McMaster."
— Dr. Bradley Johnston [02:31]

At McMaster, Dr. Johnston was mentored by Dr. Gordon Guyett, a pivotal figure who coined the term "evidence-based medicine." This mentorship solidified Dr. Johnston's commitment to evidence-based practices, a theme that permeates the entire discussion.

Understanding Evidence-Based Practice

The conversation shifts to defining evidence-based practice (EBP), emphasizing its broader applicability beyond medicine to fields like nutrition and pharmacology. Dr. Johnston outlines the three central tenets of EBP:

1. Best Available Evidence: Utilizing high-quality, up-to-date systematic reviews and meta-analyses to address clinical or public health questions.

   "Once you have clarity on that and what you're trying to resolve clinically or from a public health perspective, the first central tenet is using the best available evidence to answer that question."
   — Dr. Bradley Johnston [03:57]

2. Expertise: Incorporating clinical expertise and professional judgment into decision-making processes.

   "Dr. Lyon, you've got lots of clinical expertise that really matters. It's a part of evidence-based practice."
   — Dr. Bradley Johnston [04:20]

3. Values and Preferences: Ensuring that the values and preferences of patients or target populations guide clinical decisions, provided they are well-informed by evidence.

   "It's not the evidence that drives the decision clinically. It should be the values and preferences of your client or your patient or your target population, if they're informed."
   — Dr. Bradley Johnston [05:30]

GRADE Methodology and Certainty of Evidence

A significant portion of the discussion centers around the GRADE (Grading of Recommendations Assessment, Development and Evaluation) methodology. Dr. Johnston explains how GRADE assesses the certainty of evidence, categorizing it into high, moderate, low, or very low based on several factors, including risk of bias, inconsistency, indirectness, imprecision, and publication bias.

"GRADE has been around for 20 years. It's based on a group of methodological people from around the world... one of the goals of GRADE is to be transparent about how did you arrive at moderate certainty evidence."
— Dr. Bradley Johnston [43:11]

He underscores the importance of systematic reviews with meta-analyses in applying the GRADE approach, ensuring that recommendations are based on a robust synthesis of available evidence.

Application to Nutrition and Dietary Guidelines

Dr. Johnston shares insights from his systematic review published in the British Medical Journal (2023) comparing various dietary programs' effectiveness in reducing all-cause mortality and cardiovascular outcomes. The Mediterranean diet emerged as the top performer, followed by low-fat diets, both backed by moderate certainty evidence.

"The best available evidence for the question what is the best dietary program to prevent major hard cardiovascular outcomes and mortality is Mediterranean style diet."
— Dr. Bradley Johnston [17:12]

He advocates for evidence-based dietary guidelines that prioritize patient-important outcomes, such as quality of life, rather than solely focusing on traditional metrics like BMI or lipid profiles.

Challenges in Nutritional Research

The discussion highlights the inherent challenges in conducting rigorous nutritional research. Unlike pharmacological studies, dietary interventions are difficult to blind, and adherence can vary greatly among participants. Dr. Johnston emphasizes the need for more randomized controlled trials (RCTs) in nutrition to resolve ongoing controversies and uncertainties.

"Nutritional studies are challenging to do... because people know what they're getting. You can't blind it."
— Dr. Bradley Johnston [39:32]

He cites examples such as the limited number of RCTs on the Mediterranean diet in North America and the potential benefits of salt substitutes, underscoring the necessity for localized research to validate findings from other regions.

Core Competencies in Evidence-Based Practice

Dr. Johnston outlines six core competencies essential for professionals in evidence-based nutrition:

1. Asking Clear, Structured Questions: Formulating precise clinical or public health questions using frameworks like PICO (Population, Intervention, Comparator, Outcome).
2. Literature Search Skills: Efficiently navigating databases like PubMed to locate relevant studies.
3. Assessing Risk of Bias: Evaluating the methodological quality of studies to determine their reliability.
4. Understanding Treatment Effects: Interpreting statistical significance and practical significance (e.g., absolute risk reduction).
5. Certainty of Evidence: Using GRADE to categorize the robustness of evidence.
6. Values and Preferences: Integrating patient or public values into decision-making processes.

"One of my graduate students... came up with her paper, we boiled it down to what we think are six core competencies."
— Dr. Bradley Johnston [27:17]

Scientific Mindset and Open-Mindedness

The episode emphasizes the importance of maintaining a scientific mindset characterized by curiosity, openness to data, and the ability to manage personal biases. Dr. Johnston shares personal anecdotes illustrating the necessity of being agnostic to initial hypotheses in light of emerging evidence.

"All of us as scientists, we endeavor to have that... intellectual curiosity and being agnostic to the data."
— Dr. Bradley Johnston [84:20]

Future Directions and the Role of AI

Looking forward, Dr. Johnston acknowledges the growing role of Artificial Intelligence (AI) in evidence synthesis and systematic reviews. He advocates for leveraging AI as a research assistant to enhance efficiency while ensuring that human oversight remains central to maintaining methodological rigor and transparency.

"I tell my students that AI can either be your competition or your research assistant. Better to make it your research assistant."
— Dr. Bradley Johnston [87:56]

Conclusion

The episode concludes with Dr. Johnston affirming his commitment to promoting evidence-based practices in nutrition and his vision for fostering a collaborative community dedicated to rigorous research. Dr. Lyon expresses her gratitude for the invaluable insights shared, underscoring the episode's role in empowering listeners to make informed nutritional choices grounded in scientific evidence.

"The work that you do is tremendous, and it has been extraordinarily helpful for me, and I know many of my colleagues and many others."
— Dr. Gabrielle Lyon [90:27]

Notable Quotes:

• "Check."
  — Dr. Bradley Johnston [01:44]

• "Once you have clarity on that and what you're trying to resolve clinically or from a public health perspective, the first central tenet is using the best available evidence to answer that question."
  — Dr. Bradley Johnston [03:57]

• "The grades is the certainty of evidence is moderate."
  — Dr. Bradley Johnston [05:35]

• "Our recommendations when we follow GRADE are either strong recommendations or they're conditional."
  — Dr. Bradley Johnston [65:07]

• "AI can either be your competition or your research assistant. Better to make it your research assistant."
  — Dr. Bradley Johnston [87:56]

Key Takeaways:

1. Evidence-Based Practice (EBP): A systematic approach to making clinical and public health decisions based on the best available evidence, professional expertise, and patient values.

2. GRADE Methodology: A transparent system for rating the certainty of evidence and the strength of recommendations, widely adopted across health organizations globally.

3. Challenges in Nutrition Research: Conducting high-quality, blinded RCTs in nutrition is inherently challenging, necessitating more localized and methodologically rigorous studies.

4. Core Competencies: Professionals must develop skills in formulating structured questions, conducting thorough literature searches, assessing bias, interpreting treatment effects, evaluating evidence certainty, and integrating patient preferences.

5. Scientific Mindset: Maintaining curiosity, openness to data, and managing biases are crucial for advancing evidence-based nutrition science.

6. Role of AI: AI has the potential to enhance efficiency in evidence synthesis but must be integrated thoughtfully with human oversight to ensure methodological integrity.

Resources Mentioned:

• EvidenceBasedNutrition.org: A platform created by Dr. Bradley Johnston and collaborators to promote evidence-based practices in nutrition.

• GRADE Methodology: Adopted by organizations like WHO, CDC, Cochrane, and the American Academy of Nutrition and Dietetics for developing guidelines.

This episode serves as a critical guide for listeners seeking to navigate the complex world of nutrition science. By emphasizing evidence-based practices and showcasing the systematic approaches used by experts like Dr. Johnston, Dr. Gabrielle Lyon empowers her audience to make informed decisions that prioritize health and well-being.