Everyday Research Methods

Can Probiotics Actually Treat Obesity?

 

Should you be suspicious of a study conducted by a company that produces probiotics products? Photo: Science History Images / Alamy Stock Photo

Guest post by Dr. Dina Gohar, University of Michigan

 

Hippocrates, considered to be the Father of Medicine, reportedly said, “all disease begins in the gut. ” It took doctors centuries to start studying the connection between our gut microbiota and our health, which is now well-supported by research. We can improve the health and diversity of our gut microbiota with active strategies, such as exercising regularly, eating a healthy diet, and getting enough sleep. We might also be able to improve our gut microbiota by simply consuming live “good” bacteria and microorganisms called probiotics. Probiotics are now sold as capsules, pills, and powders, added to fruit juices, granola bars, and candy, and even put into cosmetics. Fermented foods, such as cultured yogurt, sauerkraut, and kombucha, contain them too. A cloud of hype and hope surrounds probiotics, which have been touted as a treatment (and means of prevention) for everything from intestinal disorders, mood and anxiety disorders, belly fat and obesity-related disorders. 

A recent article in the New York Times suggested that a probiotic of heat-killed bacteria can treat metabolic disorders like obesity. This suggestion was based on a study in Nature Medicine.The  New York Times journalist summarized the study as follows:

Researchers tested the bacterium, Akkermansia muciniphila, in 32 men and women who met the criteria for metabolic syndrome by having at least three of five conditions: high fasting blood sugar, high blood pressure, high triglycerides, low HDL (the “good” cholesterol) or excessive waist circumference.

…In a three-month trial, volunteers were randomized to one of three groups: daily tablets containing live bacteria, pasteurized bacteria [A. muciniphila] or a placebo. Compared with the placebo group, those who took pasteurized A. muciniphila had significantly improved insulin sensitivity and total cholesterol, and decreases in several blood markers of inflammation and liver dysfunction. They also had decreased body weight, fat mass and waist circumference, though those differences were not statistically significant. The live bacteria were largely ineffective.

1. This study was an experiment. What is the independent variable (IV) and what are its levels? What are the dependent variables (DV)? What do you think of the outcome measures chosen for this study?
   
   
2. How was the independent variable manipulated:  between or within groups? Which of the four basic experiments is it probably an example of: Pretest/postttest design? Posttest-only? Repeated measures? or Concurrent measures?
   
   
3. Can the results of this study be used to support the causal claim that “Taking pasteurized bacteria can improve people’s insulin sensitivity and total cholesterol?” Why or why not? (Apply the three criteria for causality.)
4. Look at the sample size of this study; do you think it’s a problem? Why or why not? Which of the four big validities does the sample size best fit into? 
5. Do the results above support the claim that probiotics like A. muciniphila can treat obesity? Why or why not? (Is internal validity relevant here? What about construct validity?) Can you conclude that probiotics can help you lose weight? Why or why not?
6. The New York Times article critically failed to mention that the researchers who conducted this study have a patent on the probiotic treatment and even started a company based on it. What do you think about this potential conflict of interest? 
7. Do you think it matters that this study’s somewhat promising findings were only with dead bacteria, whereas probiotics are generally defined as being live bacteria? Why or why not? (Which of the four big validities is being asked about in this question, if any?)
   
   

You might agree that the probiotic study described by this journalist has a few serious problems. For an example of probiotic research done right, check out this NPR news story on a current clinical trial examining if a specific probiotic could eliminate specific GI problems in children on antibiotics (courtesy of Dr. Jess Hartnett’s statistics blog).

Does this punctuation make me sound angry, or what.

Which of these two text messages seems the most sincere? Photo: Travis Carr

If you're an American young adult, you probably already follow certain unwritten rules about about punctuating text messages. FOR EXAMPLE, EMAILS AND TEXTS WRITTEN IN ALL CAPS ARE CONSIDERED A FORM OF SHOUTING. Text messages follow their own set of norms, and the punctuation we use can lead to different interpretations of the same words. Some linguistics researchers have studied the impact of different text-message punctuation. 

This brief article in Quartz summarizes the results of some of this research. The journalist introduced the research with this: 

Though periods can still signal the end of a sentence in a text message, many users will omit them (especially if the message is only one sentence long). This tendency now subtly influences how we interpret them.

First example

This study is an example of a 2x2 factorial design. Here's how the journalist summarized the study: 

In 2016, psychologist Danielle Gunraj tested how people perceived one-sentence text messages that used a period at the end of the sentence. Participants thought these text messages were more insincere than those that didn’t have a period. But when the researchers then tested the same messages in handwritten notes, they found that the use of a period didn’t influence how the messages were perceived.

a) What are the two independent variables (IVs) in this design? What are their levels?

b) What was the dependent variable? 

c) Do you think the IVs were manipulated as independent groups or within groups? 

d) Sketch a graph of the results of the study. Remember to put the DV on the y-axis. Put one IV on the x-axis and represent the other IV with two different lines or bar colors. 

 

Second example

For practice with a simple experiment (not a factorial), compare these two text messages. Which one do you think participants found to be more sincere?

JACKIE I AM SO SO SO SORRY! I thought you were behind us in the cab and then I saw you weren’t!!!!! I feel soooooooo bad! Catch another cab and ill pay for it for youuuuu

Jackie, I am so sorry. I thought you were behind us in the cab and then I saw you weren’t. I feel so bad! Catch another cab and I’ll pay for it for you.

e) These two messages were studied by linguist Deborah Tannen. What would have been the independent and dependent variables in the study that compared these two messages? How might you design the study--would a posttest only design be better, or a concurrent-measures design, and why? 

f) How might the results of this study change if they were conducted on an older sample compared to a younger one?