Question

Use this extract taken from the article, “L-Glutamine changes gut bacteria leading to weight loss,” (appeared in Preventdisese.com on November 2, 2019) to answer the questions that follow:

L-Glutamine is the most common amino acid found in your muscles and it plays a key role in protein metabolism, and the ability to secrete human growth hormone, which helps metabolize body fat and support new muscle growth. Researchers have now found that a daily L-glutamine dose of 30 grams per day was associated with a significant reduction in the ratio of specific biomarkers for obesity. The 30g dose studied was associated with a significant reduction in the ratio of Firmicutes to Bacteroidetes in obese and overweight people. “The finding that L-glutamine promotes changes in the gut microbiota composition provides support for the importance of some nutrients in modulating the intestinal bacterial profile,” wrote the researchers in Nutrition. “These changes resembled the weight loss programs established in the literature”. A new study, albeit small scale and of limited duration, suggested that the amino acid L-glutamine may also have weight management potential by changing the bacterial composition in the gut. The Brazilian researchers did not observe any changes in body weight during their 14 day study, but noted that a longer intervention period “may result in metabolic changes”. The researchers recruited 33 overweight and obese adults, aged between 23 and 59 and randomly assigned them to receive supplements of L-glutamine or L-alanine for two weeks. A reduction of 0.3 was observed in the ratio of Firmicutes to Bacteroidetes in the L-glutamine group, they added (from 0.85 to 0.57), while L-alanine was associated with an increase from 0.91 to 1.12. “Thus, these findings suggest that oral supplementation of L-glutamine have similar effects on gut microbiota as weight loss,” said the researchers. “We would like to highlight that although the age range of the volunteers was large (23-59 years) and aging may have an effect on intestinal microbiota, the results obtained in this study were statistically significant”.

(a) Is the study by Brazilian researchers that was cited in this article observational or experimental? In less than 50 words clearly explain your choice based on the extract given above.

(b) Identify the variable(s) of interest.

(c) Explain explicitly what a confounding variable is. Identify one plausible confounding variable in this study, explain why it is a confounding variable and suggest a possible way to overcome the impact of the confounding variable.

(d) Is the conclusion from this particular study reflected in the title of the article appropriate? Justify your response.

Answer 1

(a) The study is experimental. Experimental research studies are research designs where researchers introduce an intervention and study the effects of these interventions. Experimental studies are usually randomized, meaning the subjects are grouped by chance or randomly withiout selection. The researchers then study what happens to people in each study group. Any difference in results can then be linked to the intervention made originally.

As we see in the above study, the researchers recruited 33 overweight and obese adults, aged between 23 and 59 and randomly assigned them to receive supplements of L-glutamine or L-alanine for two weeks. This is an example of an experimental study design.

(b) The variables of interest are:

1. The supplement that was administered

2. The ratio of Firmicutes to Bacteroidete

3. Body weight

(c) Confounding variables are any variable that also has an effect on the dependent variable in a study. A confounding variable is an outside influence that changes the effect of an independent on dependent variable.

One confounding varaible could be the 'Duration' for which the supplement was administered to the sujbect. Since the duration for which the supplement was administered could have an effect on the ratio of Firmicutes to Bacteroidete as longer durations are likely to produce more pronounced effects than shorter durations. This effect could be controlled by specifing a fixed duration for the study which is considered to be reasonable to observe an effect of the supplement.

Another confounding variable could be the 'Age' of the subject as aging may have an effect on intestinal microbiota. This can be controlled by administering the test to each age group individually to reduce the confounding effect of age of the subject on the outcomes.

(d) Yes, the title of the article appropriate as it gives a quick summary of the subject matter of the article. It also give a short description of the result findings. In short, this gives an unique rationale to demonstrate what the information the reader could expect to get out of the article.