A scientist has shown how you can defend your research with a swag. In a recent correspondence published in NEJM, Dr Du, MD, PhD, from the University of Oxford, has successfully maintained his ground on his research – Fresh Fruit Consumption and Major Cardiovascular Disease in China – when it was critiqued by other healthcare providers from Singapore and Israel.
In April 2016, Huaidong Du published a research which credited fruit consumption with low rates of cardiovascular diseases in China. The research was critiqued by subsequent researchers like Melvin K Leow, MD, from Clinical Nutrition Research Center in Singapore, Eran Kopel, MD, MPH, Tel Aviv University, Israel, and Guo‑Chong Chen, from the Soochow University in China. Du effectively addressed all three of his critics and gave them very plausible explanations to their objections which have been published in the New England Journal of Medicine (NEJM).
In a letter to the editor, Leow objected saying the conclusion of the study by Du is speculative and may be misunderstood by the readers. Leow believed the actual study claimed to be “cohort-design” since the data collected had anthropometric values like body mass index (BMI), waist circumference, age, sex and geographic region, but they were measured like a cross-sectional study. Leow further advised it would have been more prudent to measure the BMI-adjusted waist circumference (WCBMI), since it is a marker of abdominal adiposity.
Du defended his research by saying they examined the link between fruit consumption with changes in waist circumference and then adjusted the results for BMI and their analysis showed that a positive association between fruit consumption and adiposity is present. Du stated that although the new finding contradicts some western studies, it is in harmony with previous findings from research on Chinese adults. Du also admitted the results are conflicting and beyond their grasp but they merit further research.
According to Kopel, in the observational study by Du et al the reported effects of fruit consumption do not take into account other effects like interaction with different foods. Especially for cardiovascular outcomes there are no interactions with risk factors of high blood glucose and high blood pressure.
Kopel also stated the absence of interaction in the conclusion of the research lowers the biological plausibility of the research and only serves as an omen or cautionary tale of nutrition. Du replied to the criticism by stating Kopel seems to have ‘misunderstood’ the results shown in a figure of the article. According to Du, none of the other risk factors for cardiovascular diseases changed or disturbed the effects of fruit consumption.
Chen, on the other hand, raised objection as to why the total energy intake of all the participants was not taken, which would have explained if the effects of higher fruit consumption retarded the effects of unhealthy foods like sugar sweetened beverages and high-sodium foods. He also stated that analyzing other dietary factors like peanuts and whole grains consumption, along with fruit intake, is also necessary and should have been carried out but was not done in this study.
Du responded by saying that in China, fresh fruit is often consumed as a snack and not eaten as a meal, so it is not likely people would replace whole grain foods with fruits. Carrying out an analysis of their association is moot. While their research adjusted fruit consumption with meat and preserved vegetables which marks the Chinese population’s salt consumption, Du admitted not adjusting for total energy intake in their research is a limitation but it does not mean their conclusions are not valid, since they measured both total physical activity and BMI in the analysis and received identical results.
Du also explained they did not collect data on sugar-sweetened beverage consumption because according to their 2013-2014 survey, only 6% of their participants consumed such beverages on a weekly basis, making this point a weak positive. Similarly, previously collected data had shown peanut and whole grain consumption in China was very low with only 2 grams per day being consumed only in Beijing, which cancels out any link of association with their findings.
Du’s research is not new. Earlier, a research carried out on US adults had shown similar results — higher intake of fruits was cited as being responsible for decreasing the risk of ischemic heart diseases like heart attack, stroke etc. According to CDC, every year more than 610,000 Americans die of heart diseases, which is equal to 1 in 4 deaths.
Fruits are recommended for daily consumption as part of a healthy diet because they contain bioactive components like potassium, folate, vitamins, fiber, and other plant based phenolic compounds which reduce the risk of cardiovascular diseases.
These nutrients are involved in processes like lowering antioxidant stress, improving lipid profile, lowering blood pressure, increasing insulin sensitivity and improving hemostasis. The presence of all these nutrients is attributed to better heart health since all prospective studies on heart health are epidemiological and cannot have a direct evidentiary association.