Key:

NH      Nahida Zaman

CS      Dr Shay

NH         You are listening Nahida Zaman on Diabetes Radio.  My guest today, Dr Christina Shay, hello and a very warm welcome.

CS         Thank you for the introduction, I am happy to be here.

NH         Dr Shay, you are an Assistant Professor at the University of Oklahoma Health Sciences Center.  Do tell us, what is your current research focus?

CS         My current area of research is mainly in the area of population based preventive and prevention research.  I specifically am interested in looking at the role of lifestyle, specifically social activities, diet, smoking and obesity and the role they play in the prevention and reduction of cardiovascular disease and diabetes.

NH         Your research culminated in a presentation of the results of a highly important study at the annual meeting of the American Heart Association.  The abstract, which has also been accepted for publication in the AHA Journal circulation is titled ‘Sugar, Sweet and Beverage Consumption, An Incident Cardiovascular Risk Factors, The Multi-Ethnic Study of Atherosclerosis’ or MESA.  Previous studies have examined and found links between drinking sugar sweetened beverages and obesity, high blood fats, high blood pressure and type II diabetes but studies following large ethnically diverse populations looking at links with cardiovascular risk factors are sparse, why has this been the case up until now?

CS         Many of the well known studies that have investigated the development of cardiovascular disease and its risk factors have mainly focused in Caucasian populations or more recently they have been enrolling both Caucasians and African Americans, however MESA is a very unique investigation that they targeted for different ethnic racial groups, non-Hispanic whites, African Americans, Hispanic and Chinese Americans.  It has only really been in the last couple of decades that disparities in the rates of cardiovascular disease and the risk factors have been clearly identified in specific race and ethnic groups and the MESA study was designed in response to these questions and it was really one of the first investigations to identify individuals of these different race and ethnic groups before they developed cardiovascular disease and they are now following them over time to examine which risk factors are associated or may be more specifically associated with developing cardiovascular disease and one of the specific ethnic racial groups or another and the atrophy that really makes this design of MESA powerful and very interesting is that it does not just examine whether people who have cardiovascular disease at one time point also has certain characteristics, this type of design has identified people that have no history of cardiovascular disease and are really following them over time to clearly identify the types of things that they are exposed to or their types of things that describe an individual and how those things can lead to the development of cardiovascular disease and its risk factors over time.

NH         Dr Shea, can you tell us more about your study, how was it designed and what type of patients were included?

CS         We looked at this question, we were originally interested in looking at the role of sugar sweetened beverage consumption and cardiovascular disease risk but when we looked in the literature there were lots of other studies that had shown that sugar sweetened beverage consumption was associated with actual higher risk of developing cardiovascular disease itself, higher risk of heart attacks and different cardiovascular disease conditions so what we were interested in doing is taking a step back and looking at the individual risk factors that are associated with developing cardiovascular disease and seeing if there is one specific risk factor or another that is associated with that sugar sweetened beverage consumption seems to influence so a research question was does sugar sweetened beverage consumption influence hypertension, does it influence glycaemia or blood glucose, does it influence blood lipids so there are certain aspects of cardiovascular risk that is influenced by sugar sweetened beverage consumption and we sought to do this in the MESA study.  We looked at all of the data from participants collected over the six years so far that we have been collecting data on MESA participants.  We went back to the very first exam and we looked at the dietary assessments.  We asked participants at the very first exam in 2000 and 2002 how many sugar sweetened beverages a day do you consume and we categorised that based on less than one, more than one but less than two and greater than two sugar sweetened beverages and after we looked at individuals that had all of the available data for their dietary assessments as well as individual risk factors, we started out with a little over 4,000 participants, 4,100 participants so we next looked at the level of sugar sweetened beverage consumption and whether or not that level of consumption was associated with developing individual risk factors so we have looked over time and we tried to find individuals who developed high triglycerides, high blood glucose, hypertension, a variety of risk factors and what we found is that in women in particular who consume two or more sugar sweetened beverages per day, they had a higher risk for increasing the size of their waist circumference so they started to develop more abdominal adiposity compared to women who consumed less than one sugar sweetened beverage per day.  What was interesting about this is that although there was an increased risk for developing their waist circumference, this risk was there, even after we accounted for whether or not they gained weight, so that was the first intriguing finding so we dug a little further.  We looked at other risk factors, we saw that again in women in particular, those that drank two or more sugar sweetened beverages per day, also had a significantly higher risk for developing high triglycerides and compared to women who consumed less than one sugar sweetened beverage per day and they also had a very high risk among women who had normal glucose tolerance at the beginning of the study, those that had normal blood glucose, they had a much higher risk for developing impaired fasting glucose or coming down with a condition called pre-diabetes compared to women who consumed less than one sugar sweetened beverage per day so these women in particular who were normal glucose tolerant at the beginning of the study, if they consume two or more sugar sweetened beverages per day were much more likely to become pre-diabetic or develop pre-diabetes compared to those that had consumed less than one sugar sweetened beverage at the beginning of the study and again what is most intriguing about these findings is these associations still remained after we accounted for whether or not they were over-weight or obese at the beginning of the study and whether or not they gained weight or became overweight or obese through the course of the study, so we find it to be very interesting and they generate a lot of questions for us.

NH         Did you obtain similar results in men?

CS         For the analysis where we looked at whether or not they increased their waist circumference, we saw similar results in men but again the association was stronger in women so when we look at it from a research perspective, the results were not statistically significant in men although the trend was similar but we cannot say in men that these results were anything greater than just what would happen by chance.  In the women though the association was statistically significant and was much stronger in the women compared with men.  For the results looking at the higher risk of triglycerides and the higher risk for developing impaired fasting glucose, those results were very strong in women and showed no trend towards a higher risk in men at all and this sample from MESA.

NH         The metabolic influence of sugar sweetened beverages is complex and is not homogenous between men and women.  What could be the reason behind these differences?

CS         The initial questions that are coming to mind for us is that there might be something from a metabolism perspective that is different in the way that women metabolise the sugars from these beverages compared to the way that men do.  Unfortunately from this type of study, although that is an interesting question and that is what I think needs to be explored next, we really cannot answer that question from this investigation so what we are hypothesising is that we think that the findings that we are seeing is based on the fact that women in general need fewer calories and less energy for metabolic function compared to a man with all things relatively being equal.  Women tend to have smaller body sizes, they tend to have less skeletal muscle mass and just require fewer calories for metabolism so if you think about a single serving of a sugar sweetened beverage being approximately 130 calories, those calories may up a larger proportion of the energy needed for a woman for metabolism than a man so that one beverage may actually exert a higher level of metabolic influence or a higher level of risk for a woman compared to a man just based solely on the fact that women require less calories and it takes up a larger proportion of their caloric intake.

NH         You found women who drank more than two sugar sweetened drinks a day had increasing waist sizes, were they also gaining weight?

CS         That is one of the intricate questions about these types of analyses.  We did see that women did tend to gain weight but overall we saw that women in the study did tend to gain weight but we did not see a specific association between sugar sweetened beverage consumption and whether or not they were gaining weight but we did see that they increased their waist sizes but that association still remained even after we accounted for whether or not they did gain weight so we did not see a higher risk for gaining weight with sugar sweetened beverage consumption but after accounting for whether or not they gained weight, women who consumed two or more sugar sweetened beverages per day were at a higher risk for increasing their waist sizes.

NH         Your research also challenged a major misconception, namely that the individuals who consume a lot of sugar sweetened drinks have an increase in obesity which in turn increases their risk for heart disease and diabetes.  Can you please address what we now know about this based upon your group’s results?

CS         I think there is this conception that sugar sweetened beverages contribute excess calories to the diet that in turn can lead to increasing rates of obesity.  I think that that concept still stands very valid in the scientific literature, I think that that still is a concept that holds true and I think that concept potentially also is holding true and the participants from MESA in this study but what we are seeing is that there may be something about sugar sweetened beverages in particular that may cause increased risk for developing cardiovascular disease through specific risk factors that may be independent or may not be solely influenced directly through levels of obesity, there may be something above and beyond the risk that is contributed by obesity that influences heart disease and diabetes risk in the women from this study.

NH         What impact did the consumption of two sugar sweetened drinks have on triglycerides in the participants and their risk of developing diabetes over time?

CS         We started at the beginning of the study with women and men both who had normal triglycerides and those that had not developed diabetes at the beginning of the study and what we saw is that women in particular who consumed two or more sugar sweetened beverages exhibited a higher risk for developing high triglycerides and for becoming a high risk for developing diabetes over time and this was compared to women who consumed less than two or more sugar sweetened beverages per day.  Again these findings were only observed in women and the association there was no indication that this level of risk was seen with two or more sugar sweetened beverages in men.

NH         Did your research shed light on exactly how such drinks influence cardiovascular risk and what biological mechanisms might be involved?

CS         Unfortunately that is a level of detail that we are not able to examine in this type of study so this type of study has large numbers of individuals, thousands of people involved and because of the resources available, this type of study, this observational design usually examines lots of questions but not a very specific detail in the participants that are involved so we were not able to examine the exact biological mechanisms in this investigation but I think these results could be an interesting foundation for other metabolic studies that have the availability to look at the specific biological mechanism in women and men as they relate to sugar sweetened beverage consumption.

NH         Dr Christina Shay, thank you so much for taking the time to speak with us today.