Refined Sugars Decrease Levels of “Good” Cholesterol (HDL-c)
Researchers from Georgia’s Emory University have found that consuming more refined sugar results in less high-density lipoprotein-cholesterol (HDL-c) and thus a greater risk of cardiovascular disease.
For 10 years, the researchers followed and tested 2,223 young females who began the study when they were aged 9 or 10 years old. During the 10-year period each of the subjects were tested individually for their blood levels of HDL-c as well as updated on dietary choices.
The researchers also eliminated the possible effects of obesity, as well as race, exercise, smoking, age, maturity and any other diet effects outside the consumption of products with refined sugars.
Products that were categorized as made of refined sugars – called “added sugars” – included sodas, dessert foods, and sweetened grain products such as sweetened cereals, donuts and so on. The sugars among fruits, 100% fruit juices, vegetables and other foods – were considered “natural sugars” and not “added sugars” (i.e., foods and beverages with refined sugars) by the researchers.
To establish a proportion of the diet containing refined sugars, the researchers calculated the amount of calories provided by the refined sugar foods divided by the total caloric intake of the person.
The researchers divided the results into five groups – those whose sugar consumption was between none and 10% of their total caloric intake; those between 10% and 15%; those between 15% and 20%; those between 20% and 25%; and those over 25%. The girls were fairly spread among all five categories.
The researchers took blood samples multiple times over the 10-year period among the girls, allowing them to track the HDL-cholesterol levels over the years along with diet.
The study found that those who consumed less than 10% of their total caloric intake from sugar had an average increase in HDL-cholesterol levels by an average of 2.2 mg/dL (milligrams per deciliter of blood). The higher refined sugar eaters had an overall 1.8 mg/dL lower levels of HDL-cholesterol than those consuming the least refined sugars.
Why is HDL-c so important?
This is significant because higher HDL-cholesterol has been linked to less atherosclerosis and lower levels linked with more artery disease. Meanwhile, higher levels of LDL-cholesterol have been associated with greater rates of atherosclerosis.
This is because low-density lipoproteins tend to oxidize and produce free radicals, which damage the artery walls. When the artery walls are damaged, they become inflamed and plaque builds up. This narrows the gap between which blood can flow, reducing circulation and making the heart work harder.
Arteries with plaque build up can also release small bits of plaque which can actually cause blockages among some of the smaller blood vessels. This is a typical scenario involved in stroke.
In their discussion, the researchers stated:
“The findings of this study provide support to the World Health Organization (WHO) Expert Consultation’s recommendation that no more than 10% of total energy be from added sugar. The American Heart Association (AHA) has recommended that adults consume no more than half of the US Department of Agriculture’s discretionary calorie allowance as added sugar. Depending on total caloric intake, this corresponds to 4% to 6% of energy from added sugars.”
The researchers added that very few of their test subjects consumed levels as low as recommended.
This is not the first study that has connected refined sugar consumption with artery disease.
Another new study from Yale University found that increased consumption of sugary beverages significantly increases the incidence of blood pressure. We report on this separately – here.
In another recent study, refined sugars were linked with increased risk of death. This study, from the National Cancer Institute of the U.S. National Institutes of Health, found that increased consumption of added sugars including fructose and sucrose – resulted in a greater incidence of death. These ranged from a 7% to 13% increase depending upon whether it was fructose (the highest), sucrose, added or total. These findings were fairly weak, possibly because of the difficulty in determining the precise sugar intake among the participants.
This point is critical because so many of today’s processed foods contain added refined sugars. Even those foods labeled as “natural” and “organic” will often contain added refined sugars. (While organic sugar is not as refined as conventional white sugar or high-fructose corn syrup, it is still a refined sugar.)
The only way to do a fair study would be to separate those people who consume added sugars from their foods (as the HDL-c study did) without confusing sugars provided from nature with those refined by humans.
The average American consumes about 77 grams per day of added sugars. This is actually down from about 100 grams per day as found in 2000 – most of the difference came from dropped sugary soda consumption. All sugary soda consumption dropped over this period except for sugary ‘energy’ drinks.
One might ask why these refined sugars are so bad for the body?
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Tasevska N, Park Y, Jiao L, Hollenbeck A, Subar AF, Potischman N. Sugars and risk of mortality in the NIH-AARP Diet and Health Study. Am J Clin Nutr. 2014 Feb
Welsh JA, Sharma AJ, Grellinger L, Vos MB. Consumption of added sugars is decreasing in the United States. Am J Clin Nutr. 2011 Sep;94(3):726-34. doi: 10.3945/ajcn.111.018366.