Soda: The Hidden Dangers
When researchers from the School of Public Health at Imperial College, London, (published in Hypertension) looked at the diets of 2700 middle-aged people in the United States and United Kingdom, they found that people drinking more than one soda or other sugar-sweetened beverage/day had higher blood pressure. The relationship was dose dependent. The more they drank, they higher their blood pressure was. Even after taking weight and other risk factors into account, the correlation still was present. Blood pressure was highest among people who consumed more glucose, fructose, and salt.
Studies have shown that consuming too much sugar might actually lead to sodium retention. The researchers also discovered that individuals drinking more than one sugar-sweetened beverage/day took in nearly 400 more calories than the people who did not drink these beverages. The people who drank the sweetened beverage also were more likely to have diets deficient in potassium, magnesium, and calcium, all of which are important for cardiovascular health. Participants who drank diet soda did not have the same blood pressure increase, but they had a higher body mass index (BMI) and lower levels of physical activity.
Drinking either regular or diet soda increases the risk of developing metabolic syndrome. Even one soda/day increases the risk of metabolic disorder by about 50%, according to the senior author of a study (Ramachandran Vasan, MD, professor of medicine at Boston University School of Medicine), published in the July 31, 2007, issue of Circulation.
For a diagnosis of metabolic disorder, a person must have three of five of the following criteria found:
- A large waistline
- Elevated fasting blood sugar
- Elevated fasting triglycerides
- Reduced high-density lipoprotein (HDL) cholesterol
The study looked at 3500 people participating in the Framingham Offspring Study, which began in 1971 and included a total of 5124 participants. Participants filled out questionnaires that asked about their soda consumption from 1987–1991, 1991–1995, and 1995–1998. During 1987–1991, individuals who drank at least one soft drink/day had a 48% increased prevalence of metabolic disorder. As the study progressed, the risk was still 44% higher. However, this study was critiqued as not necessarily proving cause and effect.
In 2009, research presented at the annual meeting of the American Society of Nephrology showed that women who drank more than two diet sodas/day had a 30% drop in kidney function. The participants (median age of 67 years) were 3256 women already participating in the Nurses’ Health Study. Questionnaires were used in which the women recorded their average beverage consumption in 1984, 1986, and 1990. Other factors such as age, hypertension, diabetes, and level of physical activity also were considered.
The glomerular filtration rate (GFR) declined about 3 milliliters (mL)/minute/year in the women who drank the diet soda. The GFR generally declines 1 mL/minute/year after the age of 40 years. A serving was defined as a glass, a can, or a bottle. The study was not published. Other studies have not found a relationship between the consumption of diet soda and a decline in kidney function.
In a cross-sectional study completed at Loyola University Medical Center, women who drank two or more cans of regular soda/day had an 86% increased risk of albuminemia, which is an indication of early kidney disease. Men who drank soda did not have similar increases. The study did not determine causality, so it is not known whether high-fructose corn syrup, overall excessive intake of sugar, or other factors that were not looked at were to blame. The data for the study came from the National Health and Nutrition Examination Survey from 1999 through 2004. The analysis included 9358 participants who were at least 20 years old. A total of 16.8% of participants drank at least two soft drinks/day according to their 24-hour dietary recall, and 11% of participants had albuminuria. Once adjustments were made for age, race, ethnicity, gender, poverty level, and whether the drinks were diet or regular, an overall 40% increased risk of albuminuria was seen among the participants who drank at least two regular soft drinks/day. Only women and those with low-to-normal body weight who drank at least two sodas/day had an increased risk of albuminuria.
It is believed that the effects of albuminuria are likely attenuated among overweight people. Subclinical diabetes and obesity are known risk factors for kidney damage. Ingredients such as fructose or phosphorus used in soda could directly injure the kidney. It also was hypothesized that the mercury found in high-fructose corn syrup was possibly to blame. The cross-sectional design of the study calls for further research.
Weight and fat distribution
Drinking diet soda is associated with a larger abdominal girth, which often goes with metabolic syndrome and type 2 diabetes. The San Antonio Longitudinal Study of Aging followed 474 people between the ages of 65 and 74 for 9 years. Individuals who drank soda had a 70% greater increase in waist girth during the study. Those who drank two or more servings of soda/day had an increase in waist circumference that was five times larger than those who drank no soda.
The authors of this study previously had done a study in 2008, which showed that individuals who drank more than 21 diet sodas/week were twice as likely to become overweight. Experts point out that these studies are observational studies and a double-blind, controlled intervention study is necessary to confirm these finding.
In the San Antonio Study, it is possible that another factor explains the increased abdominal girth other than soda consumption. Other hypotheses are that people who drink diet soda overestimate their caloric savings and thus overeat later in the day or that the sweetness imparted by the artificial sweeteners increases appetite.
Epidemiologists from the School of Medicine at The University of Texas Health Science Center, San Antonio, TX, also completed a study in which 40 diabetes-prone mice were divided into two groups. One group was given chow with both aspartame and corn oil added, while the other group was given chow with only the corn oil added for 3 months. The mice that were receiving aspartame had elevated fasting glucose levels and equal or diminished insulin levels.
In another observational study, published in Diabetes Care in April 2009, at least daily consumption of diet soda was associated with a 36% greater relative risk of incident metabolic syndrome and a 67% greater relative increase of incident type 2 diabetes, compared with individuals who drank no soda. Of the metabolic syndrome components, only waist girth and high fasting glucose levels were associated with diet soda consumption. Association between diet soda consumption and type 2 diabetes was independent of baseline measures of adiposity or changes in these measures. However, association between diet soda and metabolic syndrome was not independent of these factors. It was not possible to establish causality from this study.
A correlation between increased risk of bone fractures and soda intake exists, although experts are not in agreement regarding the cause. Some health professionals believe that people who drink soda have more fragile bones because they drink soft drinks instead of milk, while some research shows that this is not the case. Researchers at Tufts University found that women who drank three or more colas/day had ≈4% lower bone mineral density in the hip, even when controlled for calcium and vitamin D intake.
Women who drank non-cola soft drinks, such as ginger ale, did not have a reduction in bone density. It is hypothesized that the phosphorus in cola drinks is to blame. Consuming more phosphorous than calcium is believed to lead to bone damage. Phosphorus increases the acidity of the blood, and hydrogen ions bind with minerals, such as calcium and magnesium, to neutralize it. If the minerals are not available in the blood, the body will draw the calcium from bones. However, if someone is getting a good amount of both calcium and phosphorus, it is good for the skeleton.
The blame also is pointed at caffeine, which is known to inhibit calcium absorption. However, in the Tufts study, both caffeinated and decaffeinated colas were associated with decreased bone density, although the caffeinated drinks were more strongly correlated.
References and recommended readings
Calorie Control Council. Low-calorie sweeteners do not affect kidney function. Available at: http://www.caloriecontrol.org/low-calorie-sweeteners-do-not-affect-kidney-function. Accessed June 7, 2012.
Doheny K. Diet sodas may be hard on the kidneys: women who drink 2 or more diet sodas daily double their risk of kidney function decline, study shows. Available at: http://www.webmd.com/diet/news/20091102/diet-sodas-hard-on-the-kidneys. Accessed June 7, 2012.
Doheny K. 1 daily soda may boost heart disease: researchers point finger at diet, regular sodas; industry officials disagree. Available at: http://www.webmd.com/heart/metabolic-syndrome/news/20070723/1-daily-soda-may-boost-heart-disease. Accessed June 7, 2012.
Fulton A. Drinking soda may increase your blood pressure. Available at: http://www.npr.org/blogs/health/2011/03/07/134137041/drinking-soda-may-increase-your-blood-pressure. Accessed June 7, 2012.
Hendley J. Can drinking seltzers, sodas or other carbonated beverages harm bones? Available at: http://www.eatingwell.com/nutrition_health/bone_health/can_drinking_seltzers_sodas_or_other_carbonated_drinks_harm_bones. Accessed June 7, 2012.
Neale T. Drinking soda may increase kidney damage in women. Available at: http://www.medpagetoday.com/Nephrology/GeneralNephrology/12836. Accessed June 7, 2012.
Nettleton JA, Lutsey PL, Wang Y, Lima JA, Michos ED, Jacobs DR Jr. Diet soda intake and risk of incident metabolic syndrome and type 2 diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA). Diabetes Care [serial online]. 2009;32:688-694. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660468/. Accessed June 7, 2012.
Saul N. Does drinking diet soda cause diabetes? Available at: http://blog.joslin.org/2011/07/does-drinking-diet-soda-cause-diabetes/. Accessed June 7, 2012.
ScienceDaily®. Waistlines in people, glucose levels in mice hint at sweeteners’ effects: related studies point to the illusion of the artificial. Available at: http://www.sciencedaily.com/releases/2011/06/110627183944.htm. Accessed June 7, 2012.
Shaw G. Soda and osteoporosis: is there a connection? Available at: http://www.webmd.com/osteoporosis/features/soda-osteoporosis. Accessed June 7, 2012.
Contributed by Elaine Koontz RD, LD/N
Review Date 6/12