Added sugar is beneficial, but too much consumption leads to very dire health consequences. It is notable from the aforementioned that a large quantity of added sugar is consumed through food stuffs and beverages, since it forms part of the main ingredients during processing. Some of the health problems attributable to frequent or high consumption of added sugars are discussed hereafter.
Metabolic syndrome and coronary heart disease (CHD)
Added sugars may contribute to a conglomeration of biochemical and clinical features like insulin resistance, abdominal obesity and dyslipidemia. For instance, in one ten-week trial, covering 32 overweight or obese persons between ages 42 and 70 years, it was observed that concentration of lipoproteins and plasma lipids spiked up and maintained the status quo even in subjects who consumed glucose. Besides, those who consumed fructose developed insulin resistance and visceral obesity (Schwarz et al., 2009). In the trial, the level of fasting plasma glucose and insulin levels were raised, while insulin sensitivity reduced in subjects who consumed beverages sweetened with fructose, as opposed to those consuming glucose.
Moreover, a cross-sectional study, done during a National Health and Nutrition Survey among U.S. adults (> 6000), revealed that the correlation between blood lipid levels and caloric sweeteners (High- Fructose Corn Syrup- 55) was statistically significant. Another clinical study, conducted among youthful and healthy male volunteers who consumed 3 grams of 20% fructose solution per kilogram of their body weight every day for 6 days, revealed a substantial rise in plasma triglycerides coupled with suppression of adipose tissue lipolysis (Faeh et al., 2005). Even though, studies show the detrimental aspects of added sugars like fructose, the mechanism of its operation is still under scrutiny. For instance, experimental evidence has proved that the production of tumor necrosis factor (TNF), which is a pro-inflammatory cytokine that induces lipoprotein production and insulin resistance, is exacerbated by the consumption of fructose (Welsh et al., 2010; Kanuri et al., 2011).
The dynamics of lipoprotein and triglycerides levels brought about by increased intake of added sugar contribute to heart diseases. Dyslipidemia, an elevated level of triglycerides and reduced level of high density lipoprotein (“good” cholesterol), has been linked to high sugar intake; consequently, this imbalance in blood fat levels results into CHDs, as they lead to plaque development along blood vessels or deposition of fat in the heart.
Added sugars like fructose are often linked to hypertension and rice in the levels of uric acid. Epidemiological studies have proved the connection between the consumption of fructose and hypertension. An NHANES survey, done from 1999 to 2004 among adolescents, showed a strong link between drinks containing added sugar sweeteners and the levels of uric acid and hypertension. In the same vein, another survey by NHANES, conducted from 2003 to 2006, still showed that there was a correlation between fructose and elevated levels of blood pressure (Nguyen, Choi, Lustig & Hsu, 2009; Jalal, Smits, Johnson & Chonchol, 2010). In addition, a study among the people who kept to low-fructose diets showed a reduced level of blood pressure. The research involved 810 adults, whose consumption of a sugar-sweetened beverage was reduced every day during 18 months. A reduction of 1.1 mmHg and 1.8 mmHg diastolic and systolic pressures respectively was observed. Surprisingly, in this study, the observed effect was independent of levels of serum uric acid. However, since the vascular effects are pegged on the intracellular uric acid, the observed effect may still be attributable to the levels of uric acid.
On the flip side, a study done by Forman, Choi and Curhan (2009) failed to find a correlation between intake of fructose and development of hypertension. The study was based on health professionals and nurses who received large quantities of fructose derived from natural fruits. This inconsistency with the other studies was contributed by the high quantities of flavenols and antioxidants that curb the hypertensive effects of the fructose; furthermore, ascorbic acid, present in fruits, stimulates renal excretion thereby lowering the levels of uric acid. The fructose hypothesis has been further challenged by laboratory tests on rats that have revealed no association between fructose and blood pressure. However, this observation is probably due to the presence of the enzyme urease in rats that lowers the levels of uric acid and hence -countering the expected observation- a higher level of serum uric acid.
The studies, highlighted above, have shown that added sugars like fructose are contributors to the lethal conditions such as metabolic syndrome and hypertension. The occurrence of the aforementioned conditions establishes a domino effect that results into chronic kidney disease. Hitherto, there is only one human study that links consumption of sweetened beverages with chronic kidney disease. Particularly, between 1999 and 2004, the NHANES noticed that the risk of having albuminuria was enhanced by the intake of two or more beverages with added sugar as an ingredient (Kanuri et al., 2011). On the other hand, experimental studies show that the consumption of fructose is a contributory factor rather than a causative one. For instance, a 60% fructose diet to which rats were subjected worsened renal function, quickened glomerulosclerosis and enhanced proteinuria. On the contrary, the consumption of glucose never produced these dire consequences. In addition, micro puncture studies have recorded that reduced renal blood flow and glomerula hypertension are linked to intake of sucrose (Sanchez-Lozada et al., 2008).
Added sugars can exacerbate the risk of developing type 2 diabetes since, as mentioned under metabolic syndrome, it induces insulin resistance. Though a link between added sugars and development of diabetes is still elusive, some studies do prove otherwise. In a study, conducted at the Canadian Sugar Institute (2004), it was observed that consumption of soft drinks as opposed to fruit juices was strongly linked to a high risk of diabetes, even after adjusting the BMI. The mechanism in operation is that HFCS is highly absorbable and produces an effect similar to that of sucrose. Intake of large quantities of beverages, sweetened with added sugars, leads to high glycemic load which results into a poor glycemic control in diabetics due to the spikes in blood sugar levels (Foster-Powell & Brand-Miller, 2002; Willet, Manson & Liu, 2002).
Moreover, a current study, conducted among overweight subjects to investigate the impact of drinks and foods sweetened artificially or with sucrose on inflammatory biomarkers like haptoglobin and C-reactive protein, concluded that intake of products, sweetened with sucrose, significantly raised the plasma transferring and haptoglobin levels. No significant effect was observed on the C-reactive protein. Thus, it is reasonable to conclude that a high consumption of rapidly digested carbohydrates like added sugars enhances the proinflamatory process which is a risk factor for diabetes (Sorensen, Raben, Stender & Astrup, 2005).
Dental Caries, Overweight and Obesity
Intake of large quantities of added sugar feeds naturally occurring bacteria in the mouth; growing on the sugars, bacteria produce tooth-decaying acid. This erosion of the enamel is exacerbated by other factors in play, namely the duration of added sugars in the mouth, dental hygiene and fluoridation. It has been noted that this risk of dental caries is enhanced by an intake of nutritive sweeteners.
Overweight and obesity are intertwined in their occurrence, since more often than not obesity is a consequence of overweight. Some longitudinal studies have tried to link added sugar with obesity through the promotion of weight gain. The Detroit Dental Health Project was conducted in 2002-2003. It was a two-year research among 3-5 year-old African-American children coming from low income families. During the study, it was observed that the prevalence of obesity skyrocketed by doubling from 10.3 % to 20.4 % due to increased consumption of sugar-sweetened beverages (fruit drinks and regular soda) from averagely 19.2 ounces to 21.6 ounces per day. The odds of gaining weight and developing obesity rose by 4 % for every ounce of fruit drink or soda that was additionally consumed (Kumanyika, Grier, Lancaster, Lassiter, 2011, p. 8).