January 27, 2015--“Dietary sweeteners are highly debatable in the nutrition field considering that rates of hypertension, obesity, and type 2 diabetes have risen over the past decades, paralleling increased added sugar consumption (1). Of all the sweeteners, some would suggest that fructose is most detrimental since it is metabolized differently than other sugars, ultimately leading to fatty liver, high blood uric acid levels, and the production of inflammatory compounds (1,2).
In the February issue of the Journal of Clinical Hypertension, Angelopoulos et al. (3) reported on a study consisting of 268 weight-stable, normotensive individuals whose blood pressure and uric acid measurements were followed before and after 10 weeks of consuming one of 4 sugar-sweetened milk beverages, each containing a single sweetener (high-fructose corn syrup, fructose, glucose, and sucrose) at a particular percentage of calories to maintain body weight (http://bit.ly/1yrTqQb). The authors reported a significant reduction in both systolic and diastolic blood pressure with no change in uric acid levels despite an average two pound weight gain after the 10-week study.
The results of this study might be surprising for some, considering there are studies available suggesting that fructose is associated with hypertension. The intake of fructose in the form of high-fructose corn syrup is thought to be particularly concerning due to its potential for excessive intake from soft drinks and sugar-sweetened beverages (4).
Leo Galland, MD, FACN, observes, ‘The demonstration that a modest dose of fructose added to a dairy drink for 10 weeks does not raise blood pressure in healthy adults unfortunately provides no new data about the long-term metabolic effects of high-dose fructose consumption, especially from soft drinks, which has clearly been shown to contribute to weight gain, a key trigger for hypertension and the metabolic syndrome.’
There are studies suggesting that drinking sugar-sweetened beverages leads to relevant changes in blood pressure. Brown et al. (5) demonstrated that consumption of sugar-sweetened beverages, even at one serving per day, led to elevations in greater blood pressure in individuals. Le et al. (6) showed that acute consumption of one 24-ounce high-fructose corn syrup-sweetened beverage led to significant changes in metabolic biomarkers in healthy men and women, such as systolic blood pressure and serum uric acid, compared with a sucrose-sweetened beverage. Using data from the large, prospective, Nurses’ Health Study, Choi et al. (7) found that women who consumed 1 serving per day of a sugar-sweetened soda had a 74% higher risk of incident gout, with greater rates with increasing intake of fructose.
Indeed, there are several points to consider when it comes to studies addressing dietary fructose and hypertension. In this particular study by Angelopoulos et al., the subjects tested were healthy and had normal blood pressure. It remains unknown as to how moderate amounts of fructose consumed daily might have impacted various metabolic markers in prehypertensive or hypertensive individuals, who might be more vulnerable to the effects of sweeteners and any resulting metabolic disturbance.
Moreover, as is well-recognized in nutrition, “the dose makes the poison.” The authors suggested that the amount of sweetener used in the study was reflective of a “normal level of consumption”. The dose-dependent effects of fructose are key to its mechanisms in chronic disease, especially hypertension. Research indicates that higher than normal daily intake (≥ 100-200 g/d) of fructose intake may lead to a host of metabolic changes, including hyperuricemia (8-11). Most recently, Jayalath et al. (12) reported no association of fructose consumption with the incidence of hypertension in a systematic review and meta-analysis of three prospective cohort studies (n=37,375 men and 185,855 women). While they found no effect of fructose at average levels of consumption over time, a positive association was identified with high intakes of fructose.
Furthermore, it would seem that the overall nutritional composition of the fructose-containing food might be extremely relevant, considering that 24 ounces of a soft drink may not differ much in fructose content from the overall amount ingested from daily fruit intake, yet different metabolic results may be seen. The subjects in this study drank a sweetened milk beverage. It has been demonstrated that milk peptides can reduce blood pressure (13). The fact that subjects were given milk may have been significant as dairy products contain naturally-occurring ACE-inhibitory peptides that can lower blood pressure (13). Also, milk is high in a number of other nutrients have the potential to favorably alter blood pressure, such as potassium, calcium, magnesium, and vitamin D.
It may also be relevant to examine the total calories consumed in the diet vis-à-vis the amount of dietary fructose. Angelopoulos et al. had subjects consume sugar-sweetened milk to the level of weight maintenance. It is plausible that different results for fructose (or any sweetener) may have been obtained with calorie excess. However, it would remain debatable whether the sweetener or overnutrition was the true culprit. Johnston et al. (14) found no difference between high-fructose and high-glucose diets on liver enzymes in healthy overweight men who consumed an isocaloric diet; however, hypercaloric consumption led to significant changes in liver triglycerides and serum liver enzymes.
If calories are considered, the quality of those calories also have to be assessed. It is well accepted that dietary patterns such as the Mediterranean diet and the DASH diet are comprised of several nutrients and anti-oxidants that can positively impact blood pressure. For example, as mentioned previously, minerals such as calcium, magnesium, sodium, and potassium, all have a significant effect on blood pressure, as do select vitamins such as vitamin D. The thousands of phytonutrients in plant-based foods, such as flavonoids, nitrates, and isoflavones, fulfill essential functions for cardiovascular health. Thus, when evaluating any study, a full evaluation of the subjects’ dietary pattern is warranted to have a complete understanding of the dynamic interplay of nutrients on physiological factors.
Finally, hypertension is a lifestyle-initiated disease induced by multiple causes, including poor diet, lack of physical activity, obesity and heightened stress (15). The trend in nutrition science has been to focus on one nutrient as a culprit, which is difficult to effectively accomplish, considering that there are always other dietary changes that occur. A better understanding of the development of chronic disease, and, in particular, especially hypertension can be best comprehended by assessing both diet and lifestyle. It is well-known that various dietary approaches, physical activity, and stress management practices can help reduce risk for developing hypertension. Therefore, any detrimental effect of fructose (or other sweeteners or food constituents) might be negated or lessened in the context of healthy lifestyle patterns.
Physician and researcher David Perlmutter, MD, FACN adds, ‘The conclusions drawn from this 10 week study related to hypertension are of scant value in the context of the understanding that changes in baseline blood pressure in relation to a particular variable (in this case fructose consumption) may take years to manifest. Likewise, pathophysiological changes related to fructose consumption itself, especially those related to subtle changes in the microbiome and gut permeability, may similarly require extensive periods of time to become observable.’”
For further information contact the Media Relations Department of the American College of Nutrition at Media@AmericanCollegeofNutrition.org