America’s Favorite Beverage Debate and the Relation to Bone Health

America’s Favorite Beverage Debate and the Relation to Bone Health

January 1, 2024

Joy Stepinski, MSN, RN-BC

Coke or Pepsi? This is perhaps one of the most widely debated questions when considering America’s beverage options. The Pepsi Challenge, which originated nearly a half century ago in 1975, posed a great choice to consumers when offering a blind taste test across the country to determine which soda was preferred. As a huge marketing strategy, Pepsi created commercials that portrayed Coke drinkers taking the challenge and choosing Pepsi. In less than a decade later, Pepsi sold more cola than Coke in grocery stores. The challenge created a fierce rivalry between the two brands, along with iconic cultural moments in America [1]. While consumers continue to debate this seemingly important question, health literature creates a very different answer. Cola can wreak havoc in the body, especially upon the bones.

Remember that good ol’ pH scale from high school biology class? Applying different chemicals, test strips would change into one of the colors on the rainbow depending on acid (more red) or base (more yellow). The scale measures between 0 and 14, with 7 as neutral. Any pH lower than 7 is acidic and higher is basic. Imagine applying cola to one of those test strips. The color would likely be red-orange.

The acid-base balance is incredibly important for the human body. The body maintains a tight pH between 7.35 to 7.45. As it turns out, cola is a very acidic beverage with a pH range of 2.8 to 3.2. When the kidneys process urine, the lowest pH the organs can handle is 5 [2]. Why is this so important? The body must compensate for the extra acid by buffering it. The amount of buffer required is equal to 16 mEq of carbonate, or 4 Tums. Otherwise with a pH of 3, the body would need to dilute the cola 100-fold so that the urine would have a suitable pH to be excreted.

From where does the body get the buffer? Frequently, this comes from the bones as the skeleton releases calcium stores. When people consume a high acid diet (which tends to be in the form of meat, fish, cheese, and cola), the urine is not only more acidic, but also contains more calcium as it neutralizes the excess acid.

Furthermore, the cola beverage contains high levels of phosphate [3]. Phosphorus frequently occurs naturally in most foods and combines with oxygen in the body to create the compound phosphate. Although the recommended daily allowance (RDA) for phosphorus is 700 mg/d in healthy adults, most Americans consume twice the amount. This excess frequently comes in the form of inorganic phosphate additives. For example, drinking 20 fluid ounces of cola provides 55 mg of phosphorus.

The body often requires a fine balance of elements. Phosphate is an important component of cell membranes as a phospholipid, DNA in the structural phosphate backbone, and energy in the form of adenosine triphosphate (ATP). Yet, high levels of phosphate (also known as hyperphosphatemia) combine with calcium ions in the blood, causing low serum calcium. Ultimately, the body’s protective defense mechanism responds by causing the release of calcium bone stores to normalize the low blood level [4].

High phosphate levels further affect the bone by blocking one of the enzymes required in Vitamin D activation. Once the skin comes into contact with the sun, a series of steps must occur in order for Vitamin D to be available for the body. With high phosphate levels, an important renal enzyme (1-alpha hydroxylase) that activates the hormone is inhibited. Because Vitamin D is needed for the uptake of calcium (including the absorption of calcium from the intestines, reabsorption of calcium and phosphate in the kidneys, and storage of minerals by the bone), bone health is greatly affected.

In one study, 460 high school girls in 9th and 10th grade participated by self-reporting physical activity, carbonated beverage intake, and bone fractures [5]. The results showed a correlation between cola drinks and bone fractures among physically active teenage girls. The author reports that this is a similar finding to her previous work demonstrating an association between cola consumption and bone fractures among girls [6]. The connection did not occur with non-cola beverages.

The Framingham Heart Study also performed research with respect to soft drink consumption and bone mineral density [7]. Participants included 1413 women and 1125 men. Researchers evaluated dietary intake through a food frequency questionnaire and measured the subjects’ bone density at the spine and hip through dual energy x-ray absorptiometry (DEXA) scan. The results found a significant correlation between cola intake among women on bone mineral density (BMD). With the hip, BMD was 3.7% lower at the femoral neck and 5.4% decreased at Ward’s area.

While regular consumption of cola is detrimental on bones, water is a very good choice. Dehydration can cause bone tissue to become hardened and stiff [8]. Additionally, its shock-absorbing ability can decrease, such as seen in the vertebrae. This can lead to compression fractures. Water in the skeleton comprises 20 – 25% of total body weight. Among its benefits are bone mechanical and structural integrity, a mineral reservoir of essential ions, and support for body weight. Next time you are confronted with the Pepsi challenge, consider “water, please!” instead.

References:

1.  Yglesias, M. (2013). Sweet sorrow. Slate. https://slate.com/business/2013/08/pepsi-paradox-why-people-prefer-coke-even-though-pepsi-wins-in-taste-tests.html

2.  Barzel, U. S., & Massey, L. K. (1998). Excess dietary protein can adversely affect bone. The Journal of Nutrition, 128(6), 1051-1053.

3.  Vorland, C. J., Stremke, E. R., Moorthi, R. N., & Hill Gallant, K. M. (2017). Effects of Excessive Dietary Phosphorus Intake on Bone Health. Current Osteoporosis Reports, 15(5), 473–482. https://doi.org/10.1007/s11914-017-0398-4

4.  Goyal, R., & Jialal, I. (2023). Hyperphosphatemia. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK551586/

5.  Wyshak, G. (2000). Teenaged girls, carbonated beverage consumption, and bone fractures. Archives of Pediatrics & Adolescent Medicine, 154(6), 610-613.

6.  Wyshak, G., & Frisch, R. E. (1994). Carbonated beverages, dietary calcium, the dietary calcium/phosphorus ratio, and bone fractures in girls and boys. Journal of Adolescent Health, 15(3), 210-215.

7.  Tucker, K. L., Morita, K., Qiao, N., Hannan, M. T., Cupples, L. A., & Kiel, D. P. (2006). Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study. The American journal of clinical nutrition, 84(4), 936-942.

8.  Khan, M. A. (2023). Bone water: Effects of drugs on bone hydration status. Osteoporosis, Osteoarthritis and Rheumatoid Arthritis: An Agonizing Skeletal Triad, 75.