Food Frontiers Blog

Responses to Questions on Microbial Stability, Acidity, and Phosphorus Content in Carbonated Beverages

by Daniel Pellegrom

We are seeing some good questions in the comments section and I’ve shared some with our R&D team. Commenter @Passerby asked the following question:

“We could start with a simple issue first: the exceptional acidity, maintained by phosphoric and citric acids, in carbonated beverages.

If you drop the sugar content, can you raise the pH without incurring microbial contamination issues?

We should talk about the consequences of chronic phosphate acidity exposure in the oral cavity, GI tract and in particular, in stomach. It has consequences in bone mineral maintenance, ion channel transport that may affect the CNS.”

To respond, I’d like to introduce Danielle Greenberg, Senior Nutrition Fellow at PepsiCo and Loretta Chappell, VP, R&D Strategy, Global Sparkling and Energy Platform at Pepsi who co-authored the post below:

“The simple answer is no….dropping the sugar content will not allow you to raise the pH without incurring microbial contamination. A great example is bottled water which has a higher pH and no sugar but must be handled and processed within very specific guidelines to prevent microbial growth. We formulate and/or process our products to avoid microbial growth. Many factors contribute to a product’s microbial stability. The factors that need to be considered include the ingredients, the pH, carbonation level, manufacturing process, etc. Microorganisms need nutrients to grow and many ingredients we use to make beverages taste good, in addition to sugar, also provide nutrient sources. Many products that are not heat processed will require the addition of preservatives to prevent microbial growth even if the products don’t contain sugar.

There is a lot of misunderstanding about the role of phosphorus in bone health. Scientific research shows that the phosphoric acid contained in some soft drinks does not adversely affect bone health. Soft drinks provide less than 3% of phosphorus of the normal daily phosphorus intake. That is much less phosphorus than is found in milk and about the same as found in orange juice. The National Institutes of Health (NIH), the Centers for Disease Control (CDC) and the National Academy of Sciences all say that phosphorus does not negatively affect bone health. Research on the subject of soft drinks and bone health, conducted at Creighton University, funded by the dairy industry and published in the American Journal of Clinical Nutrition, shows that phosphoric acid does not affect bone density.

The purported issue with phosphoric acid relates to a potential imbalance between phosphorus and calcium levels in the blood. This imbalance only occurs in rare situations where there is a very high phosphorus intake and very low calcium intake. In this highly unusual situation phosphorus would have a negative impact on bone health. In all other situations phosphorus is a needed and necessary component for proper bone formation. Adequate calcium intake through vegetables, fruits, and milk consumption should always be encouraged. As long as calcium intake is adequate, the imbalance does not occur. Moreover, most dietary phosphorus does not come from soft drinks, but from other food sources. Specifically, 60% of the dietary phosphorus comes from foods that are high in protein, such as milk, meats, eggs, legumes, and grains. Only about 3% of the dietary phosphorus comes from carbonated soft drinks and other beverages. Both phosphorus and calcium (along with magnesium and Vitamin D) are necessary for adequate bone health.

In terms of the stomach, it has a natural acidity in order to be able to digest food. That acidity gives a pH of about 1 and has cells that secrete various chemicals to protect the stomach lining. The idea that a small amount of phosphorus from a soft drink or any other source could harm the stomach lining doesn’t really have much validity.”

References:

Storey, ML, Forshee, RA, Anderson, PA, Associations of Adequate Intake of Calcium with Diet, Beverage Consumption, and Demographic Characteristics Among Children and Asolescents, J Am Coll Nutr. 2004 Feb; 23 (1):18-33; Park, Y, Meier, E, Bianchi, P, Song, W, Trends in Children’s Consumption of Beverages: 1987-1998, Family Eco. Nutr. R. 2002; 14(2):69-79.
Grimm M, Muller A, Hein G, Funstuck R, Jahreis G., High Phosphorus Intake Only Slightly Affects Serum Minerals, Urinary Pyridinium Crosslinks And Renal Function In Young Women, Eur J Clin Nutr. 2001;55(3):153-161.
Mendez, R.O., Gomez, M.A., Lopez, A.M., Gonzalez, H. and Wyatt, C.J. (2002) Effects of calcium and phosphorus intake and excretion on bone density in postmenopausal women in Hermosillo, Mexico. Ann Nutr Metab 46(6):249-253.
Metz, J.A., Anderson, J.J. and Gallagher, P.N., Jr. (1993) Intakes of calcium, phosphorus, and protein, and physical-activity level are related to radial bone mass in young adult women. Am J Clin Nutr 58(4):537-542.
United States Institute of Medicine. (1997) Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academy Press, Washington DC.
Dietary Intake of Selected Minerals for the United States Population: 1999–2000 by R. Bethene Ervin, Ph.D., R.D.; Chia-Yih Wang, Ph.D.; Jacqueline D. Wright, M.P.H.; Jocelyn Kennedy-Stephenson, M.Sc., Division of Health and Nutrition Examination Surveys Advance Data, Vital and Health Statistics, Number 341, April 27, 2004

Chemistry Teacher

I noticed that this post did not address "the chronic phosphate acidity exposure in the oral cavity"
Daniel Pellegrom

I went back to Danielle Greenberg, who wrote the post above about the chronic phosphate acidity exposure in the oral cavity question and she recommended a good source of information on this topic: Erosion - Diagnosis and Risk Factors, Clinical Oral Investigations, by A. Lussi & T. Jaeggi.

This article notes that “dental erosion is a multifactorial condition: The interplay of chemical, biological and behavioral factors is crucial and helps explain why some individuals exhibit more erosion than others. The erosive potential of erosive agents like acidic drinks or foodstuffs depends on chemical factors, e.g. pH, titratable acidity, mineral content, clearance on tooth surface and on its calcium-chelation properties. Biological factors such as saliva, acquired pellicle, tooth structure and positioning in relation to soft tissues and tongue are related to the pathogenesis of dental erosion. Furthermore, behavioral factors like eating and drinking habits, regular exercise with dehydration and decrease of salivary flow, excessive oral hygiene and, on the other side, an unhealthy lifestyle, e.g. chronic alcoholism, are predisposing factors for dental erosion."

Danielle added that many factors determine individual dental health, including the types of food consumed, the level of oral hygiene, access to professional dental care and access to fluoridated water. Phosphates — like any substance that is acidic (lemons, citrus fruit, tomatoes etc.) — lower plaque pH. When plaque pH falls enough, tooth enamel begins to demineralize, which leads to tooth decay.

However, the natural action of saliva reverses this situation by remineralizing the teeth and neutralizing the pH. The frequency of eating and the length of contact with the teeth are some of the most important factors in determining whether or not there is decay. Carbonated soft drinks have a relatively low pH partially because of phosphate content. However, if consumed rapidly the low pH of the mouth would be very temporary as the saliva is basic and would rapidly neutralize the acids found in soft drinks.

The carbohydrates in soft drinks can come into contact with teeth and lead to demineralization, but since the duration of contact between a drink and teeth is usually very short that is rarely the case. Sticky foods like soft cookies that tend to stay in the mouth longer and/or cling to teeth are much more likely to be a significant source of dental cavities. If liquids were constantly sipped throughout the day (as in a toddler cup or baby bottle), then carbohydrate containing liquids would be more likely to lead to tooth decay.
Acmother

Stop poisining our children, you monsters!
Perplexed in Peoria

Thx. I believe I actually learned something here. For instance, I had never realized that soft-drink acidity had a preservative/anti-microbial function. In addition, Pepsi writes: "There is a lot of misunderstanding about the role of phosphorus in bone health." Well, there is certainly misunderstanding about the quantity of phosphate in soft drinks, and its role in bone health. It is not hard to find repeated claims that the quantity of phosphorus in soft drinks is large and dangerous. Yet you seem to be saying the opposite. Who am I to trust? A big bad corporation, or some folks distributing information in the public interest with that reassuring word "natural" in their masthead?

I can't offer you much advice on how to seem trustworthy to other folks, but I can tell you what works with me. Numbers. The natural folks tell me that phosphate levels in soft drinks are high. "How high?", I wonder. "Very High", they tell me. "How high, and high in relation to what?", I wonder. "Very high, unhealthily high", they reassure me. So I take a closer look at the propaganda from those corporate tools at Pepsico. "Soft drinks provide less than 3% of phosphorus of the normal daily phosphorus intake."
Yay! An actual quantitative number. 3%. But wait. "3% of what? What is the numerator and what is the denominator? Is this an estimate for a population? What population? How much soft drink is consumed by this population? And who/what is the source of this statistic?" Reading further I find that 3% number again (Yay, numbers!) being contrasted to a 60% number (Double yay, comparisons between numbers!), but still no clarity as to what these numbers mean or citations indicating where they come from.

But eventually, I reached closure on this issue when I found this resource which satisfied my craving for numbers. And guess what. I believed these numbers, even though their source was an evil corporation. I believed them because it was clear exactly what claims were being made, and therefore also clear how those claims might be falsified and their purveyors demonstrated to be liars. I don't think a big bad corporation would take that risk. Hence, I believe them. If the "natural" folks had put out numbers instead, I might have believed them. But they didn't. So it is PepsiCo ftw. But that is just me. Your results with other readers may vary.
Carl

I also wondered about the "3%".

PepsiCo

Responses to Questions on Microbial Stability, Acidity, and Phosphorus Content in Carbonated Beverages

by Daniel Pellegrom

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