DIET SODA – TRUTH OR DARE

Ilana Katz MS, RD, CSSD

Diet soda is often used as a “crutch” by many trying to lose or maintain weight. It has zero calories, so surely it has a role to play in the weight loss industry? Amazingly enough, however, there is no scientific research that demonstrates diet soda is proportional to weight loss. In fact, it has been uncovered as the culprit to much weight gain and many negative health issues. So what then is the reality behind a seemingly innocent beverage?

As a dietitian that specializes in body composition, which in my eyes is a step ahead of simple weight loss, I have often been questioned on my opinion of diet soda. Especially because dietitians recommend not to drink one’s calories. The good news first: ok, calorie free does have its silver lining – for one thing, it can lower tooth decay and help with diabetic control, but the bad news, makes diet sodas so much more of a concern in overall metabolism.  Avoiding diet sodas may lean towards optimal body composition. My reasoning is because diet soda suppresses metabolism and increases sugar cravings/appetite. Furthermore their suspect, chemically heavy ingredient list, raises much controversy.  I will thus provide the facts, the research, the debates, and then my professional opinion in the conclusion.

Lowering Metabolism

Going into the physiology of the liver would be overkill, but that is pretty much the reason why diet sodas have a potential to lower ones metabolism. So here is the simple bottom line: The liver has two main functions: one is to detoxify and the other is to metabolize nutrients.  Detoxifying becomes a priority when chemicals or toxins are ingested. This would then reduce normal metabolic functioning. Using a diet soda as an example: the liver would first break down the aspartame into its basic components phenylalanine, aspartic acid and methanol. Because these are not natural nutrients, this process requires more energy from the liver making it less available for metabolism. The result: fat storage rather than fat burning.  Now of course, this is one metabolic process that I have isolated for illustrative purposes and really, anything that requires detoxification by the liver has a role to play in metabolic depression.

Furthermore using calorie free products such as diet soda to deter eating, results in a physiological hunger later on, and a consequentially higher intake of calories.

The rollercoaster of saving calories to a point of starvation leads to overeating, which in turn leads to longer periods between meals, is set in motion. At these high peaks and low valleys, the instinctual drive to survive takes over. Drive to survive puts the metabolism into a protective state which ultimately means fat storage. In other words, the metabolism lowers itself when it is not getting expected energy. A low metabolism also means that it  burns excess fat extremely slowly in order to conserve stored energy (fat), in reaction to the starvation. Needless to say, even if good, healthy food is ingested at these times, the metabolism is so low that it would store everything. This is a physiological response to “starvation”. Starvation could actually set in within hours, unlike in the hunter gatherer days it was closer to weeks or months. The difference between us and our Paleolithic ancestors is, although we have the same genetic code, we also have a constantly available source of food and the brain knows it. So to not feed within hours causes the brain to trigger the appropriate physiological reaction:  “ I am starving, thus store”.

Increases Sugar Cravings

The artificial sweeteners in diet products stimulate taste receptors.  On the one hand this may be seen as a positive, because it seems satisfying without the calories. But then the flip side of the coin rears its head – the expected texture and real sugar taste is not typically satisfied in the longer term which causes an instinctual reach for the real sweet stuff.

Ingestion of calorie free products will still stimulate the brain to send a signal of calories entering the stomach. Yet when they do enter, there is no nourishment, so again, the brain is set in motion to seek real nutrients and nourishment and the hunt for more satisfying food. More satisfying food takes on many forms depending on the individual. In the worst case, the sweet-toother, may succumb to candy. Even in the best case, the obsessive health nut would typically over eat (ok, so the health nut may not indulge in artificially sweetened products in the first place… be patient with me, as I attempt to create an analogy).

Potential Mineral Loss

Research has shown that kids that drink more soda are less likely to satisfy the recommended daily requirements of vitamin A, calcium and magnesium (1).  The phosphoric acids in sodas bonds to calcium and magnesium resulting in a loss of these vital nutrients rather than their absorption. Furthermore, soda can act as a replacement for fruit juice and milk, which could offer a great source of nutrients for growth of healthy, dense bones. Calcium and magnesium are two of the core minerals that make up bone density.  The epiphyseal plate closes in the teenage years (meaning bones stop growing and no more minerals can be added). Therefore it is so important in the growing years to ensure intake of bone minerals to ensure maximum bone density over the lifetime.  Phosphoric acid may result in leakage of calcium and magnesium, increasing a risk of osteopenia or osteoporosis in later years.

There is current research that shows an increase in calcium measured in the urine of heavy soda drinkers (2). The calcium could be leaching out of the bones as it combines to phosphoric acid.

Other Ingredients worth mentioning  

There are many ingredients on a diet sodas ingredient list. My philosophy of nutrition, is if there is anything on the food label that you cannot pronounce, or spell, or typically know what it means, then avoid the product. The reason goes back to those opening paragraphs on the liver prioritizing detoxification taking away its availability for metabolic functioning.                                                                    

–          Artificial Sweetener (aspartame, sucralose)  

As discussed above, artificial sweeteners have a tendency to increase sweet craving as well as lower metabolic function.  There have also been some controversial responses to diet sodas playing a role in the obesity problems in the USA today because of these two symptoms. Studies have suggested that artificial sweeteners cause body weight gain, theoretically because of an insulin response to sweet (9).

–          Food coloring

For decades, there has been a suspected link to food colorings that are added to many soft drinks, and the symptoms of hyperactivity, ADD, ADHD and other various behavioral problems. The original studies related to dyes was done by Dr. Ben Feingold and many parents with behaviorally challenged kids still implement what has become to be known as the Feingold program. More recently, there have been double blind placebo controlled studies that do increase the suspected strength of the relationship between dyes and behavior (7).

Although it appears that behavior is improved by following the Feingold Program guidelines, researchers suggest that by removing sugar (in other words, empty calories) malnutrition is also reduced. It is not clear what portion of the effects can be contributed to limiting sugar intake or what portion can be attributed to the removal of the artificial colorants themselves.

–          Sodium or potassium benzoate

Sodium and potassium bezoate are the preservatives used in sodas.  In combination with ascorbic acid (vitamin C), sodium benzoate and potassium benzoate form benzene, a known carcinogen. More importantly,  heat, light and shelf life can affect the rate at which benzene is formed.

In 2006, the United States Food and Drug Administration (FDA) released its own test results of several soft drinks containing benzoates and ascorbic acid. Typically the results showed that benzene levels are below those considered dangerous for consumption. Five tested drinks contained benzene levels above the  Environmental protection Agency recommended standards and the preservative formulas were updated (5).

–       Exposure to BPA (in plastic and aluminum cans)

There has been accumulating debate recently over whether exposure to a chemical called Bisphenol A (BPA) is contributing to increased risk of various cancers, infertility, behavioral problems, impaired learning ability and growth defects. BPA is thought to come from the linings in packaged food containers, especially ones in plastic bottles like sodas.  In 2004 a study done by CDC (center for disease prevention and control) found a significant percentage of their tested subjects to have BPA in their urine (6).

–          Caffeine

The  sports dietitian in me has no problem with caffeine. It is one of those controversial elements that can actually be advantageous to an increase in metabolism and energy. It is a proven ergogenic aid, which means it may play a role in enhaning sports performance. But on the other hand, it is a central nervous system stimulant, so it may not be the best element to be giving young growing children. For one thing caffeine can be habit forming and for another, it has been shown to play a role in mineral loss of bones during the growth period (10).

–          Carbonation

Carbonation is the least of my concerns, yet it is worth mentioning in this context, since it has a tendency to cause gastric distress. There is little scientific research to support the notion that carbonation itself delays gastric empting; however, the studies are few and far between. It is often an individual response to the bubbles. Carbonation for some individuals may have a bloating effect due to air from the bubbles being released in the gastric system. This bloated feeling should be avoided mostly because it reduces the desire to drink often and thus deter from hydration. Nothing should reduce the drive to drink in order to remain appropriately hydrated.

Conclusion  

So as you can see, there is a lot of controversy around diet sodas. They have developed a bad rap for contributing to the obesity problem. They have been accused of causing osteoporosis and brain cancer, and they have also been blessed as a tool for weight management.

In my professional opinion, the obesity problem is far more complex than diet sodas or any other products for that matter that use artificial sweeteners. I am not a proponent of artificial sweeteners based on my explanations above of sweet cravings and depressed metabolism. I do however, agree that they provide no nutritional value.  But the hype that gets spread in the media of them being the cause for the obesity exponentiation is absurd. Needless to say, there is no significant scientific studies that back up this hypothesis either.

So in conclusion, I will say that unless fortified, diet sodas contain no nutrients. In other words, they are completely void of any vitamins, minerals fiber, or protein, etc. They therefore have a tendency to displace healthier choices such as water, milk or vegetable juice that could otherwise play a role in reaching recommended daily intakes of essential nutrients.  They may also lean towards sweet craving and lowering ones metabolism based on the science of the metabolic pathway for artificial substances and chemicals processed by the liver.

REFERENCES

1. Archives of Pediatric and Adolescent Medicine. Nov 200, 154:1148-52.
2. Heaney RP, Rafferty K. Carbonated beverages and urinary calcium excretion”. American Journal of Clinical Nutrition . Sept 2001, 74 (3): 343–347.
3. Tsimihodimos V, Kakaidi V, & Elisaf M.  Cola-induced hypokalaemia: pathophysiological mechanisms and clinical implications. International Journal of Clinical Practice. June 2009.  63 (6): 900–2
4. Hickman et al. Caution: some soft drinks may seriously harm your health.  The Independent, May, 2007.
5. US FDA/CFSAN – Questions and Answers on the Occurrence of Benzene in Soft Drinks and Other Beverages. http://web.archive.org/web/20080326000127/www.cfsan.fda.gov/~dms/benzqa.htm
6. A. M. Calafat, X. Ye, L.-Y. Wong, J. A. Reidy, and L. L. Needham,  CDC report. Exposure of the U.S. population to bisphenol A and 4-tertiary-octylphenol: 2003-2004., Environmental Health Perspectives.
7. Lars and Nanna Lien. Consumption of soft drinks and hyperactivity, mental distress and conduct problems. American Journal of Public Health, October 2006 (96), 10.
8. Feingold, Ben F. (1982). “The Role of Diet in Behavior.  Ecology of Disease. 1982: 2: 153–165.
9. Pope, Tara. Exploring a Surprising Link Between Obesity and Diet Soda. Health Journal: July 24, 2007.
10. Massey and K J. Wise, The effect of dietary caffeine on urinary excretion of calcium, magnesium, sodium and potassium in healthy young females. Nutr Res 4 (1989), pp. 43–50.