Diet soda’s harmful effects

May 21, 2016 by Joel Fuhrman, MD

Eliminating diet soda from your beverage arsenal will help protect your bones. Moreover, despite the word “diet”, these drinks may actually cause weight gain and be harmful to your health. On a given day, about half of Americans drink a sugar-sweetened beverage, and one in five drink a diet soda or other artificially sweetened beverage.1, 2 Soda consumption has previously been associated with lower bone mineral density in women and children3, 4 and one notable study focused specifically on the effects of diet soda on bone health. The authors commented that this research was sparked by the observation that diet soda drinking behaviors are often different than regular (sugar-sweetened) soda drinking behaviors. Women often use diet sodas in an effort to avoid weight gain, either to stave off hunger between meals or as a replacement for calorie-containing beverages. Many women drink over 20 diet sodas per week.5

These researchers discovered that parathyroid hormone (PTH) concentrations rise strongly following diet soda consumption. The job of this hormone is to increase blood calcium when it starts to get too low  by stimulating bone breakdown. As a result, calcium is removed from bone.

In the study, women aged 18-40 were given 24 ounces of either diet cola or water on two consecutive days, and urinary calcium content was measured for three hours. Women who drank diet cola did indeed excrete more calcium in their urine compared to women who drank water.   The authors concluded that this calcium loss may underlie the observed connection between soda drinking and low bone mineral density. 5

Although caffeine is known to increase calcium excretion and promote bone loss,6 caffeine is likely not the only bone-harming ingredient in sodas.  A 2006 study in the American Journal of Clinical Nutrition found consistent associations between low bone mineral density and caffeinated and non-caffeinated cola (both regular and diet), but not other carbonated beverages.4 One major difference between the two is the phosphoric acid in colas, absent from most other carbonated beverages. 

In the Western diet, phosphorus is commonly consumed in excess – at about 3 times the recommended levels, whereas dietary calcium often low. Phosphorus intake is increasing over time in the U.S., in part due to phosphorus-containing additives in foods and beverages, such as colas, commercial salad dressings and meat products. Although phosphorus is an important component of bone mineral, a high dietary ratio of phosphorus to calcium can alter mineral metabolism and increase bone breakdown, leading to lower bone mineral density. 7  Studies in which women were given increasing quantities of dietary phosphorus found increases in markers of bone breakdown and decreases in markers of bone formation.8, 9 Therefore it is likely that the phosphorus content of colas is the trigger for calcium loss.

There is nothing healthy about diet soda, and the evidence suggests that it does not help with weight loss anyway.10   Diet soda is simply water with artificial sweeteners and other additives, such as phosphoric acid. 

The safety of artificial sweeteners is questionable, and their intense sweetness disrupts the body’s natural connection between taste and nourishment, promoting weight gain.11  Diet sodas weaken our bones and are linked to kidney dysfunction, obesity and diabetes.12, 13  Furthermore, a study on older adults who drank diet soda daily had a 43 percent increased risk of heart attack or stroke compared to those that never drank diet soda.14


  1. Ogden CL, Kit BK, Carroll MD, et al: Centers for Disease Control and Prevention. NCHS Data Brief: Consumption of Sugar Drinks in the United States, 2005-2008. 2011.
  2. Fakhouri TH, Kit BK, Ogden CL: Consumption of diet drinks in the United States, 20092010. NCHS Data Brief 2012:1-8.
  3. McGartland C, Robson PJ, Murray L, et al: Carbonated soft drink consumption and bone mineral density in adolescence: the Northern Ireland Young Hearts project. J Bone Miner Res 2003;18:1563-1569.
  4. Tucker KL, Morita K, Qiao N, et al: Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study. Am J Clin Nutr 2006;84:936-942.
  5. Freiden J: Diet Soft Drinks Deplete Urinary Calcium. 2010. MedPage Today. Accessed April 28, 2014.
  6. Vondracek SF, Hansen LB, McDermott MT: Osteoporosis risk in premenopausal women. Pharmacotherapy 2009;29:305-317.
  7. Calvo MS, Tucker KL: Is phosphorus intake that exceeds dietary requirements a risk factor in bone health? Ann N Y Acad Sci 2013;1301:29-35.
  8. Kemi VE, Karkkainen MU, Karp HJ, et al: Increased calcium intake does not completely counteract the effects of increased phosphorus intake on bone: an acute dose-response study in healthy females. Br J Nutr 2008;99:832-839.
  9. Kemi VE, Karkkainen MU, Lamberg-Allardt CJ: High phosphorus intakes acutely and negatively affect Ca and bone metabolism in a dose-dependent manner in healthy young females. Br J Nutr 2006;96:545-552.
  10. Fowler SP, Williams K, Resendez RG, et al: Fueling the obesity epidemic? Artificially sweetened beverage use and long-term weight gain. Obesity (Silver Spring) 2008;16:1894-1900.
  11. Swithers SE, Martin AA, Davidson TL: High-intensity sweeteners and energy balance. Physiol Behav 2010;100:55-62.
  12. Diets High In Sodium And Artificially Sweetened Soda Linked To Kidney Function Decline. 2009. ScienceDaily. Accessed
  13. Fagherazzi G, Vilier A, Saes Sartorelli D, et al: Consumption of artificially and sugar-sweetened beverages and incident type 2 diabetes in the Etude Epidemiologique aupres des femmes de la Mutuelle Generale de l'Education Nationale-European Prospective Investigation into Cancer and Nutrition cohort. Am J Clin Nutr 2013.
  14. Gardener H, Rundek T, Markert M, et al. Diet soft drink consumption is associated with an increased risk of vascular events in the Northern Manhattan Study. J Gen Intern Med 2012, 27:1120-1126.

Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.