Acidic vs Alkaline

Apple cider vinegar (ACV) purportedly helps fat loss, lowers cholesterol and has “amazing benefits.” Alkaline water (AW) promoters say it staves off cancer and osteoporosis, and improves exercise recovery. While tap water runs around 7 pH, ACV is acidic with a low pH of about 3 and AW is more basic with a higher pH of 8-9. All this begs the question: if apple cider vinegar and alkaline water are on opposite sides of neutral, how can they both be good for you?

No wonder people think nutrition recommendations are confusing! When popular ‘news’ and testimony overshadow true science, it’s easy to get lost trying to follow nutrition advice. Well, to steer you correctly, here’s a background on acids and bases in the body and a summary from the volume of evidence on humans about the healthfulness of apple cider vinegar and alkaline water.

Background

The stomach maintains a very acidic environment of 1.2 – 3.0 pH so that it can break down food protein and kill ingested pathogens. Humans maintain a blood pH of 7.35 – 7.45¹. Respiration by the lungs and mineral buffers from the kidneys, namely calcium phosphate and calcium carbonate, keep the blood pH at a safe 7.4. *There is actually little proof that dietary changes and/or supplementation affect blood pH, though they may alter urine pH².  Alkalizing one’s urine pH through diet simply indicates that the kidneys are doing their job of filtration and protecting the blood’s pH.

APPLE CIDER VINEGAR

Like many vinegars, ACV contains acetic acid and is commercially available at 5% acidity. In comparison to other vinegars, ACV may have slightly higher B vitamins, polyphenols and the prebiotic pectin, especially if it’s unfiltered so that it contains the “mother” – leftover bacteria from the fermentation process.

Although ACV itself is not considered a beverage (it’s widely consumed in condiments and as a preservative) most people who drink it do so diluted — perhaps only a tablespoon in a glass of water. Thus, the amount of ACV and its beneficial compounds actually consumed are quite small.

Research on ACV alone is slim, and most studies involve acetic acid or vinegars in general. One such study noted that women who consumed oil and vinegar salad dressing at least 5 times per week had lower risk of death from heart disease than those who rarely consumed it³. Though the finding was attributable to the oil due to its alpha-linoleic acid content, more than one ACV-promoting source cites this study.

As far as ACV’s effects on weight, only one moderately sized (more than 20 people) research investigation on humans was found. A Japanese study of the effects of apple cider vinegar intake on body weight and abdominal fat in 155 obese subjects showed that daily intake of 15 or 30 ml ACV (diluted) reduced body weight by about a kilogram, waist and hip circumferences by a centimeter each, as well as serum triglyceride more than placebo over 12 weeks⁴. The results were modest to say the least. The mechanism of how ACV affects body weight is unclear; several theories exist but they have yet to be proven with large population studies.

Some healthcare professionals take a different approach to apple cider vinegar, citing its acidic nature as detrimental for consumption (okay for body care and hygiene). Dental professionals warn of the dangers of consuming acidic beverages due to their potential to contribute to dental erosion and tooth decay⁵. Others take the stance that “excess acid in the diet can also lead to acidosis, which causes negative systemic side effects.⁵”

ALKALINE WATER

Protecting cells from DNA damage would equate to cancer prevention, but alkaline water is not shown to affect cancer development. A 2016 systematic review of the available scientific literature found “a lack of evidence for or against diet acid load and/or alkaline water for the initiation or treatment of cancer⁶.” Additionally, it “failed to locate any studies that evaluated whether alkaline water has a role in prevention or treatment of cancer.⁶” In fact, out of 252 studies reviewed, only one actually looked at alkaline water and cancer outcomes!

For bone health, if alkaline water contains enough calcium and is consumed in sufficient quantity it could be a significant dietary calcium source. In addition, an alkali diet decreases bone resorption (loss) in humans⁷. Some studies support the effect of alkaline water on kidney markers related to bone health⁷. Like an antacid which contains calcium carbonate, highly alkaline water has the consequence of buffering the stomach’s hydrochloric acid. This inactivates human pepsin (protein enzyme) which may be an issue if you don’t consume enough protein.

Anaerobic exercise metabolism causes lactic acid production in the working muscles which can cause fatigue. Some theorize that part of that lactic acid is released to the blood reducing blood pH (see * above) and disturbing acid-base balance. It’s suggested that alkaline water combats exercise-induced metabolic acidosis and improves performance. Results are mixed, with some studies finding no effect on lactate metabolism⁸ and others showing improved rehydration^9,10.

SUMMARY

Sources

1) JL Lewis. Overview of Acid-Base Balance. Merck Manual, Consumer Version. https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/acid-base-balance/overview-of-acid-base-balance. May 2018. Accessed 9.3.2019

2) AG Bender. Another Cancer and Diet Claim: The Alkaline Diet. American Institute for Cancer Research https://blog.aicr.org/2010/07/08/another-cancer-and-diet-claim-the-alkaline-diet/  July 8, 2010. Accessed 8.30.19

3) FB Hu, et al. Dietary intake of α-linolenic acid and risk of fatal ischemic heart disease among women. The American Journal of Clinical Nutrition, May 1999, Vol. 69 (5): 890–897. https://doi.org/10.1093/ajcn/69.5.890

4) T Kondo, et al. Vinegar Intake Reduces Body Weight, Body Fat Mass, and Serum Triglyceride Levels in Obese Japanese Subjects. Bioscience, Biotechnology, and Biochemistry, 2009. 73:8, 1837-1843.  DOI: 10.1271/bbb.90231

5) KF Wright. Is Your Drinking Water Acidic? A Comparison of the Varied pH of Popular Bottled Waters. American Dental Hygienists’ Association,  Journal of Dental Hygiene. Published online 2015 Jun; 89 Suppl 2:6-12. Retrieved from https://jdh.adha.org/content/89/suppl_2/6

6) Tanis R Fenton, Tian Huang. Systematic review of the association between dietary acid load, alkaline water and cancer. BMJ Open, 2016; 6(6): e010438. Published online 2016 Jun 13. doi: 10.1136/bmjopen-2015-010438

7) E Wynn, et al. Alkaline mineral water lowers bone resorption even in calcium sufficiency: Alkaline mineral water and bone metabolism. Bone, 2009, Vol. 44 (1): 120-124. ISSN 8756-3282, https://doi.org/10.1016/j.bone.2008.09.007

8) Grossi F, et al. Behavior of various enzymes and serum electrolytes in long distance runners during training. Effect of a bicarbonate-sulfate-calcium water of medium mineral content. La Clinica Terapeutica, 1991 Mar 15; 136(5): 343-9.

9) Weidman J, et al. Effect of electrolyzed high-pH alkaline water on blood viscosity in healthy adults. Journal of International Society of Sports Nutrition, 2016; 13:45. Published 2016 Nov 28. doi:10.1186/s12970-016-0153-8

10) J Chycki, et al. The effect of mineral-based alkaline water on hydration status and the metabolic response to short-term anaerobic exercise. Biology of Sport, 2017; 34 (3): 255-261. DOI: 10.5114/biolsport.2017.66003