Posted on Sun, 19 Oct 14
There is a lot of talk about so called “alkaline diets” ranging from elaborate lists of foods to avoid, to claims that an alkaline diet can reduce the spread of cancer. But how much of this is factual, and is there anything to the alkaline diet?
Alkaline diets have a long history of popular use and enjoyed a number of proponents at the turn of the 20th Century. In fact, the founder of the macrobiotic diet Sagen Ishizuka (1851–1910) linked the equilibrium of acid and alkaline foods with the Chinese ideas of Yin and Yang (1). Move forward 100-years to the present day and popular books are still being published on alkaline diets with the general premise that eating more alkaline foods, and avoiding acid ones, can change the bodies acid-alkaline balance and deliver important health benefits.
In addition to popular books, there has also been a lot of scientific research into the influence of diet on acid-alkaline balance and its potential effects on human health in recent years. However, there is often an incongruity between popular alkaline diets and the science behind this concept. So with this in mind the following is a brief primer on the alkaline diet concept and separates some of the fact from fiction.
Diet-induced low-grade acidosis
So what is “acidosis” anyway? A popular conception of the alkaline diet is that it alkalizes your blood, however your blood pH is very tightly regulated at an alkaline pH of 7.35, which means this is not technically correct. Scientifically the concept of “acidosis” does not refer to marked alterations in blood pH but more correctly a dynamic compensatory response that occurs with an acid producing diet (2). In other words the term acidosis refers to a process, and not a change in blood pH to an acid state.
Food is linked to acidosis because it has the potential to place a more acid or alkaline “load” on your body depending on its nutritional composition, and subsequently your body quickly compensates or “buffers” this load to maintain a stable blood pH.
High-protein foods tend to increase the production of organic and sulfuric acids and increase acid load. These are mainly meat, fish, dairy and cereals, and the chloride in sodium chloride (salt) has an important acidic effect as well. On the other hand foods rich in potassium salts, like potassium citrate and malate, are metabolized to potassium bicarbonate and have a net alkaline effect. These are mainly fruit and vegetables (3). These nutritional characteristics can be reliably used to estimate the acid or alkaline effect of foods (see table 1).
Table 1: Acid or Alkaline Potential of Various Foods (4)
PRAL; Average potential renal acid loads.
But if your blood pH is not significantly altered, does this mean diet-induced acidosis is not worth worrying about? There are a few reasons why scientists think it does matter 1) it has been estimated that traditional human diets were much less acid producing than they are today, so in the same way we are not well suited to a highly processed diet we may not be suited to a predominately acid one 2) there is a trade-off for constantly countering the effect of acid foods, over time it may deplete your reserve of buffering alkaline minerals, especially in your bone, and tax your muscle, kidneys and endocrine system, and 3) there is compelling evidence to suggest that diet-induced low-grade acidosis is linked to important health effects over time (5,6).
Is diet-induced acidosis important?
There is increasing evidence to suggest that a more alkaline diet may be important for better health. Key areas include:
1. Bone health
Some, but not all, studies have suggested that a more alkaline diet or supplementation with alkaline minerals may improve bone health and prevent osteoporosis. Although a more alkaline diet may reduce the excretion of calcium from bone, the potential benefit may also be due more complex effects on cellular and hormonal bone metabolism (7-8).
2. Kidney stones
An acidic diet can increase urinary levels of citrate, a risk factor for kidney stones. In people with kidney stones a more alkaline diet predicted a lower incidence of stone formation, and supplementation with alkaline minerals was shown to reduce the risk of stone formation by 85% over a 3-year period (9,10).
3. Chronic pain
Local tissue acidosis can mediate pain through acid-sensing ion channels, suggesting an alkaline diet may be useful for pain relief. While there is limited research in this area one clinical study demonstrated important improvements in back pain with an alkaline mineral supplement (11,12).
An alkaline diet may help prevent the age-related decline in muscle mass, also known as sarcopenia. In postmenopausal women supplementation with potassium bicarbonate neutralized acidosis and improved a measure of muscle breakdown (urinary nitrogen excretion). And a more alkaline diet has been associated with better lean muscle mass in older age men and women (13,14).
5. Heart disease
Diets higher in potassium result in robust reductions in blood pressure and risk of stroke (15). In accordance, a more alkaline diet has been associated with lower blood pressure in some studies (16-18). And a more alkaline diet has been linked with other cardiovascular risk factors, notably insulin resistance and chronic kidney insufficiency (19).
There is experimental evidence to suggest that diet-induced acidosis may be a risk factor for cancer development, but this relationship is not clear and difficult to demonstrate in human research (20). And there are theoretical concerns about the safety of alkalization therapy (21).
Exposure to man-made environmental pollutants is ubiquitous, and it has been suggested that chronic, low-grade diet-induced acidosis may impair detoxification and increase risk of environmental illness over time (22). Again this idea is difficult to test, but the concept has a compelling scientific rationale (22).
Alkaline nutritional therapy
While nutritional supplements, especially alkaline salts of potassium, may be useful there are potential adverse effects in people with heart, lung or kidney disease and should consequently be used only under the guidance of a health professional (2). But for most people alkaline mineral combinations of potassium, calcium and magnesium as citrates or bicarbonates and perhaps green foods, vegetables juices or smoothies could be a simple and safe way to reduce acidosis for most people (see table 2).
Table 2: Examples of Alkalizing Dietary Supplement Studies
Nonetheless food is the clearly the best approach and improving the net alkaline potential of your diet is straightforward; increase fruit and vegetable intake. This simple strategy will displace acid forming foods and counterbalance their acidic effect. A reduction in salt will also reduce acidity, especially in people who are salt sensitive (25).
It is important to keep in mind that adequate protein intake is important for general health as well as facilitating acid excretion, so a very low-protein diet could in fact increase acidosis and have adverse health effects (2). Perhaps we should heed Sagen Ishizuka’s intuition and consider acid-alkaline nutrition as a natural balance of Yin and Yang, and not as the radical consumption of only alkaline food that is sometimes proposed.
A dietary pattern based on traditional foods that naturally change in acid-alkaline qualities from meal to meal and with shifts in seasonal food availability may well be the model (mostly) alkaline diet.
This article first featured in CAM Magazine, October 2014.
- Manz F. History of nutrition and acid-base physiology. Eur J Nutr. 2001 Oct;40(5):189-99.
- Pizzorno J, Frassetto LA, Katzinger J. Diet-induced acidosis: is it real and clinically relevant? Br J Nutr. 2010 Apr;103(8):1185-94.
- Frassetto L, Morris RC Jr, Sellmeyer DE, Todd K, Sebastian A. Diet, evolution and aging--the pathophysiologic effects of the post-agricultural inversion of the potassium-to-sodium and base-to-chloride ratios in the human diet. Eur J Nutr. 2001 Oct;40(5):200-13.
- Remer T, Manz F. Potential renal acid load of foods and its influence on urine pH. J Am Diet Assoc. 1995 Jul;95(7):791-7.
- Sebastian A, Frassetto LA, Sellmeyer DE, Merriam RL, Morris RC Jr. Estimation of the net acid load of the diet of ancestral preagricultural Homo sapiens and their hominid ancestors. Am J Clin Nutr. 2002 Dec;76(6):1308-16.
- Alpern RJ, Sakhaee K. The clinical spectrum of chronic metabolic acidosis: homeostatic mechanisms produce significant morbidity. Am J Kidney Dis. 1997 Feb;29(2):291-302.
- Remer T, Krupp D, Shi L. Dietary protein's and dietary acid load's influence on bone health. Crit Rev Food Sci Nutr. 2014;54(9):1140-50.
- Shi L, Libuda L, Schönau E, Frassetto L, Remer T. Long term higher urinary calcium excretion within the normal physiologic range predicts impaired bone status of the proximal radius in healthy children with higher potential renal acid load. Bone. 2012 May;50(5):1026-31.
- Trinchieri A, Lizzano R, Marchesotti F, Zanetti G. Effect of potential renal acid load of foods on urinary citrate excretion in calcium renal stone formers. Urol Res. 2006 Feb;34(1):1-7.
- Ettinger B, Pak CY, Citron JT, Thomas C, Adams-Huet B, Vangessel A. Potassium-magnesium citrate is an effective prophylaxis against recurrent calcium oxalate nephrolithiasis. J Urol. 1997 Dec;158(6):2069-73.
- Deval E, Gasull X, Noël J, Salinas M, Baron A, Diochot S, Lingueglia E. Acid-sensing ion channels (ASICs): pharmacology and implication in pain. Pharmacol Ther. 2010 Dec;128(3):549-58
- Vormann J, Worlitschek M, Goedecke T, Silver B. Supplementation with alkaline minerals reduces symptoms in patients with chronic low back pain. J Trace Elem Med Biol. 2001;15(2-3):179-83.
- Frassetto L, Morris RC Jr, Sebastian A. Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women. J Clin Endocrinol Metab. 1997 Jan;82(1):254-9.
- Dawson-Hughes B, Harris SS, Ceglia L. Alkaline diets favor lean tissue mass in older adults. Am J Clin Nutr. 2008 Mar;87(3):662-5.
- Aburto NJ, Hanson S, Gutierrez H, Hooper L, Elliott P, Cappuccio FP. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 2013 Apr 3;346:f1378.
- Zhang L, Curhan GC, Forman JP. Diet-dependent net acid load and risk of incident hypertension in United States women. Hypertension. 2009 Oct;54(4):751-5.
- Engberink MF, Bakker SJ, Brink EJ, van Baak MA, van Rooij FJ, Hofman A, Witteman JC, Geleijnse JM. Dietary acid load and risk of hypertension: the Rotterdam Study. Am J Clin Nutr. 2012 Jun;95(6):1438-44.
- Murakami K, Sasaki S, Takahashi Y, Uenishi K; Japan Dietetic Students' Study for Nutrition and Biomarkers Group. Association between dietary acid-base load and cardiometabolic risk factors in young Japanese women. Br J Nutr. 2008 Sep;100(3):642-51
- Souto G, Donapetry C, Calviño J, Adeva MM. Metabolic acidosis-induced insulin resistance and cardiovascular risk. Metab Syndr Relat Disord. 2011 Aug;9(4):247-53.
- Robey IF. Examining the relationship between diet-induced acidosis and cancer. Nutr Metab (Lond). 2012 Aug 1;9(1):72. doi: 10.1186/1743-7075-9-72.
- Khajah MA, Almohri I, Mathew PM, Luqmani YA. Extracellular alkaline pH leads to increased metastatic potential of estrogen receptor silenced endocrine resistant breast cancer cells. PLoS One. 2013 Oct 1;8(10):e76327.
- Minich DM, Bland JS. Acid-alkaline balance: role in chronic disease and detoxification. Altern Ther Health Med. 2007 Jul-Aug;13(4):62-5.
- Berardi JM, Logan AC, Rao AV. Plant based dietary supplement increases urinary pH. J Int Soc Sports Nutr. 2008 Nov 6;5:20.
- König D, Muser K, Dickhuth HH, Berg A, Deibert P. Effect of a supplement rich in alkaline minerals on acid-base balance in humans. Nutr J. 2009 Jun 10;8:23. doi: 10.1186/1475-2891-8-23.
- Sharma AM, Kribben A, Schattenfroh S, Cetto C, Distler A. Salt sensitivity in humans is associated with abnormal acid-base regulation. Hypertension. 1990 Oct;16(4):407-13.