The subject of acid: alkali balance has gathered much interest in recent years. True to the roots of functional medicine, it is a single area, which you can address with your clients that has potentially wide-ranging benefits.
The Western diet is typically associated with low-grade, chronic metabolic acidosis. Contemporary Western diets commonly contain acid precursors in excess of base precursors, yielding a daily systemic net acid load of varying amounts.
Even small fluctuations in H+ have significant physiological effects. When the diet has a net acid load, several of the body systems must adapt to restore balance; the skeleton, skeletal muscle, kidney and endocrine systems in particular are placed under increased strain to do this.
“Adaptations of the skeleton, skeletal muscle, kidney and endocrine systems that serve to mitigate the degree of that perturbation (caused by diet-induced acidosis) impose a cost in cumulative organ damage that the body pays out over decades of adult life.”1
Acidosis & Bone Health
There are wide-ranging clinical effects of diet-induced acidosis. Currently, bone health is the best-documented clinical consequence. The major reservoir of base is the skeleton, in the form of alkaline salts of calcium, which provide the buffer needed to maintain blood pH and plasma bicarbonate concentrations. Skeletal muscle can also act as a buffer.
Acid-promoting diets are associated with both increased calcium and bone matrix protein excretion. Acidosis is also known to inhibit mineral deposition by osteoblasts2,3.
Extracellular H+ has been found to have an influence on the activation of osteoclasts (cells involved in the resorption or breakdown of bone). A recent study has found that osteoclasts are almost inactive at a pH above 7.44,5.
- Two studies published in the American Journal of Clinical Nutrition, each involving 1000 women found that in those aged 45 -54, a lower dietary intake of acid-producing foods correlated with greater spine and hip bone mineral density, as well as greater forearm bone mass, after adjusting for age, weight, height and menstrual status. In women aged 65+, those with a high dietary ratio of animal: vegetable protein intake were found to have more rapid femoral neck bone loss and a greater risk of hip fracture than those with a low ratio6,7.
- New research has also shown that metabolic acidosis seems to be compounded by lower vitamin D levels8,9.
Assessment of Acidosis
24 hour urinary pH has been found to be the best measure of diet dependent net acid excretion and seems to be a more reliable indicator than simply testing the first morning urine10.
Dietary Effects on Acid: Alkali Balance
• In general terms, a diet high in fruits and vegetables and low in animal protein and sodium chloride reduces acid load. Interestingly, a low protein diet could also induce acidosis as this may induce catabolism of muscle protein, thus increasing acid load. It is therefore important that the diet contains neither too much, nor too little protein; and favours vegetable over animal protein11-15.
• Research has found potassium citrate to be effective supplementation for conferring a mild alkali load, and reducing bone resorption, caution is needed with patients with heart, lung or kidney disease16-19.
• Increased fruit and vegetable consumption, as well as potassium and magnesium alkali intake, is consistently associated with a base-producing diet and greater bone mineral density11,12.
Be Proactive About Your Bone Health
For many people, bone health is only a matter of concern when it becomes apparent that something is going wrong. Yet this is one area where you can be wholly proactive and start to protect early through positive dietary and lifestyle choices, before things start to go wrong. Optimizing the body’s acid: alkali balance is an important step to take towards better bone health20 and the good news is that achieving this balance has benefits for many more aspects of good health besides.
1. Frassetto L et al. 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
2. Bailey JL, et al. (1996) Influence of acid loading, extracellular pH and uremia on intracellular pH in muscle. Miner Electrolyte Metab 22, 66-68
3. Buclin T et al. (2001) Diet acids and alkalis influence calcium retention in bone. Osteoporosis Int 12, 493-499
4. Arnett TR. Extracellular pH regulates bone cell function. J Nutr. 2008 Feb; 138(2):415S-418S
5. Frick KK, et al. (2009) Metabolic acidosis increases intracellular calcium in bone cells through activation of the proton receptor OGR1. J Bone Miner Res 24. 305-313
6. New SA, et al. (2004) Lower estimates of net endogenous non-carbonic acid production are positively associated with indexes of bone health in premenopausal and perimenopausal women. Am J Clin Nutr 79, 131-138
7. Sellmeyer DE, Stone KL, Sebastian A, et al. (2001) A high ratio of dietary animal to vegetable protein increases the rate of bine loss and the risk of fracture in postmenopausal women. Study of Osteoporotic Fractures Research Group. Am J Clin Nutr 73, 118-122
8. Heaney RP, et al. Calcium absorption varies within the reference range for serum 25-hydroxyvitamin D. J Am Coll Nutr. 2003 Apr; 22(2): 142-6
9. Schwalfenberg GK, et al. Addressing vitamin D deficiency in Canada: a public health innovation whose time has come. Public Health. 2010 Jun; 124(6): 350-9
10. Whiting SJ et al. (2005) Measurement of net acid excretion by use of paper strips. Nutrition 21, 961-963
11. Jehle S et al. Partial neutralization of the acidogenic Western diet with potassium citrate increases bone mass in postmenopausal women with osteopenia. J Am Soc Nephrol. 2006 Nov; 17(11): 3213-22
12. Tucker KL et al. (1999) Potassium, magnesium and fruit and vegetable intalkes are associated with greater bone mineral density in elderly men and women. Am J Clin Nutr 69, 727-736
13. Remer T et al. (1994) Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Am J Clin Nutr 59, 1356-1361
14. Ince BA et al. (2004) Lowering dietary protein to U.S. recommended dietary allowance levels reduces urinary calcium excretion and bone resorption in young women. J Clin Endocrinol Metab 89, 3801-3807
15. Remer T (2001) Influence of nutrition on acid-base balance – metabolic aspects. Eur J Clin Nutr 40, 214-220
16. Moseley KF, et al. Potassium citrate supplementation results in sustained improvement in calcium balance in older men and women. J Bone Miner Res. 2013 Mar; 28 (3): 497-504
17. Bersin RM et al. (1989) Metabolic and hemodynamic consequences of sodium bicarbonate administration in patients with heart disease. Am J Med 87, 7-14
18. Frangiosa A, et al. (2006) Acid-base balance in heart failure. J Nephrol 19, Suppl. 9, S115-S120
19. Coppoolse R, et al. (1997) Effect of acute bicarbonate administration on exercise responses of COPD patients. Med Sci Sports Exerc 29, 725-732
20. Diet Induced Cellular Acidosis. Dr Joseph Pizzorno. Functional Medicine Conference 28-29 September 2013