Acid-forming foods and Osteoporosis

Do acid-forming foods cause osteoporosis?

Pawel Malczewski
facebook twitter google pinterest BUSTED
 

Short summary:

An acid-forming diet may cause mineral bone loss which leads to osteoporosis if it is combined with a calcium intake consistently below the recommended daily value. High calcium intake while on a high protein diet (which is considered to be acid-forming) may be actually protective to bone health. There is not enough evidence which shows that an acid-forming diet has its own negative effect on bone health. For a quick answer click here.

Explanation

This myth relates to an ash-diet hypothesis which claims that some foods containing acid-forming substances, such as animal protein from milk or meat and some plant foods, cause blood pH to drop (become less alkaline). It is, in turn, buffered by minerals released from bones. The loss of minerals from bones is supposedly responsible for osteoporosis.

This hypothesis (popular among alkaline diet enthusiasts) was supported by a number of older studies which did not actually prove that an acid-forming diet directly causes a mineral bone loss. It was assumed that an increased acidic environment in the body, an increase of calcium in urine and higher acidity of urine are indicators of mineral bone loss.

Many recent large studies (systematic reviews and meta-analysis) analyzed all currently available up to date studies and showed that there is not enough evidence to support this hypothesis and the assumptions of older studies, as explained below:

  • Higher amounts of calcium in urine in high protein diets are from higher absorption rather than mineral bone loss. (1)Kerstetter JE, O’Brien KO, Insogna KL. Low Protein Intake: The Impact on Calcium and Bone Homeostasis in Humans J. Nutr. March 1, 2003 vol. 133 no. 3 855S-861S Available here.
  • Although there is a potential for the acid-ash diet to increase acidity in the body, blood pH does not actually change. It is quickly regulated by a number of mechanisms in the body such as the intra and extra cellular buffering system and kidney-urine acid excretion. Bones don’t play a part in the buffering of blood pH caused by an acid-ash diet on its own. (2)De Santo NG, Capasso G, Malnic G, Anastasio P, Spitali L, D’Angelo A. Effect of an acute oral protein load on renal acidification in healthy humans and in patients with chronic renal failure. JASN May 1, 1997 vol. 8 no. 5 784-792. Available here. (3)Bonjour JP. Nutritional disturbance in acid–base balance and osteoporosis: a hypothesis that disregards the essential homeostatic role of the kidney. British Journal of Nutrition / Volume 110 / Issue 07 / 14 October 2013, pp 1168-1177. Available here.
  • Higher acidity in urine is a result of an efficient buffering system of the kidneys removing extra acid-forming minerals and acids. (read more..)

Although some studies show that there is a slight pH change with either a high protein diet or alkaline multi-mineral supplementation, these changes are not likely to affect the bone health or the acid-base balance of the body. In any case, there is still no scientific evidence of that.

Conclusion

Back to top
Until it is proven otherwise, the acid-ash diet remains only a hypothesis. There is strong scientific evidence that mineral bone loss and resulting osteoporosis are not caused on their own by an acid-ash diet.
More detailed studies are needed showing at what precise pH bones start to release calcium in significant amounts, and what are the amounts of acid-ash taken for specific period of time that will cause that bone loss.

References   [ + ]

1. Kerstetter JE, O’Brien KO, Insogna KL. Low Protein Intake: The Impact on Calcium and Bone Homeostasis in Humans J. Nutr. March 1, 2003 vol. 133 no. 3 855S-861S Available here.
2. De Santo NG, Capasso G, Malnic G, Anastasio P, Spitali L, D’Angelo A. Effect of an acute oral protein load on renal acidification in healthy humans and in patients with chronic renal failure. JASN May 1, 1997 vol. 8 no. 5 784-792. Available here.
3. Bonjour JP. Nutritional disturbance in acid–base balance and osteoporosis: a hypothesis that disregards the essential homeostatic role of the kidney. British Journal of Nutrition / Volume 110 / Issue 07 / 14 October 2013, pp 1168-1177. Available here.

Leave a Reply

Your email address will not be published. Required fields are marked *