The theory also claims that calcium is taken out of bones to buffer the excess acidity, leading to increased calcium excretion in the urine and weakened bones. As a result, proponents of the alkaline diet recommend limiting the consumption of meat, grains and dairy products and increasing the amount of fruits and vegetables, to help neutralize the acids. They also recommend that people check their body’s acidity level by testing the pH of their urine and/or saliva.
Researchers at the University of Calgary have done an extensive review/analysis of all the scientific literature on the subject and found that the scientific evidence provides no support for these ideas. Here is what they concluded:
- There is no association between urine pH or urinary acid excretion and loss of bone density or the incidence of fractures;
- A higher amount of acid excreted through the urine does not increase the risk of osteoporosis;
- There is no evidence from better designed studies that increasing the diet acid load promotes calcium loss;
- There is no evidence that a higher phosphorus intake contributes to calcium loss or that it is detrimental to bone health. In fact, a higher intake of phosphorus is associated with a greater retention of calcium in the body.
A closer look at protein
First, it is important to realize that protein makes up approximately 50% of the volume of bones and 1/3 of their mass, and provides their basic structure. And because bones are living tissue, they require a daily supply of protein from the diet to stay strong.
The belief used to be that protein was detrimental to bones because it leads to increased calcium excreted in the urine. However, extensive research has been done on the subject and studies now clearly show that a diet rich in calcium and sufficient protein are both necessary to maintain optimal bone health.
Second, the level of calcium in the urine is not a proper measure of bone health because it only assesses one aspect of the whole picture. It is more important to look at calcium balance or the balance of calcium absorbed and retained versus just the amount of calcium excreted by the body.
Studies have shown that while higher intakes of protein do indeed lead to increased urinary calcium loss, they also lead to an increase in intestinal calcium absorption. So when we look at calcium balance, we find that avoiding dairy products and other protein rich foods is not justified and that it can actually be detrimental to bones and overall health.
Some practical tips
- Be sure to consume sufficient protein.
- Consume milk products regularly since they provide numerous bone-building nutrients, including protein, calcium and Vitamin D.
- Increase your intake of fruits and vegetables. They may not have a role to play in “buffering acids” in the body but they are associated with overall good health. And some studies suggest that they may also play a role in healthy bones, possibly due to their content of nutrients beneficial to bones such as vitamin K, magnesium, vitamin C and A, or other yet to be identified nutrients.
Easy nutritious recipes
1. Fenton et al. Low urine pH and acid excretion do not predict bone fractures or the loss of bone mineral density: a prospective cohort study. BMC Musculoskelet Disord 2010;11:88.
2. Fenton et al. Meta analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009;24:1835-1840.
3. Fenton et al. Phosphate decreases urine calcium and increases calcium balance: A meta-analysis of the osteoporosis acid-ash hypothesis. Nutr J 2009;8:41.
4. Heaney RP and Layman DK. Amount and type of protein influences bone health. Am J Clin Nutr 2008;87:1567S-70S.