Research suggests skeletal health is damaged by high intakes of acid forming foods in combination with low levels of alkalising foods. The Western diets is generally considered to produce chronic, low grade acidosis and this acidosis is generally believed to occur because the release of noncarbonic acids from protein foods (e.g. sulphuric acid from the metabolism of certain amino acids) is greater than the release of bases from fruits and vegetables (e.g. bicarbonate from the metabolism of organic acid salts of potassium). In response to acidification of the blood, alkaline mineral stores are mobilised from bone in order to maintain a suitable blood pH. Low extracellular pH has been shown in cell studies to increase osteoclastic activity and result in resorption pits in bone. Chronic depression of blood pH is though to lead to skeletal damage that in the long-term results in decreased structural strength and increased risk of fractures.
Research has investigated the association between dietary acid forming foods and bone mass in a number of studies. For example, research1 published in the American Journal of Clinical Nutrition in 2004, investigated whether lower dietary acidity was associated with greater axial and peripheral bone mass and bone turnover. The researchers used data from a cross sectional population based study that measured spine and hip bone mineral densities in 1056 women aged 45 to 54 y, and forearm and urinary markers of bone resorption in 62 women. The net rate of noncarbonic acid production (NEAP) was estimated from measurements of protein and potassium in the diet by looking at food frequency questionnaires. From the questionnaires the ratio of acid to alkali forming foods was calculated. The researchers also controlled for possible confounding variable that are known to affect bone mineral density.
The results showed that lower estimates of NEAP were associated with greater spine and hip bone mass density and greater forearm bone mass. As NEAP estimates increased across quartiles, forearm and hip bone densities fell and the spine densities also showed similar trends. The low estimates of NEAP were significant predictors of forearm and hip bone mass. Lower estimates of NEAP were also associated with lower excretion of markers of bone resorption in the urine. Overall, the results suggest that diets lower in protein and higher in potassium are associated with greater bone mass. This bone mass could provide added structural support which may lead to a reduction in fractures later in life. Recommendation to consume greater quantities of fruit and vegetables would increase dietary potassium and could have an alkalising effect on the blood.
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