The potassium sodium ratio has been shown to be critical to the prevention of hypertension and strokes. The ratio is also felt to be important for the prevention of osteoporosis, with a higher ratio leading to improved bone density. But the evidence for its role in osteoporosis is not as strong as it is for hypertension. There are several reasons why this is so. Although there has been extensive work done in osteoporosis, there are large gaps in our knowledge of the relation of the minerals, hormones and other factors involved. What is needed is a systems approach such as that done for hypertension by Drs. Guyton and Young.
There have been a large number of studies of indigenous populations for hypertension. There have not been as many done for osteoporosis. Those that have been done have had mixed results. One problem is the lack of vitamin D and the lack of protein in many modern indigenous diets, both of which have a major effect on bone density.
Because today's methods to measure bone density were not present in the 1950s and 1960s, there were not the same kinds of studies for osteoporosis as there were for hypertension during that period. There are some studies being done more recently. However, there are fewer indigenous groups uninfluenced by modern diet than there were in the 1950s and 1960s.
Two Recent Studies Of Bone Density
Two recent studies discuss bone density and osteoporotic fractures in some modern indigenous groups. The Shuar and the Colonos of Ecuador were examined with calcaneal quantitative ultrasound (QUS) to determine their bone mineral density (1). Both groups showed increased bone density in comparison to other groups.
Since this was a study to determine norms for future comparison, factors contributing to the increased density were not reported. However, since the 1970s the Shuar and other indigenous groups from the Amazon have been exposed increasingly to outside influences. The ability to study their diet may be lost.
The Aboriginals and Torres Strait Islanders were examined for both fracture incidence and bone mineral density (2) (3). They were compared to Caucasian Australians. Both of these groups had denser bone and fewer fractures than the Caucasians at the same age. However it is not because of diet. The diet of the Aboriginals and Torres Strait Islanders is generally very deficient, and is much like a modern diet. This is the problem that will be faced by studying modern indigenous groups today. There are very few groups uninfluenced by the modern diet.
While such bone density studies are interesting, studies of indigenous groups will be unlikely to provide helpful dietary evidence. There are multiple other known factors that contribute to increased bone density. These other factors that increase bone density include a low incidence of smoking and excessive alcohol, and increased physical activity, especially weight bearing. These factors will influence bone density far more than minor dietary differences.
As indigenous groups are exposed to the modern world they shift to a modern diet. Any dietary differences will be minor. To accurately determine how much diet, physical activity and the various other factors play a part in osteoporosis, studies of indigenous groups will play only a minor role. A systems approach like that done by Drs. Guyton and Young for hypertension will be needed.
What Is Needed
The extensive experimental and integrative work done by Drs. Guyton and Young is lacking in osteoporosis. Much like hypertension, there are multiple interactions involved. For osteoporosis there are interactions between several hormones, minerals, and nutrients. Each of these interacts with the kidneys and bones to balance the calcium deposition in bone.
Potassium, especially in the form found in high potassium foods, organically bound to citrate and other bicarbonate precursors, has a positive effect on calcium resorption and deposition. Sodium leads to calcium loss in the urine. However the metabolic pathways that were discovered and put in context in hypertension, have not been as thoroughly worked out.
Population based clinical trials have been done with modern populations which help lend weight to the high potassium food contribution to preventing and correcting osteoporosis. Other important evidence comes from animal and human experimental work. We will discuss some of these in future posts.
1. Normative calcaneal quantitative ultrasound data for the indigenous Shuar and non-Shuar Colonos of the Ecuadorian Amazon. Madimenos FC, Snodgrass JJ, Blackwell AD, Liebert MA, Cepon TJ, Sugiyama LS. Arch Osteoporos. 2011 Dec;6(1-2):39-49. doi: 10.1007/s11657-011-0056-x. Epub 2011 May 21.
2. Fractures of the femoral neck in Australian Aboriginals and Torres Strait Islanders. MacIntosh DJ, Pearson B. Aust J Rural Health. 2001 Jun;9(3):127-33.
3. Increased bone mineral density in Aboriginal and Torres Strait Islander Australians: impact of body composition differences. Maple-Brown LJ, Hughes J, Piers LS, Ward LC, Meerkin J, Eisman JA, Center JR, Pocock NA, Jerums G, O'Dea K. Bone. 2012 Jul;51(1):123-30. doi: 10.1016/j.bone.2012.04.011. Epub 2012 Apr 27.