High-protein diets may cause bone loss in older women, study
March 25, -- Eating more protein could help your body absorb calcium, possibly putting a halt to bone-thinning osteoporosis, says a new. The relation between dietary protein and fracture risk is unclear. Dietary . An augmentation in calcium absorption on a high protein diet may explain, in part, the. "Even after adjusting for all the things that could impact the relationship between high animal protein intake to bone loss and hip fractures, the relationship was.
Bone health is not simply a skeletal issue; it is a musculoskeletal issue. This review intends to briefly discuss several dietary and physiologic factors that affect bone health and to provide an overview of the current status of research in these areas. Suggestions for areas of further research and investigation are also provided. High protein intakes have been shown to affect calcium homeostasis, resulting in increased calcium excretion, but findings regarding the effect of protein on calcium balance and bone health have been mixed.
Protein intake and bone health.
One study of nuns who were studied over a y period found that protein intakes ranging from 0. Other studies suggest that, as a result of increased urinary calcium excretion with high protein intake, there is an increased risk of fractures or osteoporosis 26. As protein intake increases, there is an increase in urinary calcium, with most subjects developing negative calcium balance 7 — 9.
However, the increase in urinary calcium observed with purified proteins or amino acid infusions is not readily observed with food sources of protein 1. Studies providing total parenteral nutrition found that urinary calcium output is a direct function of amino acid intake, at least under the unique circumstance of total parenteral nutrition 1.
In healthy adults, when protein intake was increased from 0. Increased calciuria does not necessarily translate to calcium loss, negative calcium balance, and reduced bone mass To the contrary, several studies have observed a positive association between dietary protein intake and increased bone mineral content or decreased risk of fracture 15 — One study found that among premenopausal women, there was a significant positive association between protein intake and bone mineral content, suggesting that dietary protein intake actually may be a determinant of the peak bone mass Another factor influenced by protein is insulin-like growth factor IGF-1which plays a key role in bone metabolism.
Higher levels of IGF-1 are osteotrophic.
Excess Dietary Protein Can Adversely Affect Bone | The Journal of Nutrition | Oxford Academic
As individuals age, there is a decline in serum concentrations of IGF-1 Both the level and type of protein in the diet may have an effect on IGF-1 levels 20 — Some, but not all 22studies have found that meat as a protein source is associated with higher serum levels of IGF-1 2021which is in turn associated with increased bone mineralization and fewer fractures Soy foods have been linked with lower levels of IGF-1 It has been suggested that animal protein—based diets might have a greater negative effect on skeletal health than do vegetable-based diets 24 because dietary animal protein induces a greater increase in urinary calcium excretion than vegetable protein.
In a large group of middle-aged and elderly women in China, urinary excretion of calcium was correlated positively with intake of animal protein However, in the Framingham Osteoporosis Study in which women and men, whose average age at baseline was 75 y, were assessed for bone mineral density and dietary intake, a higher intake of animal protein was not associated with a decrease in bone mineral density Further, in a 3-y clinical study of healthy men and women 65 y of age and older, those who consumed the most protein and were supplemented with calcium experienced the greatest improvement in bone mass density, and most of the protein consumed was animal protein Moreover, clinical studies do not support the idea that animal protein has a detrimental effect on bone health or that vegetable-based proteins are better for bone health 13 Several studies examining the effect of meat have found no effect on either bone mineral density or markers for bone mineral density.
The increase in meat intake resulted in no change in urinary calcium excretion. Protein intake increases urinary calcium loss, but whether negative calcium balance results will depend on dietary calcium intake 4. In a study of changes in bone resorption markers, 15 young, healthy men and women participated in 3 randomly assigned 5-d diet periods low-nitrogen, low-calcium; high-nitrogen, high-calcium; high-nitrogen, high-calcium.
Levels of markers were compared with the subjects' average baseline dietary intake of 0. Similar findings have been observed in older subjects. In the study of men and women cited earlier, associations between protein intake and changes in bone mass density were examined. The researchers identified a positive association between dietary protein intake and change in bone mass density in those with the highest intake of protein who were supplemented with calcium and vitamin D There was no benefit from supplementation among those with lower intakes of protein.
A Western-type diet has been reported to be associated with osteoporosis and urinary calcium loss Urinary calcium has been found to be increased with acid-forming foods, such as meat, fish, eggs, and cereal, and negatively associated with plant foods and is likely determined by the acid-base status of the total diet.
Clearly, it is not how much phosphate is consumed that affects urinary calcium, but whether it is in a chemically neutral or acid form. Similar findings were reported by Breslau et al. They compared vegetarian, ovovegetarian and animal protein diets. Although total protein, phosphorus, sodium, potassium and calcium content of all of these diets was not different, the animal protein diet contained 6. Urinary pH was more acidic, 6. Daily urinary calcium was 47 mg higher when those young adults were consuming an animal protein diet vs.
The effect of a higher protein, acid-ash diet has also been shown in elderly people who participated in a study in which they ate 0.
High-protein diets may cause bone loss in older women, study
Recently, Appel et al. Dietary protein was a constant percentage of energy, whereas dietary calcium was somewhat lower in the control diet vs.
An increase in fruit and vegetable intake from 3. Fruits and vegetables are the major source of buffer in the diet Table 1. Population studies further confirm the effect of urinary acidity on urinary calcium excretion. Urinary calcium excretion was lower when the urine was more alkaline; more acidic urine was associated with a higher urinary calcium.
Strong evidence that the effects of high protein diets are mediated through changes in acid-base balance comes from studies in which the acid loads of dietary protein are neutralized with bicarbonate. Only two studies with this design have been published to date.
- What is the effect of a high-protein diet on bone health?
Lutz supplemented a high protein diet g with bicarbonate and looked at the effect on urinary calcium and calcium balance. Subjects had similar calcium balances when consuming either the high protein g diet plus bicarbonate or a moderate protein 44 g diet.
What is the effect of a high-protein diet on bone health?
A more elaborate study was conducted by Sebastian et al. During KHCO3 supplementation, urinary calcium fell and calcium balance was more positive. A study in adult rats assessed bone formation and resorption by microradiography Barzel and Jowsey A similar effect was also seen when the rats consumed a low calcium diet.
Bone resorption was increased in rats consuming ammonium chloride regardless of the calcium content of the diet, and total bone was smaller than in the controls fed the same diet. Rats fed a low calcium diet who received bicarbonate experienced high bone formation and deposited about the same amount of bone content as rats fed a regular calcium diet.
Ammonium chloride as a source of acid caused bone resorption and decreased total bone, whereas bicarbonate increased bone formation and increased total bone, thus protecting the rat's skeleton from the negative effects of a low calcium diet.
More recently, the effects of acid ingestion on rat bones were duplicated with histomorphometry and bone markers by Myburgh et al. Overall, these studies show us that the effects of adding buffer to a high protein diet are as follows: On the other hand, when the body is challenged with a dietary acid load, the kidneys excrete more acidic urine, and the organism also turns to the skeleton for additional buffer.
The long-term consequence of a small change in calcium balance is substantial. A mg increase in urinary calcium loss per day will result in a Because the average adult female skeleton contains g calcium at its peak, this is a loss of one half of total skeletal stores!
For a male with a store of g calcium, this is about one third of the total. Both Bushinsky and Arnett and Sakhaee have documented that osteoclasts and osteoblasts respond independently to small changes in pH in the culture media in which they are growing.
A small drop in pH causes a tremendous burst in bone resorption.Protein and Bone Health
Dietary salt is known to affect urinary calcium excretion. It is generally poorly appreciated that the anion accompanying sodium is important to the overall effect of salt on calcium metabolism Massey and Whiting When Berkelhammer et al.
The blood pH was 7.