Some evidence in the nutritional literature has suggested that a high protein intake may induce hypercaluria. Such an increased excretion of calcium is worrying because calcium balance is required for the contraction of muscle and in the longer term a urinary calcium loss may initiate the development of osteoporosis. Some evidence from animal studies suggests that purified protein may indeed cause some calcium loss from the urine, but human studies using meat have not shown similar results. For example, in one study1 researchers studied the effects of a high protein intake on calcium excretion in human subjects. The subjects were consuming a basal diet containing 2200 kcals per day that included 286 grams of carbohydrate, 75 grams of protein, 87 grams of fat with 220 mg of calcium. The protein content of this diet was then increased to 142 grams per day while the calcium intake was stabilised at 800 mg per day with the addition of calcium gluconate tablets to the dietary levels of calcium.
The results of the study showed that in both the short and long term calcium excretion in the urine and faeces was not increased with increasing protein intake. There was also no change in the calcium balance of the subjects. Therefore these results tend to confirm other studies and show that a high protein content in the form of meat does not cause detrimental changes to calcium balance. Further, the fact that the faecal excretion of calcium did not increase with a high meat intake suggests that protein does not affect the absorption of calcium. The authors were able to confirm this by using radioisotopes of calcium and measuring their absorption rates, which were not affected by the protein content of the diet. Some studies involving rats have reported that calcium excretion does occur with increased protein intake, but this may require very high levels of protein. The levels seen in this study were within the realms of normal dietary intakes for an athlete and are therefore more realistic than some of the animal studies.
Dr Robert Barrington’s Nutritional Recommendation: High protein diets are not unhealthy. In fact evidence supports a role for high protein diet in weight loss and health. As with all foods it is important to eat high quality sources of protein such as whey protein, vegetable proteins and grass fed organic meat sources. One of the main problems with meat as a source of protein is that is often of low quality and contains chemicals that may interfere with metabolic regulation and upset our delicate biochemical balance.
RdB
