High Protein Diet Safe for Bones! Acid Load due to Meat Protein does not Compromise Calcium Metabolism.

Reading the caption of this post, some of you may rightly ask themselves: "Why does he even mention this? Of course, meat is safe - meat is natural and eating meat is what man is made for!" So, if you already knew all that, you can stop reading now. If, however, you still belong to the misguided brotherhood of the followers of the holy food pyramid with your "healthy" grains, pasta and cereals at the bottom, you may be interested in the results from an older scientific paper I just came across while posting an answer to a forum post of someone who was concerned that his bones will become brittle if he increases his protein intake beyond the 0.8g/kg body weight barrier.

In November 2010, Cao & Nilsen (Cao. 2010) published a review which analyzed the outcome of studies that investigated the effect of the purported renal acid load resulting from a high protein intake (above the current Recommended Dietary Allowance of 0.8 g protein/kg body weight) on increased urinary calcium excretion. With reference to more recent findings they write:

Neither whole body calcium balance is, nor are bone status indicators, negatively affected by the increased acid load. Contrary to the supposed detrimental effect of protein, the majority of epidemiological studies have shown that long-term high-protein intake increases bone mineral density and reduces bone fracture incidence. The beneficial effects of protein such as increasing intestinal calcium absorption and circulating IGF-I whereas lowering serum parathyroid hormone sufficiently offset any negative effects of the acid load of protein on bone health.

By the way, I am already looking forward to the huge steaks I am going to have for lunch, today ;-)

Vitamin D Deficiency in Athletes: Stress Fractures & Cancer

A very recent investigation by Naama et.al. (Naama. 2010) found that, even in the sun-blessed middle east, there exists a high prevalence of vitamin D defeciency in athletes and dancers. Out of the 98 athletes and dancers (age 14.7±3.0 yrs, range 10-30 yrs, 53% males) who participated in the study, 73% of participants were vitamin D insufficient, and 25% were vitamin D deficient (insufficiency was defined as a serum 25(OH)D level below 30 ng/mL and deficiency below 20 ng/ml). This leaves a very small margin of 2% with sufficient 25(OH)D levels.

Although the scientists did not evaluate the individual dietary habits of the participants, the observed correlation of low ferritin (iron storage) levels with vitamin D status suggests a major dietary influence on 25(OH)D levels.
This is in accordance with Naama's observation that there was no difference between athletes competing indoors and athletes who exercise outdoors. This strongly suggest that even with adequate sun exposure vitamin D supplementation may be indicated if not in the general public then in athletes of whom it has previously been speculated that they might have increased vitamin D requirements.