I recently presented an interesting paper at our journal club and thought I’d share the insights here.
Study Overview
A group of 30 race walkers were randomized to isocaloric diets (same amount of calories) that were either very low carbohydrate (0.5g/kg) or high carbohydrate (8.6g/kg). They then embarked on a 3.5-week training camp. The study focused on “bone turnover markers,” which are indicators of bone formation and resorption.
- P1NP: A marker of bone formation.
- CTX: A marker of bone resorption.
Osteoporosis and bone stress injuries occur when bone resorption (CTX) exceeds bone formation (P1NP). For example, menopause or estrogen deficiency is associated with bone density loss because estrogen usually inhibits osteoclasts, the cells that break down bone.
Study Findings
After the 3.5-week training camp, CTX levels increased in both the low and high carb groups due to increased physical activity and bone load. However, the increase was higher in the low carb group. More interestingly, P1NP levels increased from baseline in the high carb group but decreased in the low carb group. If this trend continued, it could result in bone density loss and an increased risk of stress fractures.
Following the low carb group, there was a three-day restoration period with high carb availability. Although CTX levels normalized, P1NP levels remained low.
Implications
This research adds to the growing evidence that, in addition to focusing on energy availability for athlete health and preventing complications of Relative Energy Deficiency in Sport (RED-S), we also need to consider carbohydrate availability. While it’s hard to know if these results translate to non-athletes on a keto diet, it further supports the idea that unless there’s a specific medical reason for a ketogenic diet, it is not recommended for general health. Instead, I encourage the Mediterranean diet, which has substantial evidence supporting its benefits for longevity and good health.