Keto and Bone Health: What You Need to Know

keto and bone health

You may not know this, but bones are not static; they are actually living tissues that are constantly changing and consist primarily of collagen and calcium phosphate. Because of this, bone health may change over time and it is important to monitor it. In fact, degenerative diseases related to bones, such as osteoporosis, are on the rise in our modern society. The benefits of a ketogenic diet are numerous, and you may be wondering if this low-carb diet is also good for your bones. Let’s read on to check the relationship between keto and bone health out.

The Study: Keto Diet and Bone Health

Starting in 2016, researchers from several different Australian universities, with research funded by the Australian Catholic University, recruited 32 elite race walkers to conduct a study on the effects of a keto diet in endurance athletes.

First, the researchers allowed the athletes to choose either a high-carbohydrate diet (about 70 percent of calories from carbohydrates) or a very low-carbohydrate, high-fat keto diet (about 30 grams of carbohydrates per day) for the duration of the study. 

The athletes then underwent monitored exercise sessions as part of their training program over a three-and-a-half week period. 

In addition, during this period, the researchers examined a number of markers in the athletes’ blood related to bone health:

  • Cross-linked C-terminal telopeptide of type I collagen (CTX)
  • Procollagen 1 N-terminal propeptide, (P1NP)
  • Osteocalcin (OC)

In addition, after completing the initial trial, some subjects on a low-carb, high-fat diet participated in a “recovery” phase where they ate a high-carb diet so that the researchers could detect any additional changes.

So, what were the results of the study?

Compared to the high-carb diet, the low-carb, high-fat diet increased post-exercise levels of CTX, a marker of bone resorption (the breakdown of bone into calcium, which is absorbed into the bloodstream). 

The low-carbohydrate, high-fat diet also decreased levels of P1NP and OC, which are markers of bone formation and metabolism, compared to baseline. 

Unfortunately, elevated CTX levels and reduced P1NP and OC levels are not good signs.

After the recovery phase, post-exercise CTX decreased to normal levels in the low-carbohydrate group, but P1NP and OC levels did not increase to normal levels.

As a result of their findings, the researchers who conducted the study wrote that for athletes, keto “may be detrimental to bone mineral density (BMD) and bone strength, with significant implications for health and performance.”

Limitations of the Keto Bone Health Study

Before you worry about your bone health on keto, let’s first look at some of the limitations and potential flaws of the Australian study before we take a broader look at the existing research on keto and bone health.

Bone Markers, Not Bone Density

First, the researchers did not examine bone mineral density.

Before anyone can draw any real conclusions about the effects of a keto diet on bone health in endurance athletes, follow-up studies that actually measure changes in bone mineral density must be conducted.

Is there a possibility that keto foods make exercise (which typically promotes bone health) bad for your bones? Yes, but another possibility is that the changes the researchers found during the study were not meaningful for long-term bone health.

In other words, the changes in CTX and other bone markers do not prove that keto causes bone loss in endurance athletes.

Length, Sample Size, and Demographics

Second, the study was short and the sample size was small. 

Do differences in skeletal markers disappear over time? Do they become more dramatic? No one knows, because the study was only 3.5 weeks long and included only about 30 people.

And again, the bone health study would have been more useful if the analysis had controlled for age, sex, and other important factors. Although the study manuscript included gender, it did not include the age of the participants, nor did it stratify the results by gender.

Body Weight and Spontaneous Weight Loss

Finally, although the dietitians monitored the athletes in the study, the researchers did not report changes in body weight.

And some studies have suggested that low-calorie (low-calorie) diets may increase CTX levels. Not only that, but people on ketosis treatment often lose weight spontaneously by reducing their diet – for example in the 2019 Ketosis Military Study.

Thus, the possibility exists that the athletes in the low-carb group were not eating enough and that inadequate caloric intake was the cause of their elevated CTX levels, rather than carbohydrate restriction per se.

Unfortunately, since the researchers did not monitor or publish weight changes, we have no way of knowing.

Monitoring Your Bone Health on Keto

There is no substantial evidence that keto foods are harmful to bone health. On the contrary, many studies have shown no adverse effects on bone health in adolescents and adults taking a keto diet compared to other diets. A mineral-rich ketogenic diet can improve bone health and overall health. More research on ketones and bone health, especially in endurance athletes, is needed to draw more definitive conclusions.

Ditch all sugars that promote inflammation and impair bone health. Keto foods have shown promise for inflammatory bone-related diseases such as rheumatoid arthritis, as well as a range of other conditions from Alzheimer’s to epilepsy.

If you are concerned about your bone health, you can ask your doctor to measure your bone mineral density with a DEXA (dual energy X-ray absorptiometry) test.

The quality and nutrient density of your keto diet is also important. Your bones need nutrients like vitamin K2 and magnesium, healthy fats, and nourishing foods like collagen-rich bone broth. Are you eating plenty of nutrient-dense natural whole foods like avocado, chicken, fish and cauliflower instead of overdoing it on processed keto snacks? Studies show that eating enough protein is also good for your bones.

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