Are low-carb and keto diets healthy for bones?
Because many variables are associated with bone health, it helps to know and understand how to maintain healthy bones as we age.
What is bone health and why is it so important?
Bone is a constantly changing living tissue, even though its hardened appearance may make you think otherwise. Bones are mostly made up of collagen, a protein which provides the soft framework, and calcium phosphate, which adds strength and hardens the framework.
Bones play many important functions in the body, such as providing structure and scaffolding for your body, allowing you to move, anchoring muscles, storing calcium, and protecting your organs (e.g., brain, heart) from injury.
In your late teens to early 20s, your bones achieve their “peak bone mass,” meaning that your body has the greatest amount of bone.2
Lifestyle habits — especially diet and exercise, and especially during the period of bone growth in childhood through young adulthood — can influence your peak bone mass by approximately 20 to 40%.3 Around midlife, you will likely start to lose bone as part of the aging process unless you incorporate several important lifestyle habits. Since bone loss is “silent,” most people are unaware that they are losing bone.
Unfortunately, poor bone health later in life increases your risk of fracture and frailty, which can have a profound effect on your independence and quality of life. That is why it pays to prioritize bone health as you age.4
What conditions are associated with poor bone health?
As bones start to slowly thin out with age, they can become less dense, more brittle, and more likely to break. When this process is accelerated, it can result in osteopenia (low bone mass) or osteoporosis (severe bone loss). Osteoporosis afflicts approximately 200 million people worldwide.5 This condition leads to more than 8.9 million fractures every year, and an osteoporotic fracture occurs every 3 seconds around the world.6
How do you know if you have poor bone health? Bone health can be measured using a bone scan machine called DEXA, short for dual x-ray absorptiometry.7 This machine measures the density of your bones. If your density values are lower than the normal ranges for your age and gender, you may be diagnosed as having osteopenia or osteoporosis.
Increasing evidence shows that several other conditions may be associated with osteoporosis and fracture risk, such as type 2 diabetes, sarcopenic obesity (having more body fat than muscle), and Alzheimer’s disease.8
This does not mean that one causes the other, but this does suggest that similar mechanisms, such as “inflammaging” (inflammation associated with aging) may be involved in the development of each of these diseases.9
Future research will hopefully help us better understand these relationships.
Are you at risk for poor bone health?
We can divide the many factors associated with bone growth and bone loss into two main categories: nonmodifiable and modifiable.
Examples of the nonmodifiable risk factors — meaning you cannot change them — are age, gender, heredity, and ethnicity or race. Research shows that being female, having a genetic predisposition, and being Caucasian or Asian all increase your risk for accelerated, age-related bone loss.10 Although you cannot do anything to change these factors, you can focus on your modifiable variables to help keep your bones healthy.
Modifiable variables are ones you can change during your lifetime to help prevent or slow age-related bone loss. Most of these variables are associated with lifestyle, such as diet, exercise, smoking habits, and alcohol intake. Good nutrition — as well as staying active, not smoking, and avoiding heavy drinking — can help to keep your bones strong as you age.11
Even though a large amount of research has explored lifestyle factors, many questions remain. Let’s take a look at them, so you can start making informed choices about how to keep your bones healthy.
Will taking calcium and Vitamin D supplements or eating foods rich in these nutrients protect your bones?
For many years, calcium and vitamin D supplements were touted as two of the best ways to protect your bones.
Early clinical trials suggested a potential benefit of calcium and vitamin D supplementation on bone health.12
However, more recent studies only suggest a very small, if any, benefit to bone. Studies have also looked at the associations of dietary calcium and vitamin D from the natural foods we eat, and the findings are comparably modest.13
In 2018, the US Preventive Services Task Force took a look at all the research to date and concluded that current evidence does not support calcium or vitamin D supplementation for prevention of fractures in men and women.14
So, where does this leave us in regards to calcium and vitamin D? Researchers still think that vitamin D may play some role in bone health, and vitamins C and D also are important for proper functioning of many other body systems.15
However, there is growing concern that too much supplemental calcium may actually be harmful to cardiovascular health, and very high vitamin D intake can be potentially toxic (although it is rare to reach these levels).16
Therefore, incorporating natural sources of calcium from foods — such as dairy products, fatty fish, and leafy green vegetables — may be the safer choice for healthy aging and bone health.
If you are currently taking or plan to start taking calcium and/or vitamin D supplements to help your bones, it is best to consult with your physician, and consider if you can get adequate amounts from food alone.
What other nutrients may help keep your bones healthy?
Can other nutrients besides calcium and vitamin D help your bones? The answer is maybe.
It is important to understand that there are no definitive answers whether a specific nutrient will improve bone health, mainly due to the limitations in nutrition research. However, a few other nutrients have been identified as potentially important for our bones and may help to prevent bone loss.
Let’s take a look at protein. Remember that collagen, which makes up the soft framework of your bones, is a protein.
Research suggests a clear association between higher protein intake and improved bone health. The most recent review of the literature shows that a high protein intake (greater than current recommended levels of 0.8 g/kg body weight/day) may be beneficial for the maintenance of bone health and the prevention of bone loss in older adults.17
Current research also suggests that higher levels of protein are needed as you age to prevent an age-related condition known as sarcopenia, the loss of muscle mass, strength, and function and, ultimately, independence.18
The evidence for protein’s effect on bone and muscle health is very promising.
Vitamins and minerals
Other nutrients worthy of mention are vitamin K, magnesium, vitamin C and potassium.
The current evidence for vitamin K suggests a beneficial role in bone health (with more evidence supporting K2), but findings from studies lack consistency.19
The evidence for magnesium, vitamin C and potassium is promising, but more research is needed to come to any conclusions because research is limited to observational data.20
It appears that these nutrients may be important for helping maintain your bones, but it’s very difficult to link one specific nutrient to a specific outcome, in this case, bone health. One of the main reasons is that we eat foods that usually contain a variety of nutrients that interact with each other, so it’s hard to separate out the specific effects of a single nutrient.
More recent studies have started to look at the relationship between whole foods, food groups, and dietary patterns (vs single nutrients), and results are favorable for nutrient-rich green leafy vegetables and dairy intake.21
So, what’s the take-home message?
Aim to eat a healthy and nutrient-rich diet that includes plenty of dairy products and protein as well as plant-based foods rich in vitamin K, magnesium and potassium, such as leafy greens, avocados, and berries — which are all part of a low-carb lifestyle, as we discuss more below.
What type of exercise is best for bone health?
An active life is beneficial for both mental and physical health. Exercise has numerous benefits, and its effects on bone health are well documented for both preventing bone loss as well as treatment for conditions associated with poor bone health.
The evidence to date suggests that a progressive strength-training program, which places increasing amounts of mechanical load on the bones, is required to stimulate bone growth showing small but significant gains in bone density.23
Studies also found that although walking doesn’t have a large impact on bone growth, it can help to prevent bone loss.24
Taken together, these findings suggest that you should combine regular physical activity, such as walking, with a strength-training program to maximize bone health.
It is important to note that when starting a new exercise program, you should consult with your doctor and a trained fitness professional if possible, especially if you have osteopenia or osteoporosis.
What are the effects of a low-carb or keto diet on bone health?
This is a question that many low-carb followers wonder about. To date, only a few studies have looked at the association between low-carb diets and bone health but so far, results are overall encouraging.
Yet the findings are not uniformly positive. One small clinical trial suggested that a ketogenic diet may be detrimental to bone. However the study had several weaknesses in the methodology, which makes the findings questionable.25
Conversely, larger and longer trials that use bone density as a measure of long-term bone health have shown adults and children maintain bone health on low-carb diets.26 By studying a broader population for longer periods of time and with more reliable outcome measures, these trials seem to be more helpful in determining the bone effects of low-carb diets.
Future studies hopefully shed more light on the association between low-carb diets and long-term bone health.
Let’s revisit the issue of protein as it relates to a low-carb diet. It has been suggested that moderate to higher amounts of protein intake on a low-carb or keto diet may have an adverse effect on bone due to the potential increased acidity from protein-rich foods. This “acid-alkaline” myth suggests that higher protein levels can lead to high acid levels in the body, thereby increasing calcium loss from the bone to “buffer” the high acidity. However, at this point, it is truly a myth and has not been supported by science.27
Emerging research supports the idea that low-carb diets may actually improve our bones. For starters, low-carb diets can reduce inflammation, and researchers have proposed that inflammation may be associated with the development of osteoporosis.28
We also know that well-formulated low-carb or keto diets emphasize the consumption of protein and nutrient-rich vegetables, which evidence suggests are important for bone health as well as overall health. No convincing evidence as of yet shows that low-carb or keto diets have any harmful effects on bone, and the new accumulating research suggests the opposite may be true.
A well-balanced, low-carb or keto diet that includes adequate amounts of high-quality protein, calcium-rich foods, and nutrient-dense vegetables may not only help keep your bones strong but help keep your body healthier as you age.
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Osteoporosis International 2016: The National Osteoporosis Foundation’s position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations [review of RCTs and observational studies; weak evidence] This study incorporates RCTs and observational studies and assigns them appropriate strengths that, for the most part, agree with our process at DietDoctor. ↩
Lancet 2007: Use of calcium or calcium in combination with vitamin D supplementation to prevent fractures and bone loss in people aged 50 years and older: a meta-analysis [meta-analysis of randomized controlled trials; strong evidence] ↩
Journal of the American Medical Association 2017: Association between calcium or vitamin D supplementation and fracture incidence in community-dwelling older adults: A systematic review and meta-analysis [systematic review and meta-analysis of randomized controlled trials; strong evidence]
British Medical Journal 2015: Calcium intake and bone mineral density: systematic review and meta-analysis [systematic review and meta-analysis of randomized controlled trials; strong evidence] ↩
Journal of the American Medical Association 2018: US Preventive Services Task Force: Vitamin D, calcium, or combined supplementation for the primary prevention of fractures in community-dwelling Adults: US Preventive Services Task Force recommendation statement [systematic review and meta-analysis; strong evidence] ↩
British Medical Journal 2010: Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis [meta-analysis of randomized controlled trials; strong evidence] ↩
Computational and Structural Biotechnology Journal: High versus low dietary protein intake and bone health in older adults: a systematic review and meta-analysis [meta-analysis of randomized controlled trials; strong evidence] ↩
Osteoporosis International 2016: Dietary magnesium intake, bone mineral density and risk of fracture: a systematic review and meta-analysis [systematic review and meta-analysis of randomized and nonrandomized trials; weak evidence]
Note that this trial used only RCTs for the outcome of bone mineral density, and thus these results would be strong evidence. For fracture risk, which takes a much longer study to measure, they used prospective cohort studies, and thus these are weak evidence. We default to the lesser of the two ratings in our overall assessment. ↩
Menopause 2017: A systematic review of the exercise effect on bone health: the importance of assessing mechanical loading in perimenopausal and postmenopausal women [systematic review of randomized controlled trials type; strong evidence]
The Cochrane Database of Systemic Reviews 2011: Exercise for preventing and treating osteoporosis in postmenopausal women [systematic review of randomized controlled trials type; strong evidence] ↩
Menopause 2013: Effects of walking on the preservation of bone mineral density in perimenopausal and postmenopausal women: a systematic review and meta-analysis [systematic review and meta-analysis of randomized controlled trials; strong evidence] ↩
The trial involved only 30 subjects for only three and a half weeks. In addition, the study population was athletes, so findings may not be as applicable to the general population.
But perhaps most importantly, they measured bone turnover (instead of fractures or DEXA changes) as a surrogate for bone health. This is a dynamic measure, so it is hard to know for certain how it relates to bone density or long-term bone health.
The following study shows the importance of measuring the right variables.
Both the 1-year and 2-year results of the trial run by Virta Health demonstrated reduced CRP and WBC, two important inflammation markers:
Frontiers in Endocrinology 2019: Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: A 2-year non-randomized clinical trial [weak evidence] ↩