What does low carb do to your bones?

What does low carb do to your bones? There is a lingering idea that eating low carb could result in osteoporosis, due to making blood acidic and leeching minerals from the bones.

However, this theory has a few problems. For example, under normal circumstances the pH of the blood does not change depending on what diet you eat. The blood pH is tightly controlled within a very narrow span – or we’d die.

Testing the theory

More importantly, this idea has been tested several times.

In four separate studies, groups of people consumed either a strict low-carb diet (around 20-30 grams of net carbs a day) or a high-carb diet and were followed for up to two years. At the end of each study, results from both groups were compared.

Whether tracking markers of bone loss, or checking the bones with radiological methods (DEXA scans), the results were the same every time. Guess what?

Zero difference between the groups. Nothing happened to bone strength.

Time to let go of the myths

It’s high time to let go of the old acid-alkaline myth. Clearly bone strength is unaffected on a strict low-carb diet. The bones do fine.

Another idea is that high protein diets could negatively impact bones. This is probably not just wrong but the opposite of the truth. Bones are partly built by protein, and a recent study showed that women’s bones seem to get weaker on a low-protein diet.

Bones – like the rest of the body – need a sufficient amount of protein to stay strong. But carbs are not required.

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22 comments

  1. tony
    What is a sufficient amount of protein for bones to stay strong?
  2. deborah
    I've read here to restrict protein for optimal ketosis but also that older women need to eat more protein as they age. At 62 which way do I go?
    Reply: #12
  3. Marika bouchon
    I have the same problem as deborah. I am 61 and have sarcopenia (but the lean mass loss is everywhere, not just muscle).
    1-how much protein?
    2- how to prevent ketones from shooting up to starvation level and making me loose appetite? It's been 6 weeks and i get this but no fat mibilisation (24% fat but looking normal - never been obese) and can't seem to recover appetite.
  4. Leonie Roberts
    I have osteoarthritis in both knees as well as in the hip. I am really struggling with pain in both knees. I am not sure if it is related to being on a ketone diet or merely coincidental. I have had knee paint for a long time and the pain is progressively worstening.

    I have started using apple cider vinegar and have been using tumeric for so e time.

    I am hoping with weight loss the pain eases.

    Any suggestions would be greatly appreciated.

  5. Robin Birkbeck
    I hope this gets answered. I have been on Keto for 14 weeks now. I've come off for an illness twice and went right back to it after getting over it. I was sick with the Keto flu after one month and 10 lb weight loss, and then about 3 weeks later it was like the flu, not Keto. I've been doing better since I increased the amount of carbs from <20g to <50g.
    5'8" 155 lbs. 61 year old female.
    Last month I fell in a rainstorm and fractured my shoulder. I'm hoping to heal without surgery. I've always been sensitive to the mineral shifts with Keto and am supplementing Magnesium, Potassium, Sodium and Zinc. I have to heal this fractured shoulder. I don't have insurance and couldn't afford surgery. Is Keto safe for me? I've just read about increasing protein, which I will do.
    Thanks for your time.
  6. Bruce Brisbane
    hmmm. this is by no means a balanced sample of studies on the subject.
    and the studies themselves?
    have a close look at the middle one with the 2 year time frame.

    The low carb diet comprised 20g/day of carbs for 3 mths, then increased carbs by 5g every week....until desired weight was achieved. The subjects had mean BMI over 35 and were not athletic. The attrition rate was high.

    This introduces a stack of problems
    1. obese people tend to have higher bone density because their bones are subjected to supporting heavier mass. These findings cannot be extrapolated to a slim or low fat person sustaining a low carb diet.
    2. The low carb diet was not specifically high fat or high protein. High protein diets have been shown to increase urinary loss of calcium and cause bone mineral depletion. This effect may have been offset by the heavier subjects used.
    3. The low carb diet was not low carb. It had a 3 mth period of 20g CHO/day, then increased CHO by 5g each week after (until a desired wt was reached). Whatever the desired weight was, who knows....but the median wt loss was 11kg over the first year. Nevertheless, at the end of the first year, these "low carb" dieters would have been eating 20g + 39weeks*5g = 215g CHO!
    Now hands up all the low carb advocates who think that constitutes a low carb diet.

    Replies: #8, #17
  7. Emmanuelle
    OMG ! The "man" on the picture lose a bone in his arm !
  8. Tim H
    Thanks Bruce. Good comments. Point 1: On the other hand, the findings ARE valid for obese persons! Point 2: I was unable to open the full text. Is there any more information about the range of protein and fat intake of the subjects? Anything about whether it was animal or plant sourced food? Point 3: Since the addition of 5 g/week of carbs after 3 months was clearly a titration, I don't think an immediate extrapolation to 39 weeks and 215 g of CHO is warranted. Have you read the full text? Does it provide any more information on that titration, what was considered to be desirable stable weight, etc? Notice that, since the primary end point was weight loss, this titration of carb back into the diet makes the comparison with low fat dieters meaningless. In effect they have added back carbs to the intake to ensure low carb does not beat low fat! A further point: Since the low fat dieters were energy restricted, that could have led to slowing of the Basal Metabolic Rate. Was that measured? It says the attrition rate was high. Any information on whether attrition between the low carb cohort and the energy restricted cohort were similar? Mmmmm....maybe I'll try some other means to access the full text.
  9. Andrea
    I’m here for the comments, and they did NOT disappoint!
  10. 2 comments removed
  11. Shay-lea
    Hi

    I would suggest staying out of ketosis. Im 27 years old never broken a bone until I went onto the Keto diet. A simple slip on the floor and I broke both my tib and fib. Now Im suffering from low bone density

  12. Debbie
    I am 53 and have a family history of Osteoporosis, so am also concerned as to whether I skould do the KETO diet. I have been told to up my intake of calcium and do strength training to increaase or at least maintain bone density. Any advice as to whether I can still use KETO. I am looking to loose about 10Kg so KETO would just be for weight loss?
    Reply: #14
  13. Kristin Parker Team Diet Doctor
    If you still have questions or concerns after reading the article and links above, please work with your medical provider to make specific dietary decisions.
  14. Schuyler
    As a woman on keto - I strongly recommend carb cycling your evening meal to get more nutrients and not stress the body out as much. Women are more complex. So be in a keto state most of the day and go off in the evening if you’re fat adapted. Be sure to eat a diet rich in calcium, vitamin D and vitamin K for bone health. Protein, unless you eat A LOT is most likely not going to take you out of ketosis and so what if it does briefly? Eat whatever amount feels good to you! Each person is different so find what works for your body.
  15. Schuyler
    Also do strength training — seriously. Skeletal muscle is so important to bone health!
  16. M. Hudson
    To reply to your comments that obese people must have more dense bones to support their weight is absurd. I work in the medical field and is see people all the time even younger than 50 diagnosed with osteoporosis that are clinically obese. Please where did you get your research. I need to add our facilities numbers to their data! Please!!!
  17. Denise
    Would love more info on this that is up to date. I am 56.. with osteoporosis. I have following this woe for 2.5 years. Leaned on a ball to stretch and just broke rib 11... any more advice on what to add..do to strengthen bones? I do not want to take reclast.. would live DD input.
    Reply: #19
  18. Kristin Parker Team Diet Doctor

    Would love more info on this that is up to date. I am 56.. with osteoporosis. I have following this woe for 2.5 years. Leaned on a ball to stretch and just broke rib 11... any more advice on what to add..do to strengthen bones? I do not want to take reclast.. would live DD input.

    You can read a little more at this link. In general, we have not reviewed anything that leads us to believe this guide needs to be updated.
    https://www.dietdoctor.com/low-carb/controversies#osteoporosis

  19. What's the frequency, Kenneth?
    Debunking diet myths with references to scientific studies is very valuable. I hope you will continue compiling these and make it easy to search for them. It's one of the reasons I'm a paying member, even though I probably don't need to be (I want to help fund this stuff.) Every time I see a new claim online, I'd like to be able to check to see how much BS (usually a lot) I'm reading. So far, I've been unable, of course, to validate any of the BS claims against keto and carnivore.
  20. What's the frequency, Kenneth?
    Many questions that are asked here, such as "How much protein?" which is a nagging question, are answered in James DiNicolantonio's "The Longevity Solution," which I highly recommend. He provides something like a formula, and backs it with scientific studies. The answer is, as you age, you need more because you absorb less, but most Americans get plenty of protein anyway. You might want LESS, and you might want around half of your protein to be plant-based, and around half to be meat-based. This is because meat-based protein is more complete and because it also includes MTOR, which can have the effect of shortening lifespan. So, you some meat-based, but less is more, according to DiNicolantonio. For more info, buy his book, and maybe skip to the last chapter.
  21. gabshaun1
    I followed the link for more info on low carb and osteoporosis but it did not really answer the question. As a post menopausal woman with a diagnosis of osteoporosis based on a dexa scan, my endocrinologist has recommended a calcium intake of 1300mg per day from food. Although it would be possible without dairy - the most simple way to achieve this is one 250 ml glass of calcium fortified milk. Would I then struggle to remain in ketosis. I would appreciate some advise.
    Reply: #23
  22. Kristin Parker Team Diet Doctor

    I followed the link for more info on low carb and osteoporosis but it did not really answer the question. As a post menopausal woman with a diagnosis of osteoporosis based on a dexa scan, my endocrinologist has recommended a calcium intake of 1300mg per day from food. Although it would be possible without dairy - the most simple way to achieve this is one 250 ml glass of calcium fortified milk. Would I then struggle to remain in ketosis. I would appreciate some advise.

    Here is a more recent article you may find helpful.
    https://www.dietdoctor.com/dietary-protein-builds-strong-bones-accord...

  23. gabshaun1
    Thank you but again not very helpful as it discusses protein intake also stating "providing dietary intake of calcium is adequate".
    I think I will just stick to my endocrinologist advise of 1300 mg /day of dietary calcium. (Australia) For me this would include a glass of calcium fortified milk, greek yoghurt and goat cheese, plus almonds and green leafy veg.

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