The Ins and Outs of Calcium and Bone Health

Caveman Doctor talks calcium and bone health in his latest post. He touches on the subjects of which foods to eat and how to exercise for bone health, as well as the complex nature in which our body uses calcium for bone health, and how it’s more than just how much we eat. He also discusses whether we actually need to drink milk. I hope you enjoy it!

Caveman Doctor has recently received several contact form inquiries from his new website (whatever a contact form or website is) asking about calcium. The questions ranged from, “Should I take calcium?” to “Should I take osteoporosis medications?” to “How do you get any calcium if you don’t drink milk?” Caveman Doctor’s bones are very strong and allow him to lift heavy rocks and his calcium levels have never been low in his life. Yet, he takes no calcium pills, never drinks milk, and never even worries about his calcium level. How could this be?


Calcium: The Underlying Issues

There are many factors that go into our calcium levels and bone health, not just how much calcium we eat. Increasing ones calcium and having it incorporated into the skeleton involves several steps, including getting the calcium in (consumption), getting the calcium where it needs to go (bone construction), and limiting calcium from exiting the body (excretion). The body involves an intricate interplay between all of these factors, as well as some hormonal manipulation that we won’t even touch upon as Caveman Doctor has the attention span of, well, a caveman. Looking at calcium and bone health as simply “are we eating enough” favors the dairy industry as we are constantly told to drink more milk, the supplement industry as we are constantly told to take more calcium pills, and Big Pharma, as they turn to the big gun medicines when our levels are low. However, thinking the one person it does not benefit is you. Yet, how often do we stop and think: Why is my calcium level low and is it only dependent on how much I’m eating?

Keep in mind that Americans eat the largest amount of calcium rich foods like dairy, yet have some of the highest rates of osteoporosis.

Yet, these issues are not limited to the U.S. In fact, in Greece the rate of hip fractures rates has steadily climbed,1 yet the consumption of milk has skyrocketed. Why isn’t this increase in calcium intake protecting them from bone fractures? The answer is because calcium intake is only one of several factors pertaining to bone health, and dwelling on this one aspect will likely result in neglect of the others.

Calcium Absorption

The first step in getting calcium is obviously eating it. However, the next step is actually absorbing it in our GI tract. Several factors in our diet may actual limit our absorption of calcium. Phytic acid, found in high amounts in grains (as we discussed here) binds to calcium and significantly decreases our ability to absorb the calcium we eat.2,3 So, in a sense you can drink all the milk you want, but if you are using it to wash down your bread and oatmeal, it’s only going to come out the other end unabsorbed. Therefore, once grains are no longer eaten, simple math tells us you won’t need to eat as much calcium. You didn’t think you would get through this article without some good old grain bashing did you?
We have already read the many benefits of vitamin D, however, studies show that higher levels of serum vitamin D result in drastically increased amounts of calcium absorption.4 It is likely better to consume less calcium and make sure you have high vitamin D levels than to eat a lot of calcium while ignoring your D levels. Pumping your car full of gasoline won’t make it go any faster if you have no tread on your tires, and in this instance, calcium is no different than gasoline.
Absorption also relies on a healthy gut, and substances in foods that increase inflammation, like gluten and lectins in grains and legumes will also damage your GI lining and cause impaired uptake.In fact, when in doubt, always aim for less inflammation: studies on patients with inflammatory bowel disease have shown that increases in inflammation are associated with lower vitamin D levels.5 Studies have shown that doctors frequently miss vitamin D depletion as a cause of osteoporosis and this is likely because the emphasis is more often placed on calcium.6 And as you read above, if vitamin D is low, you aren’t absorbing as much calcium.

Bone Construction

Just as the process of getting calcium into the body relies on a lot more than just eating it, turning this calcium into healthy bone is just as complicated. Bone mineralization relies on more vitamins and nutrients than just calcium, and has also been shown to be dependent on vitamin K intake.7 Vitamin K is found in large amounts in green leafy vegetables like broccoli and spinach, which garnish most caveman meals.8 Also, the calcium in green leafy vegetables like kale is significantly more absorbable than dairy calcium, giving us a double bonus. These vegetables provide you with a highly absorbable amount of calcium as well as large amounts of vitamin K, which further helps with even more calcium absorption. Dairy, however, remains a poor source of vitamin K and to add insult to injury, contains a much less absorbable source of calcium.9
Protein also has a stimulatory effect on the synthesis of bones. Studies have shown that supplementing elderly patients and postmenopausal women with protein causes increases in bone density, reduced bone loss on x-ray, and improved clinical symptoms in patients with a recent hip fracture.10-12 Increased protein consumption results in several anabolic processes including bone formation and is not just limited to muscle growth…

Physical Activity and Bone Construction

Increased physical activity7 and more specifically lifting heavy weights has shown to increase bone mineralization. In fact, muscle training has been shown to increase bone mineral content and density by up to 5% a year.13 Just as working your muscles causes them to repair themselves bigger and stronger, bone appears to follow this pattern. One study looked at bone mineral density in long-distance runners, sprinters, and walkers by performing a bone scan of their tibias (the bone in your lower leg). Just as sprinting (and not long-distant running) helps provide just enough stress to stimulate a healthy response to enhance our immune system, the same appears to be true with bone mineralization in our shins.14 Regardless, the bones need to undergo heavy resistance as the body clearly responds with increasing bone density to prepare our bones for the next physical challenge. Physical exercise decreases bone turnover and turns on bone formation. However, endurance training does not result in the same benefit and endurance training (from continued pounding of our bones) has actually shown a decrease in bone mineral density in the lower spine.15


Glucocorticoids are steroids (not the anabolic bodybuilding type) that are a frequently prescribed medication, such as prednisone and Medrol dose packs. They are similar to the natural corticoid steroids within our body that are secreted in response to stress, and as you may remember, they cause a rise in our blood sugar levels (see here and here). Glucocorticoids are a major risk factor for osteoporosis, through their stimulation of bone resorption and decreased bone formation. Avoiding taking them and avoiding the stress that increases our body’s production will help to keep your bones healthy and strong.

Calcium Secretion

Going back to vitamin D, not only does it help our body absorb more calcium but it also activates the kidney to reabsorb more calcium instead of allowing us to get rid of it through our urine. In fact, studies show vitamin D levels to be the dominant predictor of bone density, NOT calcium.16 Nature, in all of her beauty and infinite wisdom, has given us the sun, with its endless rays of warmth that activate vitamin D synthesis naturally in our skin. Get some sun or take some D3 and stop drinking milk!
Several other factors act on our kidney to affect calcium loss in the urine. Insulin, which often takes a beating around here, appears to negatively affect calcium secretion as well. Once again eating high amounts of carbohydrates and the resultant release of insulin appears to be detrimental to an aspect of our health. Insulin actually activates receptors on the kidneys, causing them to dump calcium in our urine, resulting in increased calcium loss.17 In fact, one study even showed that eating sugar alone caused the kidneys to lose calcium.18

In Review:


  1. Calcium levels and bone health are multifactorial and calcium intake is just the tip of the iceberg.
  2. Don’t count on dairy for calcium and instead get it naturally in highly absorbable forms in the foods nature laid out for you.
  3. Instead, avoid foods that result in decreased absorption and increased excretion of calcium like milk.
  4. Get some sun (not sun burns) or if that is not possible, take some vitamin D3.
  5. Lift heavy weights and sprint as the heavy loads stimulate bone mineralization and decrease bone breakdown.
  6. Avoid chronic stress and the increase in glucocorticoids that results.
  7. Increase your highly absorbable sources like green leafy vegetables, and decrease poorly absorbable sources like milk, and avoid its downside with its large amounts of lactose (sugar).
  8. Avoid large amounts of carbohydrates that cause significant insulin release and calcium loss in the urine.

Now that we went through all the ways to raise your calcium, ask yourself why Americans eat the largest amount of calcium-rich foods like dairy, yet have some of the highest rates of osteoporosis. Incorrectly trivializing bone health and calcium levels to one factor – how much you eat – only benefits the dairy industry and supplement companies and never us as this frequently leads to recommendations to consume more milk or take calcium pills. To add insult to injury (literally), when our levels get low from these dietary recommendations we are told to take pills and medications to correct them. In fact, hospitalizations have increased from hypercalcemia (high levels of calcium) due to markedly increased over the counter calcium supplement use.19 However, once we view the bigger picture, we realize that not only is milk unnecessary for bone health and calcium, but its calcium is less absorbable than that found in green leafy vegetables. Nature added the bonus of loading these leafy vegetables with nutrients and vitamins as well.
Getting our calcium to normal levels is easier than we think and may involve just eating and living the way in which we were originally designed, which does not include drinking milk. Humans relied on other sources than milk and calcium pills for millions of years, the sources that Nature provided, and it is no surprise that continuing to eat in this way likely provides us with optimal calcium and bone health.



1. Paspati I, Galanos A, Lyritis GP: Hip fracture epidemiology in Greece during 1977-1992. Calcified tissue international 62:542-7, 1998

2. Weaver CM, Heaney RP, Martin BR, et al: Human calcium absorption from whole-wheat products. The Journal of nutrition 121:1769-75, 1991

3. Lonnerdal B, Sandberg AS, Sandstrom B, et al: Inhibitory effects of phytic acid and other inositol phosphates on zinc and calcium absorption in suckling rats. The Journal of nutrition 119:211-4, 1989

4. Heaney RP, Dowell MS, Hale CA, et al: Calcium Absorption Varies within the Reference Range for Serum 25-Hydroxyvitamin D. Journal of the American College of Nutrition 22:142-146, 2003

5. Ulitsky A, Ananthakrishnan AN, Naik A, et al: Vitamin D Deficiency in Patients With Inflammatory Bowel Disease. Journal of Parenteral and Enteral Nutrition 35:308-316, 2011

6. Basha B, Rao DS, Han ZH, et al: Osteomalacia due to vitamin D depletion: a neglected consequence of intestinal malabsorption. The American journal of medicine 108:296-300, 2000

7. Anderson JJ, Rondano P, Holmes A: Roles of diet and physical activity in the prevention of osteoporosis. Scandinavian journal of rheumatology. Supplement 103:65-74, 1996

8. Kamao M, Suhara Y, Tsugawa N, et al: Vitamin K content of foods and dietary vitamin K intake in Japanese young women. Journal of nutritional science and vitaminology 53:464-70, 2007

9. Elder SJ, Haytowitz DB, Howe J, et al: Vitamin k contents of meat, dairy, and fast food in the u.s. Diet. Journal of agricultural and food chemistry 54:463-7, 2006

10. Hannan MT, Tucker KL, Dawson-Hughes B, et al: Effect of dietary protein on bone loss in elderly men and women: the Framingham Osteoporosis Study. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research 15:2504-12, 2000

11. Schurch M-A, Rizzoli R, Slosman D, et al: Protein Supplements Increase Serum Insulin-Like Growth Factor-I Levels and Attenuate Proximal Femur Bone Loss in Patients with Recent Hip Fracture. Annals of internal medicine 128:801-809, 1998

12. Kerstetter JE, Looker AC, Insogna KL: Low dietary protein and low bone density. Calcified tissue international 66:313, 2000

13. Suominen H: Muscle training for bone strength. Aging clinical and experimental research 18:85-93, 2006

14. Wilks DC, Winwood K, Gilliver SF, et al: Bone mass and geometry of the tibia and the radius of master sprinters, middle and long distance runners, race-walkers and sedentary control participants: a pQCT study. Bone 45:91-7, 2009

15. Dalsky GP: Effect of exercise on bone: permissive influence of estrogen and calcium. Medicine and science in sports and exercise 22:281-5, 1990

16. Bischoff-Ferrari HA, Kiel DP, Dawson-Hughes B, et al: Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research 24:935-42, 2009

17. DeFronzo RA, Cooke CR, Andres R, et al: The effect of insulin on renal handling of sodium, potassium, calcium, and phosphate in man. The Journal of clinical investigation 55:845-55, 1975

18. Holl MG, Allen LH: Sucrose ingestion, insulin response and mineral metabolism in humans. The Journal of nutrition 117:1229-33, 1987

19. Patel AM, Goldfarb S: Got calcium? Welcome to the calcium-alkali syndrome. Journal of the American Society of Nephrology : JASN 21:1440-3, 2010

© 2015 CDR Health and Nutrition, LLC. All Rights Reserved


  1. Rene Burke

    Out of all of the Caveman posts, this is my favorite. You have given me some very simple examples of how to modify my diet/lifestyle to better support bone health. Having a family history of osteoporosis, this is great news for me!

    1. cavemandoctor (Post author)

      Glad you find it helpful! I have another one coming out on osteoporosis as I have gotten some more questions about it.


    2. cavemandoctor (Post author)

      Glad you found it helpful! I have another one coming out on osteoporosis as I have gotten some more questions about it.


  2. Pingback: Calcium, Bone Health, and Menopause: What’s a Girl to Do? - Caveman Doctor : Caveman Doctor

  3. Clood

    Raw milk from grass-fed healthy cows is an optimal source of calcium.


    1. cavemandoctor (Post author)

      I agree that raw milk (assuming hormone-free, etc) contains a decent amount of calcium (which may not be as absorbable as other sources that contain less as all studies likely use pasturized commercial milk). But all things being equal, if other intake is maximized and losses are minimized, milk is not necessary.


  4. Dr. Martin Michener

    As clearly explained by Dr. Kate Rheaume-Bleue in her very recent book, “Vitamin K2 and the Calcium Paradox”, the work in the Netherlands by Cees Vermeer and team VitaK at Maastricht U has differentiated K1, phylloquinone, which activates clotting gla proteins in the liver, from K2, menaquinone, which activates other gla proteins NOT in the liver. 1. MGP is found in soft tissues, which when activated by sufficient K2 protects arteries, kidneys from over calcification. 2. Osteocalcin when activated by K2 deposits blood calcium in the bone matrix via osteoblasts, where we wish it to go. 3. Gas6 modulates cell growth, affecting metastatic tissues. Adequate K2 has disappeared from our diet animal fats as they have been taken off green pastures, placed in CAFO’s and given “feed”. Other gla proteins are being studied, and intervention trials with K2 are underway for a host of aging-degenerative diseases. Results in the last months from one show patients undergoing dialysis given K2 supplements greatly improve their blood risk factors for clots and arterial degeneration.

    1. cavemandoctor (Post author)

      Dr. Michener,

      Thanks for the great and insightful comments that will be useful for my readers. I agree with your animal fat comments and hopefully we are changing our ways with CAFO’s or at least providing more options to avoid such unethical and unhealthy sources.


  5. Pingback: Bariatric Surgery vs. Medical Therapy in Diabetes - Caveman Doctor : Caveman Doctor

  6. Pingback: URL

  7. Pingback: Salt: Collateral Damage in the War on Fat - Caveman Doctor : Caveman Doctor

  8. Pingback: Salt: Collateral Damage in the War on Fat - Caveman Doctor

  9. Dan

    Green leafies aren’t a good source of calcium though because they generally contain oxalates which does the same thing as the phytates in grains, bind it and take it straight through the bowel.

    1. Mihnea

      Oxalate content gets decreased by cooking (steaming, boiling, braising).

  10. Gia

    If I suffered a 3rd degree ankle sprain and am still recovering all while attempting a low carb low cal keto diet for weight lossw, would calcium and vitamin supplements in this case be helpful to my recovery? Just wondering, thanks 🙂

  11. Pingback: Podcast 50 - Out of Control Coffee - Caveman Doctor


  13. Biome Onboard Awareness

    Hi. Cited your information for explanation on my post, WHAT’S IN A HEALING REFRIGERATOR? relative to bone broth which now has been shown to not contain much calcium, rather the added vegetables both to the broth and subsequent soup is the source of calcium. I look forward to reading further through your posts; I would like to better understand the role of diet with cancer as I write about the microbiome and disease, and am published in the UK. I don’t have much on such for cancer oddly enough.


Leave a Comment

Your email address will not be published. Required fields are marked *