Is Calcium Needed on a Carnivore Diet?

There are plenty of people who do not consume anywhere near the recommend calcium intake and are thriving, demonstrating that there are still plenty of unknowns and more research is needed to determine calcium requirements in the context of carnivore.

While the RDI for calciumis 1000 mg/day of calcium, the RDIs are based on people eating a standardAmerican diet (SAD), and have not been adjusted for individuals following aketo, or carnivore diet.

TheRDIs may change when we drastically change our diets. Perhaps we don’t need toconsume as many vitamins and minerals following a carnivore diet since thenutrients are, in general, more bioavailable from animal based sources.

But,can we really just throw out the RDIs entirely?

Forcalcium specifically, do we know thelong-term implications of insufficient calcium intake on a carnivore diet? I would argue no, and do wewant to chance it?

Calciumis one of the reasons we encourage a nose to tail approach to carnivore, toensure we are covering our nutrient bases, since a meat only carnivore dietwill lead to very low calcium intake.

What is Calcium?

Let’s rewind a bit and start with thebasics – what is calcium?

Calcium is the most plentiful mineral found in the human body& the body cannot make this vital mineral. The teeth and bones contain themost amount of calcium (99%), and the remaining is found in nerve cells, bodytissues, blood, and other body fluids.

Some of the important biologicalroles of calcium are shown in the diagram below.

Calcium's Role in Bone Health

Of these functions, let’s focus onthe role of calcium in bone health, which requires us to briefly review thefunctions of bone, what bone is made of, and how bone remodels.

Bone Functions

Bone is a living, growing tissue with numerous important functions (shown in the following 2 diagrams), including:

Mechanical: tosupport the body and generate forces
Metabolic:secrete hormone to regulate various metabolic processes
Cell formation:including stem cells, white and red blood cells, and bone cells
Storage: act asa warehouse of various minerals

Composition of Bone

The structure of bone contains 4 maincomponents shown in the diagram below:

Cortical bone
Trabecular bone
Bone marrow
Blood vessels

The two bone phases (cortical &trabecular) are heterogeneous composite materials consisting of a mineralphase, organic phase and water. The composition percentage will depend on thetype & location of the bone, in addition to the health & age of theindividual.

One of the main minerals of theinorganic phase is Calcium, and the tendency ofbones to fracture depends on the quantity of mineralized tissue present (sizeand density) often measured as bone mineral density or BMD. Since 99% ofthe Calcium in your body is in your bones, it is important for forming strongbones!

Bone Remodeling

Our bones are metabolically activeorgans that undergoes continuous remodeling throughout life. In fact, it is estimated that the entireskeleton in the adult human body is renewed every 7 years [7].

Boneremodeling occurs to enable bones to adapt to the loads and stresses we placeon them.

Theremodeling process itself is complex, butessentially old bone is continuously replaced by new tissue, allowing themaintenance of the shape, quality and size of the skeleton. Similar tobuildings, local removal of old bone must precede new bone deposition. In ahomeostatic equilibrium, bone removal & formation are balanced so that oldbone is continuously replaced by new tissue to facilitate adaptation tochanging mechanical environments.

The entire remodeling process dependson coordinated actions between bone cells, regulated by biochemical andmechanical factors – including calcium levels in our body!

What are these bone cells?

Bones contain 2 types of stem cells: Mesenchymalstem cells (MSCs) & Hematopoietic stem cells (HSCs).

MSCs aremultipotent stem cells, meaning they can produce more than 1 type of specializedcell, but not all cell types. MSCs can differentiate (or turn into) cartilagecells (chondrocytes), bone cells (osteoblasts) & fat cells (adipocytes).
HSCs candifferentiate into any of the blood cells (white blood cells, red blood cells& platelets) & cellular blood components

Plus 3 differentiated (‘specialized’)bone cells, shown in the diagram.

Bone remodeling starts withosteoclasts to remove bone. Osteoclasts secrete enzymes & hydrogen ionsonto the bone surface, dissolving the mineral & digesting the matrix at thesame time. Bone is then formed on the previously resorbed surfaces byosteoblasts which deposit unmineralized protein matrix which is thenmineralized. Osteoblasts then lay down bone until the resorbed bone iscompletely replaced by new.

The Serum Calcium Level is Tightly Regulated

To further understand the role ofcalcium, we will now briefly review the tightly regulated calcium concentrationin bodily fluids.

The body tightly controls the amountof calcium in cells, tissues and in the blood, in order to maintain theconstant internal environment necessary for numerous body functions such asblood clotting, muscle contractility and cardiac function. Thus, the calciumconcentration is kept in a fairly narrow limit (8.5 – 10.5 mg/dl ofextracellular fluid [8]). Maintenance of this blood Calcium level is vital forproper human functioning.

Your body maintains this level evenwhen you do not consume enough calcium. With low dietary calcium, the bodycompensates in order to keep the blood calcium concentration in the desiredrange.

How? By pulling from and utilizing other resources in thebody. This bloodconcentration level is maintained by an elegant interplay of calcium absorbedfrom the intestines, movement of calcium into and out of the bones, and thekidney’s retrieval and excretion of calcium into the urine.

The threemain hormones involved in calcium regulation are shown in the diagram below.

Activationof PTH and calcitriol elevate calcium, while calcitonin activation reducescalcium levels.

When there is inadequate dietary calcium to satisfy thebody’s calcium needs, and blood levels of calcium ions decline, the parathyroid glands almostimmediately release PTH into the blood to bring the calcium level back up tonormal.

The release of PTH triggers 3 actions:

Stimulates the kidneys to enhance tubular reabsorption of calcium before it is excreted in the urine.
Stimulates the kidney to activate calcitriol, which enters the blood & travels to the small intestine where it acts to increase the absorption efficiency of dietary calcium
Signals to osteoclasts to increase bone resorption in order to release calcium from bones into circulation.

All of which bring the calcium level back to baseline.

When the body’s calcium needs are satisfied by adequatedietary intake of calcium, PTH & calcitriol signal osteoblasts to increasebone formation and mineralization (and shut off bone removal).

Additional Benefits of Calcium

Okay calcium is clearly important, but are there any otherbenefits to dietary calcium?

Yes! In addition to the previously reviewed bodyrequirements of calcium, there are some pretty neat benefits to dietary calciumin the literature.

Buffer High Acid Loads

Okay calcium is clearly important, but are there any otherbenefits to dietary calcium?

Yes! In addition to the previously reviewed bodyrequirements of calcium, there are some pretty neat benefits to dietary calciumin the literature.

Buffer High Acid Loads

The first is to buffer the higher acid loads associated withhigh protein diets. A higher protein diet leads to a higher acid load deliveredto the kidney that must be cleared [9-12]. With a higher acid load, there is achange in urine pH and an increase in mineral losses (like calcium). Dietarycalcium intake buffers this acid load and can replenish the renal minerallosses.

The first diagram highlights the results of a short termhuman interventional study [9]. The objective of [9] and the macro and mineralcontent of the three diets investigated are shown in the diagram below. Notethe mineral intake did not differ amongst the 3 diets.

The results of the study are shown in the second diagram. Previous studies have similarly shown that urinary calcium levels vary directly with net acid excretion [13].

The conclusions of this short-termmetabolic study include:

Thedemonstrated changes in urinary biochemistry enhance the probability of uricacid & calcium stone formation.
A LCHP diet mayenhance bone loss, but it is not possible to ascertain from this study whetherbone turnover was affected directly by LCHP diets, and a review of theliterature shows conflicting effects on bone turnover.
Clinicalimplications of this enhanced acid load include a decrease in estimated calciumbalance.

Additional research needs to be performed comparing LCHPdiets with low and high calcium intakes.

Protect Against Lead Toxicity

The second benefit is to protect against lead toxicity. Leadis ubiquitous in the environment as a result of industrialization, so dietarycalcium may help detoxify from exposure. Calcium decreases gastrointestinallead absorption [14-17], thereby reducing the risk of lead poisoning.

Further, the literature consistently supports theobservation that ingestion of diets low in calcium increases lead absorptionand toxicity [14,18] and lead retention [19]. For example, rats raised on alow-calcium diet have much higher blood lead concentrations [20,21] and highertissue lead concentrations [21].

Reduce Oxalate Absorption

And finally, dietary calcium can leadto a reduction in oxalate absorption. Calcium is the most potent modifier ofoxalate absorption so eating foods with calcium is a good way for oxalates toleave the body and prevent stone formation.

Two epidemiological studiesdemonstrated that dietary calcium intake was inversely associated with the risk of kidneystones [22,23], and a human trial demonstrated that calcium intakereduces oxalate absorption [24] .

The diagram below demonstrates that within the 200-1200 mgcalcium per day range, oxalate absorption depended linearly on calcium intake,and calcium intake beyond 1200 mg per day only slightly decreased absorption.

Since a carnivore diet avoids plant substances like oxalates(dark leafy greens, root veggies, nuts/seeds, chocolate, etc.), perhaps oneneeds less calcium per day relative to someone who’s diet contains plants.

So, do we need Calcium on a Carnivore Diet?

A potential study design to investigate this question wouldinclude two groups. One group would be carnivore with little to no calciumintake, and the other group would be carnivore with a calcium intake near theRDI. These groups would be followed for an extended period of time (over 10 years,potentially cohort style) to analyze long term implications of low dietarycalcium intake (using BMD and other metrics).

Unfortunately, this study does not exist, so we will analyzesome of the studies that currently exist in the literature involving highprotein diets and calcium. Most studies with high protein intake involve mixeddiets or low carb diets with a sufficient calcium intake!

While it was once thought that high protein diets are detrimental to bone, after a review of the recent literature illustrates there is no question that high protein diets are beneficial for bone health [25-27]. Adequate protein intake is essential for bone matrix formation and maintenance [28], and higher intakes of protein are associated with a reduced risk of hip fracture [29].

Further, it is clear that eating high protein (carnivore)does not lead to impaired calcium balance, IN THE CONTEXT OF ADEQUATE CALCIUMSUPPLY. The second part of that sentence is very important!

The diagrams below highlight the conclusions from some papersin this field. The first 3 diagrams highlight reviews and meta-analyses, andthe last 3 diagrams highlight some human intervention studies.

While Hunt et al. (diagram 4) found that a moderate increasein dietary protein slightly improved calcium absorption from a low-calcium dietand nearly compensated for a slight increase in urinary calcium excretion [32],the “low” calcium diet was still ~675 mg calcium per day, which is pretty closeto the calcium RDI! Plus, each diet was only followed for 7 weeks.

The studies demonstrating a high protein diet improved BMDstill included a decent amount of dietary calcium intake!

The Meat Only Study

There is one study from 1928 that followed two individualson a strict carnivore diet with very low calcium intake [43,44]. There wereonly two subjects, both were male, who ate strict carnivore for a full year. Afterthe experiment, all of their health markers were… great!

Some Background

Before diving into the study, let’s start with a littlebackground information & history about one of the individuals in the study:Vilhjalmur Stefansson, a Canadian anthropologist and explorer who becameobsessed with the Inuit peoples due to their meat-heavy diet and amazinghealth.

In 1906, during one of Stefansson’s frequent escapades tothe arctic, a ship carrying his supplies did not show up. So, he had to dependon the hospitality of a local Inuit family. He learned that people in the arcticmainly ate fish (seals, whale) and meat (caribou, waterfowl), and also hadamazing health spans! He learned from this family on how to live off the land –so he could now go exploring and be self-sustainable and did not have carryheavy supplies. He spent over 11 years in arctic exploration, 9 of which helived almost exclusively animal based.

During his explorations he became convinced the Inuit peoples were onto something and took issue with the medical dogma of the times (which is similar to the dogma that still exists today). After retiring from Artic trips in 1918, he started to defend the idea that veggies weren’t necessary for a healthy diet and braved the wrath of vegetarians. Keep in mind this was the era of John Harvey Kellogg (1920s), so Western doctors of the time thought animal-based was a terrible way to eat – the optimal diet was heavy veggies and light meat.

The Study

In 1928, Stefansson and another explorer officially began themeat-only experiment. The two spent several weeks under constant supervision ata hospital in New York’s, as doctors performed blood tests and observed fordietary distress. For the remainder of the yearlong experiment, the tworeturned home.

See the diagram below for information about the study.

The one thing lacking, however, was dietary calcium, whichwas ~ 25% of the calcium relative to the SAD. The subjects ate a nose to taildiet (without high Ca intake through food such as bones), but still had periodsof negative calcium balance (excretion > intake). Despite the negativebalance, no signs of calcium deficiency appeared during the study, butperhaps 1 year was not long enough for significant calcium deficiencies to showup?

This study was only one year long, and the question of whether there are any serious consequences with humans operating in a negative Calcium balance for prolonged periods (years) has not yet been fully answered.

Why Some People Think Calcium is Not Necessary

Some individuals on the carnivore diet claim that a meatonly diet (non nose to tail approach) is sufficient for human needs. Theargument is that in the context of a high protein, meat only diet, physiologycompensates and some of the micronutrients become less of a requirement basedon the overall dietary scheme.

So, in regards to calcium specifically, there is some evidence that we can satisfy the body’s calcium needs with a meat only diet (shown in the diagrams below).

But, low dietary calcium intake has not been tested longterm. The studies showing there is increased intestinal calcium absorption wereperformed with a mixed diet so they still had some level of calcium intake.Plus, Hunt et al. [45] provide evidence that there is a chance there could benegative long term consequences of low dietary calciumintake.

The result of the Eskimo bone analysis study (the second diagram above), however, is very interesting. But, this is one investigation. Do we know the Ca level of their diet? Perhaps they had other sources of calcium in their diet?

Some Important Questions

With insufficient intake, is progressive loss of bonecalcium over time inevitable?

Why chance it?

Why not ensure you are covering your nutrient bases by following a nose to tail carnivore diet?

Calcium Nutritional Requirements and Influences

While the calcium requirements in the context of a carnivorediet are certainly unknown, is there really a downside to getting your calciumin? Why not include it? What’s the downside?

In addition to the functions and benefits presented earlier,a few additional nutritional reasons why dietary calcium may be a good idea areshown in the diagram.

Carnivore Sources of Calcium

While a meat only carnivore diet will be relatively low incalcium, there are plenty of carnivore options for dietary calcium, shown onthe diagram.

Given these amounts, a few options to obtain the RDI’s 1000mg calcium in include:

3.83 bottles of Gerolsteiner mineral water
6.7 cans of Wild Planet sardines
3.3 cups raw milk, or 5 oz raw cheese
½ of an egg shell
1 serving bone meal, depending on brand
5-10 g bones

Afew notes on some of these sources:

Bones

The amount of calcium in bone will depend on the source, and the values aren’t well studied. A few studies that have measured the calcium content in bones are listed below:

Chicken bone powder: 196.8 mg/g [46]
Bovine rib bone: 194.3, 203.7, and 344.6 mg/g for fresh, dry and ash weight bases, respectively [47]
Bovine rib and vertebrae bones varied between 238.8 mg/g and 272.7 mg/g for fresh bone samples, depending on the diet and location of bone sample [48]

The results of these studies show that the source matters, and these values will vary depending on the diet and health status of the animal. We always encourage people to purchase from White Oak Pastures (WOP) since the animals at WOP consume a nutrient dense diet from their extremely nutrient dense soil, so the bones will likely have a higher calcium content.

Plus, bones are a good source of boron, which is hard to get in the diet and is a trace mineral that is also good for the bones since it prevents bone loss and demineralization.

Bone Broth

Several factors will influence the amount of Calcium in bone broth including cooking time, acidity, bone type and animal species [49]. Acidified broths (broth made with vinegar) increased Calcium levels by 17% [49]. However, Hsu et al. found that even when adding vinegar, the Calcium concentration in a cup of bone broth is 86.6 mg [49], which is about 8% of the RDI.

Bone Meal

It is hard to know where some brands source their bones, and there is a chance the supplement is high in heavy metals such as lead & mercury. When choosing a bone meal brand, ask the company where they source their bones and if they have tested for heavy metals.

We were not able to find where the KAL brand sources theirbones, but the ‘Whole Bone Calcium’ powder from Traditional Foods Marketsources their bones from grass fed & finished cattle from New Zealand.

How do I Know if I am Getting Enough Calcium?

It’s important to remember that blood work that shows normal Ca levels doesn’t necessarily mean your body has sufficient calcium intake since serum Ca levels MUST be held in a tight range for the body to function properly. Over time (years) the body could be pulling significant levels of Calcium from the bone in order to keep the serum calcium levels in this tight range.

We recommend consuming a dietary Calcium intake near the RDI (1000 mg/day) and to monitor a few metrics:

Check your urine pH using pH strips from amazon. Ideally the value would be > 6.5
Monitor BMD
Check serum bicarbonate. Normal levels are between 23 and 30 mEq/L

Summary

While there are certainly many unknowns (dietary calcium needed in the context of a carnivore diet), this post has shown there are numerous benefits to consuming dietary calcium. A nose to tail approach implementing some of the items in the last diagram will help us cover our nutrient bases and prevent any potential long term, negative consequences with low dietary calcium intake.

References

References:

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