Calcium Requirements for Vegans Found Lower based on WHO Data

MAIN FINDINGS

Based on data from the WHO (World Health Organization), the Recommended Daily Intake (RDI)* of calcium for adults on a fully plant-based diet is 660 mg/day, not 1,000 mg/day as suggested by official recommendations (U.S. & Western Europe) intended for people consuming the Standard Western Diet.
For the (minority of) vegans consuming salt-free diets, the RDI is even lower, at 480mg/day.

Animal protein and sodium (salt) deeply influence calcium losses and calcium balance.

Besides putting unnecessary pressure on calcium intakes, the current official RDI of 1,000mg calcium/day is misguiding people on plant-based diets (even more so with lower salt intakes) to observe calcium intakes that may lead to the typical adverse effects of calcium excess.

Vegans and vegan/plant-based information websites are invited to verify the calculations presented here, and if they agree with the demonstration, update their information to this new RDI of 660mg/day. It is time to quit perpetuating an RDI intended for people consuming 60g+ of animal protein per day.

* Disclaimer: The RDI proposed in the present article is calculated using WHO’s calcium model which accounts for animal protein and sodium. Unfortunately, it is not an official recommendation as it should be. These numbers are not endorsed (yet?) by the WHO nor the FAO.

 

PART 1  – DEMONSTRATION

INTRODUCTION

Many vegans are aware that there are some nutritional precautions they must take, which are specific to their dietary lifestyle. Typically, it is important for everybody in our sanitized world – but in particular for vegans – to take a vitamin B12 supplement or B12-fortified.

However, in the transition to a plant-based diet, it is common for people to bring with them (and perpetuate) a number of carnist nutritional myths, or concerns that are by no means exclusive to plant-based diets. Besides B12, other nutrients of common concern are:  protein, iron, omega-3, or calcium.
It’s important to study evidence and demystify these topics, relieve unnecessary concerns, and help refocus attention where it should really be as far as plant-based health is concerned.

Today, I will cover the one of the least covered of these subjects: Calcium requirements in the context of plant-based nutrition.

To my current knowledge, there exists no calcium RDI formulated anywhere specifically for people on plant-based diets. Yet, the World Health Organization has offered them to us, on a very slightly veiled golden platter, since 1997. How was  something this big ignored and never implemented? It is a mystery to me. Hopefully this article helps correct this.

This is how it started.

 

THE CHALLENGE OF MEETING THE STANDARD WESTERN DIET’S RDI WITH WHOLE PLANT FOODS

Meeting the calcium RDI of 1,00o mg is fairly easy when relying on transformed soy products and/or fortified foods and beverages. As you can see below, as little as 150 g/day of a very common type of tofu would easily meet the RDI of 1000 mg/day, and various combinations might as well.


Per 100g (WARNING: these values may vary, most drastically in transformed and fortified products):
Traditional soy products: Edamame: 63 mg; Tempeh: 96 mg; tofu made only with calcium sulfate: 683 mg; tofu made with nigari and calcium sulfate: 282 mg; silken tofu: 31 mg;
Plant milks: Pacific® fortified oat milk: 146 mg; low-calcium soy milk : 42 mg; Other fortified plant milks: wide range;
Legumes: lentils: 19 mg; chickpeas: 49 mg; black beans: 27 mg;
Other starch/carbs sources: sweet potato: 38 mg; potato: 5 mg; brown rice: 10 mg; whole-wheat pasta: 13 mg; rolled oats: 52 mg.
Green leafy vegetables: raw kale: 150 mg; amaranth leaves: 209 mg; bok choi: 96 mg; mustard greens: 118 mg;
Fruits (per 1 medium piece): orange: 52 mg; apple: 11 mg; bananas: 6 mg;
Fungi: shiitake: 3 mg; white mushroom: 6 mg; oyster mushroom: 3 mg;


Both calcium-fortified foods or transformed soy products rely on calcium salts. Adding calcium salts to whole plant foods is a form of indirect calcium supplementation.

The real challenge appears when for whatever reason you either don’t or seldom eat them, or eat them in small amounts only.

When relying exclusively on unprocessed plant foods – which excludes fortified/processed foods mentioned earlier – it is still possible to meet 1,000 mg. It would however require carefully combining high-calcium foods.

Example of a high-calcium plant-based sample menu (to be completed with other foods to meet caloric needs) using only unprocessed, non-fortified, whole plant foods:
1 cup rolled oats, 2.5 cups of cooked amaranth leaves, 2 large oranges, 2 cups chickpeas.
Total calories: 1160 kcal;
Calcium content: 1038 mg (based on Cronometer/USDA database)

In practice, very few people on plant-based diets, including whole-food plant-based, eat anything like this artificially high-calcium diet.

So, quite naturally, some questions come to mind:

  • Why is the calcium RDI so ridiculously high?!
  • Is there something about a plant-based diet that should reduce the amount calcium we need?
  • Conversely, is there something about the Standard Western Diet that makes the calcium RDI abnormally high?
  • How did mostly plant-based populations throughout the world manage to grow bones and age healthfully on diets with no tofu, no fortification, and likely at far less than 1000 mg of calcium/day?

Answer: They weren’t given health objectives based on observing a majority of overweight and obese people eating the Standard Western Diet.

 

METHOD & RESOURCES FOR DEMONSTRATION

The demonstration below is intentionally done in a detailed, step-by-step manner, and to some extent using slightly less academic language. This is so that anyone wondering where these numbers came from can follow and run the calculations for themselves as verification. I used nothing more than high-school level maths.

Unless stated otherwise, all the calculations are based on the data presented in the WHO (World Health Organization) document “Vitamin and mineral requirements in human nutrition, Second edition” which is free to download. The images below are captured from this document.

The WHO report above supports one of the highest and most conservative RDIs for calcium: that for the U.S.A. and parts of Western Europe.

 

DETAILS OF CAPITAL IMPORTANCE: EFFECT OF ANIMAL PROTEIN AND SODIUM ON CALCIUM BALANCE

According to this report, several factors influence the calcium needs. I learned that animal protein and sodium (= mainly salt) intake play an absolutely major role in the calcium RDIs because both dramatically increase calcium loss.

Ok, so accounting for urine and sweat losses (which includes hair and nails) calcium balance happens either at 840, 600, or 450 mg of calcium per day, depending on different scenarios of low-[animal] protein and/or low-salt.

That is huge! You wouldn’t thinks RDIs would vary so much based on dietary lifestyle.

That really struck me!
I immediately wondered what about no animal protein? Or no salt like we do at home?
What calcium intakes correspond to these?

So I went searching for the numbers on the relationships between sodium/calcium and between animal protein/calcium.

 

IN NUMBERS, HOW DOES SODIUM AND ANIMAL PROTEIN INCREASE CALCIUM EXCRETION?

Effect of animal protein on calcium excretion

Page 79:

Comments:
1 g of protein reduces absorbed calcium by 1 mg
“Low-protein” on the graph meant 20g of animal protein/day.
Cutting further that 20g lowers the straight line of excretion by “20g points” on the vertical axis.

Effect of sodium on calcium excretion

(…)

(…)

For someone who has no salt nor high-sodium foods (i.e.: voluntary SOS-free dietary lifestyles, or very low sodium diets for medical reasons such as kidney diseases) the daily intake is somewhere around 100mg sodium/day (from my personal rough estimations). ~100mg is is negligible compared to 3.45g. To simplify the calculations, we will round that up that to zero sodium.

“Low sodium” on the graph meant 50mmol of sodium (1.15 g sodium, ~3 g salt) which in passing, is below the current limit of 1.5g (sodium) set by the American Heart Association.

100 mmol of sodium takes out 40g of calcium, so 50 mmol takes out 20 mg. Going from “low sodium” to salt-free cuts that 50 mmol of sodium from the diet, which lowers the straight line of excretion by “20 mg points” on the vertical axis.

Total of “no sodium” + “no animal protein” : 20 mg + 20 mg = 40 mg, a reduction in excretion by exactly as much as the previous jumps.

If you’re plant-based with an average salt intake in Western Diets (~9g salt/day in the U.S., NZ, etc.), you’re looking at this:


Now the million dollar question is…what are these “?” values, precisely?
I never liked graphic resolutions of equations because it’s imprecise in a number of ways. So let’s see if we can find some equations. This is where it starts requiring high-school level mathematics. But don’t worry, we will use an online calculator to solve this.

 

EQUATIONS FOR CALCIUM ABSORPTION AND CALCIUM EXCRETION vs. CALCIUM INTAKE


Here they are:
Ca_absorbed = 174 log(Ca_intake) – 909 (note: the log here is a natural log)
Ca_excreted = 0.078.Ca_intake + 137 (note: urine losses only)
Ca_excreted = 0.078.Ca_intake + 197 (note: inclusive of +60mg of “skin” losses – see section 4.4.4 – Insensible losses)

Using x for calcium intake (horizontal axis) and y for calcium absorbed or excreted (vertical axis) the equations are:

For calcium absorption:
y = 174 log(x) – 909

For calcium excretion, we have different scenarios:

Scenarios with animal protein

Average [animal] protein (60g/day) + average sodium (3.45 g sodium/day ~ 8.6 g salt/day) :
y = 0.078 x + 197
Calcium balance equation:
absorption = excretion
174 log(x) – 909  = 0.078x + 197

Low [animal] protein  OR Low sodium => decrease of excreted calcium by 40mg
We take the calcium excretion equation above and remove 40mg:
y = 0.078 x + 197 – 40 which is the same as:
 y = 0.078 x + 157
Calcium balance equation:
174 log(x) – 909  = 0.078x + 157

Low [animal] protein AND Low sodium => further 40mg not excreted
y = 0.078 x + 117
Calcium balance equation:
174 log(x) – 909  = 0.078x + 117

Scenarios with plant-based diets

No [animal] protein AND average sodium=> further 20mg not excreted compared to same with low animal protein
y = 0.078 x + 137
Calcium balance equation:
174 log(x) – 909  = 0.078x + 137

No [animal] protein AND No salt => further 60mg not excreted because no salt: 40 mg for low-sodium + 20 mg for the further elimination of salt.
y = 0.078 x + 77
Calcium balance equation:
174 log(x) – 909  = 0.078x + 77

SOLVING THE EQUATIONS

Throw that into a solver to get the x value (calcium intake) at equilibrium. I could have done that with a scientific calculator, or using the Matlab software, but so that everyone can check for themselves, I used a public, free-of-charge solver: WolframAlpha. Click on the above equations to see them being solved.

Below is the solving of the calcium balance equation for average animal protein and average sodium just to check if we got things right:


Why did we take the lowest solution of the two ? Because any solution above 2,000 mg is not a valid solution because the absorption curve  is valid only from 0 to 2,000 mg.

So it gives me ~840 for the first equation. It’s no surprise, that’s the value in the WHO document, found with the same equations. We’re finding the same result, that’s a good start!

Now, what about “no animal protein”? or that + salt-free?

Scroll up and click on the equations above to see the calcium intakes at equilibrium, it’s the lowest of the two values among the solutions Wolfam finds.

CUSTOMISED CALCIUM INTAKES AT EQUILIBRIUM (OR EAR)

The calcium intakes at calcium balance are the following. They’re basically the solutions to the equations listed in the previous section. Note that by definition these values are the EARs (Estimated Average Intakes). This means the intakes below will meet the needs of 50% of the total population.

Scenarios with animal protein

Average [animal] protein (60 g) + average sodium (3.45 g sodium/day ~ 8.6 g salt/day):
Ca_intake = 840 mg;

Low [animal] protein (20 g) OR Low sodium (1.15 g/day ~3 g salt/day):
Ca_intake = 599 mg;

Low [animal] protein (20 g) AND Low sodium (1.15 g/day ~3 g salt/day):
Ca_intake = 444 mg;

Scenarios with plant-based diets

No [animal] protein AND Average sodium (3.45 g sodium/day ~ 8.6 g salt/day):
Ca_intake = 514 mg !

No [animal] protein AND No Salt
Ca_intake = 336 mg !!!

These intakes would cover the needs of only 50% of people in the respective populations.
How much calcium to meet the needs of almost all the respective populations though? In other words,  what are the RDIs?
That’s what we’re going to find out now.

 

CUSTOMISED CALCIUM RDI VALUES BY DIETARY LIFESTYLE

This is how you get an RDI (Recommended Daily Intake) from the EAR (Estimated Average Requirement) we just calculated.

Page 2:

Do we have the value of the “standard deviation” somewhere ?

Searching, and…Yes we do! The full equation for calcium absorption  had “± 71 (SD)” at the end. Now is the time to use that standard deviation.

Following the above method to determine RDI (which is the same as RNI) from the EARs we get:

SD = 71
2 × SD = 142

RDIs = EAR + 142

Scenarios with animal protein

Average [animal] protein + average sodium (3.45 g sodium/day ~ 8.6 g salt/day):
Calcium RDI = 840 + 142 = 982 mg/day.
With no surprise, that is very close to the official RDI of 1,000 mg.
Official RDI are often rounded up to number easy to remember.

Low [animal] protein (20 g)  OR Low sodium (1.15 g/day ~3 g salt/day):
Calcium RDI = 599 + 142 = 741 mg/day

Low [animal] protein (20 g) AND Low sodium (1.15 g/day ~3 g salt/day):
Calcium RDI = 444 + 142 = 586 mg/day

Scenarios with plant-based diets

No [animal] protein AND average sodium (3.45 g sodium/day ~ 8.6 g salt/day)
Calcium RDI = 514 + 142 = 656 mg/day (~660 mg)

No [animal] protein AND No salt
Calcium RDI = 336 + 142 = 478 mg/day (~480 mg)

 

COMPARISON WITH PUBLISHED SCIENCE ON CALCIUM BALANCE IN PLANT BASED-DIETS

The above calculations based on official WHO models for calcium requirements matches a number of others studies and articles on the lower calcium needs in plant-based nutrition:

  1. October 2007: Calcium Requirements Much Lower Than Previously Estimated, by Dr McDougall.
    In this article Dr. McDougall suggests intakes around 500mg/day are sufficient.
    cites:
    Calcium requirements: new estimations for men and women by cross-sectional statistical analyses of calcium balance data from metabolic studies.
    This study examined calcium balance, sweat losses were ignored because considered negligible after measuring them.
  2. June 2016: Long-Term Low Intake of Dietary Calcium and Fracture Risk in Older Adults With Plant-Based Diet: A Longitudinal Study From the China Health and Nutrition Survey
    This study on lifelong senior vegans in China finds the lowest rates of bone fracture happen in a range of calcium roughly from 250mg – 650 mg all genders considers.
  3. December 2014: How to Get Calcium Without Dairy, by Dr. Thomas Campbell.
    Quote: ” if all of your calories are coming from whole plant foods, including plenty of fruits, greens, beans and other vegetables, you don’t need to think twice about calcium requirements or do any fancy math or milligram counting. You’ll be fine.”
    cites:
    Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr 2007;61:1400-6.
    Note: This study suggested that vegans with intake below ~500 mg/day had more bone fractures than carnists. However, in a critique of this study, Dr. McDougall observed that the vegans were younger, healthier (lower BMI) and far more physically active. Although the study tried to adjust for that, “vegans had no hip fractures, compared to 30 in the meat eaters, 9 in the fish eaters, and 14 in the vegetarians (dairy)”. He adds:
    “The observation that the fractures were of the wrist, arm, and ankle, and not the hip, to me, means the fractures were due to trauma caused by physical activity and not due to weakened bones.”

 

CONCLUSION

The WHO/FAO matches with the most conservative and highest calcium RDIs in the world: U.S.A & Western Europe.

Using this model and applying it to plant-based diets and low-sodium diets yielded surprisingly low calcium RDIs. The plant-based calcium RDIs are more easily achievable with little to no thought put into nutrition, provided:

  • a well-planned mostly unprocessed diet (more nutrient-dense, from whole foods) even on its own,
  • and/or a particularly low sodium intake
  • and/or calcium-fortified foods.

This is consistent with observations/suggestions from previous research on calcium intake and health in plant-based populations.

 

Acknowledgements

I would like to thank one of the people I view as a role model and mentor, the lovely, brilliant and generous Jenny Cameron. Jenny pointed me towards the calcium chapter of the WHO publication when I asked if any official recommendation suggested lower nutrient requirements for people on plant-only nutrition. Now, I and hopefully many other plant-based folks, have a clearer idea what exactly these requirements are – at least according to one of the most official and publicly recognized institutions that publish dietary health guidelines: the World Health Organization (WHO).

PART 2 – DISCUSSION

(still in the process of writing – table of contents below)

RDI-related questions

• What is an RDI worth anyway?
• Factors affecting absorption
• Shouldn’t the RDI depend on body size too?
• Menopausal women (& “Ageing” men)
• Infants, Children & Adolescents

A concern about calcium excess

• Is it harmful to consume 1,000 mg calcium on a plant-based diet?

Improving calcium balance and bone health

• Reducing/cutting animal protein vs. increasing calcium
• Salt Reduction: An additional strategy for osteoporosis & bone fracture prevention?
• Is it relevant for vegans to reduce salt intake?

• Open Questions