Family Vitamin D Dosing Guide

This Family Vitamin D Dosing Resource is written for those who believe in making informed decisions based on the science, the reported experience of clinicians, and their own experience of what works for them.

We here at Cellular Medicines suggest the following daily intakes of vitamin D based on our experience in dosing vitamin D and the scientific literature.

Adult daily dose to maintain good health: 5,000 IU in summer; 10,000 IU in winter
Child (0-3 years) daily dose to maintain good health: 1000 IU
Child (3-6 years) daily dose to maintain good health: 2000 IU
Child (7-12 years) daily dose to maintain good health: 3000 IU
Child (13+ years) daily dose to maintain good health: 5000 IU

Pregnancy and breast-feeding do not affect the above recommendations.

Some people suffer vitamin D hypersensitivity, whereby they cannot take vitamin D supplements or be in the sun. This guide does not apply to people with vitamin D hypersensitivity.

It is important that you read this page entirely if you are taking more than 10,000 IU of vitamin D daily or your infant/child is taking more than 1000/3000 IU of vitamin D daily.

We start our discussion on vitamin D dosing by making summary statements.

— The vast majority of the world's population is deficient in vitamin D.
— Vitamin D toxicity, the result of taking too much vitamin D, is extraordinarily rare.
— The aim of vitamin D supplementation is to build the serum 25(OH)D level to 50-100 ng/ml (125-250 nmol/L). You can get a blood test to check your level.
— Doses of vitamin D supplementation are given as daily averages. Taking 28,000 international units (IU) vitamin D once per week is as safe and effective as taking 4000 IU vitamin D once per day.
— However, it is more effective to take repeated moderate doses (e.g., 10,000 IU daily or 50,000 IU weekly) of a vitamin D supplement rather than a single huge dose (such as a single injection of 250,000 IU given by a doctor).
— It takes time for the body to convert vitamin D (cholecalciferol) to 25(OH)D (calcidiol) and then activated vitamin D (calcitriol), which is then widely used in the body. You therefore need to build your vitamin D level over a period of weeks and months.
— Obese people need 2 or 3 times more vitamin D as people of normal weight because the body locks away vitamin D in fat cells.
— Ideally, you make your own vitamin D on and in your skin from direct sunlight rather than through supplementation. However, 30 minutes of full-body sunbathing in strong sunlight without sunscreen is needed for a light-skinned person to produce a large amount of vitamin D.
— Dark-skinned people typically require vitamin D supplementation more than light-skinned people because they need far more sunlight (up to 10 times more) to make the same amount of vitamin D on and in the skin.

Introduction

Humans are designed to live in the sun and make vitamin D, the nutrient most important to health, in and on their skin. Unfortunately, most of us work indoors and do not get to access the midday sun. To make matters worse, health authorities worldwide have encouraged us to avoid the sun without regard for the consequences.

Since we are not getting enough sunlight and it is not possible to consume meaningful quantities of vitamin D from food, supplementation with vitamin D is essential to health, at least outside of summer.

Taking vitamin D is different from taking a vitamin such as vitamin C in that we are not aiming to take a certain dose each day but rather aiming to accumulate vitamin D in the blood to a certain level, which is a plasma 25(OH)D level of 50-100 ng/ml (125-250 nmol/L).

Ideally, we take a vitamin D test, specifically a plasma 25(OH)D test, which can easily be done by a diagnostics laboratory without a referral from a doctor. We can then take high daily doses initially to reach a healthy level and then take maintenance doses thereafter. However, you do not need a test to begin supplementation with vitamin D as you are almost certainly deficient in vitamin D to begin with, and it is extraordinarily difficult to overdose from taking too much vitamin D, as discussed below.

Optimal Level of Vitamin D in the Blood

We should aim for a 25(OH)D plasma level of 50-100 ng/ml (125-250 nmol/L).

As reference points, the human species traditionally had plasma 25(OH)D levels of 50-70 ng/ml (125-175 nmol/L) before modern times, and a level of 100 ng/mol (250 nmol/L) can be achieved through a high level of sun exposure alone.

(As an aside, in determining the optimal plasma 25(OH)D level of vitamin D, researchers look at how death from all diseases (referred to as all-cause mortality) changes as the level of plasma vitamin D increases in samples of the population. There was once a belief that although all-cause mortality decreases with an increasing 25(OH)D plasma level, it then increases (slightly) beyond 30 ng/ml (75 nmol/L) (following what is referred to as a U-shaped curve). This belief is outdated but you will still find reference to it. We know that there are benefits to increasing the 25(OH)D plasma level beyond 50 ng/ml (125 nmol/L). Levels between 100 ng/ml (250 nmol/L) and 200 ng/ml (500 nmol/L) are not known to be toxic (indeed, vitamin D toxicity is rarely observed at plasma levels up to 150 ng/ml (375 nmol/L)) but are not known to be beneficial either.)

So, again, we aim for a 25(OH)D plasma level of 50-100 ng/ml (125-250 nmol/L). Note that if you get a 25(OH)D plasma test, the laboratory will state a 'normal' level as being lower than this level, because the laboratory will look at what the normal level is in a highly deficient population. We do not want to be 'normal' but rather 'healthy'.

How Much Vitamin D to Take Daily

The amount of vitamin D supplementation required daily to be healthy depends on the individual (particularly in terms of their weight and skin tone) and how much sunlight that individual is getting.

The scientific literature is only partially helpful in determining how much vitamin D people should take as it mostly looks at what vitamin D supplementation is required to raise the 25(OH)D plasma level of a population from severely deficient to moderately deficient, with the majority of the population having a level far from a healthy level.

As one example, it has been calculated that the majority of the population needs to supplement with 9000 IU of vitamin D daily to have a plasma level at or above 20 ng/ml (50 nmol/L).

As another example, the Endocrine Society Expert Committee suggested that adults need 10,000 IU/day, children aged 1-18 years need 4000 IU/day, and children younger than 1 year need 2000/day IU of vitamin D to reach a 25(OH)D plasma level between 30 and 40 ng/ml (75 and 100 nmol/L).

So, we see that supplementation of 10,000 IU of vitamin D per day is needed to make moderate gains.

Yet, you will not find a vitamin D supplement that has a recommended daily intake as high as 10,000 IU because recommended daily intakes are limited by legislation. The maximum daily dose is 4000 IU in the United States and 1000 IU in our home country, New Zealand. Yet a fair-skinned person will make 4000 IU in 10 minutes while full-body sunbathing. Any supplement company would recommend a daily dose of 10,000 IU vitamin D if allowed.

In saying that, taking as little as 1000 IU/day of vitamin D for months will raise your 25(OH)D plasma level. As an example, an increase in the plasma level of vitamin D from 8 to 12 ng/ml (20 to 30 nmol/L), which might be achieved by taking 1000 IU/day for several months, will have beneficial health effects, although the person may not be consciously aware of them and the person's health will be far from optimal.

Any recommendation of a tiny daily intake of vitamin D of 400-600 IU/day is only for the prevention of rickets and not for the wide range of needs that the body has for vitamin D.

Persisting Misconceptions

Let's look at why health authorities have been limiting the supplementation of vitamin D. Historically, vitamin D was added to foods in many countries to reduce the incidence of rickets, type-1 diabetes and other diseases. Then, in the 1950s, researchers, despite admitting they had no direct evidence, suggested that high levels of vitamin D in the population were responsible for deformities, and the fortification of food with vitamin D was banned in many countries. Despite this suggestion long being disproved, it fueled a narrative that because vitamin D is fat soluble, it is readily stored by the body at toxic levels. You will continue to hear this narrative from doctors and health authorities.

Yet vitamin D toxicity is one of the world's rarest medical conditions whereas the world population's deficiency in vitamin D is history's greatest health crisis and is responsible for immeasurable disease and countless millions of unnecessary deaths.

The rare reports of vitamin D toxicity resulting from long-term supplementation relate to a person either intentionally or inadvertently taking doses of 100,000 to 500,000 IU per day for months or years.

Acute Toxicity

We next look at acute toxicity (as in, how much can I take in a single dose?) as opposed to long-term toxicity (as in, how much can I take in a 3-month period?).

First, family doctors regularly inject their patients with ~250,000 IU of vitamin D as a one-off dose. Likewise, scientific studies give their participants single doses as high as 600,000 IU. You are thus not going to get sick from taking 50 capsules of 1000 IU of vitamin D in one hit even if the bottle is recommending you take only one a day. Acute toxicity is typically reported for accidental or intentional overdoses of many million IU.

The main vitamin D toxicity concern is hypercalcaemia. Vitamin D excels at increasing the absorption of calcium. In fact, the most critical role of vitamin D in the human body is ensuring there is sufficient calcium in the blood. However, too much calcium in the blood (i.e., hypercalcaemia) can lead to the calcification of organs. In saying that, serum calcium only begins increasing beyond a normal level when the 25(OH)D plasma level increases above 200 ng/ml (500 nm/L), which shows how difficult it is to suffer vitamin D toxicity.

Those taking more than 10,000 IU/day of vitamin D without having blood tests may wish to take vitamin K2, because vitamin K2 locks excess calcium into bones. The amount of K2 required depends on the individual, and people on blood thinners (such as Warfarin) need to take care as vitamin K2 is a blood clotter. A daily dose of 200 micrograms of vitamin K2 can be considered standard.

Co-factors

Vitamin D uses vitamin K2, magnesium, zinc and boron in carrying out its functions. We, at Cellular Medicines, include a small amount of vitamin K2 in our vitamin D3 supplement for this reason. Magnesium and zinc are not added because of their sharp taste but can be taken separately.