Vitamin D - "The Sunshine Vitamin"   by DougCuk
** Updated - October 2023 **

(1) Have we been causing many common diseases by avoiding the sun?
The facts are very simple - and understanding them could just save your life.
Fear of skin cancer, and lifestyle changes, have resulted in a significant drop
in regular sun exposure for many people. Researchers are beginning to worry this
could explain the steady increase in many "western" diseases over the last 25 years.

Want a quick introduction? Just watch a few of these videos.
GrassRootsHealth - Vitamin D Prevents Cancer
Dr John Cannell on Vitamin D
Dr Liz Lipski - Nutritionist
Canadian News Report Re Type 1 Diabetes

Some longer more detailed videos:
Dr Michael Holick - Prevention of Chronic Diseases
Dr Cedric Garland - Vitamin D & Cancer Prevention
Dr Robert Heaney - Vitamin D Deficiency

More background information:
Vitamin D Essentials - 4 part Radio Interview with Dr John Cannell
Listen to Steve Gibson's Podcast or Download Podcast mp3 - which inspired the creation of this website - Steve's Webpage.
How could a "simple" vitamin possibly affect so many different health issues?

Scroll to the bottom for links to buy Vitamin D online.

(2) Vitamin D is unique - unlike ALL other vitamins very little comes from our food.
Almost all of our Vitamin D is produced by the top layer of our skin when it is exposed to the UV radiation in strong sunlight.
However when the sun is too low in the sky you will NOT produce any Vitamin D from sunlight.
A quick way to check if the sun is too low is to look at your shadow while standing.
If your shadow is longer than you are then you will not produce any Vitamin D.

In the UK and most of the USA the sun is too low in the sky from November until March to produce ANY Vitamin D from sunlight exposure. We are supposed to build up a store during the summer to carry us through the winter, but because of lifestyle changes and the increasing use of UV sun-block this is no longer happening.

Current research shows that many people in non-equatorial regions have very low Vitamin D levels - especially during the winter. People of African decent, now living in less sunny regions, are at highest risk as the darker your skin tone the slower your Vitamin D production. If you rarely get any strong mid-day sun on unprotected skin you WILL be at high risk of deficiency - and the older you are the worse the problem, as your skin becomes less efficient at generating Vitamin D.

Vitamin D controls calcium metabolism which is vital for bone, muscle and nerve function - but recent research shows it is also critical to your immune response against viruses, bacteria and cancer.

Ever wondered why people in colder climates are more prone to colds and flu in the winter and early spring?
Researchers have discovered that as you run low on Vitamin D your immune response weakens. Trials have proved that people taking "high dose" Vitamin D3 supplements (>2000 IU/day) are extremely resistant to colds and flu. Research results published over the last 10 years show mounting evidence for major resistance to several common cancers, plus a range of neurological and auto-immune conditions.

Call to action by 48 major Vitamin-D researchers - August 2015      (PDF version)
Latest Press Releases from Grassroots Health

Recommended Books

(3) Think about this explanation for our current situation:
The human race evolved in equatorial East Africa where the sun's UVB was strong enough to manufacture all of the Vitamin D3 we required - from a natural cholesterol in our skin. When we migrated away from the equator, natural selection quickly eliminated most of the melanin pigmentation from our skin in an attempt to compensate for the much weaker levels of UV radiation in these cooler regions of the world.

This system worked well for most of human history - as the vast majority of the human population were outside in the sun for at least part of the day. But then came the industrial revolution and the majority of the workforce now remained indoors all day. This change of lifestyle caused severe Vitamin D deficiency in industrialised regions leading to mass outbreaks of the bone disease Rickets in children. Treatment with natural and artificial UV light and more recently with Vitamin D supplements had virtually eliminated this disease.

For the last 30 years sunshine has been demonised for causing skin cancer and we are advised to cover up, or apply UV sun-block, before we even go out in the sun. The unfortunate side effect of this advice, if followed rigorously, has been to remove most of the Vitamin D production from our lives. Many studies are now finding widespread Vitamin D deficiency even in sunny regions such as California and Australia - causing rising levels of osteo-malacia and osteo-porosis in adults - and in some, less sunny, northern regions cases of childhood Rickets.
Rickets in Leicester UK

The more worrying issue is that recent research has now discovered that calcium regulation is only one small part of the Vitamin D story - and in fact most tissues of the body require Vitamin D to regulate a wide range of cell processes - especially immune responses and anti-cancer mechanisms. Researchers are beginning to worry that this could explain the sudden mysterious increase in many "western" diseases over the last 25 years - diabetes, high blood pressure, various cancers including breast, prostate and colon cancer, fibromyalgia, multiple sclerosis, rheumatoid arthritis, seasonal depression, and even autism. Vitamin D Wiki - Health Conditions // Vitamin D Wiki - Autism // Vitamin D3 World - Summary of health research.

More details on these websites:
The Vitamin Society & Vitamin D Wiki
Vitamin D Health - Dr Michael Holick's Website
Grassroots Health D-Action Website & Breast Cancer Prevention Campaign
Vitamin D3 World Website

Grassroots Health Website - Disease Prevention Chart - PDF Reader required. (Blood levels in both European and US units)
Multiple Sclerosis Society - Vitamin D Factsheet - PDF Reader required.
How could a "simple" vitamin possibly affect so many different health issues?

(4) How much Vitamin D is required to avoid deficiency:
The current "recommended" supplement level of 400 IU/day was created when we discovered it prevented Rickets in children - the result of a SEVERE Vitamin D deficiency. Vitamin D3 supplements are added to most commercial baby formulas, and margarines to prevent severe deficiency in children. Many countries also add Vitamin D to milk, but NOT the UK at present. However this level supplementation was never shown to represent an adequate intake for an adult.

The American National Institutes for Health (NIH) recently stated that a supplement level of 1000 IU/day for infants (birth to 12 months) and 2000 IU/day for adults and older children is now certified as totally safe. Most Vitamin D researchers would prefer a system based on body weight - as it has now been shown that an adult will process 4000-7000 IU/day if available - while a young baby only requires 400 IU/day.

These levels equate to a dose of 90 IU/kg per day (or 40 IU/pound) - which can be used to calculate an individual daily dosage based on body weight. In the summer with moderate sun exposure you might only require half this dose.

One important point is that individual daily dosage levels are not critical as any excess is stored in the bodies fat reserves and released as required - so you can safely take two or three days worth of Vitamin D in one larger dose, instead of taking smaller daily doses.

To put all this in perspective, a young person working outside in the summer sun can make up to 25,000 IU/day of Vitamin D - while an elderly person may produce less than 5,000 IU/day under the same conditions. Vitamin D production from UV exposure is self limiting and stops once all the available 7DHC (7‑dehydrocholesterol) in the skin has been converted - the body produces more 7DHC but this takes a day or two to build up again. Any Vitamin D not used immediately is stored for use on days with no sun, and to carry you through the winter - but this only happens if you get enough sun or take "high dose" supplements.

(5) When considering taking Vitamin D supplements you should be aware of the following:
Some existing medical problems can alter the way the body processes high dose Vitamin D supplements.
Always check with your doctor if you have an existing serious illness, especially cancer, kidney or liver disease.
You may need to have your doctor monitor your Vitamin D and Calcium levels to ensure they respond as expected.

Anyone diagnosed with sarcoidosis, primary hyperparathyroidism, or any condition resulting in
elevated blood calcium levels MUST seek medical advice before taking Vitamin D supplements.

Vitamin D3 is identical to the supply from our skin - it is converted in the body to activated Vitamin D as required.
An alternative from plant sources called Vitamin D2 does exist - but behaves differently in higher doses - avoid.
You should also avoid combined Vitamin A+D supplements - as high dose Vitamin A can block the action of Vitamin D.

Some Vitamin D researchers suggest that responsible use of a UVB certified (low-pressure tube) sunbed in the winter and moderate sunbathing in the summer is a better alternative to oral supplements. Dr. Holick recommends the safe limit is 25% of the exposure required to get a slight skin reaction - longer exposures do not create any extra Vitamin D3 and could raise your risk of skin cancer. Dr Michael F. Holick's Vitamin D Website

A small number of people experience muscle cramps after they start taking Vitamin D, or even after sun-bathing. This can occur if you are deficient in Magnesium and only becomes evident as your muscle function improves due to the higher Vitamin D levels. Magnesium & Muscle Cramps

(6) All health professionals were taught that you can overdose on Vitamin D:
While this is possible - it is EXTREMELY difficult to do - see this report: Vitamin D Toxicity

For a normal healthy adult toxic levels can only be reached by taking 40,000+ IU/day for many months.
Tests have shown that a normal healthy adult CAN tolerate 10,000 IU/day indefinitely without any problems.

Dr. Cannell discusses Vitamin D toxicity
Dr. Robert Heaney discusses new Vitamin D dose-response data
Dr. Cedric Garland discusses dose levels for Cancer Prevention
New Analysis Claims Vitamin D Supplements Are Useless - Hereís Why Itís Wrong - Feb 2014

The best advice is to calculate a dosage based on your own weight - you can take 90 IU/kg or 40 IU/pound per day.
In the summer with moderate sun exposure you might only require half this dose.

(7) If in doubt ask your doctor to check your Vitamin D levels via a blood test.
Your doctor needs to order a 25-hydroxyvitamin D blood test - which can also be written as 25(OH)D.
Ordering the wrong type of Vitamin D test can falsely indicate that your levels are normal.
What you DO NOT want is a 1,25-dihydroxyvitamin D test - also written as 1,25(OH)2D.
Summary of Acceptable Vitamin D Levels

I would suggest you print the following chart and take it with you when you visit your doctor.
It will illustrate why you are concerned and provide details of the Vitamin D levels required to ensure full health.
Disease Prevention Chart - PDF Reader required. (Shows blood levels in both European and US units)

(8) If you want to purchase Vitamin D3 here are some guidelines and web-links:
You should be looking for 2000 IU or 5000 IU Softgel capsules - which contain Vitamin D3 dissolved in vegetable oil.
Dry formulations do exist but are not recommended as they require an oil rich diet to be fully absorbed by the body.
Many companies only stock the 400 IU product (10µg) - a dose suitable for a newborn baby, not an adult.

Some products quote Vitamin D3 content in micrograms (mcg or µg).
Multiply the figures quoted in micrograms by 40 to convert into IU (International Units).

For the UK - I recommend the following

BigVits UK - Vitamin D3: Health Thru Nutrition 5000 IU - 360 Softgels // Now Foods 5000 IU - 240 Softgels
BigVits UK - Vitamin D3: Now Foods 10,000 IU - 120 Softgels (Taken every other day will be same as 5000 IU x240)
BigVits UK - Vitamin D3: Healthy Origins 5000 IU - 360 Softgels
BigVits UK - Vitamin D3: Doctor's Best 5000 IU - 360 Small Softgels // Doctor's Best 5000 IU - 720 Small Softgels
BigVits UK - Vitamin D3 Liquid: Now Foods - 1000 IU per drop (30ml / 1000 drops)
BigVits UK - Vitamin D3 Liquid: Natures Answer - 2000 IU per drop (15ml / 500 drops)

Amazon UK - Vitamin D3: Nutravita 4000 IU - 400 Softgels

Bodykind UK - Doctor's Best 5000 IU 360 & 180 Softgels - Currently discontinued
Bodykind UK - Vitamin D3: 2000 IU - 180 Softgels - Suitable for Children
Bodykind UK - Vitamin D3 Liquid: 1000 IU per drop - (10ml / 300 drops)

Ordering from in California can be cost effective if you keep the order below £135
Note: Brexit regulation now require iHerb to include 20% VAT in the price you pay.
Doctor's Best - Vitamin D3: 5000 IU - 360 Softgels // 5000 IU - 720 Softgels
Other Brands - Vitamin D3: 5000 IU - 360 Softgels // 5,000 IU - 240 Softgels

A delivery guide for UK customers appears when you select items and choose View Cart.
As long as the value of the order is below £135 there should be no extra import fees.
For fastest UK delivery select DHL (4-5 days) with online tracking and no customs delays.

For the USA - I recommend purchasing from
Vitamin D3 - Various brands:
Vitamin D3 - 5000 IU - Suitable for Adults
Vitamin D3 - 2000 IU - Suitable for Children
Vitamin D3 - Drops    - Suitable for Babies

Live Long and Prosper
DougCuk - Webmaster of