In July, since sunshine is in abundance in our part of the world, let’s talk about the benefits and importance of getting out in the sun, with particular emphasis on Vitamin D synthesis.

A lot of negative things have been said about sunbathing in recent years. Sure, too much sun or bad sunbathing habits can cause sunburn, which other than causing premature ageing and other skin issues, can also be a factor in skin cancer. However, avoiding the sun altogether has been linked to a larger number of health issues, while healthy sunbathing can help maintain optimal health.

1. Sunlight and Serotonin

In one of my previous newsletters I wrote about the role of sunlight and serotonin in relation to Circadian cycles and the release of hormones in your brain. Sunlight exposure and its impact on hormones like serotonin, has the following benefits:

  • It can help with sleep and regulating wake-sleep cycles.
  • It can improve mood, including help prevent and improve SAD and depression.
  • It can help regulate appetite, and helps regulate insulin/insulin resistance levels.

2. Sunshine and Health Conditions

  • Cancer: although excessive sun exposure and bad sunbathing habits (i.e. sunburn) can be contributing factors to skin cancer, according to some research, longer daylight hours and increased exposure to sunshine have been associated with lower rates or improved outcomes in certain cancers (namely colon cancer, Hodgkin’s lymphoma, ovarian cancer, pancreatic cancer and prostate cancer). This is thought to be due to vitamin D pathways primarily (discussed further below).
  • Skin conditions: sun exposure is thought to help improve several skin conditions. These include psoriasis, eczema, jaundice, and acne. The context and use of sunshine for treatment remains individualised to the presentation so get advice if you have these conditions.
  • Other Health Conditions: Some preliminary studies have indicated links between sunshine and improved outcomes in other conditions such as diabetes, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD) and thyroiditis. Again these outcomes are thought to be linked primarily to vitamin D pathways.

3. Sunshine and Vitamin D Synthesis

Vitamin D – commonly known as the “sunshine vitamin” – is a fat-soluble vitamin responsible for increasing intestinal absorption of calcium and phosphate, and for quite a number of other physiological functions (including maintaining bone health, cell growth, neuromuscular and immune functions, and reduction of inflammation). Technically, vitamin D is actually more like a hormone (a pro-hormone) than a vitamin because it is made primarily in the skin from cholesterol – another reason adequate cholesterol levels are important – through a chemical reaction that uses UVB radiation from the sun. To a lesser extent it can also be made from certain food sources (see below). Activation of the vitamin then takes place in the liver and kidneys. Being a fat-soluble vitamin, it can be stored by your body (in fat cells) over time, though its maximum half-life is about 2 weeks only.


4. Vitamin D: What, When, Where etc…

Vitamin D has multiple essential roles in the body, including to:

  1. Regulate calcium and phosphorus absorption
  2. Maintain healthy bones and teeth
  3. Support the health of the immune system, brain and nervous system
  4. Protect against the flu
  5. Regulate insulin levels
  6. Support lung function and cardiovascular health
  7. Influence the expression of genes involved in cancer development
  8. Protect against the development of other health conditions

The absolute best way to synthesise Vitamin D is with sun exposure. Food sources exist but they don’t come close to the sun, particularly if you are vegan, in which case, supplementation is necessary.

How Much Sun?
The number of minutes you need to spend in the sun to get a daily dose of vitamin D varies according to the time of year, your skin colour and where you live. Vitamin D deficiency is especially common in infants, the elderly, people with dark skin (especially those living in low-sun areas), people living in higher altitudes and those who get little sun exposure. In order to get sufficient sun exposure, you need to expose your face, arms, legs or back. Note that sunscreen can significantly decrease the body’s ability to absorb the ultraviolet radiation B (UVB) rays required to produce Vitamin D. For instance, a sunscreen with sun protection factor (SPF) 30 is thought to reduce the body’s ability to synthesise Vitamin D by up to 95%. In addition, Vitamin D metabolism may be affected by some medications, including statin drugs.

Below is a Sunshine calendar from to help you determine how much sun exposure you need.

Vitamin D from Diet
There are two main forms of Vitamin D available from food:

  • Vitamin D3 (cholecalciferol): from animal sources e.g. oily fish, liver, egg yolks
  • Vitamin D2 (ergocalciferol): from a selection of mushrooms

Vitamin D3 is more bioavailable and effective. Vitamin D is fat soluble, and requires dietary fat for absorption as well as  magnesium to convert it into its active form. A healthy gut is also important to ensure absorption.

Vitamin D intake can be measured in two ways: in micrograms (mcg) and International Units (IU). One microgram of Vitamin D is equal to 40 IU of Vitamin D. Generally, the minimum daily recommended intakes of Vitamin D are currently set at:

  1. Infants 0-12 months – 400 IU (10 mcg)
  2. Children 1-18 years – 600 IU (15 mcg)
  3. Adults to age 70 – 600 IU (15 mcg)
  4. Adults over 70 – 800 IU (20 mcg)
  5. Pregnant or lactating women – 600 IU (15 mcg).

However, many health organisations recommend that adults get at least 600 IU daily. Some organisations even recommend up to 4000 IU/day for an adult in order to maintain a healthy concentration of Vitamin D in the blood. These guidelines should help you determine a general amount needed depending on your skin type, location, time of year and sun exposure.

It is generally difficult to obtain significant amounts of Vitamin D from food. If you are vegetarian or vegan, it is unlikely you can get sufficient daily vitamin D naturally only through food. There are of course fortified foods but usually these are not the healthiest options, and personally I recommend a good quality supplement in such cases if you cannot get sufficient sunlight. If you are vegan, bear in mind that vegan sources are generally less bio-available.

The natural (i.e. not fortified) food sources highest in Vitamin D are:

  • fatty fish and fish eggs (cod liver oil, herring, swordfish, salmon, tuna fish, mackerel, sardines)
  • some variety of mushrooms (exposed to ultraviolet light while growing)
  • egg yolks
  • raw milk and butter from grass-fed cows

In patients who don’t show signs of severe deficiency of vitamin D and who generally have healthy diets, I usually recommend that they get sunshine as soon as the sunnier days appear, and a liquid supplement the rest of the year (September/October-March/April) taken at least 3 times a week at 2000-2500 IU. My recommended vitamin D supplement is Liquid Vitamin D3 from Viridian (vegetarian) which you can find here (your can use my account Terra10 for a 10% discount).

Now go enjoy that sunshine!

Leave a Reply

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