Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health
Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health

Sunlight, Vitamin D and more benefits

Why we are deficient in vitamin D

Problems caused by vitamin D and sunlight deficiencies

How much vitamin D do you need?

Sunlight, ultraviolet and vitamin D

Sunlight has more benefits

Food sources of vitamin D

Vitamin D supplementation

Vitamin D overdose


Why we are deficient in vitamin D

Getting sufficient vitamin D is one of the keys to staying healthy and long-lived. Hundreds of studies show that most people in the Western world are deficient in vitamin D. Even the most conventional journals now acknowledge that a lack of vitamin D is responsible for a wide variety of ailments (1, 2, 44), listed below.

Humans evolved in equatorial Africa, where there is constant and regular sun throughout the year. With all that sunlight our African ancestors synthesised much higher levels of vitamin D than most humans get today. Remember that they were out all day hunting and gathering, and mostly unclothed if it wasn't too cold. About 50,000 years ago a genetic mutation occurred that was responsible for the appearance of white skin in humans. White skin, with less melanin, synthesizes vitamin D in sunlight six times faster than dark skin (3, 14, 15). These humans were able to successfully migrate to higher latitudes around the world because they could synthesise sufficient vitamin D to survive in the long winters and lower levels of sunlight.

People with black or brown skins who live far from the equator are at a particularly high risk of vitamin D deficiency. The early 2020 data on covid in Sweden found that 50% of all covid deaths were in the Swedish Somali refugee population, even though this population was a small fraction of 1% of the total. Further investigation found that their black skins prevented them from synthesising sufficient vitamin D at that high latitude, and they were not supplementing or eating a high-vitamin D diet.

We evolved to live outdoors, yet most people spend most of their time inside buildings (or vehicles). The majority of the world's population now lives above latitude 35 degrees. This means that most people are sun-deficient. The majority of these people are also unable to synthesise vitamin D from sunlight during the winter months, depending on the angle of the sun and the amount of skin exposure they get. For example, in Seattle (47 N) and London (52 N), there is insufficient sun for skin to make vitamin D from October to April. People living at high latitudes have an increased risk of diseases caused by a lack of vitamin D (8, 9, 14, 15).

Vitamin D is not really a vitamin. It is more like a hormone and is also used to make other hormones. It should probably be called a pre-hormone.

One of Vitamin D's characteristics is it behaves rather like the stress hormone cortisol. There are a range of pharmaceutical drugs that act somewhat like cortical steroids, such as prednisone, which are often prescribed for chronic muscular and joint pain. Do not take these synthetic cortical steroid look-alikes - they have terrible side effects, especially in the long term. They also create dependence on them. Instead, you can get the same relief, and gain many other healthy advantages, by ensuring vitamin D sufficiency in your body.

Vitamin D is stored in both fat and muscle.

The half-life of vitamin D circulating in the body is approximately one month. By the end of winter in the high latitudes most people are deficient in vitamin D. If you have plenty of exposure to the sun during summer months you build up a reservoir of vitamin D which can see you through the winter months.

Ageing. The precursor for vitamin D is 7-dehydrocholesterol (7-DHC), an oil in the epidermus of your skin. Sunlight on your skin converts 7-DHC to vitamin D. Young people have plenty of 7-DHC in their skin, but as people age the skin tends to dry and the level of 7-DHC in an old person is a small fraction of that when they were younger.

Obesity more than halves vitamin D production because 7-DHC is trapped in fat cells rather than being in the epidermus.

Sugar prevents the production of vitamin D in your skin. This is why diabetics are nearly always low in vitamin D. Sugar also prevents the absorption of vitamin D from the skin and from food. Sugar interferes with the activation of vitamin D before it can be used. Sugar turns into liver fat, which also interferes with the proper use of vitamin D. With so much sugar being added to foods today, and with most people having such sweet tastes, it is no wonder that most people have dangerously low levels of vitamin D.

Problems caused by vitamin D and sunlight deficiencies

Insufficient vitamin D is associated with a wide range of modern degenerative diseases. (22, 44, 45) Sunlight is absolutely essential for good physical and mental health.

How much vitamin D do you need?

The level of vitamin D needed for good health is a lot higher than the US Food and Nutrition Board set as the Recommended Dietary Allowance (RDA). The RDA recommends 200 international units (IU) per day for children and adults less than 50 years old, 400 IU for adults age 50-70, and 800 IU for adults over the age of 70. The RDA was set at a level that prevents rickets but does not prevent numerous other diseases.

Vitamin D and zinc support each other in their activities. If you are deficient in one of them, it will make you appear deficient in the other. A deficiency in one of them inhibits the production, absorption and thousands of different ways in which they are both used.

An optimal level of vitamin D can prevent and heal cancers (4, 42, 45, 46, 47, 48, 49, 50, 51, 52), multiple sclerosis (5), cardiovascular disease, autoimmune diseases, and infections such as influenza (6, 7). Here is the most recent thinking on blood vitamin D levels:



Severely deficient
Optimal *
Potentially toxic

* Optimal for good health, healing and disease prevention.

Sunlight, ultraviolet and vitamin D

When you sunbathe, vitamin D is created by the action of ultraviolet-B light on cholesterol (7-DHC) close to the skin surface (epidermus). For good health you need sufficient cholesterol in your diet. It is one of the reasons why coconut oil, a saturated fat, is used as a sunbathing oil. A better alternative with a content closer to 7-DHC is lanolin. After being in the sun, the newly created vitamin D on the oily skin surface needs 48 hours to be absorbed. Do not wash off the oil for 48 hours after sunbathing. If you have a shower after sunbathing, do not wash your skin with soap or you will wash away the newly synthesised vitamin D. I suggest that you do not ever use soap for washing your skin unless it is the only way to get off grime or a smell.

A light-skinned adult human will synthesise 5,000 IU of vitamin D in 5 minutes of naked sunbathing at midday on the equator. Five minutes per day is all this person needs to get his/her optimal daily supply. In a little over half an hour, they'll get their entire week's optimal health allowance. Your body can synthesise over 20,000 IU of vitamin D per day, provided you are not deficient in magnesium that is required for the process.

In addition to having much lower levels of 7-DHC in their skin, old people synthesise vitamin D more slowly than young people, so older people need more time in the sun to get the same amount of vitamin D.

As you move further from the equator, further from mid-summer, further from midday, or in cloudy or polluted air, less vitamin D will be synthesised by your skin. However, at a temperate latitude with a few more minutes per day it is still easy to get your full vitamin D requirement just from the sun.

The rule of thumb is that the sun must be clearly visible and at least 45 degrees above the horizon. If you stand on a flat surface, your shadow must be shorter than you and clearly visible. If your shadow is longer than you are, it is cloudy, or the air is very dirty or polluted, the sun may produce little or no vitamin D in your skin.

A black-skinned person will only synthesise one sixth as much as a white-skinned person. Dark-skinned people are much more at risk of vitamin D deficiency at temperate and cooler latitudes (3,15).

Sunlight hitting the earth has two main types of ultraviolet radiation: A and B. High frequency ultraviolet-C radiation is generally unable to penetrate through the atmosphere.

Ultraviolet-A radiation is of a lower frequency, in the range of 400-315 nm. UV-A is able to penetrate the atmosphere, including clouds and polluted air. It can even pass through glass windows.

UV-A penetrates through the outer human skin deep down to the elanocytes. UV-A is the dangerous ultraviolet radiation, which does its damage even on cloudy days, or if you are behind a glass window such as when you are driving. It is easy to get severely burned through over-exposure to the sun in cloudy weather. Most sunscreens do not block UV-A. (34)

Ultraviolet-B radiation is of a mid frequency, in the range of 315-280 nm. UV-B cannot penetrate glass, and is easily blocked by sunscreens. It is partially blocked by cloud, dust, air pollution and the atmosphere in general. It gets through best in the middle of a clear day, when the sun is immediately overhead. UV-B does not penetrate the skin deeply.

When the sun is low on the horizon, or when the sun's rays are weak, blocked by cloud or atmospheric pollution, UV-B rays are filtered out and relatively more of the UV-A rays get through.

UV-B only acts on the surface of the skin, causing sunburn if you get too much of it. Sunburn is a valuable and important signal - your body telling you that you have had too much sun. One of the (many) reasons I don't use sunscreens is that they hide this essential signal. (30) Even a little redness or burning causes skin damage, wrinkles, skin aging, and keratoses.

Sunglasses did not exist during human evolution. They are a fashion statement invented in the early 1900's when people tried to mimic early aviators. People who wear them every time they go outside (and even when they are indoors) are harming themselves. We need sunlight on the retinas of our eyes. However, sunglasses may be necessary if you are not resilient and the light seems glaring. If there is additional reflection of sunlight such as in the snow on in a sandy desert on a sunny day, sunglasses can reduce the extreme level of light entering the eyes.

The best time of day to make vitamin D is in the middle of the day when the sun is directly overhead and UV-B exposure is maximised. Expose as much skin as possible for just a few minutes (longer if you are dark-skinned). Take care not to burn or go even slightly red. You have made most of your vitamin D for the day by the time your skin is halfway to getting red.

Vitamin D from sunlight is more effective in health maintenance, and stays in the body about twice as long as vitamin D from food and supplements.

Sunlight has more benefits

In Grow Youthful, I strongly recommend getting sufficient sunlight at all times of the day as regularly as you can. Sunlight regulates sleep cycles and helps create melatonin. The infrared in sunlight warms the body and is essential for healing, immunity, energy production and other body systems. Low frequency ultra violet rays (UV-A) release the nitric oxide stored in compounds in your skin, dilating blood vessels, promoting cardiovascular health, enhancing the immune system and boosting energy production. Having sufficient nitric oxide protects your skin from sunburn. This is one reason why keeping out of the sun and slathering on sunscreen actually makes you less resilient and more susceptible to sunburn. (16)

Build up resilience. According to Weller (16), the highest risk of damage from the sun comes from intermittent exposure to excessive sun instead of regular exposure that helps your body become resilient. The worst sun damage occurs when someone who is not sun-resilient binges in the sun and gets burned. Think of someone who lives in a winter city who travels to a holiday in a sunny place and gets sunburned on the first few days. Excessive and intermittent exposure that leads to sunburn is the most damaging, especially for young people.

You need to build up your resilience with regular exposure to the sun every day if possible. After a few minutes of midday sun, immediately your skin turns the slightest pink then go indoors. This faint pink should disappear almost immediately. If it does not disappear within a couple of minutes you have had too much sun. If you repeat this procedure every day, you will find that it takes longer for your skin to get slightly pink in the sun.

Early morning sunlight is beneficial. Try to get outside between sunrise and 8 or 9 am. Early morning light on your eye's retina assists with the production of melatonin and other hormones. It also promotes production of a protein named filaggrin. Filaggrin protects the skin from radiation and other damage. In other words, getting early morning sun makes you more resilient and protects you from stronger sun in the middle of the day. Filaggrin also assists the immune system and helps prevent allergies and immune reactions such as rheumatoid arthritis and asthma.

People who avoid the sun are twice as likely to die as those who sunbathe every day. An epidemiological study (32) that followed 30,000 women for over 20 years showed that all-cause mortality was about double in those who avoided sun exposure compared to the highest sun exposure group. Outdoor workers have half the rates of skin cancers as indoor workers. Tanned people beat untanned people on virtually every health marker. Long term sun exposure is associated with less melanoma.

The researchers concluded that those who avoid the sun at all costs and slather on sunscreen to minimise sun exposure are doing themselves more harm than good. This is the exact opposite to the message we have been getting from the sunscreen industry and captured government regulatory agencies.

Food sources of vitamin D

Without sun exposure the optimal blood level of vitamin D of 50-99 ng/ml for an adult requires 5,000 - 7,000 IU per day from supplementation or food./p>

The best food sources of vitamin D are wild (not farmed) oily fish like salmon, mackerel, and sardines and cod liver oil. Other food sources include free-range eggs, free-range meat, and fresh or sun-dried mushrooms. However, the non-fish sources contain so little vitamin D that you would have to eat ridiculous quantities to get sufficient (for example, forty free-range eggs per day). Very little vitamin D is naturally present in our food, especially for those who consume a modern, processed food diet or for people who avoid animal-based foods.

Getting sufficient vitamin D from your food is difficult, so this leaves sunlight as the most beneficial, cheapest, healthiest and bountiful option. For many people, latitude, lifestyle and seasons make this impossible, so supplementation is the only option.

Vitamin D supplementation

There are three common kinds of vitamin D supplements.

Research shows that synthetic, supplemented vitamin D may be harmful (35, 36, 38, 39) or at best is ineffective. (11, 38, 39) Therefore, if you need to supplement use a form of vitamin D3.

Vitamin K2 assists with the absorption and use of vitamin D. The two work together synergistically, and are often sold in a combined capsule or liquid spray. Vitamin K2 is produced by bacteria in a healthy gut biome, and is found in animal fats. The best food sources of vitamin K2 are high quality unpasteurised artisan hard or strong cheeses which contain live bacterial culture and are made from raw milk, butter from grass-fed cows, meat from grass-fed animals, egg yolks from free-ranging hens and home made raw sauerkraut.

Also ensure that you are zinc sufficient. A zinc deficiency inhibits the production, absorption and thousands of different ways in which vitamin D is used.

Take vitamin D supplements irregularly. Rather than taking the same dose every day, take the week's dose over two or three days instead.

Vitamin D overdose

It is almost impossible to build up an excess of natural vitamin D that your body makes from sunlight, because production slows down as its level approaches optimal sufficiency.

Daily consumption of 50,000 IU of a vitamin D supplement for several months will cause hypercalcemia (elevated calcium level in the blood), which is the first symptom of vitamin D toxicity. (In contrast, the optimal level of 5,000 IU of vitamin D per day prevents the build up of calcium in blood vessels.) (12)

If you take a toxic excess of a vitamin D supplement, your body will try to pee it out. You may be dehydrated and excessively thirsty (polydipsia) at the same time, as your body produces excess urine (polyuria). You may suffer recurrent vomiting, abdominal pain, apathy and confusion.

If you take a very large dose of a vitamin D supplement, this will activate enzymes which remove it. If you then stop taking the supplement, you will become even more deficient because those enzymes continue working for up to 28 days.


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