Vitamin D and sunlight
Why we are deficient in vitamin D
Problems caused by vitamin D and sunlight deficiency
How much vitamin D do you need?
Sunlight and vitamin D
Ultraviolet radiation and vitamin D
Food sources of vitamin D
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 in the population 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, the black skin of our African ancestors synthesised much higher levels of vitamin D than most humans get today. About 50,000 years ago a single mutation that occurred 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 lower levels of sunlight there.
People with black 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 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 seriously 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.
Problems caused by vitamin D and sunlight deficiency
Insufficient vitamin D is associated with a wide range of modern degenerative diseases. (22, 44, 45) Sunlight is absolutely essential for good health.
- Hormone imbalance, particularly low levels of, or ineffective use of steroidal hormones. Symptoms of progesterone deficiency or testosterone deficiency may appear. 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.
- Weak bones / osteopenia / osteoporosis.
- Aging skin / older skin and many skin problems.
- Weak tooth structure and corrosion / decay.
- Sunburn. Having sufficient vitamin D in your body actually protects against sunburn. Avoiding the sun and using sunscreens leads to a vicious cycle of being less tolerant of sunshine. (31)
- Cancer. Having sufficient vitamin D protects against all types of cancer. (17, 31, 33, 40, 42, 45, 46, 47, 48, 49, 50, 51, 52)
- Heart disease (cardiovascular disease). (18, 20, 21, 44)
- Strokes. (19)
- Diabetes. (23)
- Low energy / fatigue.
- Weak immune system causing frequent 'flu (influenza) and other infections such as tuberculosis. There is no winter cold and 'flu season - rather, there is a season in which most people's vitamin D level is perilously low. (26, 27, 28, 29)
- Autoimmune diseases such as systemic lupus erythematosus and Sjogren's syndrome.
- Rheumatoid arthritis (another autoimmune disease).
- Inflammatory bowel disease (irritable bowel).
- Rickets, the classic result of severe deficiency in children.
- Autism. (37)
- Eye diseases and problems. (41, 43)
- Cognitive decline, dementia, including Alzheimer's disease and multiple sclerosis. (24,25,31)
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.
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:
* Optimal for good health, healing and disease prevention.
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>
Sunlight and vitamin D
When you sunbathe, vitamin D is created by the action of ultraviolet light on cholesterol close to the skin surface. For good health, you need sufficient cholesterol in your diet. It is one of the reasons why coconut oil, a saturated fat, is an excellent sunbathing oil. 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 all your skin with soap, or you will wash away the newly synthesised vitamin D. I suggest that you do not use soap for washing 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, which is required for the process.
Old people synthesise vitamin D more slowly than young people, so older people need more time in the sun to get the same amount.
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).
In my ebook Grow Youthful, I strongly recommend getting sufficient sunlight as regularly as you can. Sunlight has many beneficial effects in addition to creating vitamin D. The light regulates sleep cycles and helps create melatonin, and the far infrared warms the body and helps with other body systems. Ultra violet rays release the nitric oxide stored in compounds in your skin, dilating blood vessels and promoting cardiovascular health. (16)
Build up resilience. According to Weller (16), the highest risk of any 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.
Too much sun too soon can damage your skin and even increase the risk of melanoma. You need to build up your resilience with regular exposure to the sun every day if possible. After a few minutes of midday sun, when your skin turns the slightest pink 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.
Avoiding the sun. People who avoid sunbathing 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 old-fashioned doctors.
Ultraviolet radiation and vitamin D
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 easily able to penetrate the atmosphere, including clouds and polluted air. It can even pass through glass.
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.
It only acts on the surface of the skin, causing sunburn if you get too much of it. Sunburn is a valuable and important signal. It is your body telling you that you have had too much sun, and damage is occurring. 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.
UV-B is the light that helps your skin make vitamin D.
The best time of day to sunbathe is in the middle of the day when the sun is directly overhead. Beneficial UV-B exposure is maximised, making maximum vitamin D. Expose as much skin as possible for just a few minutes (longer if you are dark-skinned). Take care not to burn or go red. You have made most of your vitamin D for the day by the time your skin is halfway to getting red./p>
In contrast, when the sun is low on the horizon, or when the sun's rays are weak, blocked by cloud or atmospheric pollution, the beneficial UV-B rays are filtered out and relatively more of the dangerous UV-A rays get through.
It is almost impossible to overdose on vitamin D from sunlight, as the body stops making it as its level approaches sufficiency.
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.
Food sources of vitamin D
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, these other sources contain so little that you would have to eat ridiculous quantities to get sufficient vitamin D (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 people who avoid animal-based foods.
There are two kinds of vitamin D supplements: vitamin D3 (cholecalciferol), the kind our skin makes, and vitamin D2 (ergocalciferol), an inferior synthetic variant. Vitamin D2 is only 10-30% as effective in raising 25-hydroxyvitamin D blood levels compared to vitamin D3. A study concluded the "Vitamin D2 should not be regarded as a nutrient suitable for supplementation or fortification" (10).
Research shows that synthetic, supplemented vitamin D may be harmful (35, 36, 38, 39) or at best is ineffective. (11, 38, 39)
Vitamin D overdose
Most fat-soluble vitamins such as vitamin A are easy to overdose. However, Vitamin D has a built-in system to remove excess if its level is too high. If you take a very large dose of vitamin D, this will activate the enzymes which remove it. If you then stop taking vitamin D, you will become even more deficient because those enzymes continue working for up to 28 days. For this reason you should supplement vitamin D over a long period and with small regular doses.
Daily consumption of 50,000 IU for several months will cause hypercalcemia (elevated calcium level in the blood), which is the first manifestation of vitamin D toxicity. In contrast, the optimal level of 5,000 IU per day prevents the build up of calcium in blood vessels (12).
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