Natural vitamin D: how to get enough in Estonia

Natural vitamin D is in serious deficit in Estonia — in a 2007 study by the University of Tartu Clinic of Internal Medicine, 8% of adults had severe deficiency in winter and 73% had insufficiency. Only 3% of residents had optimal levels. This article explains why that is, how much vitamin D we actually need and where to get it — from sunlight, food and supplements.

Why natural vitamin D matters for your bones

Vitamin D is just as important for bone health as calcium. Without it, calcium and phosphorus simply aren’t absorbed the way they should be. When there are enough of these minerals in your diet, cholecalciferol promotes their absorption from the digestive tract. When they are scarce, it reduces their loss through the kidneys and releases reserves from the bones.

The numbers speak for themselves: when vitamin D is lacking, only about 10–15% of calcium is absorbed in the small intestine. With adequate levels, it’s about 30%. During pregnancy, breastfeeding and periods of rapid growth, this rises to as much as 80 percent.

Most body tissues have vitamin D receptors. Vitamin D is needed for about 3000 genes to function — we have 25,000 genes in total, so more than 10% of their normal functioning depends on vitamin D. Besides the bones, it plays a part in the work of the immune system, heart muscle function, nervous tissue function and blood clotting.

Why your skin doesn’t make vitamin D in Estonia

Geography is harsh: Estonia lies between the 57th and 60th parallels. The sun travels low, and UVB radiation is effective for vitamin D synthesis only between 10:00–14:00 — and even then, cloud cover limits it.

A 2009 University of Tartu study showed that even at the end of summer, 73% of Estonians are vitamin D deficient. If you live in Estonia more than 9 months a year, your blood level is probably below 20 nanograms per ml — three times less than the body needs every day.

The summer picture is better, but not good: about 29% of the population is vitamin D deficient even in summer, and only 12 percent have an optimal level. Worldwide, the number of people with insufficient vitamin D levels is estimated at about one billion.

What else affects synthesis:

• Ozone layer and angle of the sun. The ozone layer blocks all radiation with a wavelength below 290 nm and part of the UVB (290–315 nm). Between the 35th southern and northern parallels, synthesis is possible year-round. In Estonia, the “vitamin D winter” lasts from October to mid-April, and in a bad year from late September to mid-May.
• Time of day. In the morning and evening the sun is low, and less UVB reaches the ground. The peak is at midday.
• Cloud cover and smog. Both reduce UV radiation.
• Window glass. It blocks all UVB radiation — tanning indoors won’t give you vitamin D.
• Sunscreen. Correctly applied sunscreen with SPF 8 almost completely blocks vitamin D photosynthesis in the skin. Sunscreen stops more of the beneficial UVB than the harmful UVA.
• Skin color. Melanin competes with desmosterol for UVB photons. A dark-skinned person needs more time in the sun to produce the same amount of the vitamin.
• Age. By age 70, the amount of desmosterol in the skin has fallen by about 75%. The older the person, the longer they need to spend in the sun.
• Obesity. Vitamin D stores are kept in fat tissue, where they are not bioavailable — chronic deficiency often follows.

For a fair-skinned person, 10–15 minutes in the sun between the hours of 10 and 14, with face and arms uncovered, is enough to meet the need. For a dark-skinned person, it would take about 20 minutes under the same conditions, and for older adults 30 minutes.

What natural vitamin D does in the body

Vitamin D is actually a powerful steroid hormone. Over 3000 genes contain elements that respond to vitamin D — it is the only such substance in the body. The concrete benefits for everyday life:

• Promotes calcium absorption from the digestive tract and the use of phosphorus — the building materials of bones and teeth.
• Needed for normal growth in children. When it is lacking, children develop rickets, adults develop osteomalacia and, in the longer term, osteoporosis.
• Supports normal heart function, blood clotting and stable blood pressure.
• Helps maintain the balance of the nervous system and affects serotonin levels and, through them, mood.
• Supports the immune system — vitamin D deficiency has been linked to up to 17 forms of cancer (especially breast, colon, prostate and lung cancer), as well as type I diabetes, asthma, high blood pressure, multiple sclerosis, fibromyalgia, rheumatoid arthritis and depression.

Vitamin D3 circulates in the blood and, working together with intestinal cells, stimulates calcium absorption. When blood levels are below 20 ng/ml, only 10–30% of the calcium from food or supplements is absorbed — so half of your calcium pill literally goes down the toilet.

Signs of deficiency: what to look out for

Honestly, vitamin D deficiency is hard to spot on your own, because the symptoms are vague. But there are a few clues:

• Muscle weakness. If you can no longer manage as many reps in training as you used to, a vitamin D deficiency may be behind it.
• Low mood and extreme moodiness. Vitamin D cholecalciferol affects serotonin.
• Greater sensitivity to pain and chronic pain.
• Microtrauma. More fragile bones → higher risk of injury.
• High blood pressure. Natural vitamin D is involved in regulating it.
• Daytime sleepiness. A study published in The Journal of Clinical Sleep Medicine linked low levels to greater daytime sleepiness.
• Poorer aerobic endurance. Some studies in athletes have pointed this out.
• Heaviness in the legs, frequent infections.

Food as a source of natural vitamin D

You can’t get enough vitamin D from ordinary food. Over-cultivated fields, early harvesting, nutritional value lost during processing — all of this means that the amount coming off your plate doesn’t match what your body needs.

The best sources are fatty fish, eggs, butter and liver. In Finland, Sweden, Norway and the USA, dairy products are fortified with vitamin D. None of the Baltic countries currently fortify foods.

Specific amounts per serving (IU):

• Baked salmon, 100 g — 360 IU
• Sardines in oil, 100 g — 250 IU
• Tuna in oil, 100 g — 200 IU
• 1 egg (the natural vitamin D is in the yolk) — 20 IU
• Cooked animal liver, 100 g — 15 IU
• Swiss cheese, 30 g — 12 IU

Put these numbers next to the daily requirement — the gap is astonishing.

How much natural vitamin D you need per day

The recommendations given by Dr. Soram Khaisa, author of “The Vitamin D Revolution”, and other sources:

• Infants and children up to 2 years old — 2000 IU (50 micrograms) per day
• Children aged 3–12 — 5000 IU
• Teenagers — 8000 IU
• Adults — at least 10,000 IU (250 μg)

Out in the sun, a light-skinned person without sunscreen and without clothing covering the skin naturally produces 10,000–15,000 IU within 15 minutes. You don’t need to worry about overdoing it in the sun — the excess is blocked by melanin. People with darker skin, however, synthesize less vitamin D in this system, which puts them in a risk group.

One of the world’s best-known vitamin D researchers, Professor Reinhold Veith, has stated that at our latitudes the daily dose could be 5000–10,000 IU (125–250 mcg). In Estonia, the officially permitted recommendation is 1200 IU per day — lower than many researchers consider necessary.

It’s also worth knowing that general studies show vitamin D deficiency in 30–40% of the population even during the sunny season. So you can’t rely on summer alone — Khaisa recommends taking a supplement from autumn through summer.

Who needs to pay attention

• Children aged 1–11 (test whether levels are normal)
• Pregnant and breastfeeding mothers
• Smokers
• Men and women over 50
• People with osteoporosis
• People with body weight problems
• People with problems with digestion and nutrient absorption
• People who avoid sunlight and spend most of their time indoors
• Those whose diet doesn’t include enough fish, eggs, ham, salami or mushrooms
• People with type one diabetes
• People with weak immunity
• People with rheumatoid arthritis

When you get enough D3, your attention is sharper, your memory is better, your mood is more stable and you are more physically active. Cholecalciferol also supports brain development in children, helps with psoriasis, slows the progression of asthma and chronic bronchitis, prevents inflammation and calcification of the blood vessels, improves glucose tolerance and supports nerve cells. The risk of death from cancer has been linked to a reduction of up to 77%, and the risk of prostate cancer is halved.

Overdosing: how big is the risk?

The risk of overdosing is small. You would have to take 50,000 IU every day for several months in a row. Side effects may appear only after 3–4 months: nausea, high blood pressure, itching, abdominal pain, muscle weakness and intense thirst. If this happens, see a doctor — treatment is simple and takes 1–3 days.

Actual cases are extremely rare. In the United States, one patient was reported who took 150,000 IU every day for two years. When they arrived at the hospital, their blood vitamin D level was over 500 ng/ml (the level recommended by doctors in Estonia is 75 ng/ml), but after a couple of days of supportive treatment, during which their calcium levels were lowered, they were discharged.

FAQ about natural vitamin D

Can I get enough vitamin D for the whole winter by sunbathing in summer?

Usually not. Even at the end of summer, 73% of Estonians are deficient. Sunscreen, window glass, office work and Estonia’s latitude all reduce synthesis. From autumn to summer, it is worth making sure you get enough on purpose.

Is fish and eggs alone enough?

Look at the numbers: 100 g of salmon provides 360 IU, one egg 20 IU. An adult’s daily requirement is at least 10,000 IU. Food helps, but it is not enough on its own.

Do I need to take a supplement in summer too?

Studies show deficiency in 30–40% of the population even during the sunny season. If you spend your days indoors or use sunscreen, you will still need a supplement in summer.

Author: EcoLab

Source: Health Board – dietary supplements.

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