Mediterranean Diet 101

Vitamin D Deficiency

Vitamin D deficiency (hypovitaminosis D) is typically diagnosed by measuring the blood concentration of the 25-hydroxyvitamin D (Calcifediol, Calcidiol), which is a precursor to the active form of the 1,25-dihydroxy-vitamin D (Calcitriol) compound.

The blood concentration of 25-hydroxy-vitamin D reflects vitamin D produced in the skin as well as vitamin D acquired from the foods and has a relatively long circulating half-life of 15 days. It does not, however, reveal the amount of vitamin D stored in other body tissues and organs (muscles, liver, bones etc).

The blood concentration of 1,25-dihydroxy-vitamin D is rarely used to determine vitamin D levels and status because 1,25-dihydroxy-vitamin D has a very short half-life of 15 hours since it is regulated by parathyroid hormone, calcium and phosphate, so that it's blood levels don't decrease significantly until vitamin D deficiency is already well advanced.

eelThere are various proposed categories for calcifediol blood levels, but very often these four levels are used:

- Insufficient 50–100 nmol/L (20–40 ng/mL)

- Mild 25–50 nmol/L (10–20 ng/mL)

- Moderate 12.5–25.0 nmol/L (5–10 ng/mL)

- Severe < 12.5 nmol/L (< 5 ng/mL)

Note: 1.0 nmol/L = 0.4 ng/mL for calcifediol.

Low Vitamin D Levels

As one can see, anything less than 50 nmol/L (40 ng/mL) of 25-hydroxyvitamin D can be considered as low levels of vitamin D in blood. In fact, some scientist consider 80 nmol/l (32 ng/mL) as border value for elderly people that causes osteoporosis to occur. Anything less than 25 nmol/L (10 ng/mL) can cause rickets and osteomalacia. On the other hand, a concentration above 15 ng/ml (37.5 nmol/L) is considered adequate for those in good health, by some authors.

Normal Vitamin D Levels

Some authors have suggested that a 25-hydroxyvitamin D level of 75–80 nmol/L (30–32 ng/mL) may be sufficient for humans.

For example, in a study done in Hawaii, a majority of healthy young people with comparatively extreme sun exposure did not reach this level of 25-hydroxyvitamin D in blood (Binkley, N.; Novotny, R.; Krueger, D.; Kawahara, T.; Daida, Y.; Lensmeyer, G.; Hollis, B.; Drezner, M. (2007). "Low vitamin D status despite abundant sun exposure". The Journal of Clinical Endocrinology and Metabolism 92 (6): 2130–2135.).

Note that with plenty of sun exposure human body can generate 5.000 - 10.000 IU of vitamin D, day after day (in theory - remember that body has plenty of self regulation mechanisms, vitamin D blood levels included).

High Vitamin D Levels

It is believed that blood levels of 25-hydroxyvitamin D greater than 125 nmol/L (50 ng/mL) can have adverse effects on human body and health. On the other hand, more and more researchers claim that such levels of vitamin D can have only beneficial effects and toxic levels of vitamin D are much much higher.

Anywaay, such high concentrations are hard to achieve without hugh intake of vitamin D trough supplementation, foods and high sun exposure.

Vitamin D Deficiency Treatment Guidelines

While increasing vitamin D 'naturally' intake through more sun exposure (watch out - sun burns and other skin problems are increasingly common these days) and through consuming more vitamin D rich meals is great way for treating light vitamin D deficiency, serious vitamin D deficiencies should be treated with vitamin D supplements.

Today, there are plenty of vitamin D supplements with 'lower' dosages of vitamin D (400 - 1000 IU) that are great for preventing any vitamin D deficiency related problems.

Also, there supplements with much higher vitamin D doses (>1000 IU per pill) - any supplement should be taken only after consultations with your doctor or physician.

Vitamin D Benefits

pan fried marinated losos fillets 1Vitamin D benefits are quite numerous. Among others, vitamin D is very important in regulating many calcium and phosphorous related metabolism processes which are very important for health of bones, teeth, joints and many other tissues and organs.

Other vitamin D benefits include:

- vitamin D helps the digestive system to absorb nutrients (including calcium and phosphorus) ensuring overall well being and strong immune system.

- vitamin D regulates blood pressure, prevents osteomalacia and rickets, helps fight depression, reduces stress and tension, reduces respiratory infections (strong immune system!), aids in insulin secretion, improves overall skin health and makes skin soft, strong, and smooth, relieves body aches and pains by reducing muscle spasms, improves health of joints, hair and nails, helps in differentiation of the cells, improves cardiovascular strength by protecting arteries

- vitamin D is recommended in the treatment of several diseases like preaclamsia by improving kidney function, cancer by controlling abnormal multiplication of cancer cells, osteomalacia by improving bone and muscle strength, hypocalcaemia by preventing abnormal deposition of calcium, diabetes mellitus by controlling insulin production, hypophosphatemia by controlling the phosphates in the body.

Low blood levels of vitamin D over short or long time, have been associated with many symptoms.

To fully enjoy benefits of vitamin D, it is best to avoid vitamin D deficiency by regular skin sun exposure and consuming vitamin D rich foods.

If vitamin D deficiency symptoms start to develop, consult your doctor and/or physician and start to treat your vitamin D deficiency.

Vitamin D Dosage

vitamin d dosageVitamin D recommended dosage is not uniquely established. This value differ from gender to gender and from age to age. Also, some countries have different values for vitamin D RDA.

It is important to know that on average 15-20 minutes of sunlight, 3 times per week provide enough vitamin D for human body and if someone sunbathes for hours (not recommended due to skin cancer risk), daily production of vitamin D is between 8000 and 16000 IU (between eight thousands and sixteen thousands IU per day). Read more about this topic in Vitamin D and the Sun Exposure article.

Vitamin D Recommended Dosage - Vitamin D RDA

Generally, RDA for vitamin D are given in the following table:

Age Children Men Women Pregnancy Lactation
0 - 1 year 400 IU        
1 - 13 years 600 IU        
14 - 18 years   600 IU 600 IU    
19 - 50 years   600 IU 600 IU 600 IU 600 IU
51 - 70 years   800 IU 800 IU    
71+ years   800 IU 800 IU    

Note: 1 mcg vitamin D = 40 IU of vitamin D

As said before, these values differ - for example. vitamin D recommended dosage for women is anywhere from 200 to 800 IU and for men between 200 IU and 600 IU.

Age group

Tolerable Upper Intake

Infants 0–6 months 1000 IU
Infants 7–12 months 1500 IU
Children 1–3 years 2500 IU
Children 4–8 years 3000 IU
Children and Adults 9–70 years 4000 IU
Adults > 70 years 4000 IU
Pregnancy and Lactation 4000 IU

Vitamin D Tolerable Upper Intake

For vitamin D, 'tolerable upper intake' is defined as 'the highest average daily intake of a nutrient that is likely to pose no risk of adverse health effects for nearly all persons in the general population'. Tolerable upper intake levels of vitamin D are believed to be safe, but there are no complete and accurate information on long term effects of such high vitamin D dosages - anyway, they are not recommended.

Such high doses are achievable by taking supplements with high(er) vitamin D dosages and by consuming plenty of foods rich in vitamin D. Spending plenty of time outside (sunny days), will probably produce even more vitamin D, but natural production and sources (sun, food) are IMHO much better for prevention of vitamin D deficiency than pills. After all, natural production of vitamin D due to sun exposure has self-regulating mechanisms that prevent vitamin D 'overdose' (this is very simplified ...).Supplements with lower dosages (around 400 IU per pill) are great for preventing vitamin D deficiency in winter days - as usual with all supplements, before taking any of them, consult your doctor or physician.

 Vitamin D Dosage for Deficiency

Vitamin d dosage for deficiency varies greatly, again, depending on numerous things, mostly age and levels of vitamin D in blood serum. Defining 'exact' levels of vitamin D dosage must be done by your doctor after test. If you suspect vitamin D deficiency, best thing is to contact your doctor and take preventive measures like more sun exposure, eating food rich in vitamin D and taking some vitamin D supplement with low to modest vitamin D amount. Don't try to increase your daily vitamin D intake above 1000 - 2000 IU, without consulting your doctor, at least not in the long run. Anyway, what every you do, you do it on your own responsibility.

In the events of very low vitamin D levels in blood serum, vitamin D dosages can be as high as 50,000 IUs per day. It these cases, doctors usually also check if there are other problems with vitamin D, like problems with absorption in the intestinal system or problems with liver or kidneys.

Vitamin D Side Effects

now-foods-vitamin-d3Amounts of vitamin D in foods and self-regulation of vitamin D production in the body prevents any adverse side effect of naturally produced vitamin D.

Since vitamin D deficiency is often treated with vitamin D supplements in various doses, it is very important to pay close attention to the amounts of vitamin D in those supplements - vitamin D is fat soluble vitamin and any excess of this vitamin can not be removed from the body.

Side effects of taking too much vitamin D are:

- high levels of calcium in the blood that leads to: confusion, disorientation, calcium deposits in soft tissues such as the heart and lungs, kidney stones and other kidney damages,

- nausea, vomiting, constipation, poor appetite,

- muslce weakness, weight loss, dehydration, irritability


Hypervitaminosis D

 Hypervitaminosis D occurs after taking very high doses of vitamin D for longer period of time - between 600,000 IU and 1,700,000 IU per day of vitamin D over a period of several days to months. Such vitamin D dose can occur almost exclusively using prescribed vitamin D supplements and when that happens, stop taking those supplements and contact your doctor or physician.

Vitamin D overdose in adults has been observed at doses of 50,000 - 75,000 IU (or more) per day, over period of weeks to months. Adults with certain medical conditions such as hyperparathyroidism can develop vitamin D toxicity side effects in much shorter period of time.

It is believed that daily dose of 10,000 IU of vitamin D over periods of time like weeks or months is safe - tolerable upper intake for adults is around 4000 IU per day. Again, before taking any supplement with such high amount of vitamin D, consult your doctor or physician.

High doses of vitamin D from foods are possible, but only if one consumes really large amounts of foods that contain vitamin D in large doses - for example, a kilogram per day of fatty fish can increase daily intake of vitamin D up to a 10,000 IU per day.

Testing Hypervitaminosis D

 There are various tests that can be done in order to verify if hypervitaminosis D has occurred:

- test excess calcium in the blood

- test excess calcium in the urine

- test serum phosphorus

- check blood pressure for high blood pressure

- test 1,25-dihydroxy vitamin D levels

- test 25-hydroxy vitamin D levels


These tests can confirm if hypervitaminosis D has occurred or there is some other medical condition that has similar side effects. Also, these tests can determine vitamin D deficiency and other health related problems.

Vitamin D and Calcium

canned-salmonVitamin D promotes calcium absorption during digestion and maintains adequate calcium and phosphate serum levels and thus helps normal mineralization of bones. Vitamin D and calcium are also needed for bone growth and bone remodeling - without sufficient vitamin D, bones can become thin, brittle and/or misshapen.

Lack of calcium due to insufficient amount of calcium in consumed food or due to inadequate absorption during digestion can lead to various health problems.

Low calcium blood levels in children can lead to rickets, weak and brittle bones, weak immune system etc.

Low calcium blood levels in men can lead to osteoporosis/osteomalacia and to other health problems like hair loss, depression, diabetes, some forms of cancer etc. It must be noted that there are numerous ongoing research activities regarding health issues and low blood levels of vitamin D and calcium.

Low calcium blood levels in women can lead to similar health problems that men have. Also, women are more susceptible to low calcium levels during pregnancy and lactation period and during and after menopause.

Calcium and Vitamin D Rich Foods

Promoting healthy calcium blood levels is relatively easy - just combine calcium rich foods with vitamin D rich foods and/or increase skin sun exposure.

For example, if you combine low fat or cottage cheese with a canned fatty fish (canned mackerel, canned sardines, canned tuna etc) you will have a meal that is great source of calcium (cheese) and vitamin D (canned fish).

Of course, you don't have to use canned fish - fresh fish fried with no or almost no oil on non-stick frying pan tastes much better, at least for me :o)

Also, one of the best meals for supporting proper calcium and vitamin D levels is fortified milk - read labels about amounts of calcium and vitamin D, they MUST be written on the package. If they are not written, don't buy it! So if you have a kid that likes milk (with or without cocoa, cereals etc), glass or two of milk per day will provide plenty of calcium for growing youngster and readily available vitamin D (from milk or other sources) will help in both digestion and normal mineralization of bones...

Vitamin D Absorption

Vitamin D, as a fat-soluble vitamin, requires some dietary fat in the digestive system for better absorption. Pan grilled fish in combination with some olive oil, few drops of lemon juice, some garlic and parsley, represents a great meal that should be consumed on a daily basis as a great source of natural vitamin D.

However, individuals who have a reduced ability to absorb dietary fat might require vitamin D supplementation and/or should increase skin sun exposure. Problems with fat absorption is often associated with various health problems like:

- some forms of liver disease,
- cystic fibrosis,
- Crohn's disease, etc.

To verify if you have vitamin D absorption problems, contact your doctor and check your vitamin D blood levels. After that, if your vitamin D blood levels are low, without changing your living habits (sun exposure) for 'some' period of time, you are going to take vitamin D supplement.

For how long will you be taking vitamin D supplements and what kind of supplements depends on many things - things that your doctor has to determine. This period can be as short as few days and as long as few months.

By increasing dietary vitamin D and checking vitamin D levels, it is easy to conclude if you have problems with vitamin D absorption.

Vitamin D Absorption and Dieting Pills

Dieting pills act in several ways:

- energy pills provide additional energy during periods of low calorie nutrition. They contain caffeine and similar compounds that don't affect vitamin D absorption or at least not in any significant level.

- appetite killers are dieting pills that give feeling of fullness and simply 'kill' appetite. They don't affect vitamin D absorption or at least not in any significant level.

- carbs and fat blockers pills use various methods to block absorption of carbohydrates and fats in digestive system. These kind of pills block absorption all fat (good or bad) and of all carbs (good and bad). They also block absorption of other macro and micro nutrients, including vitamins soluble in fats (A, D, E and K) and they can significantly lower fat soluble vitamins absorption.

Dieting pills are type of supplements that should be taken only with approval of your doctor or physician - anyway, if you consider taking fat blocker, be careful regarding your fat soluble vitamin intake.

Vitamin D Absorption and Gastric Bypass

Gastric bypass and similar surgeries are more and more often these days - they enable obese people to lose weight permanently. Losing weight is great life saving endeavour, but such surgeries are not without side effects.

In such surgeries, food is often rerouted away from areas where it is absorbed - thus, vitamin D deficiency is common following gastric bypass and it can only progresses over time. Following such surgeries, absorption of other vitamins and minerals like iron, calcium, magnesium, vitamin E etc is also compromised.

Long story short, if you have issues with your weight, just diet it down ...

Vitamin D Metabolism

white fish 1There are numerous publications regarding metabolism of vitamin D in humans, but also in other species. These publications often deal with vitamin D metabolism down to the atoms level - not something absolutely needed for somebody wanting to prevent and avoid vitamin D deficiency.

For most people, it is important to know few facts about:

- vitamin D structure - it is based on cholesterol derivative from which body can (when exposed to UVB radiation) produce vitamin D. Daily amounts of needed cholesterol are usually more than enough for normal vitamin D production due to UVB radiation. Also, when needed, body produces it's own cholesterol, so lack or low levels of cholesterol (both HDL (good cholesterol) and LDL (bad cholesterol)) in human nutrition can't cause vitamin D deficiency.

- body can produce vitamin D with the help of UVB rays, so moderate sun exposure is good for health and well being. Actually, active form of vitamin D is NOT produced in the skin.

- vitamin D blood levels are checked relatively easily, so if you suspect that you could have vitamin D deficiency, don't wait for symptoms to develop.

- beside other roles, vitamin D takes active part in metabolism of many minerals - Calcium, Phosphorous, Magnesium etc, so lack of vitamin D can have devastating consequences on a human health.

- vitamin D is fat soluble vitamin - excess amounts of vitamin D cannot be removed from the body trough the kidneys, so be very careful when taking vitamin D supplements on your own. On the other hand, amount of recommended vitamin D intake has been increased lately.

- there are various foods rich in vitamin D. These foods, in combination with regular sun exposure are usually more than enough to prevent vitamin D deficiency.

Long story short - if you want to inform your self about vitamin D, vitamin D deficiency and how to prevent it, feel free to browse through the articles. On the other hand, if you are interested in detailed explanations about vitamin D and vitamin D deficiency down to the smallest level (you are medical student, doctor or similar), feel free to check the site where everything is, these days, written - Google! :o)

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