Vitamin D deficiency

A vitamin D deficiency can lead to the following symptoms:

• Pain in the bones or joints
• Muscle ache
• Weak muscles
• Tiredness

If you have weak muscles, walking or climbing stairs can be difficult. Physical activity might make the pain worse.

The main reason people develop a vitamin D deficiency is because their skin doesn’t get enough exposure to sunlight, which means their body can’t make enough vitamin D. In rarer cases, the body can’t make enough vitamin D due to a chronic illness in the bowel, kidneys or liver – or because of medication they’re taking.

You usually get only a small proportion (about 10 to 20%) of the vitamin D you need in the food and drinks you consume. That’s because only a few foods contain large enough amounts of vitamin D. These include sea fish, innards, some edible mushrooms and egg yolk.

The following factors increase the risk of a vitamin D deficiency that causes symptoms:

• Spending a lot of time indoors: Our bodies need UVB rays from the sun to produce vitamin D, but these rays can’t get through window panes.
• Living in Northern European countries (like Germany). People who live here can’t produce vitamin D in the fall or winter because the sun is too low in the sky.
• Frequently wearing clothes that (almost) completely cover the body, head and hands.
• Constantly protecting yourself from the sun by staying in the shade or using sunscreen.
• Dark skin color
• Older age: Our skin produces less vitamin D as we grow older.
• Chronic kidney or liver diseases, inflammatory bowel diseases like Crohn’s or celiac disease, cystic fibrosis
• Medication for epilepsy or cancer
• Being overweight

These risk factors particularly apply to

• people who are elderly or need nursing care and spend hardly any time outdoors, and
• babies – because their sensitive skin can’t handle much sun.

In Germany and similar countries, it’s rare for a lack of vitamin D to cause bone problems. There aren’t any exact figures here, though.

But there has been research on the number of people in Germany with low vitamin D levels: Roughly 13% of children and teenagers – and around 15% of adults – were found to be affected. In this research, levels under 12 nanograms per milliliter (< 12ng/ml) were considered to be low. People with low vitamin D levels are more likely to develop a vitamin D deficiency with symptoms.

A lack of vitamin D affects our bone health. Our bodies can’t absorb enough calcium from our food, causing the calcium in our blood to decrease (hypocalcemia). The parathyroid glands react by increasing their hormone production. The parathyroid hormone releases calcium from the bones to make up for the low level of calcium in the blood. Over time, the bones become less stable and “softer.” This results in osteomalacia and (in children who are still growing) rickets.

• In osteomalacia, bones become softer and bend because they lose minerals. The symptoms are dull, persistent pain in the bones and, often, decreasing strength or muscle ache. This also increases the risk of falling.
• In bones that are still growing, rickets can develop in the growth plates at the ends of the bones. Children who have rickets grow too slowly because their bones can’t absorb enough minerals. Their bones become deformed, causing things like very bowed legs, knock knees, or a head that’s square-shaped at the back. Children with rickets tend to lack energy and have weak muscles, and sometimes poor teeth and frequent infections too.

Older people who don’t get enough vitamin D may have an increased risk of bone fractures, especially if they also have osteoporosis.

People are diagnosed with a vitamin D deficiency if the level of vitamin D in their blood is too low and they have a bone disease that’s causing symptoms. The blood test measures how much 25-hydroxy vitamin D (25(OH)D) there is in their blood.

If a doctor thinks someone might have a vitamin D deficiency, they’ll ask them about past illnesses and current symptoms. They’ll also do a blood test to check the level of 25-hydroxy vitamin D (25(OH)D). Ideally, the test will be repeated several times at different times of the year. According to the Robert Koch Institute, you have low vitamin D levels if you have less than 12 nanograms per milliliter (<12 ng/ml) in your blood. Having said that, vitamin D levels vary depending on the time of year: They drop naturally in the winter and increase in the summer when our skin makes more of the vitamin again. They also differ depending on how the lab measures them. Lab results in nanomoles (nmol) can be converted into nanograms (ng) by dividing by 2.5. So, for example, 5 nmol/l would be 2 ng/ml. There are also free conversion calculators on the internet.

Blood tests can provide additional information about the condition of your bones by measuring other levels – especially the amount of parathyroid hormone, calcium, phosphorus and an enzyme in the bones known as alkaline phosphatase. Imaging techniques like x-rays (of the hand, for instance) can confirm if someone has a bone disease like rickets or osteomalacia.

Healthy people who spend enough time outdoors don’t need to worry about developing a vitamin D deficiency. Your skin can make enough vitamin D with the help of the sun’s UVB rays. It is usually enough to expose your face, hands and arms to sunlight for a few minutes roughly two to three times per week from spring to fall, without sunscreen. But people who have dark skin need much more UVB exposure to make enough vitamin D. It is important to get out of the sun before your skin turns red or burns.

We can get a small portion of the vitamin D we need from our food: especially fatty sea fish, egg yolk, innards like liver, and edible mushrooms like button mushrooms, porcini mushrooms and chanterelles. Our bodies can only absorb vitamin D from foods that contain fat because it needs the fat to be able to dissolve.

There’s generally no benefit to taking vitamin D (in the form of a supplement, for example) without a specific reason. But it is beneficial for babies and for elderly people who spend most of their time indoors – like people who live in retirement homes or nursing homes. Vitamin D supplements can also be a good idea for people with certain chronic illnesses.

People who have a vitamin D deficiency with symptoms are given vitamin D supplements, typically together with calcium. The supplements usually come in the form of tablets or capsules. Injections are less common. Vitamin D is also available as drops or sprays. The standard approach is to take the supplement once a day or (in a higher dose) once a week. It is best to talk to your doctor about how much to take, and how.

Taking too much vitamin D makes your blood calcium levels rise. This can have side effects like nausea and vomiting, stomach cramps and loss of appetite. Extreme overdoses can lead to kidney stones and kidney damage, heart rhythm disorders (arrhythmias) and unconsciousness. So it’s important to stick to the dose recommended by the doctor.

After around 4 to 6 weeks, the doctor will check the levels of parathyroid hormone and alkaline phosphatase in your blood to see whether your vitamin D levels have improved. If they have, your symptoms will usually have improved too. You then continue to take vitamin D and calcium until your reserves are full again, which typically takes about three months.

When people are ill or need medical advice, they usually go to see their family doctor or pediatrician first. Information about health care in Germany can help you to navigate the German healthcare system and find a suitable doctor. You can use this list of questions to prepare for your appointment.