Vitamin D, which plays an important role in many systems of the human body, is sometimes called “sunny”. This substance (scientists classify it not only as a vitamin, but also as a steroid hormone [1]) begins to be produced in our body under the influence of sunlight falling on the skin.
That’s why we’re often advised to take extra vitamin supplements in the fall and winter when there are fewer sunny days. But is it possible to do without supplements, just by adjusting your diet?
Let’s see which foods are especially rich in vitamin D.
This vitamin is extremely important for our health, it performs many different functions, including:
- helps the body absorb calcium and phosphorus, which is especially important for maintaining healthy bones;
- strengthens the immune system;
- helps transmit signals in the nervous system;
- has an anti-inflammatory effect;
- prevents muscle spasms.
How much vitamin D does the body need?
The dosage of this vitamin (as well as some others) is usually indicated in international units (IU). One international unit of vitamin D is equal to 0.025 mcg. The recommended intake for both children and adults is about 600 international units per day. Pregnant and lactating women usually do not need to change the dosage.
For people over 70 years of age, the recommended dosage is 800 international units per day.
How does vitamin D deficiency manifest itself?
Vitamin D is produced in the body under the influence of sunlight, we can also get it from food. Products rich in vitamin D are quite rare, so deficiency of this vitamin is quite common (especially in winter and autumn, when there are significantly fewer sunny days). Here are some possible symptoms of hypovitaminosis D:
- fatigue,
- muscle spasms and cramps,
- muscle weakness,
- bad dream,
- depressed mood, depressive symptoms,
- anxiety,
- brittleness and fragility of nails,
- hair loss,
- constipation, digestive problems.
Many of these symptoms can be caused by a variety of reasons, and a blood test is usually required to accurately determine vitamin D deficiency. Chronic vitamin D deficiency also increases the risk of fractures, osteoporosis, periodontal disease, and respiratory disease.
How to Identify Vitamin D Deficiency
Vitamin D deficiency can be determined with a blood test. A level below 20 ng/ml is considered a deficiency, and 20 to 30 ng/ml is considered insufficient. Based on the test results, the doctor can prescribe vitamin D in a certain dosage.
When taking vitamin D supplements, it is worth remembering that it is a fat-soluble vitamin – they (unlike water-soluble vitamins) can accumulate in the body, which can lead to hypervitaminosis. Hypervitaminosis D occurs almost exclusively with regular intake of high doses of this vitamin in the form of supplements.
The maximum safe dose of vitamin D is generally considered to be 4000 IU per day, but according to some data, long-term intake of more than 3200 IU per day can also cause side effects [2].
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What foods are rich in vitamin D
This vitamin is mainly found in fatty fish, meat and dairy products. In animal products, it is present in the form of vitamin D3 (cholecalciferol), and in plant foods – in the form of vitamin D2 (ergocalciferol).
Some foods (like milk) are sometimes specifically fortified with vitamin D during production. Let’s see which foods are especially rich in this vitamin.
1. Salmon and other fatty fish
Salmon flesh contains a lot of omega-3 fatty acids and vitamin D (up to 600 IU in a 100-gram serving). The method of catching the fish is important: wild salmon contains much more of this useful vitamin than farmed (artificially grown) salmon [3].
Other fatty fish are also quite rich in this substance: for example, a 100-gram serving of halibut flesh contains about 190 IU of vitamin D, and mackerel contains up to 650 IU per 100 grams.
2. Egg yolks
Some people eat only egg whites, avoiding the yolks because of their relatively high cholesterol content. In fact, in the absence of obvious contraindications, moderate consumption of yolks is quite acceptable, especially since they, unlike whites, contain vitamin D (about 35 IU in one yolk).
Interestingly, eggs from hens kept outdoors contain significantly more of this vitamin [4].
And if the chicken was fed special food enriched with vitamin D, the level of this substance in the egg yolks increases many times over (up to tens of thousands of IU per 100 g).
3. Canned fish
Canned fish is cheaper and easier to prepare than fresh fish. At the same time, it retains most of the nutrients. For example, a 100-gram serving of canned tuna contains about 270 IU of vitamin D. However, it is not recommended to eat tuna too often due to the rather high mercury content in this type of fish.
4. Mushrooms grown in the open air
Mushrooms produce vitamin D when exposed to ultraviolet radiation. Therefore, indoor-grown products (which includes most mushrooms sold in stores) contain virtually no vitamin D. However, if mushrooms are grown outdoors (or exposed to indoor ultraviolet radiation), the vitamin D content can reach 1,000 IU per serving [5].
5. Cod liver oil
Fish oil is often taken as a dietary supplement because it is very rich in beneficial omega-3 polyunsaturated fatty acids [6]. But it also contains a lot of vitamin D – up to 1,300 IU in one teaspoon.
6. Products fortified with vitamin D
This vitamin (like some others) is sometimes added to food during the manufacturing process. Milk, fruit juices, oatmeal breakfasts, and yogurts can be fortified with vitamin D. If a product contains added vitamin D, it will be indicated on the packaging.