There are some groups of people, who have higher-than-average needs for vitamin D. They are elderly people, people with darker complexion, people who live away from the equator and those who deal with certain ailments.
There are many reasons why elderly people should take more vitamin D. First of all - skin becomes thinner with age. It inhibits the production of vitamin D3, even when it is exposed to the activity of sunlight. Elderly people often spend more time at home. It means that they are rarely exposed to the activity of sunrays, which, as commonly known, is the best way to naturally increase the level of vitamin D.
Additionally, your bones along with age become more fragile. Maintaining proper level of vitamin D in blood may help to preserve optimal bone bass and may protect from fractures (25, 26). Elderly people should aim at maintaining the level of 30 ng / ml of vitamin D, as research suggests that such a level helps bones to preserve proper density. It may be achieved by the application of 1000-2000 IU (25-50 mcg) of vitamin D per day.
People with dark complexion
Studies prove that people with darker skin are more prone to the deficiencies of vitamin D. This is because they have more melanin in skin - the pigment which provides skin with color. Melanin helps to protect skin from ultraviolet radiation (UV). However, it also decreases the ability of the organism to produce vitamin D3, which may cause increased susceptibility to the deficiency of this ingredient.
People with dark skin may benefit more from supplementing 1000-2000 IU (25-50 mcg) of vitamin D per day, especially in winter months.
Residents of countries far from the equator
The countries located near the equator have a lot of sunlight throughout the year. And the other way round, the countries located away from the equator have much less light during the year.
It may cause low levels of vitamin D in blood, especially in the winter months, when there is even less sunlight than usual. For example, a study carried out by Norwegians proved that the residents of this country produce little vitamin D3 in the winter months from October to March (33). Supplementation in this case is almost essential. If you leave away from the equator, you need to obtain more vitamin D from your diet and supplements. Many experts say that people in these countries should take at least 1000 IU (25 mcg) per day.
People with diseases which decrease the absorption of fat
Since vitamin D is soluble in fats, its absorption is dependent on our ability to assimilate fat.
Therefore, people with the ailments decreasing the absorption of fat may have tendency to develop vitamin D deficiencies. They encompass irritable bowel syndrome (IBS), Crohn disease, liver diseases and also people after bariatric surgeries. People with the above ailments are often recommended to take supplements with vitamin D at the amounts prescribed by their physicians.
Can we overdose vitamin D?
While it is possible to take an excessively high dose of vitamin D, its toxicity is extremely rare. In reality, we would need to take very high doses - 50000 IU (1250 mcg) and more for a very long time.
It is also worth noticing that overdosing vitamin D by exposure to sun is impossible. Although the dose 4000 IU (250 mcg) is acknowledged as the maximal dose of vitamin D that we may safely apply, a few studies proved that the application of the doses up to 10000 IU (250 μg) per day does not cause considerable side-effects. However, the application of more than 4000 IU may not bring additional health benefits, therefore increasing the dose is nonsensical. It is best to take from 1000 IU (25 mcg) to 4000 IU (100 mcg) per day.
Vitamin D is very important for health. It helps to maintain healthy bones, supports the immune system and may decrease the risk of many harmful diseases. However, in spite of its vital role, many people suffer from its deficiency. Moreover, elderly people, people with darker skin, people who live far from the equator and those who are not able to properly absorb fats demonstrate higher need for vitamin D in a diet.
Currently, the recommended dose of vitamin D is 400-800 IU (10-20 mcg) per day. However, people who need more vitamin D may safely take 1000-4000 IU (25-100 mcg) per day. Exceeding this amount is not recommended, as it is not able to bring any additional health benefits.