Vitamin D has so many benefits, the more you take, the healthier you will be? Be careful of poisoning!

Expert in this article: Li Xue, Peking Union Medical College, Doctor of Medicine

Summer is here. Although the weather is hot, there is plenty of sunshine. Basking in the sun and doing some exercise outdoors will not only make you feel good, but also have certain benefits for your body.

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It is said that "getting more sun exposure can supplement vitamin D". Indeed, vitamin D is very important to us, but don't just know that you need to supplement it. What impact does vitamin D deficiency have on us? Will it be harmful if you supplement too much? Let's get the correct way to supplement vitamin D today!

What is Vitamin D?

Vitamins are trace nutrients that our bodies need. They are usually not produced by us and need to be obtained through diet and other means. Vitamins are divided into two types: water-soluble vitamins and fat-soluble vitamins.

Vitamin D is a fat-soluble vitamin, but it is also a relatively special vitamin because the human body can synthesize it. 7-dehydrocholesterol in the skin can produce vitamin D under ultraviolet light. Its structure is a steroid derivative, so vitamin D is also considered a hormone.

There are many types of vitamin D, the most important of which are vitamin D2 (ergocalciferol) and vitamin D3 (also known as cholecalciferol). They need to undergo two conversions in the body to become physiologically active vitamin D. The first of these two conversions occurs in the liver, where 25(OH)D is produced; the second occurs in the kidneys, where the product is physiologically active 1,25(OH)2D, also known as calcitriol.

What does vitamin D do?

Vitamin D can promote the absorption of calcium and phosphorus by the intestines and the reabsorption of calcium and phosphorus by the renal tubules, maintaining the concentration of calcium and phosphorus in the blood.

Vitamin D, under the synergistic action of hormones such as parathyroid hormone and calcitonin, calcifies the bone matrix, making the bones hard.

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In addition to its role in calcium and phosphorus metabolism and bone calcification, more and more studies have found that vitamin D receptors are distributed throughout the heart, brain, liver, kidneys, bones, urogenital organs, parathyroid glands, and various immune cells, and are involved in regulating cell growth, neuromuscular, immune function, reducing inflammatory responses, regulating the secretion of hormones such as insulin, and so on.

What are the symptoms of vitamin D deficiency?

When vitamin D is deficient, the following problems may occur:

Osteoporosis: Lack of vitamin D can make bones thinner and more brittle, so supplementing vitamin D can prevent rickets in children and osteomalacia in adults. As mentioned earlier, vitamin D promotes bone calcification, and one of the characteristics of osteoporosis is the loss of bone calcium. Therefore, osteoporosis patients should pay attention to supplementing vitamin D while supplementing calcium.

Muscle weakness and myalgia: Vitamin D deficiency can cause decreased muscle strength and mobility, especially making the elderly more susceptible to falls.

Heart problems: According to clinical data, low levels of 25(OH)D in the blood can significantly increase the mortality rate of heart disease (myocardial infarction, heart failure, etc.).

Immune system and infection: A large amount of epidemiological and clinical data show that when the 25(OH)D in the blood decreases, it may lead to a decrease in immunity and cause various acute and chronic infectious diseases.

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In addition, studies have also shown that diabetic patients are generally deficient in vitamin D; vitamin D levels are positively correlated with the functions of the nervous system (memory, logical analysis, body balance, emotions, etc.).

Can excessive intake of vitamin D cause poisoning?

Since vitamin D is a fat-soluble vitamin and cannot be excreted through urine as quickly as water-soluble vitamins, excessive intake may cause cumulative poisoning. Symptoms of excessive intake of vitamin D may include anorexia, weight loss, frequent urination, thirst, and irregular heartbeat. In severe cases, it may cause hypercalcemia and hypercalciuria, leading to vascular calcification and damage to the heart, blood vessels, and kidneys.

How to supplement vitamin D correctly?

Vitamin D can be obtained through sunlight, food, supplements, etc.

Sunbathing

Studies have shown that the human body can synthesize enough vitamin D3 by simply exposing itself to sunlight for 10 minutes a day. But in order to avoid sunburn, you can choose to sunbathe between 9-10 am and 3-4 pm.

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Food supplement

Vitamin D2 is mainly derived from fungi, while vitamin D3 is derived from animals (fish, cod liver oil, etc.). Therefore, just remember to eat mushrooms to supplement vitamin D2, and eat more fish to supplement vitamin D3.

Supplements

If you cannot get enough vitamin D from the sun or food, you may need vitamin D supplements. When purchasing, pay attention to the vitamin D content indicated on the product (expressed in IU, 1𝜇g=40IU).

Please note that no matter which method is used to supplement vitamin D, it should not be excessively supplemented.

The recommended vitamin D intake in the Dietary Reference Intake for Chinese Residents (2018 edition, WS/T 578.4-2018) is:

People under 65 years old should take 10𝜇g vitamin D (400IU) per day

People over 65 years old should take 15𝜇g vitamin D (600IU) per day

The maximum tolerable amount of vitamin D is:

The maximum tolerable dose for children under 3 years old is 20𝜇g (800IU) per day

The maximum tolerable dose for children aged 4-7 years is 30𝜇g (1200IU) per day

The maximum tolerable dose for children aged 7-11 years is 45𝜇g (1800IU) per day

The maximum tolerable dose for children over 11 years old is 50𝜇g (2000IU) per day

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