“How Much Do You Know About Food Nutrition” Series | Do you know how to supplement vitamins A and D?

We often see various vitamin supplements in pharmacies, including vitamin D, vitamin A, vitamin AD, etc. Do you know what functions vitamins A and D have? Should we supplement these vitamins? Let's take a look at how to take these nutrients in our daily diet.

Vitamin A (VA for short), also known as retinol, is related to the development of human vision. VA deficiency can lead to night blindness. It also has other important physiological functions for the human body, such as promoting the synthesis of immunoglobulins, maintaining normal bone growth and development, promoting growth and reproduction, preventing cardiovascular diseases, and delaying aging.

The direct source of VA for the human body is animal food raw materials. For example, animal liver has a high content of VA. Common cod liver oil is the best VA supplement. Eggs and milk are also rich in VA.

Although plants do not contain VA, many vegetables contain carotene, which can be converted into VA components in the human body and serve as a "source of vitamin A". Therefore, eating more of these vegetables can supplement the insufficient intake of animal food and prevent VA deficiency in the body.

Symptoms of vitamin A overdose in adults include excessive excitement and drowsiness, which may be accompanied by symptoms of increased intracranial pressure such as headaches and vomiting. For pregnant mothers, vitamin supplements should not be taken randomly, otherwise it will be counterproductive. If excessive intake of VA is taken during pregnancy, "teratogenic" conditions may occur, which are more common in craniofacial, urinary system or cardiovascular malformations.

The main manifestation of vitamin A overdose in infants and young children is increased intracranial pressure, which may include drowsiness, vomiting, full anterior fontanelle, fundus edema, etc. In contrast, children are more susceptible to VA poisoning than adults.

Vitamin D (VD for short) is a steroid substance, and its main function is to promote the absorption of calcium and phosphorus in the human body, and to prevent and treat rickets. In recent years, some experts have pointed out that heart disease, lung disease, cancer, diabetes, hypertension, schizophrenia and other diseases are all related to VD deficiency.

There are at least 10 known types of VD, the most important of which are D3 and D2.

The direct source of vitamin D3 is animal food, such as cod liver, fish oil, eggs, beef, butter, etc. The human body can also spontaneously synthesize vitamin D3 in the subcutaneous tissue when exposed to ultraviolet rays.

Ergosterol found in plant materials such as algae, mushrooms and yeast can be converted into vitamin D2 through ultraviolet radiation. It is called the "sunshine vitamin", that is, the human body can also spontaneously synthesize this vitamin if it is exposed to the sun more. Therefore, the use of outdoor sun protection facilities and sunscreen will affect the synthesis of VD.

In daily life, you should consume more foods rich in vitamin D, do more outdoor exercises, and get more sun exposure to promote your own VD synthesis; at the same time, you can also take appropriate doses of VD supplements.

It should be noted that VD is a fat-soluble vitamin and long-term and large-scale use of VD supplements can cause poisoning.

The main symptoms of vitamin D poisoning include hypercalcemia and the resulting renal damage, soft tissue calcification, etc. The clinical manifestations are loss of appetite, weakness, bradycardia, heart rhythm disorders, nausea, vomiting, thirst, constipation, polyuria, etc.

In summary, any nutrient has its benefits, but not everyone needs to eat more. There are scientific rules for "whether to eat, how much to eat, and how to eat". Understanding these scientific knowledge of diet and nutrition can make you more aware of what diet is suitable for you.

(This article was scientifically reviewed by Zhang Juanmei, associate professor of food safety and food and medicine at the School of Pharmacy of Henan University.)