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6 Benefits and Side Effects of Vitamin A (8 Contraindications To Be Noted)

Vitamin A is a fat-soluble vitamin, not a single structure, composed of a group of similar molecules, with retinol (Retinol) and β-carotene (a precursor to vitamin A) being the most common. Note 6

In the human body, vitamin A is mainly related to cell growth and differentiation, embryonic development, organ formation, immune function, and visual development.

What are the proven benefits of vitamin A?

Pneumonia is defined as an acute lung tissue infection caused by one or co-infectious pathogens, but definite bronchiolitis is excluded.

Respiratory syncytial virus is the dominant viral factor, detected in 15% to 40% of pneumonia cases, followed by influenza A and B, parainfluenza virus, human metapneumovirus and adenovirus.

Childhood pneumonia is the single leading cause of death in children under 5 years of age. The incidence in this age group is estimated to be 0.29 per year in developing countries and 0.05 per year in developed countries, with major risk factors including: malnutrition, low birth weight, lack of measles immunity, indoor air pollution, etc.

A meta-analysis (15 randomized controlled trials, 3021 patients with pneumonia) pointed out that vitamin A supplementation outside of formal treatment did not reduce mortality from pneumonia in children, but improved overall clinical response rate, shortened the duration of fever, cough, clearance of signs, and reduced abnormal chest X-ray results and length of hospital stay. Note 1

*Conclusion: Additional vitamin A supplementation in the treatment of pneumonia in children can help reduce clinical signs and symptoms and shorten hospital stay.

2. Retinitis pigmentosa

Retinitis pigmentosa is a familial genetic disease, mainly characterized by progressive degeneration of retinal sensory cells, early symptoms are mainly slowed dark adaptation and night blindness, and gradually affect peripheral and central vision, the most severe can lead to blindness.

One double-blind controlled trial (4 to 6 years, 601 patients with retinitis pigmentosa) compared with placebo reduced retinal function decline (up to 32% as measured by electroretinitis) with vitamin A supplementation. Note 1

However, considering the toxicity of large doses and the incomplete research methods, further confirmation is needed.

3. Prevent diabetes

Diabetes is a complex metabolic disorder associated with high blood sugar and poor insulin action, mainly caused by poor diet and lifestyle habits, and it is estimated that more than 4000 million adults worldwide will be affected by 4.

Both animal and human experiments have found that vitamin A can affect pancreatic islet Beta cell production and insulin resistance, and if the deficiency is positively associated with diabetes.

A retrospective study (193,803 Danes) found that consuming more vitamin A (self-fortified foods) at a young age not only reduced the risk of diabetes in middle and old age, but also reduced the incidence of diabetes in offspring. Note 2

The authors note that this result is important for undernourished low- and middle-income countries as a simple and affordable approach to nutrition.

4. Promote the health of young children

According to the World Health Organization, pneumonia, diarrhoea and malaria top the list of factors that cause death among children under 5 years of age after the neonatal period, among which diarrhoea alone kills 500,000 young children every year.

Malnutrition is the leading cause of these diseases (45%), mainly associated with poor economic health, parasites, and chronic infections, especially in low- and middle-income countries.

A Cochrane Database of Systematic Reviews (47 studies with 1,223,856 children over months and under 5 years old) noted that vitamin A supplementation helped reduce morbidity and mortality in young children, particularly in diarrhoea and measles. Note 3

5. Age-related cataract risk reduction

According to the World Health Organization, there are currently more than 3 million blind people in the world, and cataracts are the most important cause of blindness.

Although cataracts can be treated by intraocular lens replacement, some patients are still unable to receive appropriate treatment due to uneven medical resources and high costs. Therefore, it is very important to take the right precautions.

A meta-analysis (22 studies) pointed out that a higher intake of vitamin A and β-carotene did help reduce the risk of cataracts. Note 4

However, the authors mention that the results still need to be confirmed because potential biases and interference factors have not been ruled out.

6. Reduce the incidence of pancreatic cancer

Pancreatic cancer, one of the more difficult cancers of the digestive system, ranks fourth among the causes of cancer death, with about three-quarters of cases occurring after the age of 4.

Because the early symptoms of pancreatic cancer are not specific (such as loss of appetite, mild pain, nausea and weight loss), it is often unalert, and about 80% of the patients are diagnosed in the more severe intermediate and advanced stages and cannot be treated with open surgery.

A meta-analysis (including 11 studies) showed that vitamin A intake was inversely correlated with pancreatic cancer, with higher intake reducing the risk of about 16% (compared with less intake). Note 5

Are there any side effects of vitamin A supplementation?

For most people in good health, moderate intake of vitamin A from food is safe without side effects, if using health products, pay attention to the dosage to avoid long-term overdose caused by poisoning.

In general, intoxication is usually associated with long-term use of more than 10 times the recommended dietary intake (RDA), about 25,000-33,000 IU per day.

Acute and chronic symptoms of vitamin A poisoning include: nausea, headache, hair loss, fatigue, loss of appetite, dizziness, dry skin, peeling, cerebral edema, hepatosplenomegaly, bone and joint pain, etc. Severe cases can lead to liver damage, bleeding and coma.

Safety precautions

There is evidence that some ethnic groups are more susceptible to poisoning with oral vitamin A, and even lower doses may occur, including the elderly, long-term alcoholics and patients with familial hyperlipidemia.

Long-term use of high doses may increase osteoporosis and hip fractures, especially in older people.

If pregnant women, children, and people with poor liver and kidney function want to supplement health care products, they must inform medical personnel in advance to ensure safe use.

Be careful if you have low blood pressure or take blood pressure medications, which may cause low blood pressure.

There may be anticoagulant effects, so be careful if you have coagulopathy or take anticoagulants.

High-dose vitamin A combined with tetracycline antibiotics may increase the risk of intracranial hypertension.

Orlistat (diet pills) and cholesterol-lowering drugs (bile acid sequestrants) may inhibit vitamin A absorption.

Do not use it in combination with omeprazole (a digestive tract drug) or the chemotherapy drug doxorubicin, which may affect the effect of the drug.


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