Vitamin A Explained

Vitamin A is a micronutrient that is crucial for maintaining vision, promoting growth and development, and protecting epithelium and mucus integrity in the body. VitA is known as an anti-inflammation vitamin because of its critical role in enhancing immune function. The availability of vitamin A in our food is a key factor in a tolerant, highly functional immune system.

Vitamin A supplementation may cause immune system to 'forget' past infections: New research suggests that vitamin A inhibits trained immunity, leading to tolerance of the innate immune cells upon stimulation with mitogens, antigens.

What is Vitamin A

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What Does Vitamin A
Do in Your Body?

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Vitamin A In Foods

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Research Studies

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What is Vitamin A

Vitamin A, along with other vitamins, minerals and other compounds, is an essential micronutrient. This means that our bodies cannot manufacture it and therefore it has to be included in our diet.

Vitamin A from food is stored in the liver until required by the body and is bound to protein before being transported to where it is needed.

Vitamin A is an essential micronutrient for immunity, cellular differentiation, growth, reproduction, maintenance of epithelial surfaces, and vision. Vitamin A is found as preformed vitamin A in foods such as liver, cod-liver oil, butter, eggs, and dairy products and as provitamin A carotenoids in foods such as spinach, carrots, and orange fruits and vegetables. 
Vitamin A is essential for many physiological processes, including maintaining the integrity and function of all surface tissues (epithelia): for example, the skin, the lining of the respiratory tract, the gut, the bladder, the inner ear and the eye. Vitamin A supports the daily replacement of skin cells and ensures that tissues such as the conjunctiva are able to produce mucous and provide a barrier to infection. Vitamin A is also essential for vision under conditions of poor lighting, for maintaining a healthy immune system, for growth and development and for reproduction. Vitamin A supports many systems in the body. For this reason, vitamin A deficiency is now referred to as vitamin A deficiency disorders. For simplicity, however, we will continue to use the older term vitamin A deficiency (VAD).
One of the main consequences of VAD is an increased risk of severe infection. Infection increases the body's demand for vitamin A and so the deficiency gets worse. Children can therefore become involved in a vicious cycle of deficiency and infection, which is why vitamin A deficiency is such an important cause of child mortality.

Vitamin A is a fat-soluble vitamin, which is stored in your body. This means that excess consumption can lead to toxic levels.
Hypervitaminosis A is caused by consuming too much preformed vitamin A through your diet or supplements containing the vitamin.
Symptoms can include nausea, dizziness, headaches, pain and even death.
Though it can be caused by excessive intake from the diet, this is rare compared to overconsumption from supplements and medications.

Recommended Amounts

The amount of vitamin A adults aged 19 to 64 need is:
0.7mg a day for men
0.6mg a day for women
You should be able to get all the vitamin A you need from your diet.
Any vitamin A your body doesn't need immediately is stored for future use. This means you don't need it every day. [source]

How does vitamin A affect immune health?

Vitamin D is necessary for the proper functioning of your immune system, which is your body’s first line of defense against infection and disease.
This vitamin plays a critical role in promoting immune response. It has both anti-inflammatory and immunoregulatory properties and is crucial for the activation of immune system defenses (The immunological implication of the new vitamin D metabolism).
Vitamin D is known to enhance the function of immune cells, including T-cells and macrophages, that protect your body against pathogens (Vitamin D3: a helpful immuno-modulator).
In fact, the vitamin is so important for immune function that low levels of vitamin D have been associated with an increased susceptibility to infection, disease, and immune-related disorders (Vitamin D and the Immune System).
For example, low vitamin D levels are associated with an increased risk of respiratory diseases, including tuberculosis, asthma, and chronic obstructive pulmonary disease (COPD), as well as viral and bacterial respiratory infections (A review of Vitamin D effects on common respiratory diseases: Asthma, chronic obstructive pulmonary disease, and tuberculosis - Vitamin D and respiratory health - A Review on the Role of Vitamin D in Asthma - The impact of Vitamin D deficiency on asthma, allergic rhinitis and wheezing in children: An emerging public health problem)
What’s more, vitamin D deficiency has been linked to decreased lung function, which may affect your body’s ability to fight respiratory infections (Vitamin D Deficiency Causes Deficits in Lung Function and Alters Lung Structure - Association Between Severe Vitamin D Deficiency, Lung Function and Asthma Control).

What Does Vitamin A do in your Body?

Vitamin A is one of many vitamins our bodies need to stay healthy. This vitamin has many functions, including:

  • Protects Your Eyes From Night Blindness and Age-Related Decline: Vitamin A is essential for preserving your eyesight. The vitamin is needed to convert light that hits your eye into an electrical signal that can be sent to your brain. In fact, one of the first symptoms of vitamin A deficiency can be night blindness, known as nyctalopia (Vitamin A Deficiency and Clinical Disease: An Historical Overview). Eating adequate amounts of vitamin A prevents the development of night blindness and may help slow the age-related decline of your eyesight.
  • May Lower Your Risk of Certain Cancers: Cancer occurs when abnormal cells begin to grow or divide in an uncontrolled way. As vitamin A plays an important role in the growth and development of your cells, its influence on cancer risk and role in cancer prevention is of interest to scientists (Retinoids as Cancer-Preventive Agents, Retinoids and Their Receptors in Cancer Development and Chemoprevention). In observational studies, eating higher amounts of vitamin A in the form of beta-carotene has been linked to a decreased risk of certain types of cancer, including Hodgkin's lymphoma, as well as cervical, lung and bladder cancer.
  • Supports a Healthy Immune System: Vitamin A plays a vital role in maintaining your body’s natural defenses. This includes the mucous barriers in your eyes, lungs, gut and genitals which help trap bacteria and other infectious agents. It’s also involved in the production and function of white blood cells, which help capture and clear bacteria and other pathogens from your bloodstream. This means that a deficiency in vitamin A can increase your susceptibility to infections and delay your recovery when you get sick (Increased Risk of Respiratory Disease and Diarrhea in Children With Preexisting Mild Vitamin A Deficiency, Vitamin A, Infection, and Immune Function).
  • Reduces Your Risk of Acne: It has been suggested that vitamin A deficiency may increase your risk of developing acne, as it causes an overproduction of the protein keratin in your hair follicles (Role of Diet in Dermatological Conditions, Phrynoderma: A Manifestation of Vitamin A Deficiency?... The Rest of the Story). This would increase your risk of acne by making it more difficult for dead skin cells to be removed from hair follicles, leading to blockages.
  • Supports Bone Health: eating enough vitamin A is also necessary for proper bone growth and development, and a deficiency in this vitamin has been linked to poor bone health. In fact, people with lower blood levels of vitamin A are at a higher risk of bone fractures than people with healthy levels (The Effect of Vitamin A on Fracture Risk: A Meta-Analysis of Cohort Studies). Additionally, a recent meta-analysis of observational studies found that people with the highest amounts of total vitamin A in their diet had a 6% decreased risk of fractures.
  • Promotes Healthy Growth and Reproduction:

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Vitamin A in Foods

Ready-made retinol, the active form of vitamin A, only comes from animal sources. Plant-based foods contain carotenoids, antioxidant forms of vitamin A. These are converted to retinol in the body.

  • Fruits and vegetables
  • Dark green leafy vegetables, for example amaranth (red or green), spinach and chard
  • Orange-fleshed sweet potatoes
  • Carrots
  • Squashes/pumpkins
  • Yellow maize
  • Mangoes
  • Papayas
  • Animal sources
  • Liver, eggs, milk (including breast milk)
  • Oils
  • Red palm oil or biruti palm oil

Research on Vitamin A

Medical Reseach Studies on Vitamin A

  • Role of Vitamin A in the Immune System. Vitamin - IVitA has bothpromoting and regulatory roles in both the innate immune system and adaptive immunity; therefore,it can enhance the organism’s immune function and provide an enhanced defense against multipleinfectious diseases. Currently, the VitA’s effect on immune function has been studied at the molecularlevel, and more research is ongoing about the therapeutic effects of VitA on preventing and curingvarious infectious diseases. Research
  • Effects of Vitamin A Supplementation on Immune Responses and Correlation with Clinical Outcomes - Vitamin A supplementation to preschool children is known to decrease the risks of mortality and morbidity from some forms of diarrhea, measles, human immunodeficiency virus (HIV) infection, and malaria. These effects are likely to be the result of the actions of vitamin A on immunity. Some of the immunomodulatory mechanisms of vitamin A have been described in clinical trials and can be correlated with clinical outcomes of supplementation. Research
  • A Review of Micronutrients and the Immune System–Working in Harmony to Reduce the Risk of Infection: Cell-mediated processes of innate immunity, such as cell proliferation, differentiation, function, movement, and the ability to mount an effective oxidative burst, rely on adequate amounts of vitamins A, D, C, E, B6, and B12, folate, iron, zinc, copper, selenium, and magnesium. Similarly, chemical responses such as activation of the complement system and the release of proinflammatory cytokines requires certain vitamins and minerals (in particular, vitamins A, D, and C, zinc, iron, and selenium). The inflammatory response bridges the gap between innate and adaptive immunity, and is regulated by vitamins A, C, E, and B6, as well as iron, zinc, and copper. Adaptive immune responses encompassing cell-mediated and humoral immunity depend again on the presence of a variety of micronutrients at all stages (i.e., lymphocyte proliferation, differentiation, and function, and humoral- and cell-mediated immune processes) .  Research

Recommended Vitamin A Supplements

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