The Impact of Vitamin A on Gene Expression: An In-Depth Exploration of Its Biological Mechanisms

Vitamin A, as an important nutrient, is not only crucial for our daily health but also exerts profound effects at the genetic level. This article will delve into how vitamin A influences gene expression, revealing the biological mechanisms behind it, and discussing the significance of these effects on human health.

What is Vitamin A?

Vitamin A is a collective term for a group of fat-soluble vitamins, including various forms such as retinol, retinal, and retinoic acid. These compounds play an indispensable role in the human body, participating in the regulation of various physiological processes.

Sources of Vitamin A

Vitamin A mainly comes from two pathways: direct intake and precursor conversion.

1. Direct intake:

   • Animal sources: such as liver, egg yolks, and full-fat dairy products. The vitamin A in these foods primarily exists in the form of retinyl esters.
   • Plant sources: such as dark green and orange-yellow vegetables and fruits (like carrots, sweet potatoes, spinach, etc.). These foods contain carotenoids like β-carotene, which can be converted into vitamin A in the human body.

2. Precursor conversion: The human body can convert certain carotenoids (like β-carotene) from plants into active vitamin A. This conversion process mainly occurs in the intestinal mucosal cells and the liver.

It is worth noting that the bioavailability of vitamin A varies among different food sources. For example, vitamin A from animal sources is generally more easily absorbed and utilized by the body than that from plant sources.

Physiological Functions of Vitamin A

Vitamin A plays multiple important roles in the human body:

1. Vision: Vitamin A is a crucial component of the photoreceptor cells in the retina, essential for night vision and color perception.

2. Cell growth and differentiation: Vitamin A is involved in regulating the growth, differentiation, and apoptosis of various cells, which is vital for maintaining normal cell turnover and tissue repair.

3. Immune function: Vitamin A is very important for maintaining a healthy immune system, helping to enhance the body's ability to fight infections.

4. Skin health: Vitamin A promotes the renewal and repair of skin cells, helping to maintain healthy skin.

5. Reproduction: Vitamin A has significant effects on sperm production and embryonic development.

6. Regulation of gene expression: This is the focus of this article, as vitamin A regulates various physiological processes by influencing gene expression.

Understanding the sources and basic functions of vitamin A lays the foundation for our in-depth exploration of its impact on gene expression. Next, we will introduce the basic concepts of gene expression to prepare for understanding how vitamin A affects this process.

Basic Concepts of Gene Expression

Before delving into how vitamin A affects gene expression, we need to understand the basic concepts of gene expression. This will help us better comprehend the molecular mechanisms of vitamin A's action.

Definition of Gene Expression

Gene expression refers to the process by which cells selectively "read" the genetic information in DNA according to their needs and convert it into functional products (such as proteins or RNA). This process is central to life activities and determines the characteristics and functions of cells.

The main steps of gene expression include:

1. Transcription: The genetic information in DNA is transcribed into RNA. This is the first step of gene expression, carried out by RNA polymerase.

2. RNA processing: The primary transcription product (pre-mRNA) undergoes a series of modifications, such as capping, splicing, and polyadenylation, to form mature mRNA.

3. Translation: The mature mRNA is translated into proteins on ribosomes. This process converts the genetic code into an amino acid sequence.

4. Protein modification: Newly synthesized proteins may require further modifications, such as folding, cleavage, or chemical modifications, to exert their full function.

Regulatory Mechanisms of Gene Expression

The regulation of gene expression is a complex and precise process involving multiple levels:

1. Transcriptional regulation:

   • Promoters and enhancers: These DNA sequences can influence the initiation and efficiency of gene transcription.
   • Transcription factors: These proteins can bind to specific DNA sequences to promote or inhibit gene transcription.
   • Epigenetic modifications: Such as DNA methylation and histone modifications, can affect the accessibility of genes.

2. Post-transcriptional regulation:

   • RNA stability: Influences the lifespan of mRNA in the cell.
   • RNA splicing: Produces different mRNA variants through alternative splicing.
   • MicroRNA: These small RNA molecules can regulate the stability and translation efficiency of mRNA.

3. Translational regulation:

   • Translation initiation factors: Affect the efficiency of mRNA translation.
   • RNA-binding proteins: Can regulate the translation of specific mRNAs.

4. Post-translational regulation:

   • Protein modifications: Such as phosphorylation and acetylation, can alter the activity or stability of proteins.
   • Protein degradation: Regulates the lifespan of proteins through the ubiquitin-proteasome system.

These regulatory mechanisms work together to ensure that genes are expressed at the right time, in the right cells, and at appropriate levels. Vitamin A and its metabolites primarily influence gene expression by affecting transcriptional regulation, which we will explore in detail in the next section.

Understanding the basic concepts and regulatory mechanisms of gene expression lays the groundwork for our in-depth study of how vitamin A affects this process. Next, we will specifically analyze the mechanisms by which vitamin A influences gene expression.

How Vitamin A Affects Gene Expression

Vitamin A exerts profound effects on gene expression primarily through its active metabolite, retinoic acid. This influence is mainly achieved through interactions with specific nuclear receptors, thereby regulating the expression of various genes. Let us delve into the specific mechanisms of this process.

Metabolites of Vitamin A

Vitamin A undergoes a series of metabolic conversions in the body, ultimately forming its most biologically active form—retinoic acid. This process mainly includes the following steps:

1. Conversion of retinol: The ingested retinol is oxidized to retinal by retinol dehydrogenase (RDH) within cells.

2. Conversion of retinal: Retinal is further oxidized to retinoic acid by retinal dehydrogenase (RALDH).

3. Isomers of retinoic acid: Retinoic acid mainly exists in two isomeric forms: all-trans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA).

These metabolites, especially retinoic acid, are key molecules through which vitamin A influences gene expression.

Interaction of Vitamin A with Nuclear Receptors

Retinoic acid primarily affects gene expression through interactions with two families of nuclear receptors:

1. Retinoic acid receptors (RARs):

   • Includes three subtypes: RARα, RARβ, and RARγ.
   • Primarily binds to all-trans retinoic acid (ATRA).

2. Retinoid X receptors (RXRs):

   • Includes three subtypes: RXRα, RXRβ, and RXRγ.
   • Primarily binds to 9-cis retinoic acid (9-cis RA).

These nuclear receptors typically exist in the form of heterodimers, meaning RAR forms a complex with RXR. When retinoic acid binds to these receptors, it triggers a series of molecular events:

1. Conformational change: The binding of retinoic acid leads to a conformational change in the receptor protein.

2. Co-regulator recruitment: The conformational change prompts the receptor complex to recruit specific co-regulators, such as co-activators or co-repressors.

3. DNA binding: The receptor complex binds to specific DNA sequences in the promoter region of target genes, known as retinoic acid response elements (RARE).

4. Transcriptional regulation: Depending on the nature of the recruited co-regulators, this binding can promote or inhibit the transcription of target genes.

The Role of Vitamin A in Cell Differentiation

Vitamin A plays a crucial role in the process of cell differentiation by regulating gene expression:

1. Embryonic development: The retinoic acid signaling pathway is essential for normal embryonic development, influencing the formation of multiple organs, including the nervous system, heart, and eyes.

2. Hematopoiesis: Vitamin A is involved in regulating the self-renewal and differentiation of hematopoietic stem cells, affecting blood cell production.

3. Skin cell renewal: Retinoic acid promotes the differentiation of epidermal cells, maintaining normal skin turnover.

4. Immune cell differentiation: Vitamin A influences the differentiation of T cells and B cells, regulating immune responses.

5. Neuronal differentiation: Retinoic acid signaling plays an important role in the differentiation of neural progenitor cells and the maturation of neurons.

Through these mechanisms, vitamin A influences cell fate determination and functional differentiation at the level of gene expression. This influence is not limited to normal physiological processes; it also plays an important role in the occurrence and development of certain diseases, which we will further explore in subsequent sections.

Understanding the molecular mechanisms by which vitamin A affects gene expression helps us better recognize its role in physiological and pathological processes, providing a theoretical basis for developing related therapeutic strategies. Next, we will explore the impact of vitamin A deficiency on gene expression and the potential health issues that may arise from it.

The Impact of Vitamin A Deficiency on Gene Expression

Vitamin A deficiency not only leads to a series of direct physiological problems but also has profound effects on the body by influencing gene expression. These effects can lead to various health issues, ranging from vision impairment to decreased immune function. Let us delve into how vitamin A deficiency affects gene expression and the physiological consequences of these effects.

Physiological Consequences of Vitamin A Deficiency

Vitamin A deficiency affects multiple physiological systems, primarily manifesting as:

1. Vision problems:

   • Night blindness: Due to impaired synthesis of rhodopsin in the retina.
   • Dry eyes: Impaired function of the lacrimal glands and conjunctival epithelial cells.

2. Decreased immune function:

   • Increased risk of infections: Especially respiratory and gastrointestinal infections.
   • Weakened vaccine response: Affects antibody production and T cell function.

3. Skin problems:

   • Dry skin and keratinization: Abnormal differentiation of epidermal cells.
   • Slow wound healing: Decreased ability for cell regeneration and repair.

4. Growth and development delays:

   • Impeded growth in children: Affects skeletal development and overall growth.
   • Abnormal embryonic development: Severe deficiency may lead to congenital defects.

5. Anemia:

   • Impaired iron utilization: Affects red blood cell production.

These physiological consequences are closely related to the regulatory role of vitamin A on gene expression.

Related Research and Case Studies

Multiple studies have confirmed the impact of vitamin A deficiency on gene expression:

1. Retinal gene expression study: A study published in the Journal of Biological Chemistry showed that vitamin A deficiency significantly reduces the expression of several key genes in the retina, including rhodopsin genes and cone cell-specific genes. This directly explains why vitamin A deficiency leads to vision problems.

2. Immune system gene expression: An article in the Journal of Immunology reported that vitamin A deficiency alters the expression patterns of several immune-related genes in T cells, affecting T cell differentiation and function. This explains why vitamin A deficiency leads to decreased immune function.

3. Skin cell gene expression: A study published in the Journal of Investigative Dermatology found that vitamin A deficiency affects the expression of several differentiation-related genes in epidermal cells, leading to abnormal keratinization and impaired skin barrier function.

4. Embryonic development gene expression: An article in the journal Development reported that during embryonic development, vitamin A deficiency affects the expression of several key developmental genes, potentially leading to developmental abnormalities in multiple organ systems.

5. Hematopoietic system gene expression: A study published in Blood showed that vitamin A deficiency alters the expression patterns of several genes in hematopoietic stem cells, affecting blood cell production and differentiation.

These research cases clearly demonstrate how vitamin A deficiency leads to various physiological problems by affecting gene expression. It is worth noting that these effects are often multifaceted and may have long-term consequences.

Understanding the impact of vitamin A deficiency on gene expression not only helps us better recognize the importance of vitamin A but also provides scientific evidence for the prevention and treatment of related health issues. However, we also need to be aware that excessive intake of vitamin A can also pose health risks. In the next section, we will explore the effects of vitamin A overdose on gene expression and the potential hazards it may bring.

The Impact of Vitamin A Overdose on Gene Expression

Although vitamin A is crucial for human health, excessive intake can also lead to serious health problems. Vitamin A overdose not only directly causes toxic reactions but also has profound effects on the body by influencing gene expression. Let us delve into the toxic effects of vitamin A overdose and its impact on gene expression.

Toxicity of Excessive Vitamin A

Excessive vitamin A can lead to acute or chronic toxic reactions:

1. Acute toxicity:

   • Headache, nausea, and vomiting
   • Blurred vision and dizziness
   • Skin peeling
   • Severe cases may lead to liver damage

2. Chronic toxicity:

   • Liver damage and fibrosis
   • Increased risk of osteoporosis and fractures
   • Skin problems, such as dryness, peeling, and itching
   • Headaches and increased intracranial pressure
   • Increased risk of fetal malformations (in cases of overdose in pregnant women)

These toxic effects are partly due to abnormal gene expression caused by excessive vitamin A.

Potential Mechanisms Affecting Gene Expression

The impact of vitamin A overdose on gene expression is mainly realized through the following mechanisms:

1. Receptor saturation: Excessive retinoic acid may lead to saturation of retinoic acid receptors (RAR and RXR), affecting normal gene regulation.

2. Non-specific activation: High concentrations of retinoic acid may activate other nuclear receptors, such as thyroid hormone receptors or vitamin D receptors, leading to abnormal expression of non-target genes.

3. Epigenetic modifications: Excessive vitamin A may affect DNA methylation and histone modification patterns, thereby altering gene accessibility.

4. Oxidative stress: High doses of vitamin A may induce oxidative stress, affecting multiple signaling pathways and gene expression.

5. Cytotoxicity: Excessive vitamin A may directly damage cells, leading to abnormal expression of stress-related genes.

Research indicates that vitamin A overdose may affect the expression of the following types of genes:

1. Cell cycle regulatory genes: May lead to uncontrolled cell proliferation or increased apoptosis.

2. Metabolism-related genes: Affect lipid metabolism and glucose metabolism.

3. Bone metabolism-related genes: May lead to increased bone resorption and decreased bone formation.

4. Liver detoxification genes: Affect the liver's detoxification function.

5. Development-related genes: Particularly important during embryonic development, may lead to developmental abnormalities.

A study published in Toxicological Sciences showed that long-term high-dose vitamin A supplementation may lead to significant changes in the expression of multiple genes in the liver, including those related to lipid metabolism, apoptosis, and fibrosis. This explains why vitamin A overdose may lead to liver damage.

Another study published in the Journal of Bone and Mineral Research found that vitamin A overdose affects the expression of multiple genes in bone cells, including key genes regulating bone resorption and formation. This explains the connection between vitamin A overdose and osteoporosis.

Understanding the impact of vitamin A overdose on gene expression not only helps us recognize its potential hazards but also provides scientific evidence for the prevention and treatment of related health issues. It is important to recognize that vitamin A intake needs to be balanced, avoiding both deficiency and excess.

In the next section, we will explore the association between vitamin A and specific diseases, particularly its role in cancer and immune system diseases. This will help us gain a more comprehensive understanding of the complex role of vitamin A in health and disease.

The Association Between Vitamin A and Diseases

Vitamin A plays an important role in the occurrence, development, and treatment of various diseases through its regulatory effects on gene expression. Particularly in cancer and immune system diseases, the role of vitamin A is especially significant. Let us delve into the mechanisms of vitamin A's action in these diseases and its potential therapeutic applications.

The Role of Vitamin A in Cancer

Vitamin A, especially its active metabolite retinoic acid, has a complex and important role in the prevention and treatment of cancer:

1. Inhibition of tumor growth:

   • Retinoic acid can inhibit the proliferation of various cancer cells.
   • By regulating the expression of cell cycle-related genes, it promotes the differentiation and apoptosis of cancer cells.

2. Promotion of cell differentiation:

   • In certain leukemias, retinoic acid can induce immature leukemia cells to differentiate into normal cells.

3. Antioxidant effects:

   • Vitamin A has antioxidant properties, which can reduce DNA damage and lower cancer risk.

4. Epigenetic regulation:

   • Retinoic acid can affect DNA methylation and histone modifications, thereby regulating the expression of tumor suppressor genes.

5. Immune modulation:

   • Vitamin A can enhance the immune system's ability to recognize and eliminate cancer cells.

Research cases:

• A study published in Nature showed that retinoic acid can inhibit the proliferation and metastasis of breast cancer cells by regulating the expression of the HOXA1 gene.
• A study in the journal Blood reported that retinoic acid can effectively treat acute promyelocytic leukemia by regulating the expression of the PML-RARα fusion protein.

However, it is worth noting that the role of vitamin A in cancer is dual-sided. Some studies suggest that, under certain circumstances, high-dose vitamin A supplementation may increase the risk of certain cancers. Therefore, caution is needed when using vitamin A in cancer prevention and treatment.

The Relationship Between Vitamin A and the Immune System

Vitamin A is crucial for the normal function of the immune system, with its effects involving multiple aspects of both innate and adaptive immune responses:

1. T cell differentiation:

   • Retinoic acid is involved in regulating T cell differentiation, affecting the balance of Th1, Th2, and Treg cells.
   • By regulating the expression of key transcription factors (such as Foxp3), it influences the development of regulatory T cells.

2. B cell function:

   • Vitamin A affects the activation and antibody production of B cells.
   • Regulates the production of IgA, which is crucial for mucosal immunity.

3. Innate immune cells:

   • Enhances the function of macrophages and natural killer cells.
   • Regulates the chemotaxis and phagocytic ability of neutrophils.

4. Mucosal immunity:

   • Maintains the integrity of mucosal barriers.
   • Regulates the development and function of mucosa-associated lymphoid tissues.

5. Inflammation regulation:

   • Retinoic acid can inhibit excessive inflammatory responses, helping to maintain immune balance.

Research cases:

• A study published in Immunity found that retinoic acid regulates the differentiation of Th17 and Treg cells by modulating the expression of RORγt and Foxp3, thereby regulating autoimmune responses.
• A study in the Journal of Experimental Medicine showed that vitamin A deficiency significantly reduces the production of intestinal IgA, increasing the risk of intestinal infections.

These roles of vitamin A in the immune system make it an important consideration for potential therapeutic strategies for various immune-related diseases, including autoimmune diseases, allergic diseases, and chronic inflammatory diseases.

Understanding the role of vitamin A in cancer and immune system diseases not only helps us better understand the mechanisms of these diseases but also provides important clues for developing new prevention and treatment strategies. However, given the complexity of vitamin A's actions, careful consideration of its potential benefits and risks is needed in clinical applications.

In the next section, we will explore how to obtain sufficient vitamin A through diet and how to maintain appropriate levels of vitamin A intake in daily life to maximize its health benefits while avoiding the potential risks of excessive intake.

How to Obtain Sufficient Vitamin A Through Diet

Maintaining adequate vitamin A intake is crucial for overall health. While supplements can provide vitamin A, obtaining it through a balanced diet is usually the safest and most effective method. Let us explore food sources rich in vitamin A and how to reasonably incorporate vitamin A into our daily diet.

Foods Rich in Vitamin A

Vitamin A mainly exists in two forms in food: preformed vitamin A (retinol) and provitamin A (carotenoids).

1. Preformed vitamin A sources (animal foods):

   • Liver: Beef liver, chicken liver, etc., are the richest sources.
   • Cod liver oil: Such as cod liver oil.
   • Egg yolks
   • Full-fat dairy products: Such as whole milk, cheese, butter.

2. Provitamin A sources (plant foods):

   • Dark green vegetables: Spinach, kale, collard greens, broccoli.
   • Orange and yellow vegetables and fruits: Carrots, sweet potatoes, pumpkins, mangoes, cantaloupes.
   • Red vegetables: Red peppers, tomatoes.
   • Others: Apricots, papayas.

It is important to note that provitamin A from plant sources (mainly β-carotene) needs to be converted into active vitamin A in the body. The efficiency of this conversion process varies among individuals and is influenced by various factors. Therefore, relying solely on plant sources may not be sufficient to meet the needs of some individuals.

To ensure adequate vitamin A intake, it is recommended to combine both animal and plant sources in the diet:

1. Consume liver or liver-containing foods 1-2 times a week.
2. Include at least one serving of dark green or orange-yellow vegetables daily.
3. Consume full-fat dairy products in moderation.
4. Regularly eat fruits rich in vitamin A, such as mangoes or cantaloupes.

Recommendations for Vitamin A Supplementation

While a balanced diet usually meets vitamin A needs, additional supplementation may be necessary in certain situations:

1. Special populations:

   • Pregnant and breastfeeding women
   • Vegetarians or vegans
   • Patients with malabsorption disorders
   • Patients with certain chronic diseases

2. Supplementation methods:

   • Multivitamin complexes
   • Standalone vitamin A supplements
   • Cod liver oil

3. Supplementation precautions:

   • Consult a doctor or nutritionist for advice
   • Avoid excessive supplementation, especially for pregnant women
   • Choose products from reputable brands
   • Be aware of interactions with other medications

4. Monitoring:

   • Regularly check vitamin A levels in the blood
   • Be aware of symptoms of excessive intake

Important reminder: Vitamin A is a fat-soluble vitamin, and excessive intake may lead to accumulation and toxicity. Therefore, unless under medical guidance, long-term high-dose vitamin A supplementation is generally not recommended.

Through reasonable dietary planning and moderate supplementation when necessary, most people can maintain healthy levels of vitamin A, thereby supporting normal gene expression and overall health.

Conclusion

The Importance of Vitamin A in Gene Expression

Through this in-depth exploration, we can clearly see that vitamin A plays a crucial role in the regulation of gene expression:

1. Multifaceted impact: Vitamin A, through its active metabolite retinoic acid, influences multiple biological processes from cell differentiation to organ development.

2. Precise regulation: By interacting with nuclear receptors, vitamin A can precisely regulate the expression of specific genes, thereby affecting cell fate and function.

3. Health balance: Maintaining appropriate levels of vitamin A is essential for normal gene expression. Both deficiency and excess can lead to abnormal gene expression, resulting in various health issues.

4. Disease association: Vitamin A plays an important role in the occurrence, development, and potential treatment of various diseases, including cancer and immune diseases, closely related to its effects on gene expression.

5. Individual considerations: Due to individual differences, the impact of vitamin A on gene expression may vary from person to person, providing a basis for personalized nutrition and medical strategies.

Future Research Directions

Although we have gained considerable understanding of the mechanisms by which vitamin A affects gene expression, many areas still require further research:

1. Precise mechanisms: In-depth studies on how vitamin A precisely regulates the expression of specific genes at the molecular level, including the role of epigenetic modifications.

2. Individual responses: Exploring differences in vitamin A metabolism and gene expression responses among individuals to provide a basis for personalized nutrition and medical care.

3. Disease treatment: Further research on how to utilize the characteristics of vitamin A in regulating gene expression to develop new disease treatment strategies, particularly in cancer and autoimmune diseases.

4. Long-term effects: Investigating the long-term fluctuations in vitamin A intake levels on gene expression and health, including transgenerational effects.

5. Interactions with other nutrients: Exploring the synergistic effects of vitamin A with other nutrients (such as vitamin D, zinc, etc.) in regulating gene expression.

6. New delivery methods: Developing more precise and effective methods for vitamin A delivery to optimize its regulatory effects on gene expression.

7. Applications of big data and artificial intelligence: Utilizing big data and AI technologies to analyze the complex relationship between vitamin A and gene expression, predicting individual responses.

Overall, the impact of vitamin A on gene expression is a complex and fascinating research area. With advancements in technology and a deeper understanding of molecular mechanisms, this field is expected to bring breakthrough progress in improving human health and disease treatment.

This article, through an in-depth exploration of the impact of vitamin A on gene expression, not only reveals the complex biological effects of this important nutrient but also provides important perspectives for understanding the close relationship between nutrition, gene expression, and health. In the future, research in this field is expected to provide more valuable insights for personalized nutrition, precision medicine, and disease prevention.

FAQ Section

Q1: What is vitamin A? A1: Vitamin A is a fat-soluble vitamin that is crucial for various physiological functions, including vision, immune system function, and gene expression. It mainly exists in food in the forms of retinol (animal sources) and carotenoids (plant sources).

Q2: How does vitamin A affect gene expression? A2: Vitamin A regulates the expression of specific genes by binding to its metabolites (mainly retinoic acid) with nuclear receptors, influencing cell growth and differentiation. This regulatory effect involves multiple biological processes, including embryonic development, immune function, and cell differentiation.

Q3: What effects does vitamin A deficiency cause? A3: Vitamin A deficiency can lead to various health issues, including:

• Vision problems, such as night blindness
• Decreased immune function, increasing the risk of infections
• Dry skin and keratinization
• Growth and development delays
• Abnormal expression of certain genes, potentially affecting multiple physiological processes

Q4: How can I ensure adequate vitamin A intake? A4: Ensuring adequate vitamin A intake can be achieved through the following ways:

• Eating foods rich in vitamin A, such as carrots, sweet potatoes, dark green leafy vegetables, and animal liver
• Balancing animal and plant sources of vitamin A
• Moderate supplementation under the guidance of a doctor or nutritionist when necessary
• Regular nutritional assessments to ensure intake meets individual needs

Q5: What hazards can result from excessive vitamin A? A5: Excessive vitamin A can lead to:

• Acute symptoms such as headache, nausea, and vomiting
• Liver damage
• Increased risk of osteoporosis
• Abnormal expression of certain genes, potentially affecting multiple physiological processes
• Increased risk of fetal malformations from excessive intake in pregnant women

It is recommended to consume vitamin A moderately in daily diet and avoid excessive supplementation.

Q6: What role does vitamin A play in cancer treatment? A6: Vitamin A shows potential in the prevention and treatment of certain cancers:

• It may inhibit the growth of certain types of cancer cells
• It has applications in the treatment of certain leukemias
• It may enhance the immune system's ability to recognize and eliminate cancer cells. However, its effects are complex, and in some cases, it may have the opposite effect. Therefore, using vitamin A in cancer treatment should be done under professional medical guidance.

Q7: How can vegetarians ensure adequate vitamin A intake? A7: Vegetarians can ensure vitamin A intake through the following ways:

• Increasing the intake of dark green leafy vegetables and orange-yellow fruits and vegetables
• Considering adding foods rich in β-carotene, such as sweet potatoes and pumpkins
• Using plant-based vitamin A supplements under professional guidance when necessary
• Pairing with fatty foods to improve the absorption of carotenoids

The content of this article is based on publicly available information at the time of writing. If there are any inaccuracies, readers are welcome to point them out, and we will correct them promptly.