Vitamin A is essential for the proper functioning of the body and influences many important processes.

The name "vitamin A" encompasses a group of chemical compounds called retinoids, which include retinol, retinal, and retinyl esters. In addition, sources of vitamin A are carotenoids, including alpha-carotene and beta-carotene, which are provitamin A and can be converted in the body to the active form of vitamin A. Other carotenoids, such as lycopene or lutein, are not converted to vitamin A.

Beta-carotene, being a provitamin A, must be converted in the body to the active form of retinol. This process depends on diet, health status, and genetic factors. The absorption of beta-carotene is less efficient and variable, averaging from 5 to 65%. Therefore, the intake of beta-carotene requires about six times larger amounts than retinol to meet the vitamin A requirement.

The body regulates the conversion of beta-carotene, which reduces the risk of vitamin A overdose from plant-based products. Excess retinol can be toxic, while beta-carotene is safer because unused amounts are excreted from the body.

Vitamin A performs many key functions in the body:

• Responsible for proper vision through participation in the formation of rhodopsin – a light-sensitive pigment in the retina of the eye, which enables image perception, especially in low-light conditions. Vitamin A also protects the eye surface from dryness, supports regeneration of the corneal epithelium, and prevents eye inflammations.
• Regulates growth and differentiation of cells of the skin and mucous membrane epithelium, supports its regeneration, and helps maintain smooth and elastic skin. It has anti-inflammatory effects, regulates the keratinization process of the epidermis, supports collagen synthesis, and slows down skin aging processes. It supports tissue regeneration processes, including hair and nails.
• Strengthens the immune system, protecting the body from infections through influence on white blood cell function and protection of mucous membranes.
• Participates in the production of red blood cells through stimulation of the bone marrow.
• Has antioxidant potential, thanks to which, along with vitamins C and E, it prevents excessive oxidation of fatty acids, protects against harmful effects of free radicals, and delays aging processes.
• Influences skin health by regulating epidermal shedding, melanin production, and collagen synthesis, which improves skin elasticity and appearance and supports wound healing.
• Participates in proper cell differentiation of epithelial and bone tissue, and is involved in the production and release of adrenal cortex and thyroid hormones.
• Plays a role in proper fetal development, participating in bone tissue growth and maturation of the reproductive system.
• In men it supports sperm production and fertility.

Vitamin A occurs in two main forms, supplied from different sources:

Animal sources of vitamin A, retinol and its derivatives, easily absorbed by the body:

• beef, pork, and poultry liver – these are absolute leaders in vitamin A content,
• egg yolks – contain moderate amounts of retinol as well as fats that support its absorption,
• full-fat dairy products such as milk, butter, and aged cheeses,
• fatty sea fish (salmon, mackerel, herring, eel) and fish oils, including cod liver oil.

Plant sources of vitamin A (carotenoids, e.g., beta-carotene):

• vegetables and fruits with red, orange, and yellow coloring – carrots, red peppers, pumpkin, sweet potatoes, apricots, tomatoes,
• green leafy vegetables such as spinach, kale, lettuce, Swiss chard, broccoli,
• parsley leaves, dill, asparagus.

A diet rich in vitamin A should include both animal products providing easily absorbable retinol and plant products that are sources of safe and healthy carotenoids. It is particularly important to regularly consume vegetables and fruits with intense colors, which are abundant in provitamin A.

After absorption from the gastrointestinal tract, vitamin A is stored primarily in the liver - up to 90%, the rest in the kidneys, adipose tissue, plasma, and other tissues. Vitamin A excretion occurs mainly with bile.

The absorption of vitamin A is influenced by its form. Retinol is absorbed at about 80%, while carotenoids at about 30%.

Protein-rich foods and those containing fats favor the absorption of retinol. The presence of bile acids and proper thyroid hormone levels are also favorable factors.

Factors that limit its absorption include alcohol, high fiber intake, taking large amounts of iron supplements, and zinc deficiency.

Vitamin A is sensitive to culinary processing. During cooking and stewing of vegetables and fruits, losses of β-carotene can amount to about 20%. Storing vegetables and fruits in improper conditions (wrong temperature, light exposure) causes vitamin A losses of up to 80%. The vitamin A content in vegetables and fruits also depends on the season.

Stewing, baking, cooking meat or fish causes 20% losses of this vitamin.

Daily requirements for vitamin A vary depending on age, gender, and physiological state:

• adult men need about 900 micrograms (µg) of retinol per day.
• adult women – about 700 µg per day.
• pregnant women – a dose of up to 770 µg per day is recommended.
• breastfeeding women – requirements increase to about 1300 µg per day.
• children and adolescents have requirements ranging from 400 µg (for infants) to 900 µg (for teenagers).

The best vitamin A supplements are those containing natural forms of the vitamin, such as retinol and its esters (e.g., retinyl acetate), or provitamin A in the form of beta-carotene.

Vitamin A deficiency manifests primarily as:

• impaired vision in low-light conditions (so-called night blindness), dryness and keratinization of the corneal and conjunctival epithelium,
• dry, flaky skin, especially on elbows, knees, and arms,
• brittleness of hair and nails and their loss,
• increased susceptibility to infections and weakened immunity,
• growth disorders in children and fertility problems in adults,
• difficulties with wound healing and skin irritations.

Excess vitamin A (hypervitaminosis) may manifest as:

• nausea, vomiting, headaches, dizziness, and visual disturbances,
• dryness, peeling, and yellowing of the skin as well as cracking of the lips,
• brittleness of hair and nails, hair loss,
• muscle and joint pain, enlargement of the liver and spleen,
• neurological symptoms (photophobia, disorientation, convulsions),
• in pregnant women, the risk of fetal developmental defects.

Vitamin E is one of the strongest antioxidants and plays an important role in many processes occurring in the body.

The name vitamin E encompasses two groups of organic compounds: tocopherols and tocotrienols, each of which has four forms: alpha, beta, gamma, and delta. The most biologically active form is alpha-tocopherol, which is the dominant component of vitamin E in food. The other forms, although less active, also perform important functions in the body.

Acting as an antioxidant, vitamin E neutralizes free radicals that can damage cell DNA, which limits the risk of cancer development. Its antioxidant properties also delay skin aging processes, improve its condition and appearance, and positively influence eye function.

Vitamin E protects cell membranes from oxidation, improves skin and hair condition. It regulates blood clotting by inhibiting platelet aggregation, preventing clots. It also acts beneficially on the cardiovascular system, improving vessel elasticity. By preventing lipid oxidation, it helps lower LDL cholesterol levels, which is important in limiting the formation of atherosclerotic plaques.

Vitamin E protects red blood cells from premature breakdown and also supports oxygen transport to muscles, increasing their performance. People with diabetes should particularly care about its proper level, as this vitamin increases cell sensitivity to insulin. Patients with Parkinson's and Alzheimer's diseases also benefit from its action, as it slows down brain aging processes. Additionally, vitamin E plays a key role in sperm production in men, and its deficiency can lead to fertility problems.

In pregnant women, vitamin E together with folic acid helps prevent neural tube defects in the developing fetus and supports its proper development. Supplementation of vitamin E in women can also alleviate premenstrual tension syndrome symptoms such as headaches, breast swelling, or nervousness.

Additionally, vitamin E strengthens the immune system by improving the function of cells protecting the body from infections, which increases overall immunity.

Vitamin E occurs mainly in plant products. The richest sources are vegetable oils such as sunflower, rapeseed, and corn oil. It is worth noting that cold-pressed oils contain about 75% more vitamin E than refined ones. Besides oils, vitamin E is also supplied in the diet by walnuts and peanuts, almonds, pumpkin seeds, whole grains, and green leafy vegetables such as cabbage, spinach, or lettuce.

Vitamin E is stable during cooking at high temperatures, but it is very sensitive to freezing as well as to oxygen and sunlight. Therefore, vegetable oils and vegetables should be stored in a cool, shaded place to prevent degradation of this vitamin.

The absorption of vitamin E can be reduced by using contraceptives, laxatives, and thyroid hormones. Meanwhile, vitamin A, vitamin C, B vitamins, manganese, selenium, and some unsaturated fatty acids help increase its absorption.

Negative effects on vitamin E activity include smoking and iron intake, which can weaken its protective action.

Daily requirements for vitamin E vary depending on age, gender, and physiological state. For adult women, it is about 8 mg, while for men about 10 mg. In older people, the dose increases to over 20 mg per day. For children, the recommended intake ranges from 6 to 15 mg, depending on age.

Pregnant and breastfeeding women should supply about 10-19 mg of vitamin E per day. Supplementation in athletes can be increased to 15-50 mg per day.

In the case of vitamin E supplementation, it is best to choose preparations containing natural forms of this vitamin, i.e., a mixture of various tocopherols: alpha-, beta-, gamma-, and delta-. Natural tocopherols occur as D-isomers (also called RRR-tocopherols), which are more biologically active than synthetic forms.

Preparations are also available on the market that, in addition to a mixture of tocopherols, contain tocotrienols — less known but also very beneficial forms of vitamin E, characterized by better penetration into cells and stronger antioxidant activity.

It is worth remembering that vitamin E is best absorbed when consumed with fats.

Vitamin E deficiency in people with a well-balanced diet is very rare, but when it occurs, it causes many unpleasant symptoms. These may include chronic fatigue, weakened concentration, and anemia. Deficiency also contributes to muscle function disorders, increased susceptibility to infections, and worsening of vision.

People particularly at risk of vitamin E deficiencies are those with celiac disease and cystic fibrosis, smokers, and women using contraceptives. Vitamin E deficiency may additionally manifest as muscle weakness, neurological problems such as hand tremors or motor coordination disorders, as well as dry and flaky skin and hair loss. Its deficit also leads to weakening of the immune system, increasing the risk of infections.

In the case of long-term deficiency, more serious ailments may occur, such as macular degeneration, ataxia (motor coordination disorders), and significant fertility problems in both sexes.

Excess vitamin E, especially in pregnant women, can be harmful to the body. The most common symptoms of excess include muscle weakness, fatigue, and gastrointestinal problems such as abdominal pain or diarrhea. Headaches and visual disturbances may also appear.

Toxic levels of vitamin E increase the risk of serious bleeding, as excess vitamin inhibits platelet aggregation. Long-term intake of very high doses of vitamin E can also increase the risk of heart failure and hemorrhagic stroke as well as reduce the effectiveness of oncological treatment such as radiotherapy or chemotherapy.

Vitamin E overdose usually occurs only with uncontrolled supplementation and doses exceeding 300 mg per day.

Coenzyme Q10 is a substance essential for the proper functioning of the body and has the potential to become a weapon in the fight against civilization diseases, and scientists are still searching for its new applications. Coenzyme Q10 (CoQ10) is a natural chemical compound found in animal and human organisms in two forms: ubiquinone (oxidized) and ubiquinol (reduced). It plays a key role in mitochondrial function, providing energy to the body at the cellular level. Cells with the highest energy requirements have the most mitochondria, and thus the greatest need for coenzyme Q10. Its importance is so significant that the discovery of these properties by biochemist Peter Mitchell was awarded the Nobel Prize in Chemistry in 1978.

Since the 1990s, preparations with coenzyme Q10 have gained popularity, making it currently one of the most popular dietary supplements in the world.

Coenzyme Q10 is a crystalline yellow substance with a characteristic odor. It is fat-soluble but not water-soluble. Coenzyme Q10 is photostable and exhibits high temperature resistance, thanks to which it does not lose its properties during various cosmetic production processes, where it is an active substance.

• It is one of the elements of the most important metabolic cycle (Krebs cycle). It participates in the mitochondrial respiratory chain, where it enables electron transfer and synthesis of adenosine triphosphate (ATP), which is the primary energy carrier for cells. Its highest concentrations occur in the heart muscle, liver, kidneys, and pancreas, where energy demand is greatest.
• It has the ability to transport electrons, thanks to which it has oxidizing-reducing properties. Therefore, it constantly exists in the body in two active forms – oxidized and reduced, which convert into each other in the presence of appropriate enzymes. The reduced form of coenzyme Q10 – ubiquinol – helps remove free radicals from the body, being a strong antioxidant. It detoxifies cells of toxins and serves as their first line of defense against free radical damage. It stabilizes cell membranes, maintaining their integrity and fluidity, which affects receptor and ion channel functions.
• As an antioxidant, it supports the immune and circulatory systems, positively influencing heart function, blood pressure, and metabolism. It participates in cell regeneration processes, slows down aging, protects DNA, proteins, and lipids of all cells, and has a positive impact on skin health and physical performance.
• It plays an important role in metabolic diseases, especially type 2 diabetes. In people with this disease, Q10 levels are significantly reduced, affecting metabolic disorders and increased oxidative stress. Q10 supplementation can improve insulin sensitivity, lower glycated hemoglobin (HbA1c) levels, and engage antioxidant enzymes, which helps control glucose levels and reduce diabetes complications. Additionally, coenzyme Q10 supports fat metabolism, positively affects the lipid profile, helps reduce the risk of atherosclerosis, and protects the cardiovascular system.
• Its levels naturally decline with age, which may contribute to circulatory system problems, muscle fatigue, weakened immunity, and aging-related processes. Q10 supplementation is also used in metabolic, cardiovascular, and neurodegenerative diseases due to its ability to improve mitochondrial function and provide antioxidant protection.
• Strong antioxidant action and high fat solubility make coenzyme Q10 useful not only in dietary supplements but also in cosmetics. It is widely used in anti-aging cosmetics aimed at slowing skin aging processes and reducing wrinkles.

Natural sources of coenzyme Q10 are primarily animal products and some plant-based ones. The most CoQ10 is found in:

• meat: especially beef, pork, and offal such as liver, heart, kidneys, and spleen,
• fish: rich in coenzyme Q10 are sardines, mackerel, salmon, tuna, and herring,
• poultry: for example, chicken thighs are a good source of this substance,
• vegetable oils: e.g., rapeseed oil, soy oil, corn oil, or olive oil,
• nuts and seeds: pistachios, almonds, sesame,
• vegetables: spinach, cauliflower, fresh broccoli, and broccoli sprouts contain moderate amounts of coenzyme Q10,
• legumes and whole grain products,
• fruits: strawberries, oranges.

Coenzyme Q10 is sensitive to high temperatures, so thermal processing can reduce its content in food. Its bioavailability also depends on the presence of fats in the diet, which support absorption. Additionally, to increase coenzyme Q10 levels, B vitamins can be supplemented, which enhance its endogenous synthesis.

Under physiological conditions, the synthesis of coenzyme Q10 meets the body's needs. The highest concentration of this compound in tissues is observed around the age of 20. Coenzyme Q10 deficiency can manifest with many undesirable symptoms and negatively affect health. Typical symptoms include chronic fatigue, muscle weakness, headaches, sleep problems, and decreased immunity. CoQ10 deficiency can also lead to heart function disorders, reduced physical performance, and in the long term, contribute to the development of chronic diseases, including cardiovascular and neurodegenerative ones. Additionally, the body with deficiency has difficulties producing energy at the cellular level, resulting in reduced metabolic efficiency and faster cell aging.

Causes of deficiency include:

• natural decline in coenzyme Q10 production with age,
• increased demand in physically active people and those living in polluted environments, chronic stress,
• use of certain medications, e.g., statins,
• metabolic diseases and genetic disorders of CoQ10 synthesis,
• inappropriate diet, poor in components needed for its biosynthesis (e.g., B6 deficiency), smoking,
• genetic or acquired defects in synthesis or utilization of CoQ10,
• increased tissue demand for CoQ10 in the course of disease states (e.g., hyperthyroidism, cardiovascular diseases, cancer, muscle disorders, neurodegenerative diseases).

Dosing of coenzyme Q10 depends on age, health status, and the purpose of supplementation.

• For younger people and for preventive purposes, doses of 30 to 100 mg per day are typically used, often once in the morning.
• In older people and patients with heart diseases, doses may be higher, even up to 100 mg three times a day (300 mg per day) or in specific cases up to 600 mg per day, of course under medical supervision.
• In supplements, common doses are 100 mg per capsule, taken once or twice a day during a meal containing fat for better absorption.
• Supplementation should last at least 4 weeks, but optimal effects are achieved with use for at least 12 weeks.
• After the initial period (e.g., two weeks of higher loading dose), maintenance doses of 10-30 mg per day can be used.
• Coenzyme Q10 is well tolerated but may cause mild gastrointestinal discomfort. It is not recommended for pregnant and breastfeeding women without medical consultation.

Coenzyme Q10 in the form of ubiquinol is considered more bioavailable and biologically active. Ubiquinol is the reduced form of coenzyme Q10, ready for immediate use by the body, particularly effective as an antioxidant. It is more easily absorbed, especially in older people or those who have reduced ability to convert ubiquinone (oxidized form) to ubiquinol.

Ubiquinone, although an oxidized form that requires conversion to active ubiquinol in the body, is more stable, more extensively studied, and usually more affordable. For younger, healthy people who naturally convert ubiquinone to ubiquinol well, ubiquinone can be equally effective.

• Used in therapy of diseases related to mitochondrial damage, heart diseases, inflammatory conditions, and neurodegenerative diseases.
• Helps improve physical performance and body regeneration.
• Popular ingredient in anti-wrinkle cosmetics due to antioxidant action.

Supplementation with coenzyme Q10 shows beneficial effects in several mitochondrial diseases, which are often characterized by cellular energy deficits and oxidative stress.

Among these diseases that respond to Q10 supplementation are:

• mitochondrial myopathy, especially associated with mutation in the POLG gene, where Q10 improves mitochondrial functions and increases energy levels,
• mitochondrial encephalopathies, e.g., Leigh syndrome and Kearns-Sayre syndrome, where CoQ10 can reduce oxidative damage and support ATP production,
• neurodegenerative diseases with mitochondrial basis, such as Parkinson's disease and some forms of amyotrophic lateral sclerosis (ALS),
• coenzyme Q10 deficiencies caused by mutations in genes involved in CoQ10 biosynthesis (e.g., mutation in the COQ9 gene), where supplementation is key to improving the respiratory chain and energy production.

Excess coenzyme Q10 is rare because the body largely self-regulates its levels and eliminates excess. However, with long-term use of high doses of supplements, side effects such as abdominal pain, diarrhea, nausea, dizziness, rash, irritability, or sleep problems may occur. These symptoms are usually mild and subside after reducing the dose or discontinuing supplementation. Supplementation should be carried out cautiously in the case of warfarin use, as coenzyme Q10 may weaken its action. Caution should also be exercised in pregnant and breastfeeding women. In the case of taking certain medications with which CoQ10 may interact specifically, such as anthracyclines, tamoxifen, timolol, vitamin K antagonists, medical consultation is necessary.

Results of conducted studies confirm that oral supplementation with CoQ10 can also positively affect the skin - administered this way, it reaches skin cells (keratinocytes), increasing their resistance to oxidative stress and harmful UV radiation effects. Coenzyme Q10 also increases DNA synthesis in skin cells and production of hyaluronic acid, which protects collagen and supports proper skin hydration.

Slowing of biological renewal processes occurring with age is associated with a decrease in coenzyme Q10 concentration in the body. Increased supply of this compound, especially in the reduced form, can slow down aging processes. These properties of coenzyme Q10 are used in the production of anti-aging cosmetics aimed at improving skin firmness.

• Several weeks of coenzyme Q10 application on the skin causes fading of existing wrinkles and delays the formation of new ones, as well as increased hydration and skin elasticity.
• Coenzyme Q10 also protects the skin from hypoxia and environmental pollution.
• Ongoing research includes the use of coenzyme Q10 as a natural sunscreen with low irritation risk.
• The anti-aging effect is also used in the production of oral nutraceuticals to help ensure beautiful and youthful-looking complexion.

Absorption of coenzyme Q10 by our body is slow and incomplete, so it takes some time to see the effects of its use. After oral intake, coenzyme Q10 reaches maximum plasma concentration only after 6 to even 23 hours, and then is distributed throughout the body. Full effects of supplementation should be visible after 2-3 months of use.