ID 14 -
Witamina A
PL: Witamina A
EN: Vitamin A
Pdf: vitamin A
Oświadczenie (4)
- Witamina A przyczynia się do prawidłowego funkcjonowania układu odpornościowego
- Witamina A przyczynia się do prawidłowego różnicowania komórek
Oświadczenie (2)
- Różnicowania się komórek, w tym układ odpornościowy
1. Charakterystyka żywności / składnika
The food constituent that is the subject of the health claims is vitamin A which is a well recognised nutrient. It is measurable in foods by established methods.
The term vitamin A describes a group of lipid soluble compounds related metabolically to all-trans-retinol. In the diet, vitamin A is found in products of animal origin, as retinyl esters, mainly retinyl palmitate. Other esters (oleate, stearate, myristate), and retinol contribute to the dietary vitamin A intake. Some carotenoids (α- and β-carotenes, β-cryptoxanthine) can be cleaved into retinol, via an enzymatic process in the small intestine. Retinoic acids are considered as the molecular species responsible for all the functions attributed to vitamin A, with the exception of vision, where only retinal is able to exert an action (SCF, 2002).
Different forms of vitamin A are authorised for addition to foods and for use in food supplements (Annex II of the Regulation (EC) No 1925/20064 and Annex II of Directive 2002/46/EC5). This evaluation applies to vitamin A naturally present in foods and those forms authorised for addition to foods and for use in food supplements (Annex II of the Regulation (EC) No 1925/2006 and Annex II of Directive 2002/46/EC).
The Panel considers that the food constituent, vitamin A, which is the subject of the health claims is sufficiently characterised.
2.1. Różnicowanie komórek (ID 14)
The claimed effect is “cell differentiation including immune system”. The Panel assumes that the target population is the general population.
The Panel considers that normal cell differentiation is beneficial to human health.
2.2. Funkcjonowanie układu odpornościowego (ID 14)
The claimed effect is “cell differentiation including immune system”. The Panel assumes that the target population is the general population.
The Panel considers that a normal function of the immune system is beneficial to human health.
3. Naukowe uzasadnienia wpływu na zdrowie człowieka
It is recognised that vitamin A is important for normal vision, gene expression, reproduction, embryonic development, growth and immune function (IoM, 2001). Vitamin A deficiency signs include impaired dark adaptation, abnormal electroretinograms, follicular hyperkeratosis and lowered blood haemoglobin (SCF, 1992).
3.1. Różnicowanie komórek (ID 14)
Vitamin A binds to nuclear retinoid receptors leading to either the activation or the inhibition of gene expression. Depending on the cell line and dosage, cell differentiation can be stimulated or inhibited. In animal models, it has been shown that vitamin A is involved in the differentiation of the epithelium, mainly in the respiratory tract (Biesalski et al., 1995). In rapidly dividing cells, retinoids efficiently inhibit progression through the cell cycle and induce cell differentiation. Although almost all studies of retinoid mechanisms have been conducted in isolated cells, good congruence exists between their action in cells and their effect in intact animals or humans (Ross, 2006).
The Panel notes that vitamin A is involved in the differentiation of many cells showing either an inhibiting or stimulating effect.
The Panel concludes that a cause and effect relationship has been established between the dietary intake of vitamin A and normal cell differentiation. However, the evidence provided does not establish that inadequate intake of vitamin A leading to impaired cell differentiation occurs in the general EU population.
3.2. Funkcjonowanie układu odpornościowego (ID 14)
It has been reported that all-trans-retinoic acid stimulates the proliferation of T-lymphoid cells, while it inhibits the proliferation of B-cells and B-cell precursors. In particular, the lymphocyte response to mitogens is highly retinoid dependent. Retinoic acid also exerts an effect on the T-helper cell balance by suppressing Th1 development and enhancing Th2 development. In addition, it is has been indicated that vitamin A deficiency enhances macrophage-mediated inflammation by increasing production of IL-12 and IFN-γ, but impairs the ability of macrophages to ingest and kill bacteria. Dentritic cells are also a target of retinoic acid. It regulates the survival and antigen presentation by immature dentritic cells, as well as the maturation of immature to mature dentritic cells. Other effects of vitamin A on the immune system are related to apoptotic effects on immune-competent cells during back regulation of immune reactions and during thymic selection and to the alteration of genes relevant to the immune response (Ruhl, 2007).
The efficacy of supplementing vitamin A on infection rates has been examined in several randomised, double-blind, placebo-controlled trials of malnourished children in various regions of the developing world. Antibody-mediated immunity has been shown to be severely impaired in children with vitamin A deficiency. Providing vitamin A supplements has been found to improve the antibody titer response to measles vaccines, maintain gut integrity, lower the incidence of respiratory tract infections, and reduce mortality associated with diarrhoea and measles but not pneumonia. There are clinical data suggesting that vitamin A deficiency in HIV-1-infected individuals contributes to mortality, disease progression, and maternal-infant disease transfer (Field et al., 2002).
The Panel concludes that a cause and effect relationship has been established between the dietary intake of vitamin A and a normal function of the immune system. However, the evidence provided does not establish that inadequate intake of vitamin A leading to impaired function of the immune system occurs in the general EU population.
4.1. Różnicowanie komórek (ID 14)
The Panel considers that the following wording reflects the scientific evidence: “Vitamin A contributes to normal cell differentiation.”
4.2. Funkcjonowanie układu odpornościowego (ID 14)
The Panel considers that the following wording reflects the scientific evidence: “Vitamin A contributes to a normal function of the immune system.”
5. Warunki i możliwe ograniczenia stosowania oświadczenia
The Panel considers that in order to bear the claims a food should be at least a source of vitamin A as per Annex to Regulation (EC) No 1924/2006. Such amounts can be easily consumed as part of a balanced diet. The target population is the general population. Tolerable Upper Intake Levels (UL) for pre-formed vitamin A have been established for children and adults. The Tolerable Upper Intake Level for adults has been set at 3000 µg RE/day (SCF, 2002).
Warunki i możliwe ograniczenia stosowania oświadczenia
15% RDA of vitamin A is equivalent to 720 micrograms beta-carotene. Applicable to both adults and children.