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Sources and physiological effects

Dietary sources
Beta-carotene belongs to the group of carotenoids. Beta-carotene is an orange-red plant pigment. Carrots and pumpkin are especially rich in beta-carotene as are yellow and orange fruits such as persimmons, apricots, papayas, mangos, nectarines, peaches, pears, sea buckthorn and dark green vegetables such as spinach, broccoli, endive, chicory, cress, beetroot and dandelion leaves.
Physiological effects
Provitamin A	Beta-carotene is an important fat-soluble precursor to vitamin A and is converted to retinol in the intestinal mucosa.
Antioxidant	Free radical scavenger Inhibition of lipid peroxidation Antioxidative UV protection
Immune defense	Increase in NK cell activity Proliferation of B and T cells

EFSA Health Claims

Health Claims		EFSA Opinion
Beta-carotene	Contributes to the normal function of the immune system Contributes to the maintenance of mucous membranes Contributes to the maintenance normal vision Contributes to the maintenance of healthy skin

Recommended intake

D-A-C-H reference values for the intake of beta-carotene (Reference values EFSA and NHI )
	Age	Beta-carotene-retinol (mg equivalent)
Infants (months)
	0-4	0,5
	4-12	0,6
Children (Years)
	1-4	0,6
	4-7	0,7
	7-10	0,8
	10-13	0,9
	13-15	1,05
Youth/Adults (years)		Women	Men
	15-19	0,9	1,1
	19-25	0,8	1,0
	25-51	0,8	1,0
	51-65	0,8	1,0
	> 65	0,8	1,0
Pregnant women	1,1
Nursing mothers	1,5
Higher demand
Special groups at risk of for deficiency	Individuals with high sun exposure, diabetes mellitus or macular degeneration

Reccomended intake according to food labelling regulation		Beta-carotene
Conversion into retinol equivalents (REs): (6 µg beta-carotene = 1 µg RE = 1 µg vitamin A). Example: 6 mg Beta-Carotin = 1000 µg Vitamin A 1 mg Beta-Carotin = 167 µg Vitamin A		N/A
Safe level of intake
UL	Long-term daily intake, where no adverse health effects are expected (EFSA: valid for general population including heavy smokers).	15 mg/d
NOAEL	Maximum ingestion dose that has no reported harmful effect. Available studies report no side effects at doses of 25 mg/d over	N/A
Safety	The EFSA has been investigating the safety of beta-carotene.

Status according to Austrian Nutrition Report 2012

Beta-carotene status in schoolchildren

Fig.1: Beta-carotene status assessment compared to beta-carotene intake in schoolchildren (7-14 years), by sex

Beta-carotene status in adults

Fig. 2: Beta-carotene status assessment compared to beta-carotene intake in adults (18 - 64 years), by sex

Beta-carotene status in seniors

Fig. 3: Beta-carotene status assessmen in comparison to beta-carotene intake in seniors (65-80 years), by sex

Detailed information

Carotenoids and their physiological functions

As effective antioxidants, carotenoids can bind free peroxyl radicals and singlet oxygen and prevent lipid peroxidation by UVB, X-rays and cosmic radiation. The different carotenoid forms have different applications, but they complement and strengthen each other in their functions.
One of the most important carotenoids is beta-carotene, which acts as a bioactive precursor to vitamin A. Therefore it is indirectly, but nevertheless substantially involved in embryonic development, visual function and cell differentiation of the endothelia. Beta-carotene itself is stored in the skin and in the cells of the retina to act directly as an antioxidant against UV-induced free radicals.

UV protection by carotenoids

Photooxidative processes play an essential role in the development of skin changes and skin damage. Increased UV exposure not only occurs during the summer and holiday seasons, but can also occur during short outdoor exposure, during which topical sun protection (sunscreen) is usually dispensed with. Carotenoids, especially beta-carotene, are used for long-term prevention of UV damage. An intake of 15 - 30 mg beta-carotene per day over a period of 10 weeks leads to reduced development of UV-induced erythema (1). Another study also demonstrated that increased intake of 30 mg of beta-carotene per day significantly protects the skin against aging (2). However, additional topical preventative measures are essential to ensure complete protection during strong sun exposure.

Carotenoids for tumor prevention

The carotenoids are also of interest for cancer prevention due to their antioxidant properties. As potent stimulators of cell-mediated immune defense and by inhibition of the initiation of tumor cell growth, significant anticarcinogenic effects can be achieved through optimized intake. Epidemiological studies, e.g. the Linxian study, clearly show a connection between beta-carotene, vitamin E and selenium intake and a reduced cancer risk (3). Increased carotenoid and carotenoid plasma levels in men correlate with a reduced risk of prostate cancer, but cannot prevent disease progression (4)(5). This correlates with in vivo studies showing that beta-carotene primarily inhibits the initiation of tumor cells, but not its progression (3).

Natural sources of carotenoids

The green seaweed Dunaliella salina is suitable for therapeutic use for various indications as it is a concentrated and readily available natural source of carotene and carotenoid compounds. Clinical studies have also shown that Dunaliella carotenoids offer higher antioxidant protection (6) and improved biological activity (7) compared to synthetic beta-carotene or a sole beta-carotene supplement. In combination with the oxygen-containing carotenoids zeaxanthin and lutein, which are xanthophylls found in the marigold flower, a synergistic compound is formed which acts as an efficient antioxidant system on multiple target organs. Even in higher doses, carotenoids from marigolds have no proven negative effects (8).

Beta-carotene supplementation in smokers

The results of various intervention studies (e.g. the CARET study and ATBC– study) regarding beta-carotene supplementation and lung cancer risk have lead to confusion regarding the use of carotenoid supplements in smokers. Although these studies found an increase in the risk of lung cancer in the participating smoking subjects, a more detailed analysis of the results led experts to the now accepted opinion that the selection of participants in these studies did not meet the requirements of a primary preventive study design. Both studies were in a high-risk collective of relatively old, chronic smokers (3). The intake of beta-carotene in both studies was also in the upper intake range of 20 mg/day.
Nonetheless, in chronic, older smokers an orthomolecular strengthening of antioxidant systems via polyphenols from green tea is preferred.

Disputed beta-carotene restriction in pregnant and breastfeeding women

Vitamin A is one of the critical vitamins during pregnancy and lactation, as requirements increase by 40% in pregnant women and by up to 90% in breastfeeding women. Vitamin A is particularly required for the development and maturation of the child's lungs. However, long-term overdose can cause damage to the fetus. However, this does not apply to beta-carotene as a precursor of vitamin A. Nevertheless, national authorities have imposed restrictions on beta-carotene intake for pregnant women, and in some countries, beta-carotene has been completely banned in vitamin supplements for pregnant women. This measure is heavily criticized by leading nutritionists and physicians. Prof. Hans Konrad Biesalski (University of Hohenheim, Germany) urges that the warnings regarding beta-carotene on the labels be reconsidered and that pregnant and lactating women should instead be made aware of the dangers of a vitamin A or beta-carotene deficiency for the development of the fetus (9).

Reference values

Parameter	Substrate	Reference value	Description
Beta carotene	Serum/plasma	150 - 1250 µg/l	Fasting (12 h nil by mouth). High pressure liquid chromatography with UV detection after deproteinization of the serum samples and subsequent extraction of beta-carotene in n-hexane.
Interpretation
Low values		Inadequate intake of beta-carotene
Hight values		Supplementation with beta-carotene preparations. Beta-carotene has a long half-life, therefore levels return back to normal after several weeks.

Deficiency symptoms

Impact	Symptoms
Oxidative Stress	Reduced oxidation of LDL particles and PUFAs in cell membranes
Skin	Decrease in erythema
Free radical associated diseases	High risk of heart attack, cataract and tumors
Immune system	Higher susceptibility to infections Decrease in cell-mediated immunity

Indications

Effect	Indication	Dosage
Physiological effects at low nutrient intake	For prevention and therapy support in age-related macular degeneration (AMD)	15 - 60 mg/d
	For protection and prevention of free radical associated diseases, especially of the skin and eyes	5 - 20 mg/d
	Prevention and therapy for cardiovascular diseases	5 - 30 mg/d
	Tumor prevention and complementary therapy of tumor diseases	5 - 30 mg/d



Pharmacological effects at high nutrient intake	Support of the body's natural protection against UV-induced erythema	100 - 180 mg/d

Administration

General mode of administration
When	Beta-carotene should be taken with or after meals. Notes: To reduce skin photosensitivity, beta-carotene should be taken 4 weeks prior to sun exposure.
Side effects
Beta-carotene can lead to a harmless yellowing of the skin at long term and high doses (> 3 weeks, > 30 mg/d). Beta-carotene cannot cause hypervitaminosis of vitamin A.
Contraindications
Liver damage, renal failure

Interactions

Drug interactions
Estrogens (medroxyprogesterone)	Medroxyprogesterone may alter beta-carotene and vitamin A levels
Anthelmintics (e.g. pyrantel, mebendazole)	Vitamin A deficiency is associated with an increased risk of worm infections. Vitamin A or beta-carotene intake improves therapy against these infections.
Nutrient interactions
None	No relevant interactions known to date.

Description and related substances

Description

β-Carotene is a fat-soluble provitamin, which occurs exclusively in plants, but can also be produced synthetically.

References

1) Stahl, W., Krutmann, J. 2006. Systemische Photoprotektion durch Karotinoide.

2) Cho, S. et al. 2010. Differential Effects of Low-Dose and High-Dose Beta-Carotene Supplementation on the Signs of Photoaging and Type I Procollagen Gene Expression in Human Skin in vivo. Dermatology 221, Nr. 2: 160–171. doi:10.1159/000305548.

3) Hahn, A. et al. 2005. Ernährung. Physiologische Grundlagen, Prävention und Therapie.

4) Chang, S. et al. 2005. Relationship Between Plasma Carotenoids and Prostate Cancer. Nutrition and Cancer 53, Nr. 2: 127–134. doi:10.1207/s15327914nc5302_1.

5) Persson, C. et al. 2008. Plasma levels of carotenoids, retinol and tocopherol and the risk of gastric cancer in Japan: a nested case-control study. Carcinogenesis 29, Nr. 5:1042–1048. doi:10.1093/carcin/bgn072.

6) Murthy, K. et al. 2005. In vivo antioxidant activity of carotenoids from Dunaliella salina — a green microalga. Life Sciences 76, Nr. 12:1381–1390. doi:10.1016/j.lfs.2004.10.015.

7) Murthy, K. et al. 2005. Comparative Evaluation of Hepatoprotective Activity of Carotenoids of Microalgae. Journal of Medicinal Food 8, Nr. 4:523–528. doi:10.1089/jmf.2005.8.523.

8) Harikumar, K. B. et al. 2008. Toxicity Profile of Lutein and Lutein Ester Isolated From Marigold Flowers (Tagetes erecta). International Journal of Toxicology 27, Nr. 1:1–9. doi:10.1080/10915810701876265.

9) Strobel, M. et al. 2007. The importance of β-carotene as a source of vitamin A with special regard to pregnant and breastfeeding women. European Journal of Nutrition 46, Nr. S1:1–20. doi:10.1007/s00394-007-1001-z.

References Interactions:

Stargrove, M. B. et al. Herb, Nutrient and Drug Interactions: Clinical Implications and Therapeutic Strategies, 1. Auflage. St. Louis, Missouri: Elsevier Health Sciences, 2008.

Gröber, U. Mikronährstoffe: Metabolic Tuning –Prävention –Therapie, 3. Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2011.

Gröber, U. Arzneimittel und Mikronährstoffe: Medikationsorientierte Supplementierung, 3. aktualisierte und erweiterte Auflage. Stuttgart: WVG Wissenschaftliche Verlagsgesellschaft Stuttgart, 2014.