Carotenoids

Synonym(s): Beta carotene, lutein, lycopene, zeaxanthin

Nutrient group: vitaminoids, Antioxidants

Sources and physiological effects

Dietary sources
The plant precursors of vitamin A (retinol) are called carotenoids, which can be converted into vitamin A in the body. Plant foods provide vitamin A precursors, beta-carotene being the most important provitamin. Other common carotenoids are lycopene, which is frequently found in tomatoes, and the oxygen-containing carotenoids lutein and zeaxanthin, which belong to the group of xanthophylls and occur in the marigold flower. Since carotenoids are natural pigments with a yellow to reddish coloring, color-intensive yellow, orange and red vegetables and fruits, such as carrots, apricots, mangos and papayas, are particularly rich in these substances. Dark green leafy vegetables, such as spinach and kale, also contain significant amounts of the provitamins.
Physiological effects
Provitamin A	Beta-carotene is an important fat-soluble precursor to vitamin A and is reduced to retinol in the intestinal mucosa.
Eye	Lutein occurs together with zeaxanthin as a pigment in the retina, especially in the macula lutea. Protection against UV radiation.
Antioxidant	Important role as a free radical scavenger. Antioxidants “defuse“ free radicals either by acting as electron donors or by breaking down the radical molecule.
Antithrombotic	Stabilization of platelet form by inhibition of thrombin-induced aggregation and inhibition of glycoprotein 2b/3a.

Recommended intake

Increased demand

High sun exposure, diabetes mellitus, macular degeneration

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 elevated radiation. The different carotenoid forms have different applications, but can 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. Thus, it is indirectly, but nevertheless substantially involved in embryonic development, visual function and cell differentiation of the endothelia. Beta-carotene itself is increasingly stored in the skin and in the cells of the retina, where it can act directly as an antioxidant against UV-induced free radicals.

Photo protection by carotenoids

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

Carotenoids for tumor prevention

The carotenoids are also of interest for preventive use in various cancers due to their pronounced antioxidant properties. As potent stimulators of the cell-mediated immune defense and by inhibiting the activation of tumor cells, significant anticarcinogenic effects can be achieved through optimized intake. Epidemiological studies, e.g. the Linxian study, clearly showed a connection between beta-carotene, vitamin E and selenium administration 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 coincides with in vivo studies that show that beta-carotene primarily inhibits the initiation of a tumour cell, but not its progression (3).

Carotenoid protection against macular degeneration

Lutein and zeaxanthin are responsible for pigmentation in the central part of the retina, the so-called "yellow spot". There are the photoreceptors, which enable the recognition of fine details and the differentiation of colors. Increased UV exposure of these cells leads to increased oxidative stress in this part of the retina. If antioxidant protection is insufficient, the visual cells of the yellow spot degenerate, ultimately leading to age-related macular degeneration (AMD), the main cause of visual impairment and blindness in older people in industrialized countries. Lutein and zeaxanthin protect against damage from UV radiation (6) and prevent the formation of peroxides via their antioxidant properties. Several epidemiological studies confirm that people with a carotene-rich diet have a significantly lower risk of developing AMD or senile cataracts (7). The protective properties of zeaxanthin and lutein were confirmed in the French POLA (Pathologies Oculaires Liées à l’Age) study. Lowered zeaxanthin and lutein plasma values correlate significantly with the occurrence of AMD, while the zeaxanthin values in plasma correlate inverse with the occurrence of cataracts (8). The CARED study (Carotinoid in the Age-Related Eye Disease Study) confirms that women with a high intake of lutein and zeaxanthin showed 23% less cataracts (9). The ARED (Age-Related Eye Disease Study) showed that a combination of carotenoids, vitamin C, vitamin E and zinc counteracts AMD progression in the early stages (10).

Natural sources of carotenoids

The green seaweed Dunaliella salina is suitable for therapeutic use in 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 (11) and improved biological activity (2) compared to synthetic beta-carotene or a sole beta-carotene supplementation. In combination with the oxygen-containing carotenoids zeaxanthin and lutein, which belong to the group of xanthophylls and are found in marigolds, a synergistic compound is formed which acts as an efficient antioxidant system at target organs. Even in higher doses, carotenoids from marigolds have no proven negative effects (13).

Reference values

Parameter	Substrate	Reference value	Description
Lutein + Zeaxanthin	Serum	159 - 728 µg/l	Single parameter (LUTE)

Deficiency symptoms

Impact on	Symptoms
Eye	Decrease in macular pigment density Favors age-related macular degeneration
Oxidative Stress	Increased 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	More susceptible to infections Decrease in cell-mediated immunity

Indications

Effect	Indication	Dosage
Physiological effects at a low 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 the eyes	5 - 20 mg/d
	Prevention and therapy for cardiovascular diseases	5 - 30 mg/d
	Tumor prevention and complementary therapy tumor diseases	5 - 30 mg/d



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

Administration

General mode of administration
When	Carotenoids should be taken with or after meals.
Side effects
Beta-carotene can lead to harmless yellowing of the skin at long term and high doses (> 3 weeks, > 30 mg/d).
Contraindications
Liver damage, renal failure

Interactions

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

Description and related substances

Description

Fat-soluble carotenoids

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(2):160-71

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

4) Chang, S. et al. 2005. Relationship between plasma carotinoids and prostate cancer. Nutr

Cancer. 53(2):127-3.

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) Hsu, Y. W. et al. 2008. Protective effects of Dunaliella salina – A carotenoids-rich alga, against carbon tetrachloride-induced hepatotoxicity in mice. Food and Chemical Toxicology 46, Nr. 10: 3311–3317. doi:10.1016/j.fct.2008.07.027.

7) Ribaya-Mercado, J. et al. 2004. Lutein and Zeaxanthin and Their Potential Roles in Disease Prevention. Journal of the American College of Nutrition 23, Nr. sup6. doi:10.1080/07315724.2004.10719427.

8) Delcourt, Cecile, I. et al. 2006. Plasma Lutein and Zeaxanthin and Other Carotenoids as Modifiable Risk Factors for Age-Related Maculopathy and Cataract: The POLA Study. Investigative Opthalmology & Visual Science 47, Nr. 6 (January): 2329. doi:10.1167/iovs.05-1235.

9) Moeller, S. M. 2008. Associations Between Age-Related Nuclear Cataract and Lutein and Zeaxanthin in the Diet and Serum in the Carotenoids in the Age-Related Eye Disease Study (CAREDS), an Ancillary Study of the Women's Health Initiative. Archives of Ophthalmology 126, Nr. 3 (January): 354. doi:10.1001/archopht.126.3.354.

10) Anon. 2001. A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E and Beta Carotene for Age-Related Cataract and Vision Loss. Archives of Ophthalmology 119, Nr.10 (January): 1439. doi:10.1001/archopht.119.10.1439.

11) 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.

12) 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.

13) 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.

References Interaktion:

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.