Saturday, August 18

Carotene in carrots - Orange skin discoloration

Orange skin discoloration - Carotene in carrots
Excess consumption of carotene in carrots causes orange yellow skin discoloration. The β-carotene in carrots contributes to its orange color.
Though cosmetically displeasing to some, there is no apparent health impact of orange skin discoloration (carotenemia). However possible health effects of this condition have to be well researched.

Carotene in carrots

Carrots ((Daucus carota subsp. sativus) belong to Apiaceae family and are cultivated throughout the world. In a research study done in Netherlands it was found that regular consumption of carrots lowered the risk of cardiovascular disease (CVD). It was found to be due to the antioxidant activities of the carotenoids and polyacetylenes (falcarinol and falcarindiol) present in carrots.

Carotenes are a type carotenoids (tetraterpenoid organic pigments) which lack oxygen in their structure and are pure hydrocarbons. These fat-soluble carotenoids occur in the chloroplasts and chromoplasts of plants and occur in higher concentrations in some plants as in carrots giving them orange color.

Professor Heinrich Wilhelm Ferdinand Wackenroder (8 March 1798 – 4 September 1854), a German chemist and a professor at the University of Jena, isolated carotin (carotene) from carrots. Its structure was determined by Professor Paul Karrer (April 21, 1889 - June 18, 1971, a Nobel laureate, in early 1930s. Alpha-carotene present in carrots is found to be protective against the proliferation of human cancer cells.

β-carotene (C40H56) is the most studied of about fifty carotenoids identified in the human diet. Carrots are high in the (all-E)-beta-carotene isomer. It is an isomer form having higher bioavailability, provitamin A activity, and antioxidant activity when compared to Z (cis) isomer form of this carotenoid. The levels of all three Z isomers in raw carrots are low and are about 1.8% of the total isomers. Storage at low temperatures in fact increases the (all-E)-beta isomers.

There is thermal isomerization during cooking of carrots causing generation of all the three Z isomers. To get the maximum benefits, carrots should be stored at low temperatures. Carrots should be consumed raw or boiled for less than fifteen minutes to limit Z isomerization.

β-Carotene in fruits and vegetables

The β-carotene in many fruits and vegetables contributes to orange color. Orange and yellow fruits like mangoes, cantaloupe and papayas and orange roots like yam and carrots are rich sources of this carotenoid.

Though the Vietnamese gac fruit (Momordica cochinchinensis) and crude palm oil contain the highest amount of β-carotene, nearly ten times higher than carrots, gac fruit is less known outside Southeast Asia and the crude palm oil loses the β-carotene while processing and refining.

Carrots and yellow/orange skin discoloration

Excessive consumption of fruits and vegetables containing β-carotene causes carotenosis (carotenodermia, carotenemia or hypercarotenemia), a harmless condition giving a yellow-orange tint to the epidermis. This is due to deposition of these carotenoids in the outermost epidermal layer of skin.

This yellow-orange discoloration differs from that caused by the jaundice disease. In jaundice apart from yellowish pigmentation of the epidermis, the conjunctival membranes over the sclerae (whites of the eyes) also turn yellow whereas in carotenodermia sclerae remain white.

Carotenes have vitamin A activity and get partially converted into vitamin A (retinol) within the intestinal mucosa by a dioxygenase enzyme. If the vitamin A status of the individual is high, the conversion decreases and the excess carotenoids are stored/deposited in the fat tissues and epidermal layers. These carotenoids are deposited in the intercellular lipids of the stratum corneum of the skin.

Though the orange coloration can be generalised, it is more prominent in areas where stratum corneum is thicker and also in areas where there is profuse sweating. Palms, soles, nasolabial folds and behind ears are more prone to discoloration. The orange discoloration of epidermis reverses on cessation of consumption of carrots and other foods containing this carotenoid.

Some underlying health disorders may cause secondary carotenemia wherein increased serum lipids and decreased metabolism of carotenoids are the causes. In such cases treating the disease condition will resolve carotenemia.

If the orange skin discoloration is due to excess consumption of carrots, fruits or other vegetables, cessation of excess intake will reverse the skin condition without any blemishes, spots and marks.


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References:
1.Imsic M, Winkler S, Tomkins B, Jones R. Effect of storage and cooking on beta-carotene isomers in carrots ( Daucus carota L. cv. 'Stefano'). J Agric Food Chem. 2010 Apr 28;58(8):5109-13.
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