Online Resources


5 Hot Carotenoids

By Yousry Naguib, Ph.D.
Functional Foods & Nutraceuticals, March 2003

Epidemiological studies have spurred heightened interest in carotenoids as dietary supplements. High intakes of certain fruits and vegetables rich in carotenoids may significantly reduce the risk of cardiovascular diseases, cancer and some aspects of ageing. Yousry Naguib, PhD, investigates
Although formulators may be tempted to create a cocktail of carotenoids that provides a full spectrum of health benefits, it is advised to take into consideration the health benefit to be targeted

Carotenoids are a fat-soluble group of naturally occurring plant pigments. Fruits and vegetables get their vibrant colour from carotenoids. Approximately 600 carotenoids have been isolated from plants and animals. Of these, about 50 are present in a typical diet containing fruits and vegetables, and about 20 of them have been identified in our bodies.

Chemically, carotenoids can be divided into two main categories: carotenes and xanthophylls. Carotenes refer to carotenoids, which contain only carbon and hydrogen, such as beta-carotene, alpha-carotene and lycopene. Xanthophylls refer to compounds that contain an additional hydroxyl group (as with lutein, zeaxanthin and beta-cryptoxanthin), keto group (e.g., canthaxanthin) or both (e.g., astaxanthin).

Since humans cannot make carotenoids de novo, they depend upon the diet, exclusively, as the source of these important nutrients. Leafy green vegetables such as spinach and Brussels sprouts contain mostly lutein and zeaxanthin, while orange and yellow vegetables such as carrots, sweet potatoes and squash contain predominantly carotenes. Of all the carotenoids, alpha-carotene, beta-carotene and cryptoxanthin are the main vitamin A precursors.

Carotenoids are considered potential membrane antioxidants due to reactivity with singlet oxygen and oxygen free radicals. Singlet oxygen has been implicated in biological systems and is capable of damaging proteins, lipids and DNA and therefore is thought to be involved in the pathogenesis of numerous diseases. The anti-cancer activity of carotenoids may be, at least in part, attributable to its antioxidant activity insofar as oxygen radicals are related to the processes leading to human cancer.

People who eat a variety of antioxidant-rich foods are less likely to develop certain cancers than people whose diets lack antioxidants2. Increasing the intake of fruits and vegetables in an at-risk cancer population also increased serum carotenoids levels. A year-long randomised, controlled intervention study of men and women with a recent history of adenomas revealed that increasing intake of fruits and vegetables to at least eight servings per day increased by 11 per cent to 54 per cent plasma levels of these five carotenoids: alpha- and beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin.5
In a study published in 1994, researchers found that men with high serum carotenoid levels had a coronary artery disease event rate 60 per cent less than those with the low carotenoid levels.3

Researchers studied the effect of increased fruit and vegetable intake on the plasma levels of lutein, lycopene, beta-carotene and vitamin E and susceptibility of low-density lipoprotein (LDL) to oxidation in smokers and non-smokers. Volunteers increased their intake of fruits and vegetables to provide 30mg/day of carotenoids for two weeks. The carotenoid levels increased 23 per cent in smokers and 11 per cent in nonsmokers, and the resistance of LDL to oxidation increased by 14 per cent in smokers and by 28 per cent in nonsmokers. The study suggested that carotenoids’ inhibitory effect on LDL oxidation might be the underlying mechanism in their protective effect on cardiovascular disease.4

Lutein and Zeaxanthin
Lutein and zeaxanthin are found in egg yolks, marigold flowers and leafy green vegetables such as spinach, broccoli winter squash. Lutein was first extracted from the corpus luteum, and hence its name.
These two carotenoids have demonstrated antioxidant abilities, and protect against macular degeneration and some cancers.

Antioxidant: Lutein and beta-carotene, carotenoids with and without provitamin-A activity, respectively, protected human liver cells against oxidant-induced damage, indicating that the antioxidant protective effect of these carotenoids is independent of provitamin-A activity.10
An in vitro experiment found both lutein and zeaxanthin were found to protect lipid membranes against UV radiation and oxygen free radical attack.11 Another test-tube experiment showed lutein to be as effective as vitamin E in quenching singlet oxygen.12

Macular degeneration: Lutein and zeaxanthin are the only carotenoids that have been identified in the macula, a yellow spot in the retina that provides the best visual acuity of the human eye. These carotenoids are referred to as macular pigment and are strongly implicated in maintaining eye health. They filter blue light from the retina and prevent oxidative stress or free radical-induced damage in the eye’s macula.6
Observational studies have indicated that high intake of lutein and zeaxanthin from food is associated with a reduced risk of age-related macular degeneration, the leading cause of blindness in people over age 65.7
A small 2001 study in Spain found that lutein ester supplements containing 12mg/day all-trans-lutein and 3mg/day 13/15-ris-lutein and 3.3mg/day alpha-tocopherol increased the density of the macular pigment, and that 10 patients taking lutein ester supplements reported an average of 40 to 50 percent improvement in visual acuity. Tolerance of glare was also improved significantly.8

Cancer Prevention: Researchers at the University of Utah Medical School examined the association of dietary alpha-carotene, beta-carotene, lycopene, lutein, zeaxanthin and beta-cryptoxanthin and the risk of colon cancer in more than 2,000 subjects. They found that lutein is inversely associated with colon cancer in both men and women, especially amongst those whose colon cancer was diagnosed when they were young and amongst those with tumours located in the proximal segment of the colon. The major dietary sources of lutein were spinach, broccoli, oranges and greens.13

A case-control study of diet and lung cancer in South Pacific populations showed an inverse association between lung cancer and lutein and vitamin E. Data from two prospective US studies (10 and 12 years follow-up periods) indicates an inverse association between dietary lutein intake and lung cancer. Inverse associations were strongest after a four- to eight-year lag between dietary assessment and date of diagnosis. In subjects who never smoked, researchers observed a 63 per cent lower incidence of lung cancer for the top compared with the bottom quintile of alpha-carotene intake.14

A study on serum carotenoid levels in women in India with breast cancer of women showed lutein and zeaxanthin levels to be significantly lower than healthy controls in postmenopausal, but not pre-menopausal, women.15

Bioavailability: The absorption of lutein in humans depends on the type of food, food ingredients such as fibers and fats, and on the type of processing. A study involving sixty-nine volunteers showed that consumption of meals with vegetables such as broccoli, green peas and spinach (containing 1.7 to 24.6mg beta-carotene, 3.8 to 26mg lutein, 0.22 to 0.6mg folate, and 26 to 93mg vitamin C) for four days significantly increased plasma concentrations of lutein and vitamin C. Broccoli and green peas were richer sources of lutein. Disruption of the spinach matrix increased the plasma concentrations of lutein and folate, indicating that the bioavailability of lutein from spinach can be improved by cooking. (van het Hof KH et al. Br J Nutr 1999; 82:203)
                In a study on six healthy young women, researchers found that some dietary fibres, such as pectin, guar, alginate, cellulose and wheat bran, significantly reduced the bioavailability of lutein, lycopene and beta-carotene by 40 to 75 per cent. (Riedl J et al. J Nutr 1999; 129:2170)
                The bioavailability of lutein also depends on the amount of fat in the diet. This was demonstrated in a study involving healthy volunteers who were divied into four groups. Each group received one of four different supplements: vitamin E (50mg), alpha- plus beta-carotene (8mg), lutein esters (8mg lutein), or placebo for two weeks. The supplements were provided in a low- or high-fat spread. Plasma concentrations of all supplements in the supplemented group were higher than in the placebo group. The plasma lutein level was higher when lutein esters were consumed with the high-fat spread (207 per cent increase) than with the low-fat spread (88 per cent increase). The study concluded that optimal uptake of vitamin E and alpha- and beta-carotene requires a limited amount of fat whereas the amount of fat required for optimal intestinal uptake of lutein esters is higher. (Annet JC Roodenburg et al. Am J Clin Nutr 2000; 71:1187)
                Another group of researchers compared the bioavailability of lutein esters with that of crystalline lutein in humans. Healthy volunteers were given high doses of either lutein or lutein esters, and researchers analysed their plasma for lutein, finding no statistically significant difference in plasma lutein between the two products. This study demonstrated that the bioavailability of lutein from lutein esters is the same as the bioavailability of lutein from purified crystalline lutein. 9

Lycopene is most abundant in tomatoes (up to 10mg per tomato) and is responsible for its red colour. Lycopene is also present, in small amounts, in guava, rose hip, watermelon and grapefruit.

Lycopene is one of the major carotenoids in the diet of North Americans, and it appears to act as an antioxidant, protecting against prostate, cervical, breast, digestive tract and lung cancers. It may also help prevent atherosclerosis.17
Researchers in epidemiological studies have identified lycopene as the carotenoid with the clearest inverse relation to the development of prostate cancer.18 Prostate cancer is the most common cancer in US men and the second leading cause of cancer deaths among men in all Western countries.

In a six year study (1986-1992) of the dietary habits of 48,000 male health care professionals, researchers found that those eating 10 servings or more a week of cooked tomato products had prostate cancer risk one-third that of those eating less than two servings weekly. Pizza appeared to offer the most protection, suggesting lycopene may be better absorbed when cooked with fat.19

In another study, researchers found that women with the highest consumption of lycopene had one-third the risk of getting cervical cancer, compared with women who had low intakes. Eating one tomato a day appeared to reduce the risk.20
A case-controlled study involving 400 patients and 405 control subjects showed that intake of lycopene as well as vegetables, fruits, folate and vitamins C and E were inversely associated with breast cancer risk.21 The intake of vegetables, fruits, and nutrients was estimated with a food frequency questionnaire on 64 food items, from which lycopene intake was estimated.

Another case-control study conducted between 1985 and 1991 in northern Italy showed that high intake of raw tomatoes is associated with a statistically significant reduction in the incidence of gastrointestinal tract cancer. (Franceschi S et al. Tomatoes and the risk of digestive tract cancer. Int J Cancer 1994; 59:181)

In a 10- to 12-year follow-up of 47,000 men and 77,000 women, about 0.6 percent cases of lung cancer were diagnosed. Analysis of carotenoid intakes by food-frequency questionnaire revealed that alpha-carotene and lycopene intakes were significantly associated with a lower risk of lung cancer. In subjects who never smoked, a 63 percent lower incidence of lycopene cancer was observed for the top compared with the bottom quintile of alpha-carotene intake. (Michaud DS et al. Am J Clin Nutr 2000; 72:990)
A case-controlled study, comprising 108 subjects with atherosclerosis, revealed a modest inverse relationship between serum lycopene and the risk of atherosclerosis, suggesting a protective role for lycopene against the development of atherosclerosis.22

Astaxanthin is best known for its commercial use in the aquaculture industry. Farmers use it in the feed to provide the pinkish-red color to salmon, trout and crustaceans such as crabs, krill and shrimp.

Astaxanthin is found in appreciable amounts in the microorganisms yeast Phaffia rhodozma and the microlagae Haematococcus pluvalis, which have recently gained considerable interest as potential sources of natural astaxanthin. Among the natural sources, H. pluvalis contains the highest level of astaxanthin, which exists mainly as esters of various fatty acids.

Antioxidant: Research studies have shown astaxanthin to be a powerful antioxidant that can enhance secondary immune responses in humans, and helps to reduce symptoms of H. pylori infections and carpal tunnel syndrome.

Astaxanthin is considered a potential membrane antioxidant due to its reactivity with singlet oxygen and oxygen free radicals. Astaxanthin attaches itself onto cell membranes and spans the cell membrane bilayer of fat, where free radical attack first occurs, and inhibits the destruction of fatty acids and proteins in cell and mitochondrial membranes caused by lipid peroxidation.

Studies showed the singlet oxygen-quenching ability of carotenoids, in descending order: astaxanthin, canthaxanthin, beta-carotene, zeaxanthin, lutein and vitamin E.12
In one test-tube study, astaxanthin was shown to display antioxidant activity greater than vitamin E and was referred to as ‘super vitamin E.’23

However, in a recent in vitro experiment, astaxanthin showed an antioxidant activity similar to that of vitamin E, and twice that of alpha-carotene, lutein, and lycopene24. This discrepancy might be due to different experimental conditions.

This antioxidant potency of astaxanthin is thought to be important in helping to reduce symptoms associated with rheumatoid arthritis (RA). A clinical study, presented at the meeting of the American College of Nutrition in Texas on October 2002, concluded that BioAstin (containing natural astaxanthin) might be an important addition to RA treatment allowing patients to have less pain. In the eight-week, double-blind, placebo-controlled study, 14 patients with RA received a daily dose of three gel caps, each containing 4mg astaxanthin, and 7 patients with RA received a placebo. Subjects completed a health assessment questionnaire at the beginning of the study and after four and eight weeks. The astaxanthin group showed a statistically significant improvement in symptoms of RA as compared to the placebo-group.

Astaxanthin’s ability to provide protection against Helicobacter pylori (H. pylori), which in humans is associated with peptic ulcer disease and gastric carcinoma, was demonstrated in animal studies.

In one study, mice fed 40mcg/kg astaxanthin three weeks before tumour inoculation had significantly lower tumour size than controls25.

In another study, mice infected with H. pylori were given daily treatments for 10 days of algal meal rich in astaxanthin of various potencies (10, 50, and 100 mg/kg body weight), 400 mg/kg vitamin C, or control meals. After 1 and 10 days post-treatment, both the astaxanthin and vitamin C groups showed significantly lower H. pylori colonization levels and lower gastric inflammation.27

Carpal tunnel: In a recent double-blind, placebo-controlled study, sponsored by Cyanotech (Kailua-Kona, Hawaii) and presented at the scientific meeting of the American College of Nutrition in San Antonio, Texas, in October 2002, astaxanthin was shown to improve the condition of patients with carpal tunnel syndrome. Patients who took three gel caps, each containing 4mg of astaxanthin, for eight weeks reported a reduction in both the severity and duration of wrist pain as compared to the control group.28

Beta-carotene is the most well known of the carotenoids and the predominant one in carrots, sweet potatoes and broccoli. Beta-carotene from vegetables and fruits is associated with reduced risks of breast, stomach, esophageal and pancreatic cancers. People who eat a variety of vegetables and fruits containing carotenoids, including beta-carotene, are less likely to develop certain cancers than people whose diets lack these nutrients. (Nishino H et al. Cancer prevention by carotenoids. Biofactors 2000; 13:89)

In contrast to epidemiological studies, which showed lower risk of cancer among individuals eating fruits and vegetables rich in carotenoids, clinical trials indicate that beta-carotene supplements increase the incidence of lung cancer in cigarette smokers. This effect has been attributed to pro-oxidant action under the considerable oxidative stress of smokers. These clinical trials involved male heavy smokers (ATBC trial, alpha-tocopherol beta-carotene), male asbestos workers and male and female smokers (CARET, beta-carotene and retinal efficacy trial), and U.S. male physicians’ study (included 11 per cent smokers). All three trials concluded that beta-carotene provided no protection against lung cancer; two trials found a higher risk for lung cancer for those subjects given beta-carotene.30

In another study, researchers at the Johns Hopkins University School of Medicine found that smokers with the lowest blood levels of beta-carotene had about three and half times the risk of heart attack of people who had high levels of beta-carotene and did not smoke.33

A recent telephone interview study of postmenopausal women’s diets throughout their lifetimes, with 273 incident cases of breast cancer and 371 controls, revealed that women were at lower risk of breast cancer with increasing levels of reported intake of beta-carotene.34

Beta-cryptoxanthin is another major source of vitamin A, often second only to beta-carotene. It is present in fruits such as oranges, tangerines and papayas. The contents ranged from 8mcg per 100g beta-cryptoxanthin laurate in Tunisian orange to 892 mcg per 100g beta-cryptoxanthin laurate in papaya.35

The anti-carcinogenic activity of beta-cryptoxanthin was demonstrated in an animal study. Rats received methyl nitroso-urea, to induce colon cancer, and either a diet with cryptoxanthin or a diet without cryptoxanthin. At week 30, the colon cancer incidence was significantly lower in the cryptoxanthin-group, suggesting a protective effect of cryptoxanthin against colon cancer.36

The association between dietary vitamin and carotenoid intake and bladder cancer incidence was examined in a diet study on more than 120,000 subjects aged 55 to 69 years. After six years follow-up, the study found that only beta-cryptoxanthin intake appeared to be inversely associated with bladder cancer risk.37

In addition to their role as a source of vitamin A, beta-carotene and beta-cryptoxanthin play an important role in human health; and as antioxidants they protect biological cells and tissues from the damaging effects of free radicals and singlet oxygen.

Making a household name
Research studies show carotenoids scavenge harmful free radicals that play a major role in the onset and advancement of many common diseases. They inhibit lipid peroxidation, enhance eye health and immune systems and reduce the risk of certain cancers.

Although it is tempting to formulate a cocktail of carotenoids with the desire to provide a full spectrum of health benefits, it is advised to take into consideration the health benefit to be targeted. For example, it might not beneficial to include lycopene for an eye health formula because this carotenoid has no demonstrated efficacy for improved vision. The take-home message is, research shows many benefits inherent in carotenoids. A careful look at the literature will point suppliers and manufacturers in the optimal direction.

1. Nishino H, et al. Cancer prevention by carotenoids. Biofactors 2000; 13:89.
2. Smith-Warner SA, et al. Increasing vegetable and fruit intake: randomized intervention and monitoring in an at-risk population. Cancer Epidemiol Biomarkers Prev. 2000 Mar;9(3):307-17.
3. Morris DL, et al. Serum carotenoids and coronary heart disease. The Lipid Research Clinics Coronary Primary Prevention Trial and Follow-up Study. JAMA 1994 Nov 9;272(18):1439-41.
4. Wilhelm S, et al. Carotenoid mixtures protect multilamellar liposomes against oxidative damage: synergistic effects of lycopene and lutein. FEBS Lett 1998;427(2):305-8.
5. Martin KR, et al. Beta-carotene and lutein protect HepG2 human liver cells against oxidant-induced damage. J Nutr 1996 Sep;126(9):2098-106.
6. Sujak A, et al. Lutein and zeaxanthin as protectors of lipid membranes against oxidative damage: the structural aspects. Arch Biochem Biophys. 1999 Nov 15;371(2):301-7.
7. DiMascio P, et al. Carotenoids, tocopherols and thiols as biological singlet molecular oxygen quenchers. Biochem Soc Trans 1990 Dec;18(6):1054-6.
8. Seddon JM, et al. Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA 1994 Nov 9;272(18):1413-20.
9. Bone RA. Lutein and zeaxanthin in the eyes, serum and diet of human subjects. Exp Eye Res 2000 Sep;71(3):239-45.
10. Olmedilla B, et al. Licopeno ¿compuesto de interés en salud pública? J Sci Food Agric 2001;81:904.
11. Slattery ML, et al. Carotenoids and colon cancer. Am J Clin Nutr 2000 Feb;71(2):575-82.
12. Michaud DS, et al. Intake of specific carotenoids and risk of lung cancer in 2 prospective US cohorts. Am J Clin Nutr 2000 Oct;72(4):990-7.
13. Ito Y, et al. A study on serum carotenoid levels in breast cancer patients of Indian women in Chennai (Madras), India. J Epidemiol 1999 Nov;9(5):306-14.
14. van het Hof KH, et al. Influence of feeding different vegetables on plasma levels of carotenoids, folate and vitamin C. Effect of disruption of the vegetable matrix. Br J Nutr 1999 Sep;82(3):203-12.
15. Riedl J, et al. Some dietary fibers reduce the absorption of carotenoids in women. J Nutr 1999 Dec;129(12):2170-6.
16. Roodenburg AJ, et al. Amount of fat in the diet affects bioavailability of lutein esters but not of alpha-carotene, beta-carotene, and vitamin E in humans. Am J Clin Nutr 2000 May;71(5):1187-93.
17. Herbst S et al. FASEB J 1997; 11:2587 Abstracts 78.
18. Agarwal S, Rao AV. Carotenoids and chronic diseases. Drug Metabol Drug Interact 2000;17(1-4):189-210.
19. Paetau I, et al. Carotenoids in human buccal mucosa cells after 4 wk of supplementation with tomato juice or lycopene supplements. Am J Clin Nutr 1999 Oct;70(4):490-4.
20. Giovannuci E, et al. Intake of carotenoids and retinol in relation to risk of prostate cancer. J Natl Cancer Inst 1995 Dec 6;87(23):1767-76.
21. Kantesky PA, et al. Nutr Cancer 1998; 31:31.
22. Ronco A, et al. Vegetables, fruits and related nutrients and risk of breast cancer: a case-controlled study in Uruguay. Nutr Cancer 1999; 35:111.
23. Franceschi S, et al. Tomatoes and the risk of digestive tract cancer. Int J Cancer 1994;59:181.
24. Michaud DS, et al. Intake of specific carotenoids and risk of lung cancer in 2 prospective US cohorts. Am J Clin Nutr 2000 Oct;72(4):990-7.
25. Klipstein-Grobusch K, et al. Serum carotenoids and atherosclerosis. The Rotterdam Study. Atherosclerosis 2000 Jan;148(1):49-56.
26. Miki W. Biological functions and activities of animal carotenoids. Pure Appl Chem 1991;63:141.
27. Naguib YM. Antioxidant activities of astaxanthin and related carotenoids. J Agric Food Chem 2000; 48:1150.
28. Jyonouchi H, et al. Antitumor activity of astaxanthin and its mode of action. Nutr Cancer 2000;36(1):59-65.
29. Wang X, et al. Antimicrob Agents Chemother 2000 Sep;44 :2452-7.
30. Cyanotech press release.
31. Nishino H et al. Cancer prevention by carotenoids. Biofactors 2000; 13:89.
32. Pryor WA Beta carotene from biochemistry to clinical trials. Nutr Rev 2000; 58:39.
33. Street DA, et al. Serum antioxidants and myocardial infarction. Are low levels of carotenoids and alpha-tocopherol risk factors for myocardial infarction? Circulation. 1994 Sep;90(3):1154-61.
34. Jumaan AO, et al. Beta-carotene intake and risk of postmenopausal breast cancer. Epidemiology 1999 Jan;10(1):49-53.
35. Breithaupt DE, et al. Carotenoid esters in vegetables and fruits: a screening with emphasis on beta-cryptoxanthin esters. J Agric Food Chem 2001 Apr;49(4):2064-70.
36. Narisawa T, et al. Chemoprevention by the oxygenated carotenoid beta-cryptoxanthin of N-methylnitrosourea-induced colon carcinogenesis in F344 rats. Jpn J Cancer Res 1999 Oct;90(10):1061-5.
37. Zeegers MP. Are retinol, vitamin C, vitamin E, folate and carotenoids intake associated with bladder cancer risk? Results from the Netherlands Cohort Study. Br J Cancer 2001 Sep 28;85(7):977-83.