The Carotenoid Palette

The Carotenoid Palette
An array of colors, researched health benefits and formulation challenges highlight the future of carotenoids.
by Steve Myers

Carotenoids have long enhanced plants, fruits and vegetables with an astonishing palette of colors and protections; as a healthy ingredient category, carotenoids also stand to benefit the natural products industry and its consumers with an explosion of sales and healthy products.The science behind the health benefits, mechanisms of action, and various formulation and manufacturing issues associated with carotenoids might not always be definitive; but, the future growth of the carotenoid market depends upon all those involved staying abreast of the current knowledge on carotenoid research and production trends.

Carotenoids are a group of around 700 lipid-soluble phytochemicals that serve as yellow, red and orange pigments in a variety of phytoplankton, plants, algae, and certain fungi and bacteria. Fruits and vegetables are the richest sources of the roughly 50 dietary carotenoids absorbed by the body, the most common of which are alpha-carotene, beta-carotene, lutein, zeaxanthin, lycopene and betacryptoxanthin. Other carotenoids found in supplements include apocarotenal, canthaxanthin and astaxanthin.

Hydrocarbon carotenoids feature a polyene chain of single and double bonds and are called carotenes; carotenoids featuring double bonds that have been oxygenated are called xanthophylls, which were named for the yellow in autumn leaves. The carbon-carbon double bonds interact with each other in a process called conjugation, by which stability is increased and overall molecular energy is lowered. The color of carotenoids is related to its number of double bonds. For instance, as the number of double bonds increases, the wavelength of absorbed light also increases, providing a redder coloration.

In plants, these colorful nutrients serve numerous protective functions, many of which are also thought to translate to humans. Carotenoids help protect plants from singlet oxygen, a non-free radical form of reactive oxygen species (ROS), during photosynthesis, as well as protecting from various free radical forms of ROS.¹ While its impact on plants is well established, the role of singlet oxygen in humans is not as definitive. However, some carotenoids have also been shown as potent inhibitors of lipid peroxidation, although this action in humans is complex and still relatively undefined, scientifically.²

Among carotenoids, the most effective antioxidant may be lycopene, which is abundant in tomatoes and other red fruits. Study reviews have found lycopene protects against oxidation of low density lipoprotein (LDL) cholesterol,³ while test tube investigations have revealed tomato oleoresin is more potent than pure lycopene in inhibiting LDL oxidation.⁴ In humans, supplementation of the diet with 96 g/d of lycopene-rich tomato puree significantly increased plasma lycopene and other carotenoids, as well as total antioxidant capacity.⁵ Similarly, daily intake of a beverage containing natural tomato extract (as Lyc-O-Mato®, from LycoRed) increased plasma carotenoids and reduced DNA damage in lymphocytes subjected to oxidation,⁶ a conclusion confirmed in a subsequent study.⁷

Newer to the carotenoid antioxidant research scene is astaxanthin, a long-chain, red-pigment carotenoid predominant in crustaceans but commonly sourced from certain algae, which contain greater concentrations. Astaxanthin binds to proteins, forming carotenoproteins that can appear as green, yellow, blue or brown. Heat denatures or breaks these carotenoid-protein pairings and gives the carotenoid more of a red appearance.

A Hawaiian research review credited astaxanthin with strong antioxidant actions, including protection from UV radiation.¹³ Likewise, in vitro research from Japan demonstrated astaxanthin can significantly inhibit lipid peroxidation in LDL cholesterol.¹⁴ And, studies on ischemic rats given astaxanthin lend credence to its neuroprotective capability, also credited to antioxidant action.¹⁵

The antioxidant activity of astaxanthin appears to also impact inflammation. Japanese researchers induced inflammation in the eyes of rats and found astaxanthin could suppress the development of inflammation by inhibiting TNF-alpha production and stalling nitric oxide synthase (NOS) activity.¹⁶ Subsequent study on astaxanthin’s antioxidant mechanisms of action concluded the carotenoid can limit serum NOS and certain inflammatory cytokines.¹⁷ In one trial, astaxanthin (as BioAstin®, from Cyanotech) regulated production of NO and PGE2, an inflammatory prostaglandin, in addition to controlling production of inducible NOS, COX-2, TNF-alpha and interleukin-1 (IL-1).¹⁸

As for certain inflammatory conditions, astaxanthin-rich extract from Haematococcus algae has been studied for its effect on H. pylori bacterial infection and associated gastric inflammation. An animal study concluded astaxanthin regulated lipid peroxidation and H. pylori growth,¹⁹ while in vitro research revealed the xanthophyll can limit oxidative damage in the gut and protect against gastric ulcers.²⁰ Scientists have reported astaxanthin works particularly well with antioxidant vitamin C in scavenging free radicals and counteracting microbial action.²¹

Astaxanthin can also protect against oxidative damage due to strenuous exercise, as Japanese scientists studying astaxanthin in mice found the xanthophyll reduced markers of oxidative damage in the calf muscle and heart following strenuous exercise.²²

Fellow xanthophylls lutein and zeaxanthin have exhibited potent antioxidant activity in the eye. The alternating single and double bonds common to carotenoids allow them to absorb a wide spectrum visible light; due to their bond structure, lutein and zeaxanthin absorb blue light that could otherwise cause oxidative damage to various eye structures, including the macula. Continuous oxidative damage from UV light entering the macula leads to photoreceptor death and is linked to the development of age-related macular degeneration (AMD).

Research on lutein esters (as Xangold®, from Cognis Nutrition) showed lutein is accumulated in the macula of both healthy eyes and those in early stages of AMD.²³ A study conducted by scientists at the University Medical Center Utrecht, The Netherlands, confirmed oral supplementation with lutein esters (as Xangold) increases both plasma and macula concentrations of the carotenoid.²⁴

Kemin Health, which manufactures FloraGLO® lutein, conducted a review of eye research, finding lutein can quench and scavenge photoinduced ROS in the eye,²⁵ and both lutein and zeaxanthin play a role in protecting lipid peroxidation in both LDL and HDL cholesterol. Researchers from Tufts University, Boston, similarly discovered lutein and zeaxanthin protect the photoreceptor cell layer in the eye from light damage caused by ROS.²⁶ The Veterans Lutein Antioxidant Supplementation Trial (LAST) further demonstrated a significant benefit from lutein on AMD in humans.²⁷ The 12-month, randomized, double-masked, placebo-controlled trial involved 90 patients with atrophic AMD who received either 10 mg of purified, crystalline lutein (as FloraGLO), lutein plus a broad spectrum antioxidant formula (as OcuPower®, from Vitacost) or a placebo. Both lutein groups showed significantly improved macula pigment optical density (MPOD), glare recovery, visual acuity and quality of vision.

The ability of these two xanthophylls to limit the damage from UV light also extends to the skin, as Cornell University, New York, scientists found lutein modulated skin response to UVB radiationinduced inflammation and immunosupression in an animal model.²⁸ Harvard researchers went one step further, showing both lutein and zeaxanthin limited the negative effects of UVB radiation by reducing acute inflammation response in hairless mice.²⁹

While antioxidant activity is one of the burgeoning carotenoid research targets, the ability of certain carotenes to convert in the human body to retinol (vitamin A) was one of the first biological mechanisms investigated and is the primary essential function of carotenoids in human health. As vitamin A, also called the antiinfective vitamin, is important to immune function,³⁰ pro-vitamin A carotenoids, which include alpha-, beta- and gamma-carotene, as well as beta-cryptoxanthin, have been studied for similar immune benefits.

Consuming a carotenoid-rich diet can moderate T-cell function, according to German researchers, who added carotenoids appear to influence secretion of cytokines by T-helper cells, a function suppressed by low carotenoid intake.³¹ On specific carotenes, Dutch researchers concluded high plasma levels of beta-carotene may lower occurrence of acute respiratory infections in elderly people;³² and Swedish scientists found low serum beta-carotene in coronary artery disease (CAD) patients reflects an activated immune system and inflammatory activity.³³ Hungarian research showed retinol and provitamin A carotenoid concentrations were lower in children with acute infections compared to healthy controls.³⁴ They drew an inverse correlation between C-reactive protein (an inflammation marker) and beta-carotene, and they added non-provitamin A carotenoid levels were also low in the infected children.

In fact, non-provitamin A carotenoids have fared much better in recent immune research than has beta-carotene. Lutein appears to stimulate both active and passive immune response, as an animal study revealed dietary lutein increased production of immune lymphocytes and IgG antibodies.³⁵ A subsequent study by the same researchers confirmed an immunomodulatory response in animal models fed lutein.³⁶ Lycopene can also benefit immune function, as researchers report lycopene may protect immune cells from oxidative damage.^37,38 However, astaxanthin has delivered many positive study results for its apparent ability to stimulate lymphocyte proliferation, increase T-cell production and amplify natural killer (NK) cell activity. Astaxanthin-fed mice have shown increased resistance to tumor growth, as well as higher cytotoxic T-cell and interferon-gamma activity.³⁹ The carotenoid also prevented liver tissue damage and related NK cell activity in stressed mice in one study,⁴⁰ while it enhanced spleen lymphocyte production and lymphocyte cytotoxic activity in another mouse study.⁴¹ In vitro, astaxanthin enhanced splenocyte proliferation and function,⁴² and stimulated human IgM and IgA antibody response.⁴³

Immune response is critical to development and progression of cancer cells. Because of their provitamin A and antioxidant activities in immune function, dietary carotenoids have been investigated for benefits to various cancers. Beta-carotene was the first carotenoid measured in food and human blood by researchers, who also noticed an inverse relationship between intake of beta-carotene and lung cancer. More recently, however, a 10-year study involving 100,000 people found no link between beta-carotene intake and risk of lung cancer.⁴⁴ A subsequent 14-year study of 27,000 Finnish smokers concluded dietary intakes of total carotenoids, lycopene, betacryptoxanthin, lutein and zeaxanthin were associated with significant reductions in lung cancer, but beta-carotene exhibited no such correlation.⁴⁵ While such large and lengthy trials would seem definitive on the subject, a more recent Japanese trial catalyzed the debate, showing risk of lung cancer death is reduced in conjunction with high serum levels of carotenoids, including beta-carotene, alpha-carotene, lycopene and beta-cryptoxanthin.⁴⁶

The class of carotenoids has earned increased attention from breast cancer researchers. A population study found a decreased risk of breast cancer in postmenopausal women who combined high intakes of carotenoids and the essential fatty acid DHA (docosahexaenoic acid).⁴⁷ Inhibition of breast cancer development has also been credited to beta-carotene⁴⁸ and lutein.⁴⁹ Channing Laboratory, Boston, researchers linked total carotenoid levels with reduced breast cancer risk, noting the strongest association was with alpha-carotene, which reduced risk by 35 percent among the highest intakes.⁵⁰ Johns Hopkins scientists studying carotenoids and breast cancer found women with the highest intakes of total carotenoids, beta-carotene and lycopene had half the risk of developing breast cancer than did women with the lowest intakes.⁵¹

Carotenoids appear to address cancer in men, as well as in women. Researchers from the University of Illinois, Chicago, probed lycopene’s effect on prostate cancer. In one trial, they found lycopene inhibited cancer cell growth by 31 percent compared to placebo, after 48-hour incubation.⁵² In another trial, they found 30 mg/d of lycopene supplementation reduced cancer cells by 40 percent in mean nuclear density and by 36 percent in mean area, compared with presupplementation biopsies.⁵³ They concluded significant lycopene uptake in the prostate gland could reduce DNA damage in leukocyte and prostate tissue. Researchers from Taiwan further report lycopene inhibits cancer growth by upregulating expression of nm23-H1, a metastasis suppressor gene, which it does more than 800 times more effectively than does beta-carotene.⁵⁴

Carotenoids have made some advances against other forms of cancer, including bladder, colon and pancreatic cancers. A casecontrolled study from the University of Ottawa, Ontario, found lycopene from tomato intake reduced pancreatic cancer risk by 31 percent among men;⁵⁵ the researchers noted beta-carotene and total carotenoids also reduced risk by a significant amount among male and female non-smokers. Another case-controlled trial of carotenoids compared intakes between 423 bladder cancer patients and 467 healthy controls, finding lower carotenoid intakes among the cancer patients.⁵⁶ The scientists concluded carotenoids may have a preventive role in bladder cancer, and the study data may have important implications for general cancer prevention, especially for individuals susceptible to DNA damage. A University of North Carolina, Chapel Hill, study concluded higher alpha-carotene and vitamin A concentrations may reduce recurrence of various colon polyps, growths that can develop into cancer.⁵⁷ The researchers added beta-carotene intake was inversely related to multiple adenoma recurrence.

Despite the focus on antioxidant and provitamin A activities, scientists have theorized carotenoids might also impact cancer by facilitating intercellular communication commonly lost in cancer cell models. According to the Linus Pauling Institute, University of Oregon, carotenoids can stimulate the production of connexins,⁵⁸ proteins that form pores or gap junctions in cell membranes. This allows cells to communicate through the exchange of small molecules and is critical in maintaining cells in a differentiated state. Researchers have shown carotenoids can stimulate expression of the connexin 43 gene, but the mechanisms by which retinoids and non-provitamin A carotenoids prompt such expression appear to be different.⁵⁹ This is an area of ongoing study and debate.

The disease-fighting actions of carotenoids are not exclusive to cancer, as antioxidant abilities have linked carotenoids to decreased risk of heart disease and diabetes. Lycopene is abundant in tomatoes, which are considered an important part of a cardioprotective diet.⁶⁰ People with higher adipose concentrations of lycopene have demonstrated a reduced risk of myocardial infarction (heart attack),⁶¹ a benefit also credited to beta-carotene in a Harvard University study.⁶² In conjunction with the University of Costa Rica, the Harvard researchers drew an inverse relationship between incidence of heart attack and intake of fruits and vegetables rich in beta-carotene, noting increased adipose levels and dietary intake of lutein and zeaxanthin appeared to elevate such risk. However, researchers from Oregon Health and Science University, Portland, found low intakes of folate, and carotenoids— lutein, zeaxanthin and beta-carotene—among coronary mortality data from more than 16 countries.They reported low intake of these nutrients is most common in Central and Eastern Europe and is detrimental to heart health.

Astaxanthin has also impacted coronary disease, as Japanese researchers determined BioAstin significantly reduced arterial blood pressure and inhibited stroke in hypertensive rats.⁶³ They noted the extract also reduced damage to the animals’ nervous systems caused by stroke and improved memory in vascular dementia.

Fruits and vegetables contain decent levels of carotenoids, in alltrans form. Alpha- and beta-carotene are abundant in yellow and orange vegetables such as pumpkins, carrots and squash; spinach is another good source of beta-carotene, but the chlorophyll hides the yellow pigment. Pumpkin is also rich in beta-cryptoxanthin, as are sweet peppers, papayas and oranges. Tomatoes and watermelons are the best food sources of lycopene. Spinach, mustard greens, collard greens and turnips are rich food sources of lutein and zeaxanthin—although ingredient suppliers commonly source these carotenoids from marigold flowers, which contain highly concentrated amounts of both nutrients.

Despite their abundant supply of naturally occurring carotenoids, foods can be an unreliable source of these nutrients. Carotenoids are associated in the plant matrix with certain proteins—chloroplasts in green leafy vegetables and chromoplasts in fruit, for instance. To improve bioavailability of carotenoids in foods, this plant matrix must be disrupted, which occurs in food processing—chopping, pureeing and cooking. Thus, tomato puree and tomato sauce contain more lycopene than do whole tomatoes, and fruit and vegetable juices contain more carotenes than their whole counterparts. Consequently, supplemental carotenoids may be more bioavailable than food sources. “The general consensus is that the bioavailability of purified carotenoids is better than from diet,” said Lars Rasmussen, Allied Biotech Corp., a supplier of beta-carotene. In fact, studies have shown lutein is more bioavailable from supplements than from spinach;⁶⁴ tomato paste has increased beta-carotene and lycopene bioavailability;65 and beta-carotene is more bioavailable in capsules than in cooked carrots.⁶⁶

While the plant matrix is a key to bioavailability, Manuel Pavon, general manager of Chrysantis, which supplies EZ Eyes™ zeaxanthin and lutein, explained that because carotenoids are fat soluble, their bioavailability from the diet is influenced by the presence of fat. “Lipid ingestion at the same time one takes a carotenoid supplement improves its bioavailability,” he said. “A study by researchers at Ohio State University⁶⁷ showed that carotenoid absorption from a salad is severely impaired when the salad dressing is a non-fat one.” He reported a particular influence of body fat on the absorption of lutein and zeaxanthin into the macula. EZ Eyes 50/50™ from Chrysantis features a 1-to-1 ratio of these two xanthophylls, the same ratio found in the macula. However, Pavon said bioavailability and intestinal absorption play less of a role than does a person’s body fat. “Obese people tend to have less macular pigment because the fat tissue acts as a ‘sink’ for both lutein and zeaxanthin,” he said. “And since there are differences in how carotenoids are stored in fat tissue in men vs. women, the ratio can be altered by body fat.”

Despite their dependence on fat for absorption, carotenoid finished supplements or functional foods need not contain fat, according to Rasmussen and other carotenoid experts. “No limitations exist if you choose the appropriate form for your application,” confirmed Christine Peggau, global market segment manager for Cognis Nutrition & Health. “The oil forms are used in oil- based matrices such as cheese and salad dressing, while the microencapsulated beadlet and powder forms are used in dry applications or mixed into soluble beverages.”

Craig Maltby, spokesperson for Kemin Health, said fat in other parts of the diet would aid absorption of a carotenoid product. “This is an advantage of free lutein over lutein esters, because studies indicate that lutein esters require more fat for absorption,” he said.

A somewhat related issue in the formulation of carotenoid products is the natural vs. synthetic debate. It appears the issue is addressed on a case-by-case basis, as some carotenoids can be sourced abundantly from natural sources, while others are best supplied in synthetic form. Regulation and purity are also key factors in the debate. For instance, Rasmussen explained the Food and Drug Administration (FDA) does not distinguish between natural and synthetic carotenoids used as colorants.

“With beta carotene, the synthetic material is minimally 96-percent all-trans beta-carotene, which is responsible for the well known coloration and holds the highest vitamin A activity,” he said. “The synthetic molecule is identical to the molecule found in natural sources of beta-carotene, hence the term ‘nature-identical’ is often applied.” He further noted synthetic carotenoids deliver better batch consistency and economies of scale.

In contrast, Cognis supplies Betatene® mixed natural carotenoids, and Peggau noted approximately 30 percent of natural beta-carotene is cis-isomers, the structure linked with health benefits, whereas synthetic beta-carotene contains mostly all-trans isomers. “Marketing data clearly demonstrates consumers prefer natural products,” she added.

To some degree, it appears the marketing position may determine the ingredient selection, but choice is not always clear from a scientific standpoint. “With the exception of beta-carotene, which our body converts to vitamin A, and other carotenoids with vitamin A activity, synthetic carotenoids are chemically identical to what’s found in nature, and our bodies typically do not distinguish between the two,” said Lynda Doyle, director of business development for DSM Nutritional Products, which produces both natural and synthetic carotenoids. She noted DSM’s redivivo™ synthetic lycopene is chemically identical to the lycopene found in tomatoes and has been shown to have similar bioavailability to lycopene found in highly processed tomato products.

As for astaxanthin, Bob Capelli, director of sales for Cyanotech, noted synthetic supplies are made from petrochemicals and are not approved by FDA and other international regulatory bodies for use in human nutrition. “Synthetic astaxanthin may not be able to enter all parts of the body as natural astaxanthin can because it is not esterified—does not have fatty acids attached to the molecule,” he said. Synthetic astaxanthin, according to Capelli, has a different chemical structure than the natural version and is not as potent an antioxidant or anti-inflammatory as is natural astaxanthin—which Cyanotech derives from Haematococcus microalgae.

Formulators also need heed the issue of coloration. “Carotenoids tend to be very powerful colorants, which are difficult to suppress,” Rasmussen said. He suggested controlling finished product pigmentation by adding other colorants to the formula. According to Doyle, cross-linked beadlets are available for food fortification without adding color to certain foods. Furthermore, directly compressible beadlets are highly stable and have minimal extrusion loss; therefore, they do not “bleed,” but appear as specks in the tablet core. In the case of lutein, Maltby stated color contribution to a finished product corresponds directly to the inclusion level of the carotenoid, depending on both the original color of a given product as well as the lutein delivery system. “If there is color to the product already, either no color change is observed or the change can be very slight, even at higher levels, when lutein is added,” he said.

Capelli noted astaxanthin is, perhaps, the most powerful colorant of all dietary carotenoids, as even a small quantity of the xanthophyll imparts its reddish pigment to cosmetics and functional foods. “For this reason companies must use a very small amount of astaxanthin unless they want to use the pigmenting properties of astaxanthin to lend color to their finished product,” he said. “Most of our customers incorporating BioAstin in their cosmetic and food formulas are using only about 20 to 50 ppm.” He added, even in this small dose, astaxanthin delivers the powerful antioxidant and anti-inflammatory benefits revealed in research.

There are still more challenges facing formulators working with carotenoids. “The most important challenge in working with carotenoids is stability,” Pavon said. He noted carotenoids, in general, are sensitive to light, pressure, oxygen and temperature, and manufacturers have to make sure the ingredients they buy withstand the production processes.

The market for carotenoids is currently about $887 million, according to recent data from Business Communications Co., which expects the market to reach $1 billion by 2009. Leading the growth spurt, lutein has experienced rapid growth of 6.1 percent, and astaxanthin is making strides with a 1.9-percent growth rate.

“Carotenoids are most commonly used as nutrients in dietary supplement applications, colorants in foods and, to a lesser extent, as antioxidants in cosmetics,” Doyle said. Globally, carotenoids are used far more in foods (as colorants and vitamin A) than in supplements, with cosmetic use only a minor percentage, according to Rasmussen. In the United States, the situation is nearly reversed, with carotenoid use in supplements exceeding that in foods, due to costs.

Carotenoid product trends appear also to be driven by the increased research findings on health benefits. For instance, Capelli reported more companies are adding astaxanthin to joint and inflammation products. Studies have shown increased carotenoids can reduce the risk of arthritis⁶⁸ and osteoporosis.⁶⁹ “Additionally, there is a big move toward internal beauty formulas featuring natural astaxanthin, based on positive human clinical trials conducted in Japan and Canada,” Capelli said.

Rasmussen reported beta-carotene has enjoyed widespread use as provitamin A and a colorant, with a recent trend toward replacing artificial colors; but, other carotenoids, including lutein and lycopene, are being included together in more finished product formulas, as science reveals their combined health benefits and as supplies become more commercially available. In fact, Peggau cited a significant increase in recent lutein supplement sales. “We are seeing solid demand for Xangold natural lutein esters for eye health products including both foods and dietary supplements,” she said. Similarly, Maltby noted Kemin is realizing growth in lutein purchases. “We’re seeing interest in new drinks and bars, as well as new dietary supplements in the form of gummies, chewables, liquid multivitamins, effervescents and oral strips,” he said.

Numerous carotenoid suppliers reported increased use of mixed carotenoid formulas, as mixed carotenoids reflect the variety found in food sources. “Disturbing nature’s balance with a particularly high level of any single compound may interfere with absorption and bioavailability of individual carotenoids,” Doyle said. However, the effectiveness of this trend is not clear. “Some studies have shown that some carotenoids (beta-carotene, for example) affect or reduce the absorption of other carotenoids, since they essentially ‘compete’ for the same absorption sites in the small intestine,” Pavon stated. “These are complex issues, and there is not enough information about this, because there are too many variables.”

There are numerous factors to consider in creating and manufacturing a carotenoid product. The expanding body of research can help target a carotenoid product to a specific benefit, at a designated and researched dosage. Then careful consideration must be given to the effect of a particular dosage of carotenoid, with respect to color and bioavailability. In addition to the heightened sensitivity of carotenoid ingredients, and the associated handling issues, formulators must think about how a carotenoid will interact with other ingredients, especially other carotenoids.

Share this article: Email, Slashdot, Digg, Del.icio.us, Yahoo!MyWeb, Windows Live Favorites, Furl
Add this article feed to: RSS, My Yahoo, Newsgator, Bloglines