The Colorful World of Carotenoids: How These Antioxidant Pigments Support Healthy Aging, From Mitochondria to Muscles to Memory
From the vivid pinks of salmon and shrimp to the bright oranges and reds of fall foliage to the golden yellow of egg yolks, pigments called carotenoids help create the rich hues of our colorful world. But these compounds in plants and animals do more than just appeal to our eyes — they also provide potent antioxidant action that supports healthy aging.
Named carotenoids due to first being discovered in carrots, these pigments are now known to play a role in everything from mitochondrial health and muscle function to skin health and sight. In recent years, the declining function of the mitochondria — our cells’ energy production centers — has been implicated in many aging-related processes, including inflammation and oxidative stress, a buildup of harmful compounds called reactive oxygen species (ROS). Having a diet rich in carotenoids, whether from diet or supplements, could be one way to combat both age-related mitochondrial dysfunction and bodily decline — let’s take a closer look at the top five carotenoids known to impact health.
Carotenoids, From A to Z
While researchers have identified over 750 different carotenoids in nature, humans just use a mere 20 or so. The most abundant carotenoids we consume and utilize are α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene, and zeaxanthin. The carotene family consists of α-carotene, β-carotene, and lycopene, while β-cryptoxanthin, lutein, and zeaxanthin (among others) are known as xanthophylls.
Although all of these pigmented compounds function as antioxidants, astaxanthin and lycopene are thought to be the most potent in scavenging for free radicals and ROS and fighting inflammation in the whole body. However, the carotenoids lutein and zeaxanthin are highly abundant in the eye and are most associated with supporting vision and eye health.
There are also some differences regarding what these compounds turn into when we eat them. While they come from different families, α-carotene, β-carotene, and β-cryptoxanthin are considered pro-vitamin A carotenoids, meaning they can be converted in the body to vitamin A in the form of retinol. Conversely, no vitamin A activity can come from consuming lutein, lycopene, or zeaxanthin — but that doesn’t mean they aren’t useful. In this article, learn more about astaxanthin, β-carotene, lutein, lycopene, and zeaxanthin and how they support a healthier aging process.
Astaxanthin is a carotenoid that gives certain animals their pink or red colorings, including salmon, trout, krill, shrimp, crab, and lobster. Astaxanthin is produced by algae and bacteria that get eaten by fish and seafood, moving up the food chain. It also gives flamingos their pink coloring, as the birds consume astaxanthin-rich algae.
Research shows that astaxanthin may have higher antioxidant activity than other carotenoids, including lutein, lycopene, and β-carotene. This is due to astaxanthin’s unique structure — the compound remains both inside and outside of the cell membrane, allowing it to inhibit fat oxidation and scavenge for inflammatory ROS from all sides.
This carotenoid also protects mitochondrial function. With age, the energy-producing mitochondria in our cells decline in quality and function. When mitochondria produce ATP (adenosine triphosphate) for energy, a small amount of ROS is created as a byproduct, which needs to be neutralized by antioxidants. When there are not enough antioxidants present or mitochondrial function declines — as seen with age — the harmful ROS accumulate, and chronic disease may develop.
Astaxanthin inhibits this oxidative stress-induced mitochondrial decline, protecting mitochondrial integrity and preventing accelerated aging and diseases related to oxidative stress. Astaxanthin also inhibits the production and release of pro-inflammatory signaling molecules called cytokines, resulting in dampened inflammatory responses.
In a study of older adults aged 65 to 82, combining supplemental astaxanthin and exercise training improved muscle endurance, exercise efficiency, and fat oxidation — meaning, the body was better able to burn fat for fuel during exercise. These metabolic improvements combined with an exercise-related increase in muscle strength and size suggest that astaxanthin could enhance older adults' quality of life and physical abilities.
Lastly, this powerful carotenoid is also thought to support eye, brain, and joint health. Notably, a study with mice found that astaxanthin was significantly linked to improved spatial memory and neurogenesis — the creation of new neurons that can slow down brain aging, preserve cognition and memory, and reduce the risk of cognitive disease development.
The other carotene, β-carotene, is found in many plant foods, notably in orange and red fruits and vegetables like carrots, tomatoes, sweet potatoes, pumpkin, red bell peppers, melon, and squash. It’s also found in some green vegetables, like spinach, but the chlorophyll in these green plants overpowers the orange-red pigments.
As mentioned, β-carotene is a pro-vitamin A carotenoid, contributing to about one-third of total dietary vitamin A intake in Western countries. However, research shows that β-carotene absorption from plant foods is both low and varied, with 5 to 65% of the carotenoid being absorbed and used by humans. This variability depends on many factors, including fat and fiber in the food — while dietary fat increases β-carotene bioavailability, fiber content reduces it. As most β-carotene-rich foods also contain fiber, consuming dietary fat with the food can help to boost bioavailability. For example, eating avocado with β-carotene foods increases absorption of the carotenoid by up to 6-fold.
This orange-red carotenoid is associated with eye, brain, and skin health — likely due to its status as an antioxidant (albeit a less potent one than astaxanthin and lycopene). In a study of lead-exposed male workers, supplemental β-carotene (10 mg per day for 12 weeks) increased the activity of three enzymes (G6PD, catalase, and superoxide dismutase) that fight oxidative stress. However, the β-carotene group also saw reductions in glutathione peroxidase, an important enzyme for neutralizing certain free radicals.
In the brain, β-carotene may improve aspects of cognition. In a clinical trial of almost 6,000 physicians, those supplemented long-term with β-carotene (up to 18 years!) performed significantly better on cognitive tasks, including general cognition, verbal memory, and verbal fluency. However, short-term supplementation of less than one year did not show the same benefits.
One caveat about β-carotene supplementation is that not all populations experience benefits — in some cases, adverse effects are seen. Two large randomized controlled trials (Goodman, 2004; Middha, 2019) found that high doses of β-carotene supplements significantly increased the risk of mortality and carcinogenesis in the lungs, stomach, or bladder in smokers, heavy alcohol users, and workers exposed to asbestos. This is likely because these toxic compounds (cigarette smoke, alcohol, asbestos) interfere with normal β-carotene metabolism and convert it into other highly reactive compounds. For this reason, aiming to get β-carotene from dietary sources is typically preferable to using supplements — especially if you are a current or former smoker.
Similar to β-carotene, lutein imparts pigment to orange-yellow foods like corn, carrots, and egg yolk but is also found abundantly in dark green vegetables, including spinach, kale, and parsley. Lutein and zeaxanthin are commonly seen together in research and supplements, as they are both highly concentrated in the eye. Lutein and zeaxanthin are the only dietary carotenoids pigmenting the yellow spot of the retina, which protects the eye’s macula from blue light damage and scavenges for ROS in the eye.
The preservation of macular health with age is vital to maintaining normal vision. The ability of lutein (and zeaxanthin) to filtrate blue light is essential to visual preservation because this specific wavelength of light is highly reactive, increasing oxidative damage in sensitive layers of the eye and leading to macular degeneration — the leading cause of blindness in older adults. Lutein also enhances the function of healthy eyes, as seen by improved contrast sensitivity, better visual signal processing, and reduced glare.
Lutein is the carotenoid with the highest concentration in brain tissue, providing support to the processing of visual and auditory signals, motor coordination, and visual perception. In a study of centenarians (people over age 100), higher blood levels of lutein, zeaxanthin, and β-carotene were consistently associated with better cognition. In octogenarians (those over age 80), only lutein was connected to the cognitive improvements.
Further, a six-month trial of daily lutein-zeaxanthin supplementation in adults aged 40-75 found significant improvements in computer tests of visual learning and episodic memory — the long-term memory that recalls specific events or experiences in your past. However, there were no changes to self-reported measures of executive function, memory, mood, or physical function.
Lycopene, a red-pigmented carotenoid and antioxidant, is most celebrated for its role in supporting male prostate health. While tomatoes are the most well-known high-lycopene food, it is also found in guava, watermelon, grapefruit, red bell peppers, and papaya.
This carotenoid is the one most linked to cardiovascular health. Research shows that lycopene reduces LDL (“bad”) cholesterol, increases HDL (“good”) cholesterol, and protects against oxidative stress in the cardiovascular and endothelial systems. Some studies suggest that more benefits are gained from consuming whole lycopene-containing foods, like tomatoes, instead of lycopene supplements. A review of dozens of trials supports consuming tomato-based foods as a first-line approach to supporting cardiovascular health — except blood pressure management, where lycopene supplementation was superior to tomatoes.
In the brain, lycopene boosts antioxidant defense systems inside cells, including superoxide dismutase, catalase, glutathione peroxidase, and glutathione, which are important for protecting mitochondria. In the muscles, lycopene has been shown to positively affect skeletal muscle metabolism and increase the activity of slow-twitch fibers — muscle fibers that contain an abundance of mitochondria and are used for sustained, smaller movements (as opposed to extreme bursts of energy with fast-twitch fibers).
Lastly, zeaxanthin is a carotenoid found in orange bell peppers, corn, egg yolk, goji berries, and dark leafy green vegetables. As mentioned, zeaxanthin is often grouped with lutein due to its similar functions in the eye and because humans can convert dietary lutein into zeaxanthin in the body.
Research has indicated that zeaxanthin provides a greater photoprotective capacity in the eyes than lutein, possibly because it confers greater antioxidant activity. In a study with mice, zeaxanthin supplementation increased antioxidant enzymes and protected cells in the RPE (retinal pigment epithelium) — a pigmented layer of cells that absorb light and protect sensitive retinal tissue. Zeaxanthin reduced mitochondrial-induced oxidative stress in the RPE, which is a leading cause of age-related degenerative eye conditions.
Zeaxanthin may confer more benefits when combined with lutein, but the synergistic effect between the two is not entirely clear. A clinical trial looked at the effects of supplementing with zeaxanthin and lutein for one year in a group of healthy young adults. The researchers found that those in the treatment group significantly increased MPOD (macular pigment optical density; a measure of how many carotenoids are in the central nervous system). The combined treatment also improved cognitive abilities, including spatial memory, complex attention (maintaining information in the mind for a short time and manipulating that information, like doing mental math), and reasoning abilities. Although this study was done with young adults, the researchers speculate that the results may be even more pronounced in older adults with diminishing cognitive status.
- Carotenoids are a group of pigment-containing compounds that provide color to various plants and animals.
- The carotenoids most studied for supporting human health are astaxanthin, β-carotene, lutein, lycopene, and zeaxanthin.
- These compounds are well-associated with supporting vision and eye health, brain health and cognition, skin health, mitochondrial function, antioxidant activity, and skeletal muscle function.
- Some carotenoids are better consumed in their food forms rather than supplements — especially β-carotene, which can be detrimental to smokers, heavy alcohol users, or those exposed to environmental toxins when taken in supplemental form.
- To increase the bioavailability of dietary carotenoids, consume them with a healthy fat source, like avocado or olive oil.
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