We acquire carotenoids from eating certain plant foods, especially fruits and vegetables like carrots, sweet potatoes, tomatoes and squash. What are carotenoids? They’re fat-soluble nutrients, which means we absorb them best when we eat them along with a source of fat, such as olive oil, nuts, seeds, coconut or avocado.
Why do we need carotenoids? For starters, they’re phytonutrients that help fight free radical damage and provide important antioxidants to ward off disease and lower inflammation. And the benefits don’t end there.
What Are Carotenoids?
Carotenoids are types of natural chemical compounds created by plants that help give them their bright yellow, orange or red pigments. There are more than 600 different carotenoids in existence, but several of the most well-known include: α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin.
While researchers believe that most carotenoids have strong antioxidant capabilities — which is why we associate superfoods high in these nutrients with fighting inflammation, cancer and heart disease — not all seem to work in the same way at slowing the aging process.
Certain carotenoids, including α-Carotene, β-carotene and β-cryptoxanthin, are types of “provitamin A” compounds. This means they’re converted in the body once we eat foods that contain them in order to synthesize vitamin A, which is also sometimes called retinol. Contrary to popular belief, not all carotenoid-containing foods supply us with vitamin A. That’s because lutein, zeaxanthin and lycopene have no vitamin A activity once consumed. (14)
Another interesting, and somewhat unique, treat of carotenoids is that their availability improves when they’re cooked. Many antioxidants and phytonutrients are not very shelf-stable and become at least partially destroyed when exposed to high heats, but carotenoids in general are one exception to this rule.
Although you don’t want to overcook fruits and veggies with carotenoids, chopping, puréeing and cooking foods that contain carotenoids seem to help increase how much the human body can absorb and actually use. (15)
Different carotenoids have various uses and benefits once synthesized. Some of these include:
Beta-Carotene (β-Carotene) and A-Carotene (α-Carotene)
These two carotenoids are closely related, as they’re both synthesized to form active A. Both are found in foods like squash, spinach, sweet potatoes and carrots. Studies have found that beta-carotene foods have anti-inflammatory, cancer-protective effects. (1)
While study results have been mixed over the years, many have found that an inverse relationship between carotenoid intake, including beta-carotene, and lung cancer risk exists. (2) β-cryptoxanthin is another similar provitamin A carotenoid that has many of the same anticancer benefits.
Lutein and Zeaxanthin
These carotenoids are the only two that are found in the retina and lens of the human eye, which is why they’re accredited with improving eye health and protecting vision. The best sources of these carotenoids are dark leafy green vegetables and cruciferous vegetables (spinach, kale, turnip greens, Brussels sprouts, etc.).
Studies have shown that people who consume high amounts of lutein and zeaxanthin tend to experience less age-related eye problems, including macular degeneration and cataracts. Concentrated lutein and zeaxanthin supplements are now available, but research hasn’t shown that these definitely help stall development of these age-related eye diseases as much as a high-antioxidant diet does.
One of the biggest benefits of tomato nutrition is tomatoes are the best source of lycopene, especially when they’re cooked. Many epidemiological studies have found that people who consume high amounts of tomato products (including fresh, whole tomatoes and tomato sauce) experience a reduced risk for developing diseases like prostate cancer.
In a prospective study of more than 47,000 adults followed for over eight years, those with the highest lycopene intake had a risk of prostate cancer that was 21 percent lower than those with the lowest intake. (3)
Some of the major benefits of a well-rounded diet that includes carotenoids of all kinds include:
1. Lowering Inflammation
Once consumed, carotenoids have antioxidant activities that help block the formation of oxidative stress, the primary cause of aging and degeneration. Two of the ways that carotenoids function as powerful antioxidants include deactivating singlet oxygen and inhibiting the oxidation of fats.
When it comes to the strength of various carotenoids, research shows that lycopene is one of the strongest. A lower level of inflammation is one of the best forms of protection against heart disease, the disease that causes the most deaths every year in many developed nations. (4)
Carotenoids circulate in lipoproteins along with cholesterol and other fats, which makes them beneficial for protecting arteries against blockages, free radical damage and inflammation. A number of case-control and cross-sectional studies have found higher blood levels of carotenoids to be associated with significantly lower risk for arteriosclerosis, a disease characterized by thickening/hardening of the arteries. Other studies have found that higher carotenoid intake is associated with significant reductions in the risk of other types of cardiovascular diseases. (5)
2. Promoting Healthy Growth and Development
Infants and toddlers need vitamin A for normal growth, development and building a strong immune system. One of the ways that carotenoids help with growth is because they allow cells to communicate with one another by playing a role in the synthesis of connexin proteins. Connexin proteins are needed to form a protective membrane layer around cells and the gap between cells where chemical signals are sent.
This whole process of communication between cells allows them to effectively differentiate and take on various roles in the body without overproducing — which is why a loss of cell communication is tied to cancer development and tumor growth. (6)
3. Eye and Vision Health
Several carotenoids (especially lutein and zeaxanthin) are essential for forming the lens and retina of the eye and protecting vision into older age. They do this by absorbing UV light and other rays within the spectrum that damage our eyes, such as blue light that’s omitted from technological devices. (7)
By lowering the amount of blue light that’s able to enter the eye, carotenoids help preserve healthy cells and slow down oxidative damage that leads to vision loss. In the U.S .and other Western countries, macular degeneration is the leading cause of blindness in older adults, and unfortunately there is no cure for age-related degeneration. This is why researchers urge people to consume plenty brightly colored fruits and veggies that contain carotenoids and offer eye-disease prevention.
4. Boosting Immunity
Carotenoids are proven immune system boosters. In fact, higher carotenoid intake is associated with improvements in several biomarkers of strong immune function. Carotenoids have anti-inflammatory, antitumor, chemoprotective properties that help us ward off common infections, illnesses and serious diseases like cancer too. (8)
5. Protects the Skin from Damage
Carotenoids, along with active vitamin A, help prevent premature skin damage and skin cancer. Diets high in carotenoids are beneficial for preventing UV light damage, which can lead to melanoma, aged-looking skin, wrinkles, drying, scaling and follicular thickening of the skin. (9)
Once converted, vitamin A helps prevent keratinization of the skin, which occurs when the epithelial cells lose their moisture and become dry. Active vitamin A fights skin cancer because it helps stop oxidative damage and control malignant cells in the body, while facilitating with the process of correct cell differentiation.
As of the year 2000, the Food and Nutrition Board of the Institute of Medicine concluded that there’s not enough conclusive evidence available to establish a recommended dietary allowance or adequate intake for most carotenoids.
There is a RDA for vitamin A, (700–900 micrograms for adults), but otherwise advice from organizations like the National Cancer Institute, American Cancer Society and American Heart Association is to make sure to vary your diet and consume plenty of brightly pigmented fruits and vegetables every day. (11, 12)
Carotenoid pigments are naturally synthesized by more than just several plant species. They’re also made from certain species of algae and even some bacteria. The best food sources of carotenoids are fruits and veggies that are bright yellow, orange and red — one reason we’re told to “eat the rainbow.”
Research shows that several types of plants are responsible for providing humans with the vast majority of carotenoids. The list below shows the best food sources of carotenoids, roughly listed in order from the highest concentration of various carotenoids to the lowest:
- Winter squash or butternut squash
- Carrots and carrot juice
- Sweet potato
- Collard/turnip greens
- Citrus fruits (grapefruit, oranges and tangerines)
- Red peppers
How Carotenoids Work
Carotenoids, which are sometimes also called tetraterpenoids, are stored within certain plant’s chloroplasts and chromoplasts. Scientists categorize carotenoids into two primary groups: carotene (which includes α-carotene, β-carotene and lycopene) and xanthophylls (β-cryptoxanthin, lutein and zeaxanthin).
Once we eat a food that contains carotenoids and the food makes its way to our intestines, the carotenoids comes into contact with our bile salts and several types of lipids (fats) that help break them down.
This is why we absorb carotenoids best when we eat them as part of a meal that also has some healthy fats. You don’t need a large amount of fat to help utilize these nutrients best. Studies show that as little as three to five grams of fat with a meal (equivalent to about one teaspoon of oil) is sufficient for proper absorption.
Vitamin A is found in two primary forms: active vitamin A and provitamin A, which are carotenoids that need to be converted. Active vitamin A (called retinol) comes from animal-derived foods like liver, milk, yogurt, oily fish and eggs. This type can be used directly by the body since it doesn’t need to first be converted. The type of provitamin A, which is obtained from colorful fruits and vegetables with carotenoids, cannot be directly utilized by the body without undergoing several metabolic steps.
In regard to nutrient breakdown and absorption, the human digestive system is an amazing thing. Cells that line our intestines help dissect the chemicals that make up cartoenoids and release them into our bloodstreams. A portion of carotenoids are incorporated into lipoprotein, which makes it way to the bloodstream, while others are sent to the liver. Within the liver and intestines, active vitamin A is created, but luckily the human body has a mechanism in place that will stall this process when vitamin A levels are already high enough.
While we know that carotenoids have antioxidant properties that help decrease free radical damage, researchers are still trying to figure out how else they promote better health. Studies show that diets high in vitamin A-rich foods and carotenoid-rich fruit and vegetables help lower the risk for heart disease, cancer, eye disorders and other problems, but exactly how they do this still isn’t totally understood.
What’s interesting is that the use of synthetic carotenoid supplements, as opposed to eating foods that naturally supply them, doesn’t always result in the same health benefits. This suggests that the complex interactions of different chemicals and nutrients within carotenoid-rich foods are actually what makes them so good for you. In fact, isolating certain carotenoids might actually be harmful in some instances.
Several controlled trials have found that giving patients high doses of carotenoids that convert to vitamin A (including β-carotene) might actually do the reverse of what we’re hoping for — it can potentially increase the risk of certain health problems like lung cancer, for example. (16)
- Beta-carotene, A-carotene, lutein, zeaxanthin and lycopene are the most common types of carotenoids.
- The benefits of carotenoids include lowering inflammation, promoting healthy growth and development, maintaining eye and vision health, boosting immunity, and protecting the skin from damage.
- Chlorophyll and carotenoids are similar in that they both form the pigments found in various fruits, algae and vegetables. Chlorophyll is the green pigment in many leafy green plants or sea vegetables, while carotenoids are the yellows and greens of the produce world.
- The best food sources of carotenoids are fruits and veggies that are bright yellow, orange and red — one reason we’re told to “eat the rainbow.”
- Their availability improves when they’re cooked, which is atypical of most foods.