Carotenoids color our world orange and yellow, being natural pigments present in many living organisms. To date, more than 1,000 of these fat-soluble molecules have been identified, although scientists believe we have only discovered part of their diversity. In fact, among these hundreds of compounds, approximately 600 are currently documented, of which around sixty have provitamin A activity.
We now know that these precious nutrients are synthesized by all algae, all green plants and by many fungi and bacteria. Additionally, in humans, 34 carotenoid forms have been isolated from tissues, plasma and secretions. Their importance for our health is considerable, particularly as precursors of vitamin A, whose nutritional references recommend that 60% of intakes be obtained from carotenoids. In this article, we will explore together the exact definition of carotenoids, their benefits for our body, and how to effectively integrate them into our daily diet.
What is a carotenoid?
Chemically, carotenoids constitute a large family of tetraterpene pigments formed by the assembly of eight isoprene units, thus creating a chain of 40 carbon atoms. This particular molecular structure gives them their characteristic properties and their ability to interact with our body in a unique way.
Simple definition and classification
Carotenoids are organic pigments naturally occurring in the chloroplasts and chromoplasts of plants and other photosynthetic organisms. There are mainly two categories: carotenes and xanthophylls. Together, these molecules form a family comprising more than 600 different compounds identified to date. Each has specific properties and distinct biological roles.
The basic structure of carotenoids is characterized by a system of conjugated double bonds that allows them to efficiently absorb visible light. It is this particularity which explains why these compounds generally appear to us in shades ranging from yellow to orange-red. Furthermore, this double bond system is also responsible for their ability to neutralize free radicals and therefore for their powerful antioxidant activity.
Difference Between Carotenes and Xanthophylls
Carotenes represent purely hydrocarbon carotenoids, consisting exclusively of carbon and hydrogen atoms. β-carotene and lycopene are two well-known examples of this subclass. In contrast, xanthophylls contain oxygen atoms in their structure, usually in the form of hydroxyl groups or ketones. Lutein, zeaxanthin and astaxanthin belong to this second category.
This structural difference influences not only their physicochemical properties but also their distribution in foods and their biological functions. While carotenes are mainly found in orange or red fruits and vegetables, xanthophylls are often found in green leafy vegetables, yellow corn or some shellfish.
Why they are fat soluble
Carotenoids are called fat-soluble because they dissolve in fats and not in water. This characteristic arises directly from their non-polar molecular structure composed mainly of hydrocarbons. This fat solubility has important implications for our nutrition.
First, it explains why the intestinal absorption of carotenoids requires the presence of fat in our diet. Without lipids, these precious nutrients would pass through our digestive system without being assimilated. Furthermore, this property also justifies their preferential storage in adipose tissues and the liver, where they can accumulate and constitute reserves that can be mobilized by the body according to its needs.
The role of carotenoids in the human body
In our body, carotenoids play multiple and essential roles in maintaining optimal health. These compounds, beyond their coloring function, act as true physiological allies with varied and complementary effects.
Vitamin A precursors
Beta-carotene is undoubtedly the best-known carotenoid, particularly because it is a major precursor of vitamin A. Concretely, when our body needs it, it can transform this carotenoid into active vitamin A (retinol) in the liver. This conversion is done on demand: 6 mg of β-carotene is equivalent to 1 mg of retinol. This characteristic is particularly interesting since, unlike preformed vitamin A, an excess of beta-carotene does not cause toxicity but simply a temporary yellow coloring of the skin.
The vitamin A thus produced plays crucial roles in:
- Maintaining normal vision, particularly at night
- Tissue renewal and healing
- Regulation of cell growth
Skin and eye protection
Furthermore, carotenoids concentrate in certain specific tissues to protect them. Lutein and zeaxanthin accumulate in the macula, in the center of the retina, where they form a natural filter against blue light. These macular pigments thus help prevent age-related macular degeneration.
At the skin level, carotenoids help regulate the absorption of UV rays and neutralize free radicals induced by sun exposure. Beta-carotene, in particular, intervenes in the improvement of epithelial cells of the skin and promotes the synthesis of melanin.
Immune system support
In addition, carotenoids, particularly beta-carotene, strengthen our immune system by stimulating the production of immune cells and improving their effectiveness. Vitamin A contributes to the normal functioning of the immune system, which explains why a diet rich in carotenoids helps maintain our natural defenses.
Antioxidant effect against free radicals
Finally, one of the most valuable properties of carotenoids is their powerful antioxidant action. They protect our cells against oxidative damage caused by free radicals, these unstable molecules that contribute to premature aging and various chronic diseases.
This antioxidant action gradually transforms free radicals into less harmful compounds until they are completely eliminated. For example, singlet oxygen, which is particularly harmful, is transformed into water and oxygen thanks to the intervention of carotenoids and specific enzymes.
Specific benefits depending on the type of carotenoid
Each type of carotenoid has unique properties that target specific aspects of our health. Let's take a closer look at the particular benefits of the main representatives of this family of nutrients.
Beta-carotene: vision and tanning
Beta-carotene is transformed into vitamin A in our liver according to the body's needs. This conversion is essential to maintain normal vision, particularly at night. Interestingly, 6 mg of beta-carotene is equivalent to 1 mg of retinol (active form of vitamin A). At the skin level, this pigment stimulates the synthesis of melanin, thus promoting a natural and protective tan. It also prepares the skin for the sun by strengthening its natural defenses against UV rays. Unlike pure vitamin A which can be toxic in high doses, beta-carotene has the advantage of being converted only according to the body's needs.
Lutein and zeaxanthin: eye protection
These two yellowish macular pigments belong to the xanthophyll family. They are mainly concentrated in the central area of the retina, particularly at the level of the macula essential for visual acuity. Their role is crucial: they filter and attenuate short-wave light radiation, including harmful blue light emitted by the sun and digital screens. Optimal supplementation (10 mg of lutein combined with 2 mg of zeaxanthin) has demonstrated significant benefits on eye health and visual acuity, particularly in seniors.
Astaxanthin: powerful anti-aging
Astaxanthin, a carotenoid of natural origin present in algae and certain shellfish, has an antioxidant capacity up to 6000 times more powerful than vitamin C. This exceptional property makes it a major ally against skin aging. It neutralizes free radicals, reduces inflammation and improves mitochondrial function, thereby optimizing cellular energy. On the skin, its effects are visible: reduction of wrinkles, improvement of hydration, brightening of the complexion and protection against photoaging.
Lycopene: prostate health
Lycopene, responsible for the red coloring of tomatoes and watermelons, is particularly beneficial for men's health. Studies have shown that a plasma concentration of less than 0.25 µg/mL of lycopene is associated with an increased risk of prostate cancer. This carotenoid accumulates mainly in the liver, adrenals and prostate. The World Cancer Research Fund concluded, after analyzing nearly 500,000 studies, that foods rich in lycopene could offer protection against this cancer. In addition, lycopene is also a powerful antioxidant beneficial for the cardiovascular system.
Where to find carotenoids in food?
To fully benefit from the multiple benefits of carotenoids, it is essential to know where to find them in our daily diet. These precious pigments are present in various foods, but certain sources stand out for their exceptional richness.
Fruits and vegetables rich in carotenoids
Colorful plants are the main source of carotenoids. Orange, red or yellow hues often signal their presence. The carrot undoubtedly remains the champion of beta-carotene with 8 mg per 100g. Furthermore, sweet potato (14 mg/100g) and apricot (1.6 mg/100g) are also well endowed. For lycopene, choose cooked tomatoes (15 mg/100g), whose assimilation is optimized by cooking. As for lutein and zeaxanthin, they are abundant in dark green leafy vegetables such as spinach (10 mg/100g) and kale.
Algae and crustaceans
Certain marine organisms represent exceptional sources of specific carotenoids. Thus, astaxanthin is mainly concentrated in microalgae such as Haematococcus pluvialis as well as in shellfish (shrimp, lobsters) and pink fish (salmon). This microalgae can contain up to 40,000 mg of astaxanthin per kg, making it the most concentrated natural source in the world.
Food supplements: when and why?
Supplements become relevant when diet alone is not enough. Notably, older adults with increased lutein needs for eye protection may benefit from supplementation. However, you should favor natural formulas and respect the recommended dosages. For beta-carotene, the daily dose should not exceed 15 mg. Astaxanthin supplements show optimal results between 4 and 12 mg daily, depending on the goal.
Conclusion
Carotenoids therefore represent much more than just colored pigments in our food. Their impact on our health is considerable and diverse. We have seen that these fat-soluble compounds act as essential precursors of vitamin A, protectors of our skin and eyes, and powerful allies of our immune system.
Each carotenoid provides its specific benefits. Beta-carotene supports our vision and prepares our skin for the sun. Lutein and zeaxanthin protect our eyes against harmful blue light. Astaxanthin effectively fights skin aging. Lycopene, on the other hand, plays a particular role in prostate health.
Our daily diet can easily incorporate these valuable nutrients. Colorful fruits and vegetables, especially those with orange, red or yellow hues, are our best natural sources. Certain marine organisms such as algae and crustaceans also offer significant contributions, particularly astaxanthin.
Finally, dietary supplements can be useful in certain specific situations, although natural sources are always preferable. The important thing remains the regularity and diversity of our consumption of carotenoids to fully benefit from their protective effects.
Thus, these natural pigments deserve a special place on our plate. Our body will thank us for this supply of essential nutrients which, day after day, help maintain our health and vitality.
