Découvertes scientifiques 28/09/2020

The benefits & properties of carotenoids on health

Carotenoids are pigments naturally found in many fruits, vegetables, algae, and plants. Powerful antioxidants, they are known for their numerous health benefits, particularly for the eyes, cardiovascular system, and skin. Widely studied, the benefits of carotenoids have been the subject of several scientific researches. But the results are sometimes controversial. What is the real situation? A look back at the research by Eggersdorfer & Wyss.

Published in 2018 in the scientific journal Archives of biochemistry and biophysics, the study by Eggersdorfer & Wyss [1] offers a synthesis of the health benefits of carotenoids identified in the scientific literature.

But before going into the details of this synthesis, do you know why and how to consume carotenoids?

Why and how to consume carotenoids?

Carotenoids are a family of fat-soluble substances mainly composed of beta-carotene, astaxanthin, lutein, zeaxanthin, and lycopene. While they are found in most fruits and vegetables, carotenoids cannot be synthesized by the human body [2]. That is why it is important to consume them from external sources, either through diet or as part of dietary supplementation.

In the diet, carotenoids are present in most colorful fruits and green leafy vegetables. For example, beta-carotene is found in carrots, oranges, broccoli, and spinach. Lutein and zeaxanthin are found in kale, zucchini, broccoli, peas, and kiwis. For lycopene, tomatoes, watermelon, and guava are particularly recommended. But carotenoids are also found in sweet potatoes and certain types of squash. The only exception is astaxanthin, which is found only in crustaceans or microscopic algae. Furthermore, carotenoids can also be consumed as dietary supplements. For astaxanthin, for example, capsules are practical because one would have to eat a very large quantity of crustaceans to get a sufficient dose of this carotenoid. While some dietary supplements provide broad carotenoid supplementation, others are more targeted. There are notably dietary supplements of beta-carotene, lutein, zeaxanthin, or lycopene.

Thus, ideally, one should prioritize sources of carotenoids in their diet and complement these intakes with targeted dietary supplements according to their needs.

Carotenoids and health

Consuming carotenoids is important because the human body cannot synthesize them. But what are the health benefits of carotenoids?

Studies on the health benefits of carotenoids are sometimes contradictory. To clarify, let's revisit the research by Eggersdorfer & Wyss [1] which highlighted the properties and role of carotenoids identified in the scientific literature.

According to this research, carotenoids would act on human health in several ways, notably through their antioxidant powers but also through other mechanisms.

Provitamin A: cell renewal and immune system
Beta-carotene, also called provitamin A, is a precursor of vitamin A. Depending on the body's needs, this provitamin is converted into vitamin A, essential for our health. It plays a crucial role especially at the level of our cells and our immune system.

Eye health
Lutein and zeaxanthin are present in the human retina. In particular, they are concentrated in the macula, hence their name macular pigment. This is how they act for eye health.

Their antioxidant properties are believed to have the ability to neutralize singlet oxygen, protect against UV-induced peroxidation, and reduce the formation of lipofuscin [3]. Also, these carotenoids absorb wavelengths of light, blue light, which would help protect the eyes from photochemical damage [4]. Other studies have shown that supplementation with lutein/zeaxanthin can improve visual performance, notably contrast sensitivity and glare tolerance [5,6,7]. Finally, they may have a protective role against age-related macular degeneration (AMD). Indeed, according to a secondary analysis of AREDS2 [8], supplementation with lutein/zeaxanthin would help reduce the risk of progression to advanced AMD.

Sun protection
Carotenoids are also believed to have protective properties for the skin against aging, damage caused by UV rays and sunburn. This is notably due to their unique structure composed of at least ten conjugated double bonds. This structure gives them a high potential for trapping reactive oxygen species, such as peroxide or singlet oxygen molecules [9]. However, photoprotection with dietary carotenoids is inferior to that obtained by applying sunscreens. Thus, they do not replace sunscreens but can be good allies for sun protection due to their ability to protect against UV irradiation and maintain good skin health.

Cognitive performance
Although the underlying mechanisms are unclear, several carotenoids appear to have effects on cognitive function. These effects seem to be related to antioxidant activity [10]. This is notably the case for beta-carotene, which helps maintain cognitive performance [11], and lutein and zeaxanthin, which have effects on attention, memory, and cognitive flexibility [12].

Cardiovascular health
Astaxanthin and lutein in particular seem to help prevent heart diseases.

Astaxanthin is recognized for reducing low-density lipoprotein peroxidation [13] and improving blood lipid profiles [14]. Additionally, it helps shorten the average blood transit time, which can be beneficial for microcirculation.

As for lutein, its consumption and concentration in the blood are associated with a lower risk of coronary heart disease and stroke [15].

Weight management
The antioxidant properties of carotenoids could, by reducing overall oxidative load, exert beneficial effects on weight management and obesity [16]. Furthermore, according to recent findings, carotenoids may have a beneficial effect on adipocyte differentiation [16], which would promote a reduction in abdominal and subcutaneous fat.