Mechanistic aspects of carotenoid health benefits – where are we now?

Abstract

Dietary intake and tissue levels of carotenoids have been associated with a reduced risk of several chronic diseases, including cardiovascular diseases, type 2 diabetes, obesity, brain related diseases and some types of cancer. However, intervention trials with isolated carotenoid supplements have mostly failed to confirm the postulated health benefits. It has thereby been speculated that dosing, matrix and synergistic effects, as well as underlying health and the individual nutritional status plus genetic background do play a role. It appears that our knowledge on carotenoid-mediated health benefits may still be incomplete, as the underlying mechanisms of action are poorly understood in relation to human relevance. Antioxidant mechanisms – direct or via transcription factors such as NRF2 and NF-κB - and activation of nuclear hormone receptor pathways such as of RAR/RXR or also PPARs, via carotenoid-metabolites, are the basic principles which we try to connect with carotenoid-transmitted health benefits as exemplified with described common diseases including obesity/diabetes and cancer. Depending on the targeted diseases, single or multiple mechanisms of actions may play a role. In this review and position paper, we try to highlight our present knowledge on carotenoid metabolism and mechanisms translatable into health benefits related to several chronic diseases.

What Is the Current Direction of the Research on Carotenoids and Human Health? An Overview of Registered Clinical Trials

“…In particular, correlations with α and ß-carotene were found [ 54 ]. The effects of carotenoid supplementation on gut composition are few, and a recent review tried to summarize the main findings by concluding that the “carotenoids–gut” interaction still represents a fundamental research question that must be addressed [ 55 ].…”

Red Seaweed Pigments from a Biotechnological Perspective

“…Carotenoids are a family of long conjugated isoprenoid pigments that have a cosmopolitan presence among the vegetal kingdom, as well as in photosynthetic organisms and fungi [146], whereas the animal kingdom lacks the ability to produce them, probably due to the evolutionary loss of the required genes needed to encode the enzymes for carotenoid biosynthesis [147]. These accessory pigments are part of a light-harvesting antenna complex in the thylakoid membrane of chloroplasts [146], and contribute to the photosynthetic process by enhancing light harvest in the blue spectrum, and thus extending the light-absorption range [147]. Additionally, they have a key role as photo-protective and antioxidant agents, by shielding organisms from excess light energy, by performing the thermal dissipation of any energy surplus in the photosynthetic apparatus, and by acting as direct quenchers of reactive oxygen damage [148][149][150].…”

“…Recent reviews regarding carotenoids (from 2016 onwards) can be found, that deal with their potential health benefits [147,151,[162][163][164], bio-accessibility [148,164], metabolism and biosynthesis [149,165], dietary sources [158], production [157,[166][167][168], extraction and analysis [158], and biotechnological potential [167]; again, most of these examples focus on either microalgae or fungi or, at least, they are not solely focused on macroalgae. By searching the word "carotenoid", Patentscope holds 4701 registered patents, using the search field "front page" [16].…”

43 Natural Anticancer Products: Classified under the Cancer Hallmarks and the Available Evidence of their Anticancer Activities

“…Although dietary intake and tissue levels of provitamin A and related carotenoids have been associated with reduced risk of several types of cancer and many of the same carotenoids have shown anticancer activity in preclinical models, both in vitro and in vivo, intervention trials with isolated carotenoid supplements other than lycopene have not shown anticancer activity, and in fact 1% of current and former smokers as well as patients with a history of asbestos exposure who took long-term high daily doses of isolated carotenoid supplements actually developed lung cancer which similar patients in the control group did not [21].…”