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April 26, 2014

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Bioactive Compounds

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Carotenoids

A version of this post appears on the Vital Juice blog.
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What is the one nutritional fact that you know about carrots? If you’re like most people you will answer that is has a lot of beta-carotene. This is true. You might also be aware that beta-carotene plays some kind of role in eye function. This is also true. But carrots and carotenoids do far more than that. Settle in with some freshly made carrot juice and hear all about the benefits of carotenoids.

Beta-carotene is part of a class of compounds called carotenoids that play many different roles in the body. Carotenoids are molecules that are responsible for a great majority of the yellow to red colors that we see and have a wide range of functions in the natural world, from light-harvesting pigments to protecting chloroplasts from reactive oxygen to cell-to-cell communication to their prominent role in the structure of eyes (Figure 1).1,2 Carrots are excellent sources of carotenoids, mostly in the form of alpha and beta-carotene.3,4 Carotenoids may be best known for their role as a precursor to vitamin A, but beyond that carotenoids have been shown to be associated with a wide range of beneficial properties.

Figure 1. Carotenoids in Nature from Von Lintig, J. & Sies, H. (2013)

Figure 1. Carotenoids in Nature from Von Lintig, J. & Sies, H. (2013)

 

One of the major roles of carotenoids is that many of them can be converted into vitamin A by enzymes within the body. This is why carotenoids like beta-carotene are sometimes called “pre-vitamin A” or “pro-vitamin A.” It is important to realize that carotenoids like beta-carotene, while very similar, are not the same thing as vitamin A. This is actually a very good thing. Let me explain… Although your body needs vitamin A to function optimally, ingesting too much vitamin A is highly toxic to the body and can cause all sorts of problems. If you want to learn about it in more detail visit the Wikipedia page on hypervitaminosis A, but some of the problems include weakness, nausea, bone fractures, hair loss, and fetal deformation if taken while pregnant. However, you can essentially eat or drink all the beta-carotene you want and be completely fine. The worst that can happen is that if you consume quite a bit then your body will begin storing the carotenoids in your skin making you appear slightly orange, but this condition is completely benign and might even save you from fake-baking to get a tan. The body will then selectively convert the stored carotenoids into vitamin A when it is needed.

Carotenoids and Cancer

Carotenoids, especially lycopene, have been associated with a lower risk of prostate cancer in several studies.5–12 The evidence regarding the link between carotenoids and lung cancer is mixed. While some earlier studies in the 1990s suggested that carotenoids increase the risk of lung cancer in heavy smokers13,14 newer reports suggest the opposite.15–17 Nevertheless, epidemiological evidence suggests that a diet rich in carotenoids is generally protective against breast and other cancers.18–24

Other Benefits of Carotenoids

Because of their role in eye health, carotenoids have been shown to be protective of age-related macular degeneration (AMD) as well as generally increasing visual acuity.10,25–31 There is also evidence that carotenoids help prevent skin damage from ultraviolet light.32–35

If you’d like to know more about carotenoids and their benefits, check out the Linus Pauling Institute’s page on the subject. LPI is actually a fantastic evidence-based resource on all kinds of phytochemicals, minerals, vitamins, and other important issues relating to nutrition.

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