What is the Difference Between Alpha and Beta Carotene

The main difference between alpha and beta carotene is that alpha carotene contains a single retinyl group, whereas beta carotene contains two retinyl groups. Furthermore, alpha carotene has a kind of vitamin A activity, which is less than beta carotene while beta carotene is broken down into retinal, a form of vitamin A in the small intestine.  

Alpha carotene and beta carotene are two types of carotene, which are unsaturated hydrocarbon substances exclusively synthesized by plants but, not by animals. However, both alpha and beta carotene are important as precursors for vitamin A. 

Key Areas Covered 

1. What is Alpha Carotene
     – Definition, Structure, Importance
2. What is Beta Carotene
     – Definition, Structure, Importance
3. What are the Similarities Between Alpha and Beta Carotene
     – Outline of Common Features
4. What is the Difference Between Alpha and Beta Carotene
     – Comparison of Key Differences

Key Terms 

Alpha Carotene, Beta Carotene, Carotene, Carotenoids, Provitamin A

What is Alpha Carotene 

Alpha carotene is the second most abundant form of carotene. Generally, it contains a β-ionone ring at one end and an α-ionone ring at the opposite end. Also, dietary sources of alpha carotene include yellow-orange vegetables such as carrots, sweet potatoes, pumpkin, and winter squash and dark-green vegetables such as broccoli, green beans, green peas, collard, spinach, leaf lettuce, and avocado. 

Figure 1: Carrots

Usually, the serum level of alpha carotene in adult males is 4.22 μg/dL while in adult females, it is 5.31 μg/dL. Furthermore, alpha carotene has half of the potential of beta carotene to synthesize vitamin A. Still; it has some potential longevity benefits. Significantly, the high levels of alpha carotene are associated with cancer death, cardiovascular disease, death from diabetes, etc. 

What is Beta Carotene 

Beta carotene is the most abundant form of carotene. Generally, it consists of 40 carbons arranged into eight isoprene units with beta-rings at both ends of the molecule. Significantly, beta carotene causes the red-orange pigmentation in plants and fruits. Basically, some of the richest sources of beta carotene include Vietnamese gac, crude palm oil, mangoes, pumpkin, papayas, cantaloupe, root vegetables such as carrots, sweet potatoes, etc. Also, leafy vegetables such as spinach, kale, etc. For instance, Vietnamese gac and palm oil are the richest sources of beta carotene, containing amounts ten times higher than carrot. 

Figure 2: Alpha Carotene

Moreover, beta carotene is a type of carotenoid the precursor or the inactive form of vitamin A. Basically; carotenoids are plant pigments hue in many fruits and vegetables while being responsible for their yellow, red, and orange color. Significantly, they are antioxidants, which serve as strong cancer-fighting agents. For instance, the two types of carotenoids are carotene and xanthophylls. Also, the other two types of provitamin A carotenoids include alpha carotene, which is a carotene same as beta carotene and beta-cryptoxanthin, which is a xanthophyll. In the meanwhile, beta carotene provides the protection against sunlight while lowering the risk of metabolic syndrome and lung cancer. However, in smokers and former asbestos workers, beta carotene increases the risk of lung cancers. 

Similarities Between Alpha and Beta Carotene 

• Alpha and beta carotene are two types of unsaturated hydrocarbons, serving as precursors to vitamin A synthesis. 
• Both have the molecular formula, C40H56. They do not contain oxygen atoms. 
• Plants exclusively synthesize these carotenes. But, animals excluding some aphids and spider mites are unable to synthesize them. However, some fungi synthesize carotene. 
• Both are photosynthetic pigments, absorbing ultraviolet, violet, and blue light while scattering red or orange and yellow light. 
• Therefore, they are responsible for the colors of many fruits, vegetables, an fungi. 

Difference Between Alpha and Beta Carotene

Definition 

Alpha carotene refers to a form of carotene with a β-ionone ring at one end and an α-ionone ring at the opposite end while beta carotene refers to an organic, strongly colored, red-orange pigment abundant in plants and fruits. 

Abundance 

Alpha carotene is the second most abundant form of carotene, while beta carotene is the most abundant form of carotene. 

Retinyl Groups 

Alpha carotene contains a single retinyl group while beta carotene contains two retinyl groups. 

As a Precursor of Vitamin A 

Alpha carotene produces 50% of vitamin A as beta carotene does while beta carotene is the most powerful carotene, which produces vitamin A in the small intestine. 

Dietary Sources 

Alpha carotene is more abundant in yellow-orange vegetables such as carrots, sweet potatoes, pumpkin, etc. and dark-green vegetables such as broccoli, spinach, green beans, green peas, etc. In contrast, beta carotene is rich in Vietnamese gac, crude palm oil, cantaloupe, mangoes, pumpkin, and orange root vegetables such as carrot and sweet potatoes.  

Heath Benefits

The high levels of alpha carotene are associated with cancer death, cardiovascular disease, death from diabetes, etc. while beta carotene provides the protection against sunlight while lowering the risk of metabolic syndrome and lung cancer.

Conclusion 

Alpha carotene is the second most abundant form of carotene mainly resent in yellow-orange and dark-green vegetables. Also, it contains two retinyl groups and contributes to the synthesize of 50% of vitamin A than beta carotene does. In contrast, beta carotene is the most abundant form of carotene with the highest potency to synthesize vitamin A. Generally; it occurs in orange, root vegetables. Therefore, the main difference between alpha and beta carotene is structure and importance. 

References:

1. Szalay, Jessie. “What Are Carotenoids?” LiveScience, Purch, Available Here.

Image Courtesy:

1. “CarrotDiversityLg” By User Larsinio on en.wikipedia (Public Domain) via Commons Wikimedia   
2. “Beta-carotene” (CC BY-SA 3.0) via Commons Wikimedia