Β-Carotene

β-Carotene (beta-carotene) is a red-orange pigment found in many plants, fruits, and fungi. It belongs to a group of compounds called carotenes, which are made from eight isoprene units and contain 40 carbons. This natural coloring gives many foods their bright colors.

When we eat foods with β-carotene, our bodies can change it into retinol, which is vitamin A. This helps keep our eyes, skin, and immune system healthy. Foods like carrots, pumpkin, spinach, and sweet potato are great sources of β-carotene.

People sometimes take β-carotene as a dietary supplement, and doctors may recommend it for a condition called erythropoietic protoporphyria, where the skin is very sensitive to sunlight. β-carotene is also used to add color to foods and has the E number E160a. Scientists figured out its structure in 1930.

To get β-carotene from natural sources, scientists use a method called column chromatography. It can be extracted from algae like Dunaliella salina. Because β-carotene does not mix with water, it is separated using a non-polar solvent such as hexane. Its strong color comes from its conjugated structure, and because it is a hydrocarbon without special groups, it easily mixes with fats, making it lipophilic.

Provitamin A activity

Plants give us important nutrients called provitamin A, and β-carotene is the most well-known one. Other carotenoids that also work like this are α-carotene and β-cryptoxanthin. Our bodies can only take in these carotenoids in a part of our digestive system called the duodenum, which is in the small intestine. When β-carotene gets there, a special enzyme can split it into two molecules of vitamin A.

Absorption, metabolism and excretion

When we eat foods that contain β-carotene, our bodies need to break it down so it can be used. First, the β-carotene needs to be released from the plant cells and mixed with fats in our food. This helps our gut absorb it.

Once inside our body, β-carotene is taken up by special cells in our gut. It can either be used directly or changed into a form of vitamin A called retinol. This process helps make sure our body gets the vitamin A it needs. The body carefully controls how much β-carotene is absorbed to keep everything balanced.

Eventually, β-carotene travels to the liver and then into the blood. From there, it can go to different parts of the body, such as the skin, lungs, and liver, where it is used to help make vitamin A or other important molecules. This helps keep our body healthy in many ways.

Conversion factors

β-carotene can help your body make vitamin A, and there are two ways to measure this.

One way is called retinol activity equivalents (RAE). Since 2001, this has been used to measure how much vitamin A you get from food. For example, 12 micrograms of β-carotene from food equal 1 microgram of RAE.

Another older way is called international units (IU). Many food labels still use IU, but it is less exact than RAE because it does not consider how well the body absorbs and uses β-carotene.

Dietary sources

Beta-carotene is found in many foods and gives them their orange color. Foods like cantaloupe, mangoes, pumpkin, papayas, carrots, and sweet potatoes are rich in beta-carotene. It is also sold as a dietary supplement.

Green leafy vegetables like spinach and kale have beta-carotene too, but its color is hidden by the green chlorophyll.

Government organizations have not set a specific daily amount for beta-carotene.

Side effects

Taking too much β-carotene can cause a harmless change in your skin, making it look orange. This happens when β-carotene builds up in the top layer of your skin. It can happen if you eat lots of carrots, carrot juice, or other foods rich in β-carotene for a few months.

β-carotene is safe to eat and won’t cause too much vitamin A in your body. However, taking β-carotene with certain medicines might make those medicines less effective. Also, people who smoke and take high amounts of β-carotene as a supplement may have a higher chance of getting lung cancer. This is not a problem when β-carotene comes from food.

Industrial sources

β-Carotene is made in factories in two ways. One way is to build it from smaller parts in a process called total synthesis. Another way is to take it from natural sources like vegetables and tiny water plants called microalgae. These methods make β-carotene in large amounts at a lower cost.

Research

Doctors usually suggest getting beta-carotene from food instead of supplements. Studies show that taking high amounts of beta-carotene as supplements might increase health risks, especially for people who smoke.

Beta-carotene has been studied for helping with eye health and some diseases. For a condition called age-related macular degeneration, which can cause loss of vision in older people, some studies say eating more beta-carotene might help, while others do not find any benefit. For cancer, taking beta-carotene as a supplement does not seem to lower the risk of many types of cancer and might even increase the risk of lung cancer in smokers.

For cataracts, which cloud the eyes, studies have not found that beta-carotene supplements help prevent or slow them down. In a rare condition where the skin is very sensitive to sunlight, beta-carotene can be used as a safe treatment.