Carotenoids: a great family of an enormous nutritional and sanitary interest
Carotenoids are chemical substances which are responsible for the diversity of yellow, orange, and red colors that can be found in vegetable foods, as well as the orange colors that are found in some foods of animal origin.
Chemically, they are a group inside flavonoids which belong to a family known as terpenes. Among all that are known, only a 10% has the biological potential as vitamin A. In this group, which is made of more than six hundred elements, beta-carotene stands out, along with alpha-carotene, and beta-cryptoxanthin.
The reason why all of them have a biological activity as vitamin A once they are consumed lies on a detail related to their chemical structure: terpenes are characterized by having terminal rings in their structure and in this case, at least one of them must be closed and in a reduced state, which means “not oxidized”. This discard from this group some famous carotenoids like lycopene, zeaxanthin, and lutein, which are relevant as antioxidant pigments, but they lack vitamin value.
All in all, it is a group to which experts attribute an interesting amount of beneficial effects for our health, specially in:
- Ocular health: they have a high therapeutic value against degenerative diseases of the retina.
- Cardiovascular health: by acting together with others active ingredients such as glutathione and vitamins C and E.
- Tumors blocker: all carotenoids are made of acetyl compounds, which are in charge of combating the development of tumors and some organism which cause infections through a cytotoxic effect.
- Male fertility: an action that, according to the data obtained from recent studies, seems to come from its antioxidant power.
- Skin health: it protects it from the aggressive action of toxic substances and agents that cause diseases.
- Some act more specifically, such as the lycopene, a carotenoid which can be found specially in tomatoes and which has highly favorable effects on the liver, the prostate, the mammal gland, the colon, and the lungs.
The retinol is a fat-soluble vitamin which is present in food in two possible chemical forms: preformed vitamin A from certain foods of animal origin, and pro-vitamin A, which is abundant in the vegetable kingdom and mainly represented by beta-carotene.
Beta-carotene, the icon of carotenoids
Beta-carotene was the first carotenoid that achieved a pure form in a laboratory. The scientist Wackenroder discovered it in 1831, when he managed to isolate it with the structure of micro-crystals by using as substrate a sample of carrot. Precisely it was the carrot what inspired him to name it, which is a derivation of the scientific nomenclature of this plant in Latin, Daucus carota.
Beta-carotene behaves as a fat-soluble substance of a yellowish tone and it is the most extended and efficient of all the pro-vitamin A carotenoids, which are programmed for their metabolic conversion in vitamin A within the organism, and which can be provided through several nutritional sources.
How does beta-carotene evolve inside the organism
The human body is capable of dividing in two halves each beta-carotene molecule which is consumed in order to get two of vitamin A. This is a remarkable advantage over other types of carotenoids, since normally they just provide one molecule of vitamin A, which is the reason why the biological efficiency of beta-carotene is higher. Nevertheless, it should be pointed out that in order to ensure a correct absorption, beta-carotene must be consumed along with certain amount of fat.
It metabolizes almost completely in the intestine an an important unaltered amount is destined to the fat deposit.
Once in the small bowel, beta-carotene is transformed into vitamin A due to the intervention of a specific enzyme, 15:15 monooxygenase, then it goes to the bloodstream to perform its tasks in target organs.
If a retinol excess is synthesized, it is deposited in the liver, which acts as a reserve organ, in order to release it when the situation demands it. On the other hand, the amount of beta-carotene that has not been transformed into vitamin A due to a saturation of the metabolic pathway, becomes part of the adipose tissue inside its specialized cells to store fat. It will remain there until it is necessary to use it, as well as in the suprarenal glands, and the ovaries in the case of women.
Physical and chemical characteristics of beta-carotene
At an industrial level, beta-carotene can be obtained from two possible methods: one is called chemical synthesis and the other is of a biological type, by using an Dunaliella salina algae culture, which is very common in waters with a high concentration of sodium chloride.
As with the rest of substances that form the carotenoids family, it is liable to experiment an isomerization phenomenon, which is probable specially under critical processing conditions, like lack of oxygen, high temperatures, etc.
The intensity of the transformation into isomers is something that depends on each food and on the degree of aggressiveness of the environment where it is found; it should be expected that it isomerizes up to a 30-40% of beta-carotene in the form of trans, transforming into isomers 9-cis and 13-cis, which are the most common.
This chemical phenomenon is a double-edged sword. On the one hand, it is a problem since it produces a sensitive decrease of the equivalent value of vitamin of beta-carotene. Not in vain, isomer 13-cis barely reaches a 50% of the vitamin value that it has in its trans form, even less (around 40%) if we talk about 9-cis. However, the other side of the coin is that said decrease is compensated by an increase of the bioavailability of this molecule, which is mostly due to the denaturation of proteins with which it frequently forms a binding complex, specially in vegetable foods.
On the other hand, it must be taken into account that the temperature that is reached during the cooking process produces a softening of the cell walls, which makes the vitamins and the beta-carotene within these foods more accessible for their digestive absorption.
Apart from its nutritional and quasi-therapeutic uses, its use as food color is quite frequent, specially in drinks, although its insolubility in water makes it quite complex. It is solved by using the physical form of ultrafine powder (particles with a diameter not longer than 0.4 micron), using the polysaccharide arabic gum as a support dispersing agent.
Moreover, synthetic beta-carotene is common as a raw material in the nutrition industry and it has two uses: color and vitamin A source. For example, it is used in the bread and milk industry in order to make ice cream, fruit juices, chewing gum, sauces, and confectionery.
What are the natural sources of beta-carotene
Generally speaking, we can say that we are normally surrounded by nutritional products that can be found in our shopping list, in which beta-carotene is an important component. They can be classified in three big groups:
- Orange and yellow fruit, such as peach, apricot, orange, and khaki.
- Green leaf vegetables, such as spinach, chard, lettuce, cress, broccoli, etc.
- Vegetables such as carrots, tomatoes, pumpkins, red pepper, etc.
In order to give more detailed information, we will provide a list which is not definitive at all, of foods which are ordered from highest to lowest according to their content of beta-carotene in micro-grams per gram of product:
- Purslane 4650
- Spinach 690
- Carrot 673
- Cress 560
- Beetroot 468
- Pepper 460
- Peanut 360
- Kale 345
- Parsley 267
- Khaki 253
- Green bean 245
- Fennel 241
- Endive 240
- Cilantro 228
- Radish 214
- Cantaloupe 200
- Lettuce 190
- Bear berry 172
- Papaya 123
- Pumpkin 114
- Tomato 113
- Mango 96
- Bean 66
- Watermelon 48
- Brussels sprouts 41
- Orange 28
In green vegetables, beta-carotene and xanthophyls form part of the composition of certain specialized organelles within the vegetable cell called chloroplasts, which are responsible for the photosynthesis process, since they also contain chlorophyll. In this group of vegetables, the most common thing is that carotenoids are the most abundant element.
However, the abundance of carotenoids in fruit will depend on their species; in the case of mango or khaki they will be beta-carotene. This unequal distribution will have to be taken into account when it comes to the diet, since we will need to provide a wide variety of the different groups in order to guarantee a proper intake of beta-carotene.
In quantitative terms, if we use vitamin A as a reference, its value in beta-carotene does not surpass the one from retinol, which is metabolically efficient vitamin A. However, it is so abundant in the vegetable kingdom, as well as in some foods of animal origin such as milk or egg yolk (rich in carotenoids but not all of them are beta-carotene), that it has become an important source of vitamin A for a lot of people.
We can even point out to the fact that developed countries, such as the United States, where the diet does not stand out precisely due to the excess of vegetables which are responsible for a third of the intake of vitamin A to the organism. On the contrary, it is remarkable the role of beta-carotene as a vitamin A supplier in vegetarian diets, which normally surpass the 50%.
All these foods that are rich in beta-carotene possess an important feature: they help to stop aging and they reduce the risk of suffering from several types of cancer; it has even been proven that it produces a certain degree of inhibition of the invasive growth of tumor cells in the case of prostate cancer.
The wide range of the functions of beta-carotene and its benefits for health
Without any doubt, beta-carotene is the most reliable source of vitamin A, which has an essential role in the development of the body, the integrity of the immune system, and the organs of sight.
Due to its intrinsic properties as an antioxidant substance, beta-carotene becomes an obstacle for the formation of free radicals, which are over-active oxygen molecules which are highly harmful to the cell membranes and to the genetic material contained in the nucleus of the cells. Their activity can result in an endless list of cardiovascular diseases and cancers.
Even though the satisfactory intervention of beta-carotene and other carotenoids is undeniable, there are numerous effects that are yet to be determined which may be caused by its powerful antioxidant capacity, or maybe they could be related to other mechanisms.
Some studies have been published about experiments carried out in vitro that reveal that, under certain laboratory conditions, carotenoids, and particularly beta-carotene, have the power to inhibit the beta-oxidation of fatty acids. These studies are related to others whose purpose was to establish or discard a cause-effect relation between the presence of beta-carotene and the blocking of the formation of atheroma plates which are characteristic from the coronary disease. There is evidence that this relation exists, even though it may be influenced by other diverse factors within the human body that make it more complex.
Its presence influences the expression of a gen that codifies the structure of a protein, which organizes itself in the form of channels that go through the cell membranes, which allow the exchange of little molecules. This effect seems to be exclusive to beta-carotene, not even vitamin A nor the antioxidant activities of other carotenoids play any role in this aspect.
Adding fruits and vegetables to our diet is a decision that will greatly reduce the risk of suffering breast cancer, which is something that can help even pre-menopausal women with a family history of this type of cancer and those who drink alcohol in excess. A study published in 2012 in the journal “Breast Cancer Research and Treatment” revealed that its consumption reduces the risk of developing breast cancer in a 6%, a number that is equally applicable to alpha-carotene, but not to other carotenoids.
There are also clinical trials carried out on AIDS patients that reveal that a beta-carotene supplementation can stimulate the formation of white cells (specifically lymphocytes) and the activity of NK cells (natural killers), which are one of the main fight mechanism against aggressive agents. However, it must be pointed out that it is not known with certainty if this function derives from the activity of beta-carotene as vitamin A once it is transformed, or to other intrinsic features of its family.
It should also be remarked that, within the immune system, it contributes to the activation of a gland called thymus, which is one of the main cores of immune machinery during the first years of life.
Apart from its evident results in well-known pathologies, it can be interesting to point out other less obvious functions carried out by beta-carotene:
- There is a congenital disease, of scarce causality, which is known as erythropoietic protoporphyria, which causes sensitivity to sun rays. The intake of beta-carotene can produce a palliative effect.
- It has been proven that maintaining a proper rate of beta-carotene in the tissues reduces the susceptibility to glucose intolerance, which can offer protection from diabetes.
- It is possible to buffer the macular degeneration process related to age, which causes a wear down of central sight, with a consumption of 15mg of beta-carotene.
- Oral leukoplakia is a peculiar disease, which appears in the form of white spots in the mouth and the tongue, normally due to unhealthy habits like smoking or drinking alcohol, whose development can be controlled throughout a sustained beta-carotene consumption.
- Scleroderma is quite similar, it is a disease of the connective tissue that can be externally appreciated by a thickening and hardening of the skin. One of its causes can be a beta-carotene deficiency.
- A diet that lacks beta-carotene and vitamin C can involve the risk of suffering rheumatoid arthritis, one of the autoimmune diseases that is caused by anomalous reactions within the organism against its own elements.
A review of beta-carotene supplements
The first thing we must notice is that the main sanitary authorities such as the American Heart Association, the International Agency for Research on Cancer, or the OMS among others, advocate for an optimization of the diet when it comes to the intake of active ingredients before recurring to dietary supplements. In order to confirm this statement, a very eloquent point is that
Five portions of fruit and one of vegetables, which have to be mainly green, provide between 6 and 10 mg of beta-carotene.
However, it is commonly used in a wide range of pathological situations, among which we will mention a bad absorption of fat, alterations of the bile pathways (hepatic deficiency, cirrhosis…), pancreas deficiency or cystic fibrosis
A long time ago, scientists looked for the statistically significant differences between natural and synthetic beta-carotene when it comes to its influence in the prevention of lung cancer. This research started to provide answers that followed the argument that was previously mentioned. A diet made of foods rich in beta-carotene (logically natural) and the prevention of this type of cancer are related, which is something not manifested in those who were administered synthetic preparations. In fact, among those who were tested with synthetic beta-carotene, a segment made up of smokers, there was an increase in the risk of suffering from that neoplasia.
Beta-carotene supplements are available with aqueous and oily base, the latter are easily to absorb orally, as long as there is an adjustment to the intake pattern. The common amount is of 25 000 IU, which corresponds to 15 milligrams per day; in spite of this, it is not uncommon to see people who reach even 100 000 IU or 60 mg, without any evidence that proves that an excess provides any benefit for the organism. However, intakes can even reach 180 mg per day in the case of dermatological disorders, which have not revealed to cause any side effects that should be worth considering. When it comes to children, around 1300 IU between 4 and 8 years and 2000 IU until 14 would the most balanced amounts.
We should keep in mind that the amount of beta-carotene that the organism is capable of absorbing varies according to several factors, among which stand out the rhythm and intensity of the individual metabolism and the presence of fatty matter available in the digestive tube, which is a determinant factor for a complete and efficient absorption of beta-carotene.
After the experience obtained from the dietary supplementation with this substance, it seems to provide better results with special formulas, such as the ones that can be found in the online HSN shop, which combine natural carotenoid blends (beta-carotene, alpha-carotene, cryptoxanthin, lutein, and zeaxanthin), multi-vitamin/minerals complexes and other antioxidant substances, against the commonly believed practice of consuming just isolated synthetic beta-carotene. An extraordinary cocktail that could be taken as reference is an alpha and beta-carotene complex from carrot along with lutein from marigold flowers and lycopene from tomato.
The most part of the synthetic beta-carotene that is sold for supplementation is formed by the molecule that responds to the chemical name “all-trans-beta-carotene”, while the one that is found in food combines two molecules, the previous one and 9-cis isomer beta-carotene, whose proportion is not standard, it rather fluctuates according to the source of food.
When it comes to purchasing a supplement, if you wish to know its origin you have to pay attention to the information that can be found on the label; if it is natural beta-carotene there are several possibilities, such as: “from D.salina”, “from algae”, “from palm oil”, or simply “natural beta-carotene”.
Benefits of Beta-carotene and biotin
Biotin is a hydro-soluble group B vitamin that provides the organism an indispensable tool to metabolize carbohydrates, fat, and amino acids, ingredients from which we obtain energy; its interest lies on the fact that they are frequently associated to an excellent interaction with other dietary supplements.
Side effects and contraindications of Beta-carotene
In reality, it is a substance that is practically free from any side effects when it is consumed within the recommended amounts for certain clinical conditions; we simply can point out to the fact that a sustained intake of 100 000 IU or 60 mg per day can produce a yellow-orange color of the skin, which does not entail any risk for our health and which disappears after eliminating that extra intake. Even though we can also number certain negative reactions:
- Localized allergic reactions.
- Pressure in the chest.
- Spontaneous bleeding.
It also needs to be pointed out that there is a general consensus among specialists that, for smokers, consuming synthetic beta-carotene increases the risk of developing lung or prostate cancer.
It should be taken into account that when we carry out a sustained supplementation with beta-carotene, it is recommended to combine it with extra intakes of vitamin E, since it is expected to experience declines of this vitamin within the organism.
When it comes to the contraindications of beta-carotene:
- It can reduce the efficiency of medicines aimed at the reduction of cholesterol levels.
- It is not recommended for those who have been exposed to asbestos for a long time due to work.
- Due to its antioxidant properties, it can inhibit the efficiency of the treatment for angioplasty.
- Due to the lack of data about its excretion through breast milk, it is advisable to avoid its consumption while lactating.
Beta-carotene and caffeine
To conclude, we will point to the last fact about the combination of beta-carotene and caffeine, which has sometimes caused controversy. Nowadays, the experts agree that its combination is completely compatible, since caffeine exerts a double action: laxative and diuretic. Both of them encourage the loss of liquids and mineral salts, but it does not hinder the intestinal absorption of beta-carotene. This means that consuming a beta-carotene supplement with coffee for breakfast does not entail any contraindication.