Carrots are high in vitamin A and beta carotene, hence their name, and are important for the eyes and the immune system. Most of them do not know more about these vital substances – and this statement is sometimes even incorrect.

Vitamin A, provitamin A and beta carotene – what are they?

Because vitamin A is a complex of vitamins that includes retinol and retinyl esters . These forms are mainly found in animal foods.

There is also provitamin A as a precursor, which is found in plant-based foods. “There are also various representatives of provitamin A, the best known is beta carotene,” explains Andrea Henze, nutritionist at the University of Potsdam. The body has to convert provitamin A such as beta carotene into vitamin A so that it can be used. This processing takes place mainly in the intestines and liver.

Beta carotene – like all provitamins A – in turn belongs to the large group of carotenoids, of which there are more than 600 different ones. All of them have the property, as a natural coloring agent, of coloring plants yellow, orange, red and are therefore found in many orange-red vegetables. “But green vegetables such as spinach can also contain a lot of carotenoids,” adds the scientist, who is also researching the subject of vitamin A. In green vegetables, however, the orange-red color of the carotenoids is masked by the green plant substance chlorophyll.

The function of vitamin A.

Vitamin A is vital. “We need vitamin A for almost all body functions because it enables cells to differentiate,” explains Andrea Henze. This means that under the influence of this vital substance, the cell can become a skin cell, a mucous membrane or nerve cell. The other functions of vitamin A:

• Immune system: Vitamin A primarily promotes the development of lymphocytes and thus a strong immune response to foreign substances and pathogens.
• Skin and mucous membranes: It ensures healthy cell growth and cell integrity, thus preventing cracks and other damage, improving wound healing, i.e. regenerating. In this sense, vitamin A also acts on the lung epithelium and supports the constant renewal of the fine cilia that line the lung surface. It is similar in the intestine with the intestinal epithelium. Vitamin A is responsible for this constant renewal.
• Blood formation: Vitamin A promotes the formation of red blood cells (erythrocytes) and thus improves the transport of oxygen into every cell.
• Bones: It influences the storage of calcium phosphate in the bones.
• Reproduction and fertility: Vitamin A is extremely important for the formation of healthy egg cells and sperm as well as for embryonic development. “We know from studies that vitamin A deficiency in animals often causes infertility or, if fertilization does take place, the offspring can have deformities of the limbs,” adds the scientist.
• Seeing: Vitamin A is important in the eye as a pigment that enables the process of vision. It plays a key role in the nerve impulse that is triggered by the incidence of light and sent to the brain. Vitamin A, so to speak, mediates this signal cascade during the visual process.

Vitamin A does not have an antioxidant effect

From a purely chemical point of view, vitamin A is an antioxidant, but it does not play a role in the body in this context, for example because of its binding to transport proteins and its intracellular localization. As is often assumed, it is not a radical catcher and does not protect against “cell rust”, i.e. oxidation. “Vitamin A has no direct effect in this context, only an indirect one,” explains Andrea Henze more precisely: Vitamin A increases the absorption of vitamin E and selenium in the intestine, which have an antioxidant effect.

Pro-vitamins A such as beta carotene, on the other hand, can develop an antioxidant effect in the body before they are converted into vitamin A.

Why is this distinction important? Andrea Henze explains why it is best to use both animal and vegetable sources of vitamin A: Only then can the full spectrum of activity of these vital substances be used to the full.

Foods that are high in vitamin A and beta carotene

Among the foods of animal origin, the following are particularly rich in vitamin A:

• Beef liver
• Pork liver
• poultry
• butter
• cheese
• Eggs

When it comes to plant-based fruits and vegetables, these are good provitamin A suppliers:

• Carrots
• Cabbage
• spinach
• Apricots
• paprika

Store and prepare foods rich in vitamin A correctly

Vitamin A is sensitive to light, so food should be stored in the dark. In addition, the vital substance is relatively heat-stable and fat-soluble. This means that it is bound to fat and can therefore best be absorbed by the body.

In the case of animal sources, this is usually given or due to the preparation, for example the extremely low-fat liver is fried in oil. For the preliminary stage vitamin A, however, the corresponding vegetables should be prepared together with fat. “Studies have shown that it is particularly well absorbed by the body when it is crushed and steamed with a little fat,” reports Andrea Henze. Grinding is important so that the provitamin is released from the cellular structures.

An example: carrot vegetables, chopped up and steamed with a little safflower oil, provide the body with the vitamin better than nibbling raw carrots.

This is how much vitamin A you need every day

According to the reference value of the German Nutrition Society, the daily requirement for vitamin A is around one milligram per day. However, this is a bit simplified. Other units are used in nutritional science, the requirement is given as so-called retinol equivalents (RE) or retinol activity equivalents (RAE), explains the scientist and explains in more detail. 1 milligram of retinol corresponds to 1 milligram of RE or RAE. For provitamin A carotenoids, the calculation is more complex because additional factors have to be taken into account:

• Efficiency of absorption in the intestine (this is generally lower for carotenoids than for retinol or retinyl ester and depends on the food matrix)
• Conversion efficiency of provitamin A into vitamin A (this differs greatly between the provitamin A carotenoids, it is highest for beta carotene)

When using RAE, a conversion factor of 12: 1 is assumed for beta carotene and 24: 1 for all other provitamin A carotenoids. This means that 12 milligrams of beta carotene or 24 milligrams of other provitamin A carotenoids must be ingested with food to meet the requirement of 1 milligram of RAE. If, on the other hand, the intake takes place in the form of retinol or retinyl esters (i.e. from animal foods), the required intake is correspondingly lower.

According to this calculation, the daily requirement for vitamin A is covered with 150 grams of carrots, for example, or with a mixed diet: 1 egg, 100 grams of Gouda cheese and 75 grams of carrots.

Vitamin A deficiency affects certain risk groups

Because these foods are so rich in vitamin A, there is virtually no deficiency in this vital substance in Germany and other industrialized nations. However, that’s only true at first glance. Because experts differentiate between primary deficiency and secondary causes when it comes to undersupply.

Primary means that too few foods rich in vitamin A are eaten. This is almost never the case in this country. Even those who only eat fast food are adequately supplied with vitamin A. Vegans and vegetarians also get enough vitamin A from the preliminary stage.

It is different, however, with a secondary deficiency. In this context, secondary is used when the deficiency arises as a result of illnesses. Digestive diseases that affect absorption, such as:

• inflammatory bowel disease such as Crohn’s disease
• Celiac disease
• chronic liver disease, because vitamin A can then no longer be stored
• Diseases of the pancreas, because the digestive enzymes that are important for the absorption of the vitamin are not sufficiently produced.

In addition, there is a risk of undersupply if the vitamin A requirement is increased, this is the case with:

• pronounced inflammatory processes
• massive injuries such as burns when much of the skin surface is destroyed
• Kidney disease, which causes vitamin A to be excreted in the urine without being used
• Alcohol abuse because liver function is impaired
• pregnancy

Vitamin A Deficiency: Symptoms can be dramatic

As a rule, these risk groups are well looked after by a doctor, so that symptoms of deficiency rarely occur. Exception: alcoholics and very overweight people with massive fatty liver who do not seek medical advice. Apart from these patients, little is known about vitamin A deficiency in Germany. “Vitamin A deficiency occurs mainly in developing countries, where it is the main cause of blindness,” adds the scientist. Because one of the signs of vitamin A deficiency is night blindness, which can increase to complete blindness and is then no longer treatable.

There are also many other causes of night blindness, which are primarily age-related. The adaptive ability of the eye declines, for example as a result of cataracts, macular degeneration or retinopathia pigmentosa (hereditary disease). In any case, a doctor should always clarify if twilight vision deteriorates.

The other signs are a bit unspecific

• Susceptibility to infection
• dry skin and eyes
• brittle hair
• Loss of appetite
• Muscle weakness
• Fertility disorders

Vitamin A deficiency is best compensated for naturally

Anyone who thinks they are undersupplied with vitamin A should simply use more of the corresponding fruits and vegetables. Overdosing is not possible because the body only converts as much provitamin as it needs and it still makes sense to store it.

Over-the-counter supplements are the next step. It is best to get advice from a doctor and trust products from Germany. “Over-the-counter products only contain provitamin A, so overdosing is difficult, and absorption in the intestine is reduced if there is sufficient quantity,” explains Andrea Henze in more detail.

Beware of vitamin A supplements

Vitamin A supplements, on the other hand, can be more problematic, and poisoning is possible if overdosed. In Germany such products are therefore not freely available, but in other countries they are. “Vitamin A supplements should only be used under medical supervision and not for self-medication,” warns Andrea Henze.

Vitamin A poisoning – the first signs

The excess supply of vitamin A does not slow down the body, as is usually the case with provitamin A. The excess vitamin A is mainly stored in the liver; if it becomes too much, the detoxification organ can no longer work. “It leads to intoxication,” says the scientist. In pregnant women, this can also have negative consequences for the embryo.

The signs of vitamin A hypervitaminosis:

• Nausea and headache ,
• the bone tissue becomes porous.

If the oversupply lasts longer, it can even lead to death.

Incidentally, high doses of vitamin A supplements also led to the increase in lung cancer among smokers, previous studies warn.

There is no risk of intoxication from vitamin A through food – with one exception

What is certain is that over-the-counter supplements, which mainly contain beta-carotene, are usually harmless even if taken regularly. It is different with products that contain vitamin A, such as retinol. With them, intoxication is quite possible and can occur with a daily intake of 3 milligrams or more. By the way, retinol can also be found in many care products to keep the skin young and firm. “In this context, there is no need to fear overdosing, the substance does not pass from the skin into the bloodstream,” reassures the expert.

And hypervitaminosis A is hardly to be feared with food either. “Unless you eat liver several times a week,” warns Andrea Henze. Liver can contain over 30 milligrams per 100 grams of goods and thus exceeds the daily requirement by more than 30 times!

A historical anecdote shows how tragic this can end: More than 100 years ago, three researchers set out on an Antarctic expedition, Douglas Mawson, Belgrave Ninnis and Xavier Mertz. The expedition was not a lucky star, the men had to gradually eat the sled dogs in their distress in order not to starve to death. Mertz is said to have eaten the livers as well, subsequently complained of stomach pain, and his skin was partially peeling. After he fell into delirium, he passed away. Experts suspect that it was vitamin A poisoning from the dogs’ liver .

Therefore do not demonize the liver

Nobody knows for sure whether the story is really true. However, it is scientifically proven that hypervitaminosis A from natural foods is not to be feared, unless one eats a liver daily. Apart from that, the liver is an extremely valuable food from a nutritional point of view, contains vitamin A, iron, zinc , copper, vitamin B12 and folic acid, the supply of which is sometimes critical.

The most sensible recommendation: A lack of vitamin A can best be prevented with a balanced mixed diet, i.e. eat a lot of fruit and vegetables, whole grain and low-fat dairy products, sometimes a little fish or poultry.

The latest news from German slaughterhouses have certainly given the vegetarians and vegans community a new boost. In addition to animal welfare and ecological aspects, avoiding meat is usually also based on the desire for a healthy diet. What does science say

1. Consensus: little meat is okay, but not really necessary

Every German eats 150 grams of meat and meat products on average every day. That doesn’t sound like a lot, but it clearly exceeds the maximum 600 grams that the German Nutrition Society per week finds acceptable. Many consumers are also significantly higher. It is these “meat eaters” who are mentioned in the studies on the harmful effects of meat consumption.

But even with those who eat a lot of meat, there are differences: because those who eat a lot of unprocessed meat, and at the same time high in fiber and low in sugar, have a low risk of disease. This is the case, for example, with the Paleo diet.

Experts consider the Mediterranean diet to be the best nutritional method in the world, and it has been for two decades. In 2019 she was once again named the best diet of the year by “US News” . A lot of vegetables, fish and olive oil end up on the plate, but little meat and processed foods.

In comparative studies, it is not vegetarians and vegans who do well, but people who eat little meat.

But you can also say with a clear conscience to Tilmann Kühn, nutritional epidemiologist at the German Cancer Research Center (DKFZ) in Heidelberg: “If you eat wholesome vegetarian food, your body is fine. On the contrary, according to scientific findings, a vegetarian diet is actually very healthy. ”With one small caveat:“ Less meat ”only makes sense if the calorie advantage is not topped up with pizza, biscuits or meat imitations.

2. Those who do not eat meat also live more healthily in other ways

Numerous studies have shown that the biggest meat fans usually do not have good eating habits. Even if you neglect the nutritional value of individual foods, a diet high in meat and sausage as well as sugar, white flour and saturated fats from ready-made foods is unhealthy. Because healthy foods such as vegetables, fruit, legumes, whole grains or nuts are definitely neglected.

3. meat or plant? Nutritional studies are conditionally meaningful

In the laboratory, it is possible to determine how certain nutrients affect human cells. Studies with humans don’t work like that. The health comparison “meat eaters versus vegetarians” is only possible in observational studies. Their conclusions are only an approximation of reality. Too many factors play a role in health for the question to be reduced to schnitzel and tofu . For example: is a chain-smoking vegan healthier than an athletic meat eater?

Epidemiological studies can never conclusively prove that meat consumption is unhealthy. And it is also not conclusively clear which individual ingredients are harmful to health.

4. When it comes to meat, it depends on the color

Beef, pork, lamb or sheep provide the so-called red meat. It is said to cause cardiovascular diseases and problems with the blood vessels.

For US researcher Stanley Hazen from the Cleveland Clinic, a metabolic product of the carnitine contained in red meat is responsible for this. To prove this, he had 113 test subjects eat 250 grams of steak a day for four weeks. A two-week break was followed by four weeks with a correspondingly large amount of (white) poultry meat and, at the end, a meat-free month.

The result , published in the “European Heart Journal”, showed a significant 3-fold increase in the TMAO plasma concentration during the steak weeks. TMAO is produced during the metabolism of carnitine and is a risk marker for hardening of the arteries in the blood vessels. The diet with poultry and vegetables led to a decrease in plasma concentrations in the test subjects.

Red meat is also directly or indirectly involved in the development of cancer.

For example, studies by the DKFZ have shown that people who eat a lot of red meat have increased biomarkers of certain roasting substances, such as those produced during roasting and grilling, swim in the blood. These people were at an increased risk of developing colon cancer.

In the large-scale EPIC study across Europe, 519,000 test persons were examined to find out the connection between diet and cancer .

The results show that red meat can increase the risk of colon cancer. Accordingly, the risk of the disease increases by almost 50 percent if the daily consumption of meat is 100 grams above the recommended amount. The same amount of sausage products increases the risk by as much as 70 percent.

The risk of stomach cancer is also said to be related to heavy meat consumption. In people infected with the Helicobacter pylori bacterium, the risk increases by a factor of five.

5. Theory 1: Iron makes meat unhealthy

There are various theories about why red meat is so problematic. The so-called iron load hypothesis is based on the fact that red meat contains a comparatively high amount of iron. This so-called heme iron has a high bioavailability, unlike iron from plant food, and thus enters the organism in larger quantities.

It has long been suggested that high levels of iron in the blood increase the risk of cancer . However, this theory has not yet been proven by studies.

6. Theory 2: BMMF make meat unhealthy

Scientists working with Nobel laureate Harald zur Hausen believe they have found another cause: a previously unknown class of pathogens is responsible for the increased risk of colon cancer .

These “Bovine Milk and Meat Factors (BMMF)” enter the human intestines through the consumption of meat and dairy products from European cattle. There it comes to a chronic inflammation, which indirectly promotes the development of colon cancer.

7. Avoiding meat protects the intestines

Vegetarian foods contain fiber, which has a positive effect on the microbiome in the gut. Vegans have a particularly large number of them. In addition to fruit and vegetables, lactic acid foods such as yogurt also support the intestinal flora. Vegetarians often consume these. Researchers from the University of New York have confirmed that vegans and vegetarians have more protective types of gut bacteria than meat eaters.

Meat also poses a cancer risk through its preparation and processing: for example, when meat is heated up, several potentially harmful substances are formed at the same time, including so-called polycyclic aromatic hydrocarbons (PAHs); curing also produces nitrosamines. These substances can promote the development of cancer, and above all they increase the risk of colon cancer. Methods such as curing and intense heating are particularly used for industrially processed meat, such as sausage and ham. Accordingly, processed meat products are particularly unhealthy.

8. Avoiding meat makes you slim

Researchers at the Max Planck Institute for Cognitive and Neurosciences (MPI CBS) and the Leipzig University Hospital examined almost 9,000 people, what connections there are between body and mind on the one hand and not consuming animal products on the other. regardless of age, gender and level of education. The study was published in June 2020 in the specialist magazine “Nutrients”.

The result of the physical impact: the less food of animal origin was on the menu, the lower the average body mass index (BMI) and thus the body weight. “Products that are excessively high in fat and sugar make you fat. They stimulate the appetite and delay the feeling of satiety. If you do without animal foods, you eat fewer such products on average, ”explains Evelyn Medawar, first author of the work.

9. Avoiding meat and the psyche

With regard to the psychological effects of the meatless diet, the Leipzig study found no particular susceptibility to neuroses in vegetarians. The study director Veronica Witte says: “Previous analyzes had found that more neurotic people generally leave out certain food groups more often. We focused solely on avoiding animal products and could not observe any correlation. ”No connection was found between a predominantly plant-based diet and depressive moods. There was evidence of this in previous studies.

However, the researchers found a difference in one of the determining factors of personality: the extroversion or introversion. People with predominantly plant-based foods on the menu are more introverted than those who eat primarily animal products. The study authors have not yet found an explanation for this.

The intestine affects our health much more than was known a few years ago. The intestinal mucous membrane with its special flora made up of billions of microorganisms has a decisive influence on how well our defenses are set up, whether there is a risk of chronic inflammation, acne, autoimmune diseases or obesity.

But even if these connections have now been proven, the way we deal with the most important factor influencing intestinal health has hardly changed: diet.

We know how important the intestines are, but we still don’t pay attention to them

Most of us still eat too much meat and sausage, sugar and fat, fast food and ready meals, plus the “intestinal enemies” smoking and alcohol .

• The direct consequences: The intestinal flora is out of balance, flatulence , constipation and obesity result.
• The indirect ones: there is a risk of immunodeficiency, skin problems, inflammation and, last but not least, an increased risk of cancer, at least for colon cancer.

Particularly harmful: Leftovers lie in the intestines for days

Especially when food remains in the intestine for a long time, it is harmful to health. In the process, animal protein (from meat and sausage residues) in particular forms toxins that can cause damage not only in the intestines, but also in the whole body.

The medical term is intestinal auto-intoxication. Typical toxins that arise in the intestine: including neurin, putrescin, indican and cadaverine, the dead body poison.