Are apple seeds poisonous?

Is it safe to eat apple seeds or are they poisonous? Check out this post to find out. We describe various substances contained in apple seeds, which may actually be harmful if eaten in too much quantity.

While apples are very tasty and healthy one should be careful when eating apple seeds. These tiny brown to black items can be found inside the apple and they contain substances, which may be harmful in larger quantities.

A little something about apple growing

Apples belong to the rose family. The main reason for the popularity of apple fruit is its sweetness. Apple tree is widely cultivated as a fruit tree and its place of origin is Central Asia.  Apples have been grown for thousands of years. The colonists of Europe brought apple tree in the North America. Apples are considered quite popular in different cultures, such as in the European Christian and Greek Traditions.

Some apples grow from the roots, whereas others are grown from the seeds. There are more than 7,500 varieties of apples around the world. All these varieties have different features when compared to others. Apples are cultivated for different reasons and they have different uses and tastes. The genome of this fruit was used for research purposes in 2010 in selective breeding and control of disease.

In 2010, the quantity apples grown all over the world was 69 million tons. Almost half of them were produced in China. The second leader of apple production, after China, is America, followed by Turkey, Italy and Poland. Apples are usually eaten in raw form, however, they can also be eaten in the form of prepared foods. A person can get many benefits from eating apples.

Now let us look at the apple tree in more detail. In general, apple tree is about 1.8 to 4.6 m high. The size and shape of the apple are usually determined by the method of trimming and rootstock selection. The trees give blossoms, usually in the spring season. The blossoms are also produced on some long shots and spurs. The color of the flowers is white, with a bit of fadeness. Cyme is present on the inflorescence. The name of the central flower of the inflorescence is “King Bloom”. It can be formed into a large fruit.

The apple fruit usually ripens in autumn or late summer. There are different sizes and shapes of apples. According to the preference of their market, the target of the commercial growers of the apple is to produce a fruit that is 7 to 8.3 cm in diameter. Even larger apples are grown by the people in Japan. Juices are usually made from the apples below 5.7 cm diameter. A fully mature apple has yellow, pink or red skin color. An epicuticular wax is used for covering the skin. The color of the apple fruit is usually pale yellowish.

Apple is obtained from its ancestor Malus Domestica. The ancestor of Malus Domestica was Malus sieversii. This ancestral variety is found in the mountains of China, Xinjiang, Tajikistan, Kyrgyzstan, and Central Asia. The cultivation of the species usually began from the Tian Shan Mountains, and the trees continued to progress in their design and structure. It is said that when the seeds of this wild ancestor and that of Malus Sylvestris, mixed together, crabapples were formed, which are, more or less, similar to the current variety of the apple fruit.

The genomicists at the Washington State University, claimed in 2010, that they had found the genome of the apple fruit. According to them, the total number of species of apple fruit to this date are 57,000- this is greater than any plant genome. There are more species in the apple genome, in comparison to human genome. This information is quite beneficial for the scientists as it helps them in knowing more about apples and the different benefits and characteristics of apple fruit. Better selective breeding will be performed by scientists if they know more characteristics of the apple fruit.

History

Now let us look at some history of apples. The place of origin of genus Malus is Eastern Turkey. It is said that the earliest cultivated tree was apple tree, and for thousands of years, the apple fruits improved through selection. Alexander discovered dwarf apples in 328 B.C. in Kazakhstan. The winter apples have been part of the food for over thousand years, in Asia and Europe. The apples were first found in the 17th century. Reverend William Baxton planted the apple seeds in North America for the first time, in 1625. Crab apples are the apples found in North America. The apple varieties are spread and cultivated on different colonial farms. In 1845, about 350 of the best apple varieties were produced. Several irrigation projects in Eastern Washington began in the 20th century. A billion dollar industry was formed as a result of this and apple was the leading product of this industry.

Apples were stored in frost proof cellars until the 20th century. However, the storing of the fruit was no longer needed once the transportation improved by train and road. The storage facilities again became popular in the 20th century, when a controlled atmosphere was used by apple manufacturers to store the apple plants. There is low humidity, low carbon dioxide and low oxygen in all the controlled atmospheric rooms. The main benefits of this controlled atmosphere is that the apple plant remains fresh throughout the year.

Substances contained in apple seeds

Now that you have a brief information about apples and apple seeds, let us discuss effects of substances contained in apple seeds. Apple seeds contain many substances, but the three most important substances in apple seeds are cyanide, arsenic and vitamin B17 (Amygdalin), which are described below in more detail:

Cyanides

Apple seeds contain cyanide in them. First you should know what cyanide is. Cyanide is any chemical compound, in which ‘CN group’ is present. The name Cyano (CN) group is usually given to this group of cyanide and it is composed of nitrogen and carbon having a triple bond in between them. The polyatomic cyanide ion (CN-) is usually present in the form of negative charge; this is usually present in the form of sodium cyanide. Cyanide is considered toxic due to the presence of these compounds. Nitrogen and carbon monoxide are present in the formation of cyanide ion. High toxicity is seen with most of the cyanides. Nitriles is the name given to organic cyanides. Cyanide bonds itself with methyl cyanide and methyl. In general, cyanide bonds itself with a carbon containing compound. Another name for hydrogen cyanide is hydrocyanic acid. Acrylonitrile is prepared from hydrogen cyanide. It is used to prepare plastics and synthetic rubber. Cyanides are used in a number of chemical reactions. For example, cyanides are used for the hardening of steel and iron and in the process of electroplating. Apple seeds are the natural sources of cyanide.

Now let us look at the nomenclature of these organic compounds. The name of the functioning group of cyanide is Nitriles. Thus, in general, nitriles are actually organic compounds. Acetonitrile is an example of a nitrile. Another name for this nitrile is methyl cyanide. Cyanide ions aren’t released by nitriles. A bonded group of cyanide and hydroxyl is called as Cyanohydrin. Hydrogen cyanides is usually released by cyanohydrins. Cyanides are also the salts containing the negatively charged cyanide ion.

There are many other sources of cyanide, other than apple seeds. Cyanide is present in many plants, fungi and algae. Cyanide is also present in different fruits and seeds e.g. peaches and apricots. Cyanide is also present in a potato-like food, known as cassava roots. Cyanide is also produced from the Madagascar bamboo. Other than this, cyanide is also present in interstellar mediums (1). The temperature of interstellar gas cloud is measured by the cyanide radical. Hydrogen cyanide is also produced in combustion process. In 328 B.C. in Kazakhstan, Cyanide is present in tobacco smoke and combustion engine. Hydrogen cyanide is also present in certain plastics.

The cyanide is a ligand in many different transition metals. The main reason for the high affinity of anion is the negative charge and the compactness. Some popular known complexes of cyanide are Dicyanides, tetracyanides and hexacyanides. The Prussian Blue dye was first made in 1706. Carbon, nitrogen and iron were heated in this process. Ferrocyanide is an iron containing compound, which is present in Prussian Blue. Prussian blue is used for making blueprints.

Now let us see how the cyanide is manufactured. The Andrussow process is used for the manufacturing of cyanides. In this process, cyanide is produced from methane and ammonia, in the presence of platinum catalyst. To produce sodium cyanide, gaseous hydrogen cyanide is passed through an aqueous solution of sodium hydroxide.

Toxic nature of cyanides

Now let us see whether cyanides are toxic or not. High toxicity is present in most cyanides. Enzyme Cytochrome c oxidase is inhibited by cyanide ion. Iron is attached to this protein. The transportation of electrons from cytochrome C to oxygen doesn’t happen, when cyanide is bound to this enzyme. Due to this, the chain of electron transport is destroyed. This basically means that ATP for energy isn’t produced by the cells. The nervous system and the heart tissues, which depend on aerobic respiration, are particularly affected in an adverse way.

Hydrogen cyanide is quite a dangerous compound. It is a gas at normal temperature and pressure. Therefore, while working with hydrogen cyanide, an air respirator is supplied through an external oxygen resource. Hydrogen cyanide is usually produced when a labile cyanide containing solution is made acidic. In general, alkaline solutions are safer for usage. The reason is that they don’t evolve to hydrogen cyanide. Hydrogen cyanide is also produced when polyurethanes are produced through the combustion process. This is probably the reason why polyurethanes aren’t recommended for domestic usage. Cyanide is considered dangerous because death can occur, if it is consumed even in a small quantity, say 200 mg. Instant death can ensue by breathing in air containing 270 ppm of cyanide.

Cyanide can result in serious poisoning. The sources of cyanide poisoning have already been discussed. Now let us talk about some symptoms of cyanide poisoning. The detection of cyanide poisoning can be quite difficult. The effects of cyanide poisoning are similar to suffocation. The reason is that cyanide doesn’t let oxygen to reach to the cells, which is needed for all cells to survive. You can say that climbing at high altitudes and cyanide poisoning have similar symptoms. Some of the symptoms of cyanide poisoning are as follows: 

• The general symptoms of cyanide poisoning include confusion, strange behavior, coma, sleepiness, dizziness, headaches and seizure.
• The most affected part as a result of cyanide consumption is heart. This can cause a person to collapse suddenly. Seizures are common as the brain is immediately affected by cyanide intake.
• Regular consumption of small amounts of cyanide (such as from apple seeds) can result in chronic poisoning.
• A person who has been poisoned has pink or cherry-red skin. The reason behind this is that cyanide remains in the blood and doesn’t enter the cells. When a person takes cyanide a person breathes quite fast. The breath of a person can, sometimes, smell like bitter almonds.

Luckily there is not much cyanide in apple seeds but one still needs to be careful and not to consume apple seeds in large quantities (e.g. if you eat apple seeds from one apple and just swallow them without biting, they will get out of the body without doing any harm. If bitten and swallowed, they might cause some health issues). Children should not consume apple seeds at all).

Arsenic

Arsenic is another compound present in apple seeds. It is either present in the form of pure metal crystal or along with other metals and sulfur. Actually, arsenic is neither a metal, nor a non-metal, it is a metalloid, meaning it has the properties in between metals and non-metals. Arsenic can exist in the form of many allotropes. It is generally used for strengthening lead and copper. Arsenic is a common dopant in semi-conductor devices. Arsenic is generally used for producing pesticides, insecticides and herbicides. When applied on apple trees (or apples) it may actually get in the fruit (and seeds). While pesticides and herbicides are used less and less these days you should still avoid eating apples, which grow on trees around busy roads or industrial areas.

Also, some species of bacteria use arsenic as respiratory metabolite. Arsenic is present in small quantities in hamster, goat, chicken, rat and humans. If it is present in more quantities than needed, it can become quite toxic. Many people across the world are affected by the arsenic containing water. As far as apples are concerned you should avoid eating apples and apples seeds contaminated by arsenic containing water or stool and urine of above mentioned animals. Due to number of issues with arsenic in apple juices and other apple products, FDA now limits the amount of arsenic in apples (1)

Different poisons are present in arsenic and its compounds. Arsenic and its compounds are regarded as poisonous in The European Union. Some compounds of arsenic like arsenic salts and arsenic pentoxide are grouped as first category carcinogens. Sometimes, arsenic can mix with drinking water and cause arsenicosis; it is also known as arsenic poisoning. It is generally caused due to the consumption of arsenic to dangerous levels.

Toxic nature of arsenic

Arsenic is highly toxic (2). The high toxicity is generally due to the affinity of arsenic oxides to disrupt energy production within cells. Arsenic can destroy the production of ATP, through different mechanisms. It stops the production of lipoic acid during the citric acid cycle. Oxidative phosphorylation is also stopped by arsenic. This stops the proper functioning of mitochondria and the production of ATP. The production of hydrogen peroxide in the body is also increased due to the consumption of arsenic. Thus, arsenic can also be the cause of increased oxidative stress. This can lead to death by organ failure. The death of the organs is caused at the cellular level. Apoptosis doesn’t occur, because for Apoptosis to occur, the cells have to be depleted.

Arsenic has proved to have a toxic effect in the sea urchin embryos. This means it is a teratogen as well. The list of the side effects of arsenic is quite a long one. Some side effects of arsenic include convulsion, chills, pain in the eyes, dryness of mouth, loss of appetite, nausea, sore throat, vomiting, breathing troubles, tiredness, fever, dry skin, sweating, pain in the stomach, swollen glands, increased hunger, weight gain, anxiety, bruising, bleeding, sore mouth and tongue, eye lids swelling and vomiting. Arsenic has also some cardiovascular side effects. QT interval prolongation is the common side effect of arsenic. This can be fatal in some cases. Palpitations and ECG abnormalities can also be caused due to arsenic. Endema, fever, chest pain, weight loss and weakness is also caused due to arsenic. Hypersensitivity is also one of the side effects of arsenic. Some respiratory side effects are also caused by arsenic, which include dyspnea, epistaxis, hypoxia, wheezing and coughing. Renal failure, and renal impairment are also some other side effects of arsenic. Other than this, arsenic can also cause infection in patients, which include herpes simplex, upper respiratory tract infection, nasopharyngitis, sepsis and oral candidiasis.

Vitamin B17

Vitamin B17 (Amygdalin) is another constituent of apple seeds. Amygdalin is present in many other fruits, like bitter almonds, black cherry and apricot. These were first separated from bitter almonds by Antoine Boutron-Charlard in 1830. Amygdalin has been quite beneficial since the 1950s. Amygdalin and its other forms named vitamin B17 have been used for curing cancer. However, they weren’t that much beneficial back then. Some studies have even regarded these compounds as highly toxic. When taken through the mouth, they can be quite poisonous. The reason behind this is that, cyanide can be produced when vitamin B17 reacts with certain enzymes. And you should know by now that cyanide is highly toxic.

Toxic nature

Hydrogen cyanide is the toxin which is produced by the metabolism of amygdalin. Beta-glucosidase is the enzyme that helps in the cataclysm of cyanide from amygdalin. It is present in a variety of foods and also in the small intestine. So, amygdalin can be quite poisonous when taken orally. This is the reason why eating apricot kernels and amygdalin can cause death. Some researches have shown that some cancer patients died when they took amygdalin repeatedly, thinking that it would cure their cancer. However in apple seeds the amount of amygdalin is so low that it is unlikely to produce any health problems (3).

Benefits of vitamin B17
 

There are a number of benefits of the consumption of vitamin B17. It has been seen that vitamin B17 increases the ability of the body to fight cancer. Once amygdalin goes inside the human body, it is converted into hydrogen cyanide which then destroy cancer cells. However, this process doesn’t happen on its own but happens when many enzymes combine with vitamin B17. Vitamin B17 is also quite beneficial against arthritis pain. Some studies have also shown that vitamin B17 is beneficial for lowering blood pressure and giving strength to immune system of the body.

Conclusion

This article provides a detailed description of substances contained in apple seeds, which may be a threat to human health. Despite of the fact that apple seeds contain some toxic substances like cyanides, arsenic and amygdalin (vitamin B17 - not toxic itself but may produce toxic metabolites). However the quantity of each of these elements contained in apple seeds is very low and will not do harm to adults. On the other hand children should not eat apple seeds as they may get poisoned even when taking in a small quantity. Also when you accidentally swallow some apple seeds (not more than the amount contained in one medium sized apple) they pass through digestive system without being digested. Therefore they will do no harm to you. However if you bite (crush or chew) them before, some of these toxic substances are released and may do you harm. Children should avoid swallowing and/or biting apple seeds at all cost. If you have any further questions or feel some of the symptoms described above (e.g. confusion, strange behavior, coma, sleepiness, dizziness, headaches and seizure) after swallowing apple seeds, go and see your physician without undue delay.