Benefits and misfortunes of garlic
Garlic for horses
Antioxidant, worm- and insect-repellent... The benefits of garlic are endless and feature increasingly in food supplements. However, despite being natural, garlic still has side effects, which can be serious when used incorrectly or over long periods. Let’s take a closer look at this popular ingredient..
Garlic can be used in dried form (as shavings, pellets or powder), fresh, mashed or simply peeled, depending on the flavour preferred by the horse and the ease of administering it. Garlic is found more and more often, both in discussion forums and on the shelves of specialist shops. If you believe some people, this little plant is a miracle cure for all ills because it’s not only 100% natural, but also worm- and insect-repellent, antiseptic, good for the respiratory system, good for circulation and even protects against cancer, in addition to a whole host of other good reasons to incorporate one of the key ingredients of the Mediterranean diet into our horses’ routines.
So, is garlic all it is cracked up to be? Animaderm has taken a look at the supposed benefits and the claims made about this familiar ingredient.
Garlic is a natural remedy, so it can't be harmful. False!
Just because a product is natural does not mean it is without its dangers.As the old saying goes, the dose makes the poison. The main problem lies in setting the right dose, which varies depending on the plant, the form in which it is administered (fresh, essential oils, dried extract, purified extract, crushed, etc.), the nature of the main active ingredients, and the target species, as well as on each creature’s own level of sensitivity. Garlic is no exception to this rule. When ingested in large quantities or over long periods, garlic can cause a number of problems, as it contains high levels of sulphates. For example:
- Damage to the digestive tract: High doses of fresh or powdered garlic can damage the digestive tract’s mucous membrane to the extent that it leads to bleeding ulcers and a drop in nutrient absorption, especially when administered regularly [1,2,3,4].
- Anaemia: Disulphides in garlic (and onion) promote haemoglobin oxidation inside red blood cells, leading to increased haemolysis (destruction of red blood cells). This phenomenon is well known and documented in dogs, but it has also been shown to occur in horses after giving large doses of garlic (0.2 g of dried garlic per kilogram of body weight, i.e. 100 g for a 500 kg horse) [5,6], or after small doses administered over long periods of time (32 mg/kg body weight over 3 months, i.e. 16 kg for a 500 kg horse, which is less than the recommended dose for dehydrated garlic) . In the latter case, anaemia develops progressively and insidiously, affecting the horse’s general health without showing obvious signs.
- Clotting problems: The sulphates contained in garlic inhibit platelet aggregation and prolong bleeding.
It is strongly advised that you do not give your horse garlic—in any form—in overly high doses or as a long-term cure (longer than one month). In all cases, garlic is contraindicated for animals with clotting problems or anaemia.Care should also be taken to ensure that the garlic will not interact with any other medicines.
Garlic is a powerful antibiotic. True!
At least when used externally. However, garlic can cause burns or an allergic reaction when applied to skin.
The antibacterial properties of garlic have been known since ancient times. In 1858, Louis Pasteur proved that garlic had antibacterial properties. Garlic was even used as an antiseptic during the First and Second World Wars, during which it was applied directly to wounds on the battlefield, earning it the nickname ‘Russian penicillin’. Garlic is granted this property by allicin and its derivatives . Allicin is a powerful broad-spectrum antibacterial agent which is effective against various strains of streptococcus, staphylococcus, enterococcus, salmonella and shigella, as well as fungi (aspergillus, candida, etc.) .
Little is known about its effects when ingested, as few clinical studies have been carried out on the subject. Allicin is a highly unstable compound, and it is therefore unlikely that it has the same antibiotic effect once inside an organism. Once ingested, in fact, allicin quickly starts to decompose into a hundred other sulphate compounds, such as allyl disulphide, diallyl disulphide and ajoene, in various proportions. Allicin can therefore be detected in the blood only for very short periods, if at all [10,11].
Garlic is a good source of vitamins and minerals. Not really!
It is true that, compared to other foods, garlic is relatively rich in vitamins (particularly B vitamins and vitamin C), minerals (such as selenium and iron) and oligo-elements (such as calcium and phosphorus). However, as the amount consumed is usually no more than a few grams (one clove weighs around 3 g), the benefits remain insignificant.
Garlic repels insects. Uncertain...
It all depends on how the garlic is prepared and administered (whether fresh, in oil, ingested or applied directly to the skin), the dose used and the species of insect being targeted.
When applied to the skin in fresh form or as a decoction or oil, garlic is thought to effectively repel most insects. It is very volatile and unstable, however, as its components degrade quickly, meaning that it is effective against insects only for a short period. Be aware, however, than long-term use can cause irritation or burns, and even allergic reactions. And its powerful odour can keep more than just insects at bay!
Its effectiveness against insects when ingested is disputed, however. Few scientific studies have been carried out on the effectiveness of garlic as an insect-repellent once it has been ingested by either humans or animals. In general, the results are not very convincing.
Only testimonies from users give this idea weight. In fact, on the whole, the results are very mediocre (some users see a difference, but others not). Users also need to be aware of the unwanted effects that are sometimes associated with regular consumption of garlic, even at low doses, such as anaemia, digestive problems and clotting problems.
Garlic is a natural, effective worming treatment. Hard to be sure...
Again, this one is hard to confirm or deny. Even though garlic has been used for centuries as a worming treatment for humans and animals alike, its use is based largely on empirical knowledge rather than scientific evidence. Although positive results have been obtained in vitro on various species of internal parasites , the few articles that have been published on in vivo experiments give contrasting results [13,14]. The diversity in the protocols used (in terms of duration, dose, and method of preparing the garlic) makes analysing the results difficult.
User testimonies can also be difficult to verify, as it is hard to assess the extent of the infestation before and after treatment without a carpological examination. Even where such examinations are performed after treatment, few are carried out beforehand to provide a comparison. In all cases, however, droppings should be assessed after treatment to ensure that it was effective.
Fresh, crushed, dried, boiled... Garlic works in all forms. False!
The content and nature of garlic’s main active ingredients depend on a wide range of factors and, therefore, are influenced by the methods of preparation and/or extraction used.
The main forms given to horses are:
- raw garlic (whole or crushed),
- dried garlic,
- powdered or in shavings,
- and as pellets.
Other forms are also available, however, such as:
- garlic essential oil,
- garlic oil,
- and even aged extracts.
Allicin is not found in whole cloves; it appears only when the clove is “threatened” (for example by crushing or cutting it) and is converted from a different odourless, biologically inactive compound, alliin (which comprises 0.5 to 1% of garlic). The garlic plant uses allicin—which is a powerful antiparasitic and an irritant—to defend itself in the wild against herbivores, parasites and insect pests. Allicin is released quickly once the plant is threatened. It takes several minutes (around 15 minutes at room temperature) for the majority of the alliin to be converted into allicin. Alliinase, the enzyme responsible for converting alliin is very sensitive to temperature and pH, however.
Any form of cooking or of exposure to an overly acidic pH (pH <3) inactivates the enzyme irreversibly. The reaction cannot take place once the garlic enters the stomach or intestines, or when slightly crushed garlic is cooked.
Dried powdered garlic, furthermore, contains only alliin, and not allicin. Therefore, simply giving your horse a whole garlic clove or cooked or dried garlic does not, appear to be the most effective way of using this ingredient. Pouring water over the dried garlic and waiting a few minutes before feeding it to your horse allows the allicin to form.
1- Amagase H, Petesch BL, Matsuura H, Kasuga S, Itakura Y. Intake of garlic and its bioactive components. J Nutr. 2001 Mar;131(3s):955S-62S.
2- Hoshino T, Kashimoto N, Kasuga S. Effects of garlic preparations on the gastrointestinal mucosa. J Nutr. 2001 Mar;131(3s):1109S-13S.
3- Sood DR, Vinod C, Shupa. Effect of garlic (Allium sativum) extract on degree of hydration, fructose, sulphur and phosphorus contents of eye lens and intestinal absorption of nutrients. Indian Journal of Clinical Biochemistry. 2003;18(2):190–196.
4- Omotoso G, Muonagolu J, Enaibe B. Histological evaluation of the jejunum and ileum of rats after administration of high dose garlic aqueous extract. Int J Health Sci (Qassim). 2012 Jun;6(2):135-40.
5- Pearson W, Boermans HJ, Bettger WJ, McBride BW, Lindinger MI. Association of maximum voluntary dietary intake of freeze-dried garlic with Heinz body anemia in horses. Am J Vet Res. 2005 Mar;66(3):457-65.
6- Valle E, Moro E. Padalino B. Garlic effects in the horse: a clinical report. Societa Italiana Veterinari per Equini, Cremona, Italy, Ippologia, 2006, 17, 4, pp 35-39.
7- Saastamoinen MT, Hyyppä S, Särkijärvi S, Ellis AD, Longland AC, Coenen M, Miraglia N. Influence of garlic supplementation on respiratory health and incidence of anaemia in horses. In : The Impact of Nutrition on the Health and Welfare of Horses: 5th European Workshop Equine Nutrition: Cirencester, United Kingdom, 19-22 September 2010. Wageningen Academic Pub, 2010. p. 280.8- Londhe VP, Gavasane AT, Nipate SS, Bandawane DD, Chaudhari PD. Role of garlic (Allium sativum) in various diseases: An overview. J Pharm Res Opin, 2011, 1:129-134.
9- Ilic DP, Nikolic VD, Nikolic LB, Stankovic MZ, Stanojevic LP, Cakic MD. Allicin and related compounds: Biosynthesis, synthesis and pharmacological activity. Facta universitatis-series: Physics, Chemistry and Technology, 2011, vol. 9, no 1, p. 9-20.
10- Lawson LD, Ransom DK, Hughes BG. Inhibition of whole blood platelet-aggregation by compounds in garlic clove extracts and commercial garlic products. Thromb Res.1992 65(2):141-156.
11- Freeman F, Kodera Y. Garlic Chemistry: Stability of S-(2-Propenyl)-2-Propene-1-sulfinothioate (Allicin) in Blood, Solvents, and Simulated Physiological Fluids. J. Agric. Food Chem., 1995, 43 (9) :2332–2338
12- Shalaby HA, Farag TK. Body Surface Changes in Gastrointestinal Helminthes Following in vitro Treatment with Allium sativum Oil. J Veterinar Sci Technolo 2014, 5:1
13- Sutton GA, Haik R. Efficacy of garlic as an anthelmintic in donkeys. Israel Journal of Veterinary Medicine, 1999, 54(1): 23-27
14- Burke JM, Wells A, Casey P, Miller JE. Garlic and papaya lack control over gastrointestinal nematodes in goats and lambs. Vet Parasitol. 2009, 159(2):171-174.