How much garlic is too much?

A garlic clove a day would keep the doctor away, but a bulb of garlic or more may be way too much, and might negatively affect health. Most medical experts agree that clove or two a day is an ideal dose, that would be enough for most of the beneficial effects. Consumption of more than four cloves (about half a bulb) is maximum. 1 2 Excess use of garlic may cause several unwanted effects.

Garlic side effects

  • Garlic has sulfuric compounds that are responsible for bad breath or “garlic breath,” these compounds irritate mucous membranes and cause burning sensation in the mouth (when raw garlic in consumed). 3
  • Garlic can cause severe gastric irritation, especially if consumed raw. However, it does not cause that much irritation in cooked form, and may not cause gastric irritation at all if consumed as aged garlic extract (like that sold in capsules). 4
  • Since garlic is a robust gastric irritant, over-consumption of it may lead to other gastric issues like heartburn, nausea, bloating, or even vomiting, in certain cases.
  • In fewer cases, garlic may also cause irritation of intestine, and thus causing diarrhea.
  • Garlic is not just related to bad breath; it may cause unpleasant body odor, that may have an adverse effect on specific parameters of life3.
  • Garlic has some opposing effects on our body, thus in optimal doses, it is a powerful antioxidant, while if it is consumed in excess, it may be toxic to heart, liver, and kidney. 5
  • Garlic also acts as a blood thinner, it changes the functioning of platelets and also affects the blood coagulation. Thus it increases the risk of bleeding. It should be taken with caution with blood thinning medications6. The blood-thinning effect is also responsible for hyphema.
  • Some people may be allergic to garlic; it may worsen the symptoms of certain allergic conditions like asthma, it may cause skin eruptions and aggravate eczema.
  • Garlic causes a burning sensation if applied to the skin, and may cause skin irritation.
  • Garlic is beneficial for those living with high blood pressure. However, it healthy subjects blood pressure lowering effect may be unwanted. 6
  • Garlic may also cause excessive sweating or dizziness in some cases.
  • In rare cases, garlic may also cause headaches or worsen a migraine.

Precautions to be taken while consuming garlic

  • Anything can be harmful in excess, and garlic is no exception. Hence, take it in moderation, do not exceed the recommended dose, especially if you are taking supplements. Some of the cautions to consider are:
  • Avoid consuming it with blood thinning medications; such medications are typically prescribed in heart conditions, taking garlic supplements concomitantly may increase the bleeding risk.
  • If a person is undergoing surgery, he or she should stop taking garlic at least two weeks before as garlic has been demonstrated to increase bleeding. 7
  • Though garlic may be safe in moderation, however, high amounts should be avoided during pregnancy or when breastfeeding.
  • Garlic lowers blood pressure, that may be good in hypertension, but not in cases with low blood pressure.

In conclusion, it can be said that garlic or its supplements are useful in wide variety of health conditions. However, it does not mean that garlic can be taken as much as one feels like, there is need to consume it in moderation, know about certain precautions and contraindications.

  1. Ali M, Thomson M. Consumption of a garlic clove a day could be beneficial in preventing thrombosis. Prostaglandins Leukot Essent Fatty Acids. 1995;53(3):211-212. doi:10.1016/0952-3278(95)90118-3.

  2. Garlic and Cancer Prevention. National Cancer Institute. Published January 22, 2008. Accessed April 6, 2018.

  3. Borrelli F, Capasso R, Izzo AA. Garlic (Allium sativum L.): adverse effects and drug interactions in humans. Mol Nutr Food Res. 2007;51(11):1386-1397. doi:10.1002/mnfr.200700072.

  4. Hoshino T, Kashimoto N, Kasuga S. Effects of garlic preparations on the gastrointestinal mucosa. J Nutr. 2001;131(3s):1109S-13S.

  5. Banerjee SK, Mukherjee PK, Maulik SK. Garlic as an antioxidant: the good, the bad and the ugly. Phytother Res PTR. 2003;17(2):97-106. doi:10.1002/ptr.1281.

  6. Ried K, Frank OR, Stocks NP. Aged garlic extract reduces blood pressure in hypertensives: a dose-response trial. Eur J Clin Nutr. 2013;67(1):64-70. doi:10.1038/ejcn.2012.178.

  7. Burnham BE. Garlic as a possible risk for postoperative bleeding. Plast Reconstr Surg. 1995;95(1):213.

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