Can Garlic Benefit Thyroid Health?
February 10 2014
For people with thyroid and autoimmune thyroid conditions, eating a diet based on whole foods is of course important. What’s just as important is eating a variety of different foods so that one consumes a wide range of different nutrients and phytonutrients. Part of your regular diet should include some raw garlic, or at the very least a garlic supplement. Garlic has numerous health benefits, and after reading this you should understand why everyone should be consuming garlic on a regular basis…especially those people with Graves’ Disease and Hashimoto’s Thyroiditis.
Garlic is also known as Allium sativum. There are numerous constituents of garlic, such as allicin, ajoene, 10-devinylajoene, diallyl sulfide, and allyl methyl sulfide. I’ll be talking about the properties of some of these constituents below when I discuss some of the common conditions that garlic can help with.
Garlic and Cardiovascular Disease. There is plenty of evidence that garlic and its active compounds are effective in reducing cardiovascular and metabolic risk by normalizing abnormal plasma lipids, oxidized low density lipoproteins, abnormal platelet aggregation, high blood pressure, and cardiac injury (1). Garlic has the potential to protect the heart against myocardial infarction, doxorubicin-induced cardiotoxicity, arrhythmia, hypertrophy, and ischemia-reperfusion injury (1). A meta-analysis of 26 studies showed that garlic was superior to a placebo in reducing serum total cholesterol and triglyceride levels (2). These studies showed that garlic powder and aged garlic extract were more effective in reducing serum triglyceride levels, while garlic oil was more effective in lowering serum cholesterol levels. Another study confirmed that taking garlic can lower serum cholesterol levels, but it needs to be taken for longer than two months (3). Another study showed that garlic can help decrease the reduction of myocardial infarction and sudden death in patients with coronary heart disease (4). There is also evidence that garlic, along with other antidiabetic agents, can help in the treatment and prevention of long-term complications of type 2 diabetes mellitus (5).
Garlic and Cancer.Numerous studies show that garlic might be a therapeutic agent for the treatment of certain types of cancer. A few studies have demonstrated that the allicin from garlic can induce apoptotic cell death in human hepatoma cells (6) (7). Hepatocellular carcinoma is the most common type of liver cancer. There is also evidence that garlic can inhibit proliferation and induce apoptosis in gastric cancer cells (8), as well as colon cancer cells (9). Other studies have shown that a high intake of garlic can provide protection against stomach and colorectal cancers (10). And there is also evidence that garlic can have anticancer effects when it comes to breast cancer (11). Garlic might even help with lung cancer (12). I also came across one article which showed that diallyl sulfide, which is a constituent of garlic, can induce growth inhibition and apoptosis in anaplastic thyroid carcinoma, which is one of the most lethal solid tumors (13).
This doesn’t mean that eating garlic alone or taking garlic supplements will provide a cure for cancer. But regular consumption of garlic can provide a protective effect against certain types of cancer. For those who currently have cancer, garlic can help to kill cancer cells, but should be combined with other therapeutic agents.
Garlic and Inflammation/immunity. Numerous studies demonstrate that garlic has a positive effect against pro-inflammatory cytokines. One study showed that the garlic derivative diallyl sulfide inhibited the production of cytokines by suppressing nitric oxide and prostaglandin E2 production in activated macrophages (14). The same study showed that diallyl disulfide repressed the production of stimulated TNF-alpha and IL-10 and increased the production of activated IL-1beta and, to a lesser extent, IL-6, while allyl methyl sulfide slightly suppressed the stimulated TNF-alpha but enhanced IL-10 production. A different study also confirmed that garlic can inhibit the production of nitric oxide and prostaglandin E2, and that the sulfur-containing compounds of garlic suppressed nuclear factor-κB (NF-kappaB) transcriptional activity and the degradation of inhibitory-κBα in LPS-activated macrophages (15). I’ve spoken about NF-kappaB in past articles, and how suppressing this is important with any autoimmune condition.
Another study looked at the potential therapeutic effects of garlic in the treatment of patients with inflammatory bowel disease (IBD), and showed that garlic might help to resolve inflammation associated with IBD by inhibiting Th1 and inflammatory cytokines while upregulating IL-10 production (16). Another study looked to determine the effect of garlic supplementation on pro-inflammatory cytokines in postmenopausal osteoporotic women, and concluded that there is evidence for an immunomodulatory effect of garlic, as well as the modulation of cytokine production (17). Yet another study looked at the effect of garlic consumption on the Th1/Th2 balance, and showed that oral garlic treatment may favor a Th2 or humoral immune response (18). Since Graves’ Disease is thought to be a Th2 dominant condition this evidence might suggest that garlic should be avoided in those people with Graves’ Disease, and would benefit those people with Hashimoto’s Thyroiditis, which in most cases is a Th1 dominant condition. Just keep in mind that using nutrients to balance the Th1/Th2 pathways is controversial, and I have recommended garlic to many of my patients with Graves’ Disease without a problem.
Garlic and Infections. There is plenty of evidence which demonstrates the antimicrobial properties of garlic. Garlic can potentially be effective against bacteria such as Escherichia coli, Shigella, Salmonella, and Proteus mirabilis (19). H. Pylori is common in autoimmune thyroid conditions, and there is evidence that garlic can eradicate this pathogen (20) (21).
Garlic can also provide antimicrobial actions against some antibiotic-resistant strains of bacteria. This is of course extremely important, as we’re seeing a greater number of pathogens become antibiotic-resistant. I just spoke about H. Pylori, which is becoming more and more resistant to antibiotics, yet some antibiotic-resistant H. pylori strains are susceptible to garlic (20). Many strains of tuberculosis are also becoming antibiotic resistant, and there is evidence that garlic can help against multi-drug resistant TB (22) (23). Another study showed how garlic was effective against streptomycin-resistant strains of Staphylococcus aureus (24).
The main antimicrobial effect of allicin is due to a chemical reaction with thiol groups of numerous enzymes, which in turn can affect the virulence of certain pathogens (25). Allicin in its pure form has been found to exhibit antibacterial activity against a wide range of gram-negative and gram-positive bacteria, antifungal activity (particularly against Candida albicans), antiparasitic activity, including some major human intestinal protozoan parasites such as Entamoeba histolytica and Giardia lamblia; and antiviral activity (25).
Ajoene is another constituent of garlic, and it shows antifungal activity against fungi such as Aspergillus niger and Candida albicans (26) (27). Ajoene also has antithrombotic, anti-tumoral, and antiparasitic activities (27). Garlic also appears to have antiviral activity due to the constituents ajoene, allicin, and thiosulfinates (28). Since garlic has both antibacterial and antiviral activity it would make sense to give garlic to help prevent or relieve the common cold. And while there is evidence that garlic can be used in the prevention or treatment of the common cold by enhancing the immune system (29), more research needs to be done in this area (30).
Garlic and Liver Detoxification
Phase 2 biotransformation enzymes help with the elimination of toxins from the body. As a result, increasing the activity of phase 2 enzymes can help to increase the elimination of these toxins. Glutathione S-transferases (GSTs) are phase 2 biotransformation enzymes, and they are encoded by the GSTP1 gene (31). Garlic upregulates GSTP mRNA and protein expression (32). In summary, taking garlic will help with detoxification by increasing certain phase 2 biotransformation enzymes.
How Can Taking Garlic Benefit People With Thyroid And Autoimmune Thyroid Conditions?
There are a few different ways in which garlic can help with thyroid health. First of all, many people with these conditions have problems with cardiovascular health. Those with hypothyroid conditions frequently have elevated cholesterol levels and triglycerides, and while balancing the thyroid hormone levels can play a big role in this, taking garlic can also help. Those with hyperthyroid conditions are more susceptible to cardiovascular complications such as arrhythmias, and so garlic might be able to offer a protective effect, although many people with hyperthyroidism and Graves’ Disease will need to take antithyroid medication or herbs to manage the cardiac symptoms.
Autoimmune thyroid conditions such as Graves’ Disease and Hashimoto’s Thyroiditis involve pro-inflammatory cytokines. And as I discussed in this article, garlic can help to inhibit these pro-inflammatory cytokines. Many people with these conditions have infections, and perhaps this is the biggest area garlic can help with. Garlic has been proven to have anti-bacterial, anti-viral, anti-fungal, and even anti-parasitic activity. While there are numerous natural anti-microbials people can take for pathogens, most people with any type of an infection should be taking garlic.
Contraindications of Garlic
Those who are taking blood thinning medication such as warfarin need to be cautious about eating garlic or taking garlic supplements. The reason is due to the antiplatelet effect of garlic. Eating small amounts of garlic probably is fine in most people who take warfarin, but taking garlic supplements on a daily basis can cause problems. One study showed that the administration of enteric coated 2g/dose x twice daily garlic for two weeks did not alter warfarin pharmacokinetics or its effects in healthy male volunteers (33). However, those who are on warfarin need to be cautious about eating large amounts of garlic or taking garlic supplements, especially on a long term basis.
In summary, garlic has many different health benefits, and therefore can be an important nutrient in people with thyroid and autoimmune thyroid conditions. Some of the constituents of garlic include allicin, ajoene, diallyl sulfide, and allyl methyl sulfide. These constituents of garlic can help improve the health of people with cardiovascular disease, cancer, inflammation, and infections. Garlic also can help with liver detoxification by increasing phase 2 biotransformation enzymes. As a result of all of these benefits, many people with thyroid and autoimmune thyroid conditions should consider eating more garlic and/or take a garlic supplement while following a natural treatment protocol.