Does the scientific evidence support traditional beliefs?
Love it or hate it, garlic deserves its revered recognition as a super nutrient. This blog will tell you about:
• The traditional uses
• Whether those traditional beliefs are supported by scientific research
• Its role in digestive health
• Its medicinal properties – what gives it ‘that’ odour
• Its nutritional highlights
• Its uses in digestive health by nutritional therapists
• Food or supplements
• How to use fresh garlic
Garlic (Allium sativum) has long been recognised as a malodorous but important medicinal herb with remarkable health benefits. Until recently when turmeric overtook it, garlic had the greatest number of research papers in PubMed for a food-derived health supporting ingredient. A powerhouse of nutrients, the compounds in garlic that cause the putrid ‘garlic breath’ are also responsible for its beneficial properties.
“Let food be thy medicine and medicine be thy food” Hippocrates
Garlic has been used traditionally for both medicinal and culinary purposes for thousands of years, although its ancient use focused on its medicinal properties. Uses date as far back as the Egyptians who prescribed it to enhance physical strength and as a deterrent of evil spirits. Garlic was mentioned in the Egyptian Ebers Codex in 1550BC for a variety of therapies and Hippocrates (460-370 BC) often referred to as the ‘Father of Western Medicine’ recommended its use to treat infections, digestive disorders, parasites and for use as a diuretic.
During the first century, the Greeks utilised it as a laxative and for athletic strength. Additionally, they dispensed the herb for infections, coughs, animal bites and also introduced its use as an aid for unclogging arteries. For this reason, garlic became customary in Chinese medicine for reducing blood pressure. Centuries later, it was believed to enhance immunity to the plague in the middle ages.
As scientific understanding progressed, it became apparent garlic was able to fight infection. In 1858 Louis Pasteur observed the antibacterial activity of garlic. Consequently, it was used as an antiseptic to prevent gangrene for wounded soldiers in World War I and II. Garlic has been considered throughout history an edible antibiotic and was often applied topically as well as being consumed as a medicine.
Does the scientific evidence support traditional beliefs?
Garlic has a wide range of well-documented effects where scientific evidence appears to support the traditional beliefs. This includes helping to fight infection and boosting immune function; preventing cancer and the cardiovascular benefits of lowering cholesterol and blood pressure. Therefore its use is encouraged for those with elevated cholesterol, heart disease, high blood pressure, diabetes, asthma, candida, infections (particularly respiratory) and gastrointestinal complaints.
Garlic and digestive health
Recent studies have confirmed garlic’s effectiveness against parasites, bacteria, viruses and fungi making it a noble all-rounder for immune support. Garlic has exhibited good antimicrobial activity and has also been shown to hinder the fungi that cause athlete’s foot, thrush and ear infections. It may be as effective as anti-fungal medications particularly against Helicobacter pylori that is believed to cause most ulcers.
Eating plenty of fresh garlic lowered risk of colorectal cancer by 30%.
Population studies have shown that consumption of cooked or raw garlic decreases the likelihood of developing colon and stomach cancers. University of Maryland researchers in 2011 reviewing 7 studies found that people eating plenty of fresh garlic lowered their risk of colorectal cancer by 30%. The herb has a protective effect and has also been shown to stop the growth of cancer cells once they develop.
It is advised that garlic should be left for 10 minutes after chopping or crushing to activate the powerful properties of its compounds
Garlic’s pungent aroma and distinctive spicy flavour is due to sulphur containing amino acids including allicin and its potent derivatives including ajoene and diallyl disulphide. These are believed to provide the medicinal qualities to the herb and also the unfortunate odour on the breath and skin which is due to the metabolising of its sulphur compounds. When raw garlic is crushed or chopped, allicin is formed when alliin, an amino acid containing sulphur, is enzymatically altered. It is advised that garlic should be left for 10 minutes after chopping or crushing to activate the powerful properties of its compounds. Upon cooking it sweetens and mellows to a less spicy essence, however if the enzyme denatures with heat, cooked garlic may be found to be less effective for medicinal uses.
Garlic is a powerhouse of micronutrients; it is particularly a good source of vitamin B6 and vitamin C. Mineral content includes good values of manganese, selenium, phosphorus, copper, calcium, iron and potassium. In addition, garlic’s antioxidant properties are particularly valuable regarding its ability to neutralise damaged cells, known as free radicals which may help in cancer and heart disease. It is believed that the sulphur compounds may be responsible for its high antioxidant potential.
The table below shows the main constituents of garlic in a 100g serving and an approximate daily portion of 3g.
Source adapted from: United States Department of Agriculture, Garlic, raw. Accessed: http://www.nal.usda.gov/fnic/foodcomp/cgi-bin/measure.pl , 26th November 2014.
Use of garlic in nutritional therapy
Garlic is widely used in nutritional therapy most often for digestive and cardiovascular support. In digestive health, as a potent broad spectrum natural antiseptic and mild antibiotic its clinical use supports building the body’s immune defences and helps to protect against candida, parasites and pathogenic bacteria.
However, one of the increasing problems in clinical care is the increasing resistance some bacteria demonstrate to current antibiotics and to natural interventions as well. Whilst numerous compounds, in particular oregano, have been able to produce good results there is increasing adaptation of bacterial defences, namely biofilms. These are made by bacteria clumping together to form protective ‘nets’, an innovative way to ensure their survival in their host by becoming resistant to antibiotics.
Garlic’s potential as an anti-pathogenic drug
One of garlic’s active ingredients, ajoene, in early studies appears to damage biofilms and disrupt the bacterial communication, known as quorum sensing (QS), with the outcome of more effective antibiotic intervention – often required in difficult cases. Ajoene is the major component in a cocktail of QS inhibitory sulphur-containing compounds, which is produced when garlic is crushed. These QS inhibitors do not kill target bacteria; however they weaken their biofilms to the exposure of conventional antibiotics and the immune system. Garlic’s mild antibiotic properties mean it is not a substitute for antibiotics, but it can be considered as a support, often alongside other supplements against some bacterial infections. Candida albicans growth however is inhibited by garlic, and the herb has shown long-term benefit for recurrent yeast infections such as thrush.
“This work is very exciting to me because it shows that this compound has the potential to reduce disease-causing bacteria in the environment and in our food supply.”
Dr X Lu, Washington State University
Another garlic compound, diallyl sulfide, has shown to be more effective than two popular antibiotics in fighting the Campylobacter bacterium, according to a 2012 study published in the Journal of Antimicrobial Chemotherapy. Campylobacter is one of the most common causes of intestinal infections. Senior author, Dr. Xiaonan Lu, from Washington State University, said “This work is very exciting to me because it shows that this compound has the potential to reduce disease-causing bacteria in the environment and in our food supply.”
Food source or supplement?
For overall well-being, then food source is perfectly adequate, ideally 1-3 cloves per day – crush or chop to release the allicin and consume as raw as possible.
For challenging gastrointestinal cases, food sources will not have sufficient concentration to weaken biofilms, therefore concentrated garlic supplements may be required. Such cases may benefit from conjoined used of concentrated garlic and other anti-microbials such as oregano to help manage persistent bacterial infections, change microbial compositions and disrupt biofilms.
Available forms of garlic supplements are fresh, dried, freeze dried, oil and aged extracts which, in studies, appear to have variable effects on the body. There is a lot of variation and quality among garlic products sold for medicinal purposes. The concentration of allicin and the source of garlic’s distinctive odour depend on processing method. Allicin is unstable, and changes into different chemicals quickly. Some products have a coating (enteric coating) to deliver the active ingredient into the intestines and protect them against attack by stomach acid, not to mention reduce the ‘garlic breath’ by being absorbed further down the gastrointestinal tract. Getting advice from a qualified and registered nutritional therapist is advised.
There are no known safety issues; true allergy to garlic is rare. However, some people can experience mild digestive upset when consuming garlic. Due to its high FODMAP (Fermentable oligo-, di-, mono- saccharides & polyols) content, garlic may be best avoided by those with IBS symptoms. The FODMAPs diet (a reduction in indigestible sugars – garlic being one of them) is often recommended for IBS sufferers.
Interaction with medications
Theoretically, garlic preparations may potentiate the effects of the blood thinning drug Coumadin® (warfarin) as well as enhance the antiplatelet effects of drugs like aspirin and Ticlid® (ticlopidine). If you are taking these drugs, please consult a physician before taking a garlic product.
Garlic may increase the effectiveness of drugs that lower blood sugar levels in the treatment of non-insulin dependent diabetes (Type 2 diabetes) such as glyburide (Diabeta, Micronase). Consult a physician to discuss proper monitoring of blood sugar levels before taking a garlic product.
Interaction with other supplements
Fish oil (containing EPA) can slow blood clotting. Garlic can also slow clotting. Taken together, garlic and fish oil may increase the risk of bleeding in some people.
How to store and use garlic
Fresh is best – store at room temperature in a cool, dark place to prevent sprouting. Once you break a head of garlic, it reduces its shelf life to a few days.
Ideas on how to use fresh garlic
First, always leave crushed or chopped for 10 minutes to release the active compounds.
1. Chopped, crushed or sliced into soups, stews, sauces. Add in during cooking for the flavour then add some at the last minute to get the raw high allicin content.
2. Puree two cloves with 350g tinned chickpeas, 2 tbsp. tahini, 2 tbsp. olive oil and 2-3 tbsp. lemon juice for a quick and easy humous
3. Chop garlic and infuse in olive oil for a garlic tasting dressing, add chilli if required
4. FODMAP variation on infused oil: Infuse whole cloves in warm olive oil in a saucepan to release the flavour, then pour into glass jar. Do not eat the cloves!
Home-made garlic or herb- infused oil should be prepared and stored immediately in the fridge as there is a risk of illness if left at room temperature. Keep no longer than a week to prevent rancidity.
Garlic is a wonder food with many health benefits; science does indeed support the traditional beliefs. Enjoy garlic with friends, and then no one notices malodorous breath!
Jane is a nutritional therapist helping adults and children with digestive issues take control of their health through nutrition. By getting to the root cause of your health issue, she can help you cut through the confusion of what to eat and create a plan that’s made just for you. She practises in Guildford, Surrey and on Skype. For a free 20 minute chat call Jane on 01483 697121.
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