SCIENTIFIC RESEARCH ON BLACK GARLIC
Louis Camille Maillard (1878-1936) from http://www.food-info.net/uk/colour/maillard.htm
This is a brief review of recent research on black garlic and is not intended to claim any health benefits for black garlic. The review is provided for interest only.
Garlic has appeared as a healing health agent in several cultures: Sumerian clay tablets dating from 2600–2100 BC refer to garlic as a medicinal and culinary plant; the medical text Codex Ebers (about 1550 BC) highlights garlic as an antidote to hard work and allegedly garlic was fed to Olympic athletes to increase stamina. Ancient Chinese medicine used garlic to aid respiration and digestion and several Indian traditions see garlic as a plant of healing. Pietro Mattiali of Siena, a 16th Century doctor, prescribed garlic for childbirth, digestive and renal disorders. In England, conditions as diverse as toothache, constipation, dropsy and plague attracted garlic therapy. Since then the hunt has been on for the active properties of garlic, their mechanisms of action and exploring the potential benefits as food supplements (1).
Korean interest in black garlic as a potential superfood is more recent. Various trials on aged black garlic (and its extracts) have identified a number of biologically active compounds. Black garlic has more water soluble sulphurous compounds such as S-allylcysteine and S-allyl-mercaptocysteine than raw garlic, with less oil soluble compounds that are smelly and sharp in flavour. The change in colour is the result of slow sugar break down over time using the Maillard reaction. This is a complex rearrangement of protein and sugar molecules described by Maillard (pronounced my-YAR), a French scientist, responsible for giving baked or fried food such a lovely aroma. This non enzymatic browning is specific to each food, producing molecules key in the finished flavour.
Key research has focused on the chemical properties of black garlic, cell and animal effects of black garlic, and more recently human trials on the lipid lowering properties of black garlic.
Chemical properties of black garlic
Whole garlic bulbs (Allium sativum L.) when aged at controlled temperature and humidity over 35 days develop increased acid (ph reducing from 6.3 to 3.7), darken in colour and increase in sugars. Antioxidant levels, present in raw garlic, increase significantly over the ageing period, peaking at Day 21 (polyphenols and bioactive sulphurs) (2).
Cell studies on black garlic
Various promising beneficial actions of garlic have been described: antitumour development, antiatherosclerosis, reduction in blood sugar and inhibition of cancer growth. Cell studies using black garlic extracts on in vitro cell division of human gastric cancer cells, demonstrated a relationship between dose of black garlic extract and rates of cell death (effectively removing tumour cells through apoptosis or planned cell death) (3).
Animal models and black garlic
Similarly, aged black garlic extract given to mice with induced gastric tumours, reduced tumour growth. This effect appears to have been caused by increased levels of antioxidants and positive immune system effects induced by the aged black garlic extract (3). Rat hearts subject to ischaemia, had less reduced contractility and better coronary artery vasodilation when taking aged black garlic extract (4).
Human trials of health properties of black garlic
Garlic has been claimed to reduce cholesterol but trials have been mixed. A 12 week randomised control trial was undertaken of aged black garlic versus placebo amongst 60 people with mildly raised lipids (low density lipoprotein C greater than 130mg/dL) not currently taking lipid lowering drugs. Researchers found that the group taking aged back garlic extract had significant improvement in parts of the lipid profile implicated in atherosclerosis (5). A good overview is provided by Kimura et al. (6).
References
Garlic has appeared as a healing health agent in several cultures: Sumerian clay tablets dating from 2600–2100 BC refer to garlic as a medicinal and culinary plant; the medical text Codex Ebers (about 1550 BC) highlights garlic as an antidote to hard work and allegedly garlic was fed to Olympic athletes to increase stamina. Ancient Chinese medicine used garlic to aid respiration and digestion and several Indian traditions see garlic as a plant of healing. Pietro Mattiali of Siena, a 16th Century doctor, prescribed garlic for childbirth, digestive and renal disorders. In England, conditions as diverse as toothache, constipation, dropsy and plague attracted garlic therapy. Since then the hunt has been on for the active properties of garlic, their mechanisms of action and exploring the potential benefits as food supplements (1).
Korean interest in black garlic as a potential superfood is more recent. Various trials on aged black garlic (and its extracts) have identified a number of biologically active compounds. Black garlic has more water soluble sulphurous compounds such as S-allylcysteine and S-allyl-mercaptocysteine than raw garlic, with less oil soluble compounds that are smelly and sharp in flavour. The change in colour is the result of slow sugar break down over time using the Maillard reaction. This is a complex rearrangement of protein and sugar molecules described by Maillard (pronounced my-YAR), a French scientist, responsible for giving baked or fried food such a lovely aroma. This non enzymatic browning is specific to each food, producing molecules key in the finished flavour.
Key research has focused on the chemical properties of black garlic, cell and animal effects of black garlic, and more recently human trials on the lipid lowering properties of black garlic.
Chemical properties of black garlic
Whole garlic bulbs (Allium sativum L.) when aged at controlled temperature and humidity over 35 days develop increased acid (ph reducing from 6.3 to 3.7), darken in colour and increase in sugars. Antioxidant levels, present in raw garlic, increase significantly over the ageing period, peaking at Day 21 (polyphenols and bioactive sulphurs) (2).
Cell studies on black garlic
Various promising beneficial actions of garlic have been described: antitumour development, antiatherosclerosis, reduction in blood sugar and inhibition of cancer growth. Cell studies using black garlic extracts on in vitro cell division of human gastric cancer cells, demonstrated a relationship between dose of black garlic extract and rates of cell death (effectively removing tumour cells through apoptosis or planned cell death) (3).
Animal models and black garlic
Similarly, aged black garlic extract given to mice with induced gastric tumours, reduced tumour growth. This effect appears to have been caused by increased levels of antioxidants and positive immune system effects induced by the aged black garlic extract (3). Rat hearts subject to ischaemia, had less reduced contractility and better coronary artery vasodilation when taking aged black garlic extract (4).
Human trials of health properties of black garlic
Garlic has been claimed to reduce cholesterol but trials have been mixed. A 12 week randomised control trial was undertaken of aged black garlic versus placebo amongst 60 people with mildly raised lipids (low density lipoprotein C greater than 130mg/dL) not currently taking lipid lowering drugs. Researchers found that the group taking aged back garlic extract had significant improvement in parts of the lipid profile implicated in atherosclerosis (5). A good overview is provided by Kimura et al. (6).
References
- Banerjee, S.K.; Maulik, S.K. Effect of garlic on cardiovascular disorders: A review. Journal of Nutrition 2002; 1: 1-14
- Choi IS, Cha HS, Lee YS. Physicochemical and antioxidant properties of black garlic. Molecules 2014; 19: 16811-16823; doi:10.3390/molecules191016811 accessed 18/11/14
- Wang X, Jiao F, Wang QW et al. Aged black garlic extract induces inhibition of gastric cancer cell growth in vitro and in vivo. Molecular Medicine Reports 2012; 5: 66-72
- García-Villalóna AL, Amora S, Mongea L. et al. In vitro studies of an aged black garlic extract enriched in S-allylcysteine and polyphenols with cardioprotective effects. Journal of Functional Foods 2016; 27:189-200
- Jung ES, Park SH, Choi EK et al. Reduction of blood lipid parameters by a 12-wk supplementation of aged black garlic: A randomized controlled trial. Nutrition 2014; 30: 1034–1039
- Kimura S, Tung YC, Pan MH et al. Black garlic: A critical review of its production,
bioactivity, and application. Journal of Food and Drug Analysis 2017; 25:62-70
