When it comes to human health, histidine is an essential amino acid that wears many hats. As a protein building block and a precursor for important biochemical products, it is involved in protecting the skin against UV radiation and reducing inflammation and oxidative stress. Read on to learn more about the importance of maintaining healthy levels.
What Is Histidine?
Histidine (L-histidine) is one of the 20 amino acids that make up the proteins in our body . These building blocks are generally classified as either nonessential or essential . Nonessential amino acids are those that the body can produce by itself, while essential amino acids must be acquired through diet because the body cannot make its own supply [ 1 ].
Histidine is an essential amino acid . A long-term study demonstrated that adults who consume a diet deficient in histidine over long periods of time may experience negative health effects such as reduced hemoglobin (the protein that carries oxygen in red blood cells) levels [ 2 , 3 , 4 ].
Histidine is produced by the liver in small quantities . Hence, it must be consumed in the diet to maintain necessary histidine levels in the body. Here, it is converted into a number of important substances such as histamine and carnosine [ 5 , 6 , 7 ]. Function
Histidine is required for the growth and repair of tissues , red blood cell production , and protecting tissues from damage from radiation and heavy metals . It is especially necessary for the formation of myelin sheaths , which are layers surrounding nerves that enables faster transmission of signals to the brain [ 1 , 8 ].
In both human and animal studies, histidine functioned in maintaining normal levels of hemoglobin , the protein responsible for delivering oxygen from the lungs to the tissues of the body [ 9 , 3 ].
Urocanic acid, produced through histidine, is a major absorber of ultraviolet (UV) radiation. This protects skin cells from damage [ 10 , 1 ].
Additionally, it is converted to histamine , a messenger molecule involved in immunity, digestion, and sexual function [ 7 , 1 ].
It is also a major component ( along with β-alanine ) of carnosine , an important antioxidant that slows the progression of multiple degenerative diseases and reduces plaque buildup in the arteries. It may also help improve muscle performance for high-intensity exercise [ 5 , 6 ]. Snapshot
Essential amino acid
HKT solution routinely used in surgical procedures
Antioxidant and anti-inflammatory
May protect the heart and lower blood pressure
May lower blood sugar
May help lose weight
May help with brain function
May protect the skin
May reduce blood clots
Very few clinical trials carried out so far
High doses of histidine supplements may have some adverse effects
Surgical Procedures Bretschneider’s histidine-tryptophan-ketoglutarate solution (HTK) is a histidine-containing buffering solution routinely used to induce heart arrest during surgical procedures and protect the heart muscle from low blood supply.Several clinical trials attest to its effectiveness to reduce damage due to low oxygen in not only the heart, but also the kidneys [ 11 , 12 , 13 , 14 , 15 , 16 ]. Insufficient Evidence for: The following purported benefits are only supported by limited, low-quality clinical studies and some animal and cell-based research. There is insufficient evidence to support the use of histidine supplements for any of the below-listed uses until larger, more robust clinical trials are conducted. Remember to speak with a doctor before taking histidine supplements. They should never be used as a replacement for approved medical therapies. 1) Protecting the Heart Mutations resulting in increased histidine levels were associated with lower incidence of coronary heart disease in an observational study on over 1,100 African Americans [ 21 ].The histidine derivative carnosine improved exercise performance and quality of life in a clinical trial on 50 people with congestive heart failure [ 22 ].Damaged rat hearts (due to restored blood supply after a heart stroke) treated with histidine showed better recovery. Histidine presumably reduced reactive oxidative species and helped preserve energy (ATP) [ 23 ].In diabetic mice, supplementation with carnosine reduced blood fat levels and plaque build-up in the arteries [ 24 ]. 2) Reducing Blood Pressure Dietary histidine was associated with lower blood pressure , especially at higher doses, in a study on 92 people with heart disease [ 25 ].In a study in rats with elevated blood pressure, oral histidine supplementation significantly reduced it. Similarly, carnosine reduced blood pressure in obese rats [ 26 , 27 ]. 3) Antioxidant In a study involving 92 obese women with histidine deficiency, supplementing this amino acid over 12 weeks reduced oxidative stress [ 28 ].Another study on over 400 women found an association between low histidine levels and oxidative stress. Additionally, obese women had worse antioxidant status, possibly due to their abnormal histidine and arginine metabolism [ 29 ]. 4) Inflammation In 2 studies on over 500 women, histidine supplementation led to reduced inflammation by blocking the production of inflammatory cytokines [ 29 , 28 ]. 5) Blood Sugar Levels In a clinical trial on 92 obese women with metabolic syndrome, histidine supplementation (4 g/day for 12 weeks) significantly decreased insulin resistance .An observational study on 88 obese people associated higher dietary histidine with lower fasting blood glucose levels and increased insulin sensitivity [ 30 ].In mice, supplementation with histidine and carnosine helped prevent diabetic complications [ 31 ]. 6) Brain Function In a clinical trial on 20 people with chronic fatigue and sleep disturbances, supplementation with histidine for 2 weeks improved attention, memory, and clarity of thinking while reducing fatigue [ 32 ].In another trial on 25 Gulf War I veterans, carnosine treatment improved cognitive function [ 33 ].In rats, histidine supplementation improved short-term memory and protected the brain from the damage caused by reduced oxygen supply (cerebral ischemia ) [ 34 , […]