Histidine symbolized as H or His, is an α-amino acid used in protein biosynthesis. It encloses a carboxylic acid group (deprotonated –COO− form under biological conditions), α-amino group (protonated –NH3+ form under biological conditions) and an imidazole side chain (partially protonated) classified as a positively charged amino acid at physiological pH. At first, it was thought to be essential for infants but long term studies showed that it is essential for adults as well. Histidine is encoded by codons CAU and CAC. First it was isolated in 1896 by German physician Sven Hedin and Albrecht Kossel. It acts as a precursor to histamine which is an inflammatory agent in immune responses.
It is an alpha amino acid having imidazole functional group. It has various possible functions as it is a precursor of ubiquitous neurohormone neurotransmitter histamine. Histidine promotes histamine in blood and in brain probably. Histidine is found to be a useful therapy for patients having low histamine levels.
Food Sources of Histidine
| Food name | Weight (g) | Histidine (g) | DV% |
| Turkey | 863 | 7 | 568% |
| Soybeans | 186 | 2 | 162% |
| Lupins | 180 | 1 | 81% |
| Cottonseed kernels | 149 | 1 | 81% |
| Mothbeans | 196 | 1 | 81% |
| Provolone cheese | 132 | 1 | 81% |
| Mung beans | 207 | 1 | 81% |
| Winged beans | 182 | 1 | 81% |
| Swiss cheese | 132 | 1 | 81% |
| Kielbasa | 370 | 1 | 81% |
| Kidney beans | 184 | 1 | 81% |
| Fontina cheese | 132 | 1 | 81% |
| Yardlong beans | 167 | 1 | 81% |
| Spirulina | 112 | 1 | 81% |
| Lima beans | 178 | 1 | 81% |
| Monterey cheese | 132 | 1 | 81% |
| Black turtle beans | 184 | 1 | 81% |
| Navy beans | 208 | 1 | 81% |
| Adzuki beans | 197 | 1 | 81% |
| Haddock fish | 150 | 1 | 81% |
Health Benefits of Histidine
Here are some health benefits discussed about Histidine:
- Heart health
Histidine is helpful to have healthy heart. Study shows that 30 patients undergoing open heart surgery when treated with histidine tryptophan ketoglutarate solution lowered the chances of irregular heartbeats, need of drugs and length of stay in intensive care unit. Other study evaluated use of histidine tryptophan ketoglutarate solution on heart patients. Study concluded that solution showed to be an effective alternative to other treatment in protecting heart. Study evaluated use of histidine-tryptophan-ketoglutarate solution for preserving donor hearts from 67 patients undergoing transplant surgery. This solution is found to be helpful to preserve heart. Study conducted on chickens showed that supplementation of histidine enhanced level of carnosine.
- Lower blood pressure
Histidine lowered blood pressure with high doses shown to be effective in study which involved 92 heart disease patients. Study conducted on rats having elevated blood pressure, oral use of histidine supplementation lowered blood pressure. Moreover, carnosine lowered blood pressure in obese rats.
- Antioxidant activity
Study with 92 obese women having deficiency of histidine which caused oxidative stress. Supplementation of histidine helps to lower oxidative stress. Other study with 235 obese women and 217 non-obese individuals showed significant reduction in levels of histidine in obese women. This shows that histidine is strongly related with low oxidative stress that shows role in antioxidation.
- Lower inflammation
Study shows reduction of histidine levels in obese women. The supplementation of histidine helps to lower inflammation by blocking inflammatory cytokines production.
- Helpful for diabetes
Study conducted on 92 obese women found that supplementation of histidine lowered insulin resistance. Extra study indicated that high dietary histidine was related with low fasting blood sugar levels. Other study shows that mice supplemented with carnosine and histidine concluded that it has potential to prevent and treat diabetic complications.
- Prevent obesity
High histidine was related with low body mass index, blood pressure and waist circumference in overall population. It is converted to histamine in brain and histidine supplementation lowered the feeding behavior of rats with action of histamine. Further study shows that supplementation of histidine lowered the feeding or fat accumulation in rats. Histidines suppress appetite in humans and assist to lose weight.
- Skin health
It is a precursor for producing urocanic acid which is a substance accumulate in human skin cells and absorb UV radiation. Urocanic acid prevent DNA from being damaged by sunlight and is referred as natural sunscreen. Patients with skin disease when supplemented histidine for four weeks lowered severity of disease by 34% and 39% of patients which made them feel much better. Mice study shows that supplementation of histidine promotes urocanic acid levels on skin and protects from UV radiation.
- Brain health
People with sleep disruption and chronic fatigue with histidine supplements showed clear thinking and improvement in memory and attention. It also concluded that regular ingestion of histidine lowered fatigue. Moreover, supplements of histidine in rats improve their short term memory. Other study found long term protection on brain activity and lowered scarring after brain is being deprived of oxygen.
- Prevent blood clot
Histidine is effective for blocked spontaneous blood clots and effects are mediated by activity of arachidonic acid metabolite.
- Suppress seizure
Study conducted on rats discovered injection of histidine to be effective in reducing severity of seizures. Researchers believed the role of histidine as a precursor to histamine known for inhibiting seizures.
Symptoms of Deficiency
Deficiency of histidine has adverse effects on the body. It shows symptoms such as dry or scaly skin lesions, poor hearing, anemia and general feelings of unwellness. It also causes oxidative stress and inflammation. The low blood levels of histidine in patients having chronic kidney disease are correlated with oxidative stress, more inflammation and death.
- Causes anemia
Study was conducted by feeding histidine free diet to four healthy adults for 48 days. Their protein levels and hemoglobin levels were monitored. It was observed that 11% decrease in hemoglobin levels with depletion of histidine. Its deficiency caused anemia.
- Reduce brain function
Study involved 17 healthy individuals which evaluated outcome of deficiency of histidine on brain function. It showed that its deficiency has a major role in lowering brain function though the effects should be confirmed with further studies.
- Skin
Patients having wounds were evaluated for their amino acid and protein levels. About 16 in 18 with wounds have significantly low level of histidine. Histidine deficiency could weaken skin resulting larger wounds.
- Cause anxiety
The diet of mice with histidine deficiency showed low histamine in brains which caused anxiety like behavior.
Side Effects
Excess intake of histidine causes weakness, headaches, nausea, fatigue, anorexia, memory failure and depression. In rats, excess consumption of histidine resulted copper deficiency in liver, an enlarged liver, high cholesterol and appetite suppression.
References:
https://en.wikipedia.org/wiki/Histidine
https://pubchem.ncbi.nlm.nih.gov/compound/L-histidine#section=Top
https://www.britannica.com/science/histidine
https://www.livestrong.com/article/527035-l-histidine-benefits/
https://www.selfhacked.com/blog/histidine/