After entering the human body, vitamin B1 is mainly absorbed in the small intestine, converted into pyrophosphate vinegar through phosphorylation in the mucosal cells of the jejunum, transported to the liver through the portal vein, and then transported to the body tissues through the blood. The total amount of vitamin B1 in adults is approximately 25-30 milligrams, with a distribution rate of approximately 50% in muscles. The rest is mainly distributed in the heart, brain, liver, and kidneys.
Vitamin B1 is metabolized in the liver, and its metabolites are mainly excreted through the kidneys and urine, with a small amount being excreted through sweat and related to intake. The biological half-life of vitamin B1 in the human body is 9-18 days. If vitamin B1 is lacking in the diet, the content of vitamin B1 in human tissues will decrease after 1-2 weeks.
Food sources and intake recommendations for vitamin B1
1. Recommended intake
The human body's demand for vitamin B1 is closely related to the body's energy metabolism, and the reference intake of vitamin B1 should generally be calculated based on the total energy requirement. At present, the average requirement for vitamin B1 among adults in China is 0.5 milligrams/4186 kilojoules (approximately 1000 kilocalories). The recommended intake for special populations such as pregnant women, lactating mothers, and the elderly is relatively high, ranging from 0.5 to 0.6 milligrams/4186 kilojoules (approximately 1000 kilocalories). The recommended intake of vitamin B1 in the "Reference Intake of Dietary Nutrients for Chinese Residents (2013 Edition)" is 1.4 mg/day for adult males and 1.2 mg/day for females. Vitamin B1 is generally not toxic due to excessive intake. Headache, convulsions, and arrhythmias may only occur when a dosage exceeding 100 times the recommended intake is taken in a short period of time, which is rare.
2. High content in grains
Vitamin B1 is widely present in natural foods such as grains, beans, and fruits. Animal viscera (liver, heart, kidneys), lean meat, and poultry eggs also have a higher content. In daily diet, vitamin B1 mainly comes from cereal foods and is mostly present in the epidermis and germ of cereals. Fine processing of rice and noodles can cause significant loss of vitamin B1.
3. Reduce cooking losses
Due to the solubility of vitamin B1 in water and its susceptibility to thermal decomposition under alkaline conditions, excessive washing of rice or adding alkali during cooking can lead to significant loss. Vitamin B1 is not lost much during the steaming process, and during high-temperature cooking such as frying and barbecue, the loss of vitamin B1 can reach 30% to 40%. It is recommended not to add alkali when boiling, do not excessively rinse the rice with flowing water when washing, and do not forcefully rub the rice or soak it in water for too long.