October 20th every year is World Osteoporosis Day,which attracts global attention.In 2024,the theme for the China region will be"Managing Weight and Strengthening Bones",aiming to raise public awareness of bone health and advocate for scientific weight management to strengthen bones and prevent osteoporosis.

　　Recently,Ms.Zhao discovered after a physical examination that her 25 hydroxyvitamin D level was 38.5nmol/L,which is lower than the normal range of 75-150nmol/L.This result surprised her because she has always focused on balanced nutrition and actively exercised,and there are many patients with the same problem as Ms.Zhao.What do we need to know about 25 hydroxyvitamin D.

　　Doctor,why is there a low level of 25 hydroxyvitamin D?

　　The reasons for low levels of 25 hydroxyvitamin D are multifaceted,mainly including the following aspects:

　　Reduced synthesis-Vitamin D is a steroid derivative,and 90%of vitamin D is synthesized by the skin under ultraviolet radiation.If the sunshine duration is insufficient,the body may not be able to synthesize sufficient vitamin D,which may lead to a low level of 25 hydroxyvitamin D,especially in winter or high latitude areas where the sunshine duration is short and the ultraviolet intensity is weak.

　　Insufficient intake-Dietary intake accounts for 10%of vitamin D intake,an unreasonable dietary structure,and picky or selective eating can lead to insufficient vitamin D intake.Especially pregnant women,the elderly,and children in rapid growth and development are more likely to experience insufficient intake due to increased demand for vitamin D.Fish liver,egg yolk,dairy products,vegetables,and fungi in food are rich in vitamin D,which can be appropriately increased in intake.

　　Taking certain medications-taking medications that affect vitamin D metabolism,such as anticonvulsants,corticosteroids,cimetidine,anti tuberculosis drugs,aminophylline,orlistat,etc.,can accelerate the breakdown of vitamin D and lead to a decrease in vitamin D levels in the body.

　　Who is prone to low levels of 25 hydroxyvitamin D?

　　The following groups are prone to low levels of 25 hydroxyvitamin D:

　　1.People who work or live indoors for a long time,and those who use sunscreen.SPF-8 sunscreen can reduce the amount of vitamin D produced by the skin by 92.5%,while SPF-15 sunscreen can reduce the amount of vitamin D by 99%.Due to insufficient effective sunlight exposure,the skin is unable to synthesize sufficient vitamin D.

　　2.Elderly people.Under the same lighting conditions,the amount of vitamin D synthesized by the skin of elderly people over 70 years old is only 30%of that of young people.As age increases,the ability of the skin to synthesize vitamin D gradually decreases,which may be accompanied by weakened gastrointestinal absorption function,leading to insufficient vitamin D synthesis,reduced intake,and absorption disorders.

　　3.Pregnant and lactating women.Pregnant and lactating women have an increased demand for vitamin D,and if intake is insufficient or malabsorption is poor,it can easily lead to underestimation.

　　4.Infants,young children,and adolescents.Infants,young children,and adolescents who are in the growth and development stage have a high demand for vitamin D.If their intake is insufficient or their growth rate is too fast,leading to increased consumption,it is easy to have a low demand.

　　5.People with chronic diseases such as gastrointestinal disorders,liver and kidney diseases.These diseases can affect the absorption and utilization of vitamin D.

　　What health problems may low 25 hydroxyvitamin D bring?

　　1.Osteoporosis.25 hydroxyvitamin D is a key promoter of calcium absorption,and its deficiency can lead to reduced calcium deposition in the bones,decreased bone mass,and ultimately osteoporosis,increasing the risk of fractures.

　　2.Rickets.Especially during adolescence,insufficient 25 hydroxyvitamin D can affect normal growth and development,leading to rickets,manifested as skeletal deformities such as chicken chest and funnel chest.

　　3.Hypocalcemia.Vitamin D deficiency can affect the absorption of calcium,leading to a decrease in blood calcium levels.Patients may experience symptoms such as cramps,seizures,general pain,and even arrhythmia.

　　4.Other system impacts.Affects the cardiovascular system,increases the risk of hypertension and cardiovascular disease;Affects the immune system,leading to weakened immunity and increased susceptibility to diseases;Affects emotions,leading to low mood and cognitive impairment.

　　How to deal with low levels of 25 hydroxyvitamin D found?

　　1.Increase outdoor activities.Expose the skin directly to sunlight to promote the synthesis of vitamin D.Expose larger skin areas such as legs,shoulders,and arms when sunbathing to increase the synthesis of vitamin D.It is recommended to use the shadow principle for sun exposure time:when one's own shadow is longer than their height,the ultraviolet rays are already very weak,and the skin cannot synthesize vitamin D;So the recommended sun exposure time is within 2 hours before and after noon,when the shadow is shorter than the height.

　　2.Pay attention to sun protection.Although sun exposure helps with the synthesis of vitamin D,it is also important to avoid prolonged exposure to strong ultraviolet radiation to prevent damage to the skin.Reduce sun exposure time when the summer sun is strong,and choose a sun hat to avoid overheating of the head and direct sunlight on the eyes.

　　3.Pay attention to diet:Eat more foods rich in vitamin D and calcium,such as seafood,animal liver,egg yolks,milk,cheese,shrimp skin,soy products,sesame paste,etc.These foods not only contain abundant vitamin D,but also provide calcium,which helps promote the absorption and utilization of calcium.

　　4.Supplementary medication:If dietary adjustments cannot meet the needs,vitamin D drops or capsules can be taken under the guidance of a doctor for supplementation.Calcium can also be supplemented in moderation,such as calcium carbonate,calcium citrate,etc.