维生素D z-bo 2020-10-30 424

　　When it comes to vitamin D, most adults either show a significant deficiency, which results in obvious clinical symptoms, or show a deficiency, which is often undetected. However, it has been difficult to determine how this deficiency affects physical health and the frailty of the elderly as they age. Now, in a new study, researchers from the Western New York Medical System of the U.S. Department of Veterans Affairs and the University of Buffalo performed experiments on mice 24 to 28 months old (equivalent to adults between 65 and 80 years old). Studies have found that supplementing with larger doses of vitamin D can alleviate weakness.

　　Seldeen explained that a study they published in 2018 has found that young mice with chronically insufficient vitamin D levels can lead to impaired physical performance. However, this new study shows that even if mice have sufficient vitamin D levels throughout their lives, their vitamin D levels become inadequate after old age, and physical damage occurs much earlier.

　　Seldeen said, "We found that in elderly mice, low levels of vitamin D can cause a decline in physical functions, such as grip strength and grip endurance--the ability to maintain grip strength---decreased, and this decline is in vitamin D. It began to appear after a month of reduction in D intake."

　　Decreased balance and coordination skills

　　He continued, “We have also found that low vitamin D levels are associated with decreased balance and coordination. Human studies have shown that low vitamin D levels are associated with a greater risk of falls, especially in frail elderly people. The data supports this view."

　　A key finding of this study is that during the four months of treatment, vitamin D status plays an important role in the development of weakness. These researchers used a method similar to humans to measure the degree of weakness in mice, where weakness is defined as having three or more of the following conditions: unexpected weight loss, weak grip, poor grip endurance, low activity level, and gait speed slow. These researchers found that in the two groups of mice that consumed 125 international units (IU) of vitamin D per kilogram of food per day and 1,000 IU of vitamin D per kilogram of food per day, their weakness was exacerbated, and the former caused The serum vitamin D level in mice is insufficient, and the serum vitamin D level caused by the latter is sufficient for humans, but still insufficient for mice.

　　Seldeen said, "Only when the mice were given the highest amount of vitamin D---that is, 8000 IU of vitamin D per kilogram of food per day---, their weakness did not increase during the time frame of the study. ."

　　These findings are particularly relevant to the ongoing discussion about how much vitamin D the elderly need to stay healthy.

　　Research results may support higher doses of vitamin D supplementation

　　Seldeen said, “For adults, there are differences in what level of vitamin D is sufficient.”

　　He explained that the National Academy of Medical Sciences (NAM) has determined that 20 ng/ml of vitamin D in the blood is the level required for adequate vitamin D in adults, which is mainly based on the need to maintain bone health. The Food and Nutrition Board of the National Academy of Medical Sciences recommends that adults between the ages of 19 and 70 should consume 600 IU of vitamin D per day, and those over 70 should consume 800 IU of vitamin D per day.

　　Troen explained that more and more literature shows that vitamin D is important for other aspects of health, and some researchers in this field believe that 30 ng/ml is the necessary minimum level.

　　He said, “We recommend that the elderly take at least 2000 IU of vitamin D a day. This is especially important for our frail elderly patients. However, according to our research, we believe that a lifelong supplement of adequate vitamin D will optimize long-term functional ability. (Functional capacity refers to the ability to complete tasks with purpose, meaning, beginning and end, and measurable results) and health."

　　Seldeen said, "Our research results suggest that even the level of 30 ng/ml is not enough. In fact, 60 ng/ml is needed to prevent these old mice from getting weaker." This is what the National Academy of Medical Sciences believes. The safe upper limit of vitamin D levels in the blood, this level can roughly be reached by consuming a maximum dose of 4000 IU of vitamin D per day. Seldeen said, “In order to delay the increase in weakness, the actual vitamin D dose that needs to be supplemented is greater than the dose currently considered sufficient for humans.”

　　Although this finding is particularly interesting, Seldeen pointed out that, of course, a study will not give a clear answer. He said, "Unfortunately, vitamin D supplementation in excess of the standard amount is rarely studied. However, this study raises the possibility of including a high-dose group in future human clinical trials involving vitamin D."

　　Seldeen, Troen and their collaborators plan to conduct human research on vitamin D in the future. They also started a new mouse study that will explore the effect of vitamin D status on muscle biology during aging to better understand why vitamin D affects physical performance and weakness.

　　Seldeen said, "It is quite difficult to study the direct effects of human serum vitamin D levels, because this effect may take many years to manifest, and it may not be safe to test for effects with persistently low or high vitamin D levels. By using In animal models, we are able to study these potentially higher vitamin D levels and their biological effects in the aging process. In addition, compared with the complex human diversity, it is performed in mice with the same genetics and the same lifestyle Research in this area can make people pay more attention to the specific effects of different vitamin D levels."