vitamin k

In a normal, healthy individual eating a diet rich in vitamin C, we might expect adequate levels of vitamin C for normal cell functions. Any condition that would decrease these levels, such as smoking or chronic diseases, would therefore result in a decline in cell function. Of particular interest to our laboratory is the observation that vitamin C levels appear to decline in the elderly. This has been observed not only in human plasma, but also in plasma and tissues in rats, our model system. Why do vitamin C levels decline with age? The most straightforward answer is that vitamin C uptake declines with age. In other words, our bodies don't have the same capacity to absorb vitamin C, so vitamin C levels in the plasma and tissues become lower. This has been supported by a recent meta-analysis, which showed that the elderly had much lower plasma vitamin C levels than younger adults following a given dose of vitamin C. This suggests that vitamin C absorption in the gut declines with age. Vitamin C absorption is

The molecular basis for the cancer-preventive activity of selenium is not known. One idea is that selenium boosts the activity of enzymes that contain the unusual amino acid selenocysteine. Such selenoproteins are rare. Mammalian genomes may encode about twenty selenoproteins, of which about half have actually been biochemically identified. All of the selenoproteins thus far characterized seem to have a role in protecting the cell against oxidants or maintaining redox homeostasis. Selenium is chemically similar to sulphur and, like sulphur, can accept or donate electrons during oxidation and reduction reactions. When selenocysteine is removed from proteins, their activity decreases dramatically. Given that most, if not all, selenoproteins have a role in combating oxidative stress, and that the selenocysteine is required for protein activity, a reasonable hypothesis for the cancer- preventive activity of dietary selenium is that it ensures that the selenoproteins are present at levels sufficient to prevent or

Vitamin D synthesis in the skin declines with age..

Potassium (K) in the form of K+ is the most essential cation of the cells. Its high intracellular concentration is regulated by the cell membrane through the sodium-potassium pump. Most of the total body potassium is found in muscle tissue. Total body potassium has been used as a measure of lean body mass, of muscle mass, or (more accurately) of cell mass. Because of its association with the metabolizing, oxygen-consuming portion of the body, a decline in total body potassium is usually interpreted as a loss of muscle mass due to a catabolic condition. Potassium exists in nature in three isotopes: 39K (93.26%), 40K (0.0117%) and 41K (6.73%). 40K is radioactive and responsible for most of the naturally occurring internal radioactivity in the body. This property enables investigators to monitor total body potassium values as a function of age and disease.

Working with pigeons who were fed a diet of rice hulls, Funk was able to show the existence of a substance, later known as thiamine, which could cure beriberi. Because this compound was an amine, Funk coined the term "vitamine" to describe a set of amines essential for life. When further research showed that not all vitamins were amines, the term was shortened to vitamin..