The human body works synergistically, no one organ works alone or without being influenced or having an effect on another area of the body. When one area of the body is not working properly others will also be affected. Similarly, when a nutrient is required for the healthy maintenance of the human body several organs need to be properly functioning so as to allow for proper absorption and accumulation.
In order for vitamin d to become active when it is derived from the skin or food, both the liver and kidneys need to be properly functioning. When one is low in vitamin d it may be a sign of either Kidney or Liver disease.
Activation of Vitamin D
Vitamin D is a hormone (a cholesterol-like substance) and in order to be effective in the body, it needs to be properly processed and activated. This involves a two-step process, which begins with either the consumption of vitamin d rich foods or the exposure of skin to sunlight. When skin is exposed to sunlight (UVB radiation) it interacts and stimulates the cholesterol underneath the skin is known as 7-dehydrocholesterol, which transforms into cholecalciferol. Cholecalciferol then moves from lymphatic system to bloodstream to end up in the liver where it is converted to 25-hydroxycholecalciferol also known as calcidiol.
It is not until calcidiol moves to the kidneys that it becomes the active form of vitamin d. The kidneys active calcidiol into 125-dihydroxycholecalciferol or calcitriol – which is known by many as vitamin D3. This is the most active form of vitamin d, allowing and enabling the absorption of calcium from the intestines as well the structuring and rigidity of bones. If either of the organs, the liver or kidneys, are not functioning to par as a result of a need for detoxification or disease the proper activation of vitamin D cannot occur leading to a deficiency in the hormone, resulting in a dysfunction to not only said organs but also to the skeletal system of the body as well as the bodies immune system.
Role of the liver is to maintain homeostasis of macronutrients including carbohydrates and protein and fat.
- bile production
- interconversion of nutrients
- Vitamin D production
- synthesis of blood components
When vitamin D levels are tested within the body 25-hydroxycholecalciferol or calcidiol is taken into account. This is the form of vitamin d that the liver gives out before it becomes activated by the kidneys. When the liver is not functioning properly due to disease or an imbalanced pathway of elimination, the absorption and utilization of vitamin d is impaired. This places further strain on the liver as it affects the production of bile (thus affecting digestion and absorption of nutrients) and can result in gut edema as well as other forms of inflammation.
Liver disease occurs when severe damage – often irreversible – takes place to the cells of the liver, resulting in impairment of its normal function. A major issue associated with the Liver and Vitamin D is fat malabsorption during liver disease. Vitamin D needs fat for absorption, without it levels will continue to decline in the body. This further affects the body by decreasing the levels of absorption of dietary calcium (to 10-15%) and phosphorus (to 60%). Making sure that there are adequate levels of Vitamin D in the body will increase the absorption of both nutrients in the body aiding in the health of bones and joints.
The kidneys have many important functions in the body aside from producing the active form of Vitamin D.
- filtration and removal of waste products from the blood
- regulating the levels of sodium, potassium, chloride and bicarbonate in the body – aiding in homeostasis
- Maintaining a balanced pH level
Vitamin D levels in the body, particularly the active form of 1,25 – dihydroxycholecalciferol has a great potential in predicting early signs of kidney disease as there is a direct relationship between the two. If the kidneys are not functioning to par they are not able to provide the body with a source of metabolic vitamin D. This not only affects the integrity of the joints and bones of an individual but also the immune system, lipid metabolism, regulating insulin resistance and protecting the nervous system. Low levels of vitamin D can also lead to malnutrition and weakness in the body as a decrease in serum vitamin D levels increases the probability of having protein in the urine.
Kidney disease such as albuminuria, glomerulonephritis, hypertension or diabetic nephropathy, is serious and if left untreated can result in kidney failure which can be deadly. When toxic substances accumulate in the body (due to ingestion or a decline in the bodies ability to detoxify), particularly in the blood can severely negatively affect the functioning of the kidneys as well as another part of the body. This can result in an increased production of urea within the body, leading to a feeling of nausea, vomiting and diarrhea.
Kidney disease and failure can be sudden, therefore it is important to make sure that the body is regularly checked on and that when Vitamin D blood serum levels are checked, the functioning of the kidney is taken into account.
Vitamin D3 Supplementation
About half of the world’s population does not receive enough sunshine (UVB radiation) to produce Vitamin D naturally year round, this has resulted in an estimated 1 billion people being deficient in the hormone. Deficiency in vitamin D increases the risk factor in mortality, this makes it a crucial nutrient to supplement with on a daily base. Furthermore, if one is experiencing issues with either the liver or kidneys it is crucial to make sure the one is supplementing with vitamin D3.
Vitamin D3 supplement is the equivalent to the active form the kidney gives out the end of the hormonal processing. As a result, it is important to make sure that when supplementing with vitamin d it is D3 and not D2 that is taken. The absorption and utilization of Vitamin D2 is far less than that of Vitamin D3.
Haas, E. (2006). Staying Healthy with Nutrition. New York: Random House.
Nair, R., & Maseeh, A. (2012). Vitamin D: The “sunshine” vitamin.Journal of Pharmacology & Pharmacotherapeutics,3(2), 118–126. Available online at NCBI
Nair, S. (2010). Vitamin D Deficiency and Liver Disease. Gastroenterol Hepatol. 6 (8), 491-493.
National Kidney Foundation. (2013). Low Vitamin D levels linked to early signs of kidney disease. Online Available at; www.kidney.org
Williams, S., Malatesta, K., & Norris, K. (2009). Vitamin D and Chronic Kidney Disease.Ethnicity & Disease,19(4 Suppl 5), S5–8–11. Available online at PubMed