Vitamin D, commonly known as the sunshine vitamin is a fat-soluble vitamin with amazing benefits in bone development, improved immunity, and weight loss. In this blog, we shall principally focus on the relationship between weight loss and this vitamin, and how it functions in weight loss.
The best source is the sun followed by oily fish (herring, salmon, sardine, mackerel, etc). Other food sources include egg yolks, red meat, mushrooms, liver, fortified foods (orange juice, cereal, oatmeal, etc).
It is difficult to get a substantial amount from these foods, thus a good quantity of these vitamins are usually gotten from supplements.
The active form of Vitamin D.
Vit D from these sources is biologically unreactive and will have to undergo two hydroxylation processes to become active and useful. We have two types of Vit D; D2 (ergocalciferol) mainly from plant sources and D3 (cholecalciferol) from animal products. In the liver, vitamin D is hydroxylated at carbon-25 forming 25-hydroxyvitamin D [25-(OH)D] commonly called calcidiol.
The second hydroxylation takes place in the kidney at carbon-1 forming the active 1,25-hydroxyvitamin D [1,25-(OH)2D], commonly called calcitriol.
The vitamin metabolites called 25-hydroxyvitamin D are measured in serum to determine an individual’s Vit D status, as highlighted by the American Association for Clinical Chemistry (23, 2013). 25(OH)D is the major circulating form of Vit D while the most active circulating form is 1,25-dihydroxyvitamin D.
Relationship Between Vitamin D and Body Mass.
Obesity is generally defined by the WHO as a Body Mass Index (BMI) equal to or above 30 kg/m2, and overweight arises when BMI lies between 25-29.9 kg/m2. These are usually linked to low serum 25(OH)D levels. Some studies report that fat content and BMI have a very strong inverse relationship with serum 25-hydroxyvitamin D concentrations.
A bidirectional genetic study also proves that higher BMI gives rise to lower levels of 25(OH)D.
Moreover, vitamin D supplements were given to some obese and overweight ladies in Isfahan whose ages range between 20 and 40. After a few weeks, these women experienced a decrease in waist circumference, mean BMI, and overall weight gain.
Some Possible Reasons for low levels of 25-hydroxyvitamin D in the serum.
Some obesity experts suggest:
- A decrease in the exposure to sunlight.
- Clothing habits that can reduce vitamin D synthesis.
- Spending more time indoors than outdoors.
- The efficient use of sunscreen slows the absorption of vitamin D by approximately 90% as suggested by Holiek M.F.
- The old with a lower amount of 7-dehydrocholesterol ( a precursor of vitamin D found on the skin and converts to vitamin D when one of its chemical bonds undergoes photolysis) levels and changes in the skin.
- Changes of the season particularly during limited sunshine.
- Darker skin with greater melanin content serving as a natural sunscreen.
How Does Vitamin D aid in Weight Loss?
Vitamin D plays significant roles in weight loss in the following ways:
It has been proven to suppress the formation of adipocytes or fat cells. That is, it slows down adipogenesis.
Moreover, 1, 25-dihydroxyvitamin D has been reported to inhibit the storage of fat cells.
Vitamin D has also been shown to regulate the synthesis of serotonin, a neurotransmitter and hormone often involved in wellbeing and happiness. Serotonin has been confirmed to induce weight loss with little or no side effects due to its low-calorie intake, increase satiety, and anti-appetite properties.
A positive relationship between testosterone and vitamin D was also studied and appreciated, where low testosterone caused an increase in body fat and adiposity (obesity). This was also confirmed when testosterone replacement was given to induce weight loss in obese older men. Generally, an increase in vitamin D usually leads to an increase in testosterone that often induces weight loss in an overweight individual. It is suggested that increasing the concentration of 25(OH)D encourages the production of testosterone in non-diabetic males and this is probably because 25(OH)D inhibits the aromatization of testosterone (conversion of testosterone to estrogen by the enzyme aromatase), and that vitamin D receptors, as well as vitamin D metabolizing enzymes, are found clouded in rat testis. Moreover, studies conducted on HIV male patients with abdominal fat mass and low testosterone arrived at the conclusion that there was a significant reduction in abdominal fat mass after subjecting these patients to testosterone therapy. More studies also reveal that men subjected to testosterone treatment for a year had a slight reduction in body fat. Testosterone does this by boosting the body’s metabolism, inhibiting the formation and differentiation of adipocytes (fat cells), and inducing the body to burn down more calories.
Be careful of Dosage.
The US institute of medicine (IOM) in 2004 provided adequate intake (AI) levels of this vitamin based on IU/day for all individuals according to age. For infants or those below the age of 50, 400 to 800IU (international unit) is required per day. For those between 50-70 years, 50nmol/L was recommended. Above 70 years, 600IU/day is suggested.
The Endocrine Society (ES) proposed a slightly higher dosage for infants to be 400-1000IU/day, 600-1000IU/day for children, 1500-2000IU/day for adults.
When taken in a higher dosage of above 10,000IU/day for a long period, vitamin D can cause toxicity which may lead to hypercalcemia.
All in all, an increase in the concentration of 25-hydroxyvitamin D in the serum as a result of exposure to UV radiations of the sun and consumption of vitamin D rich-foods usually leads to a decrease in body mass index (BMI) and hence weight loss via the regulation of serotonin and testosterone-which serves as two great parameters in weight management.
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