Do you feel exhausted and have painful muscles and joints all the time? This could be a sign of Vitamin D deficiency. Vitamin D is a fat-soluble vitamin essentially required by our body. It is found in a very few foods but sunlight is an abundant source of this vitamin. Vitamin D plays a major role in our bone strengthening, bone density and absorption of certain critical nutrients like calcium and phosphorus.
Even when there is plenty of sunshine available, the deficiency of Vitamin D is still prevalent amongst us. We prefer staying indoors within our air-conditioned comfort zones, apply sunscreen as soon as we step out in the sun and less intake of vitamin-rich foods are some of the practices which invite Vitamin D deficiency. The available sources of vitamin D are usually in their inactivate forms (Cholecalciferol) which have to be converted to their activated form (Calcitriol) in order to be absorbed by our body. Apart from sunlight, dietary sources of vitamin D include egg yolk, fatty fish, liver, ghee and fortified foods. Deficiency of vitamin D is associated with low bone density, weak bones, osteoporosis, joint pain, arthritis, fatigue and muscle pain. It has been observed that people involved in intense physical activities like strength or endurance athletes are more prone to developing vitamin D deficiency. Apart from providing bone strength, vitamin D levels have a significant effect on the physical performance of an athlete. It increases the aerobic performance, reduces levels of stress and prevents injury. As per the National Institute of Nutrition (NIN), 400 IU or 10 micrograms of activated Vitamin D is required per day in case of minimum exposure to sunlight. These requirements may go up to 2000 IU depending upon the intensity of physical activity, dietary intake and exposure to sunlight.
Vitamin D was discovered by Adolf Windaus who received the Nobel Prize for the same in 1928. Rickets or weak bones is a deficiency disorder of Vitamin D. Though this vitamin got its recognition in 1928, rickets came into consideration early in 18th century. At that time several studies were conducted to know the exact cause and cure for rickets. In 1914, another scientist named McCollum and his team separated a fat-soluble factor from butter fat and stated that rickets is caused by the deficiency of this factor, as it prevented xerophthalmia in rats, which was later named as Vitamin A. In 1920, a scientist named Hopkins found that this cofactor got destroyed by heating and many experimental subject rats died due to xerophthalmia.
Later in 1922, McCollum and his team again performed an experiment in which they found that cod liver oil which was oxidised could not cure xerophthalmia but could cure Rickets in rats. After this experiment, it was concluded that this fat-soluble factor has two substances - one vitamin A and second an anti-rickets factor. In 1925, A.F. Hess and his team proposed that the precursor of this anti-rickets factor gets activated by sunlight. This was the sign that led to the perception of Vitamin D.
ACTIVATED VS. NON-ACTIVATED VITAMIN D
Vitamins D enters our body in its inactive form. The 7-dehydrocholesterol is present in our skin gets converted into Vitamin D3 (cholecalciferol) when exposed to ultra-violet rays. Further, this vitamin D3 gets converted to 25-hydroxycholecalciferol (25OHD3) in the liver and it is the form of vitamin D3 found in most of the dietary supplements.
Then, 25-hydroxycholecalciferol transforms into the activated form of Vitamin D3 which is Calcitriol. This reaction triggered by Parathyroid Hormone (PTH) takes place in the cells of kidneys under the presence of an enzyme - 1-alpha-hydroxylase.
The presence of activated Vitamin D3 is necessary for the absorption of calcium and phosphorus heling keep our bones healthier. In order to prevent any deficiency, we need to have activated form in our body otherwise it will be of no use.
VITAMIN D - NEW CALCIUM
You must have noticed that whenever experts talk about the benefits of vitamin D, calcium plays a key role. This is because absorption of calcium and vitamin D are inter-linked with each other. Lack of any one nutrient might lead to a deficiency of both. Let’s understand why and how.
We now know how the active form of vitamin D which is Calcitriol is achieved. After the formation of calcitriol in our kidneys, it results in an increased level of serum calcium and phosphorus in our body. This rise in the level is a result of increased absorption of calcium and phosphorus from our bones. Therefore, insufficient calcium levels lead to the draining of the calcium stores of the body. Thus, the dietary supplement of calcium and vitamin D should go hand in hand. Hopefully, now you have realized that why vitamin D is so crucial for bone strength and density.
ROLE IN BOOSTING ATHLETIC PERFORMANCE
Adequate Vitamin D levels are one of the crucial necessities of an athlete to perform well. Optimal vitamin D levels ensure reduced risk of injury, pain in muscles and joints and stress fracture. These levels should be a combined effect of sunlight, dietary intake and supplements (if required). It has been observed that athletes are prone to developing vitamin D deficiency as workouts are usually avoided during peak sunlight hours. Alkoot M. J. (2016) submitted a study in which results stated that athletes with injuries had inadequate vitamin D levels.
Vitamin D receptors present in skeletal and cardiac muscles initiate the synthesis of an activated form of vitamin D which may increase the intake of oxygen transported to our various tissues. A study was conducted by Dahlquits D.T. et al (2015).to examine the effects of vitamin D and its role in an athletic performance. Findings revealed that different dosages of vitamin D have potential effects on the performance and they might vary in context to muscle growth, aerobic capacity and overall recovery time from exercise. Research studies have also claimed that vitamin D is not only required for bone health but also has a positive effect on muscle health. To support this claim, Chiang et al (2017) led a study on athletic participants between 18-45 years of age. They were given vitamin D supplements, dosages ranging from 600-5000 IU/ day. Data showed a significant improvement in their muscle strength from 1.37-18.75% with the help of vitamin D3 supplementation.
HOW MUCH TO CONSUME?
Vitamin D dietary supplements come to our rescue when meeting the adequacy levels only through diet becomes a challenge. You must have noticed that supplements come in varied dosages and servings. This is due to the simple fact that every individual has a specific requirement, and supplements help provide the flexibility to accomplish them. Vitamin D3 requirement is high for individuals who are deficit, than people who consume them for maintenance. Therapeutic dosages for deficit people will always be higher than the ones for general well-being.
Usually, supplements containing 60,000 IU vitamin D per serving are taken on a weekly basis to cure the deficiency. For maintenance of vitamin D levels, a person can opt for 1000-3000 IU of vitamin D supplement. Athletes can increase their supplement intake frequency as per the sport specific requirement.
Below mentioned are the requirements of Vitamin D per day as per the body’s requirement :
Vitamin D Dosage
600-800 IU / day
600-800 IU / day
1500-2000 IU / day
DIETARY SOURCES OF VITAMIN D
- Cod liver oil
- Fatty fish like salmon, tuna, mackerel
- Egg yolk
- Beef Liver
- Fortified products like milk, mushrooms, breakfast cereals
WHAT HAPPENS WHEN VITAMIN D IS EXCESS?
Since vitamin D is a fat-soluble vitamin, it needs fat as a medium to get absorbed in our body. Due to this property, in case of an excess amount, it can not be excreted out of our body through urine. Hence an intake of more than the required amount might result in toxicity which is usually termed as Hypervitaminosis. Excess vitamin D might result in excess blood calcium levels which can result in nausea, vomiting and fatigue. High levels may also interfere with the activity of vitamin K (vitamin required for blood clotting and regulation of calcium deposition) resulting in bone loss. Further, excess calcium in our body might lead to stone formation.
To summarise this literature, we can say that vitamin D acts as a performance booster. Not only it helps in intensifying our bone and joint health but also boosts muscle strength. Deficit levels make our body more prone to stress fractures and porous bones leading to osteoporosis. Vitamin D helps in giving an additional kick to an athlete for excelling or achieving his/her fitness goal. From the above-stated studies, we can not rule out a significant association between one's vitamin D levels and athletic performance. Its receptors present on our cells are involved in calcium and phosphorus absorption. Sufficient exposure to sunlight and diet rich in vitamin D helps in preventing its deficiency. In the case of inadequate levels, vitamin D supplements come to rescue. So always remember that not only calcium, vitamin D is equally pivotal for our health.
Sesikeran B. (2010) Revised RDA for Indians. Hyderabad: National Institute of Nutrition
G, R., & Gupta, A. (2014). Vitamin D deficiency in India: prevalence, causalities and interventions. Nutrients, 6(2), 729-75. doi:10.3390/nu6020729
Sanwalka N. Vitamin D Deficiency in Indians – Prevalence and the Way Ahead. J Clin Nutr Diet. 2016, 1:1
Alkoot MJ. (2016) The Prevalence and Risk Factors of Vitamin D Deficiency in Athletes in Kuwait [MD Thesis]. Dublin: Royal College of Surgeons in Ireland;.