Vitamin D is vital for strong, healthy lives. Whether you’re a youngster just learning how to walk, a bodybuilder in his prime, or a retiree who likes to spend his days playing chess in the park, ensuring that you consume enough Vitamin D each day will help ensure you can keep doing what you love.
What Is It?
Vitamin D is a fat-soluble vitamin  that, while required by the body for optimal health, is very difficult to get from diet alone. Supplementation, either in the form of fortified foods or the use of oral supplements, is commonly used to achieve sufficient levels of Vitamin D consumption.
Regardless of how you choose to consume your Vitamin D, it must also go through several stages of change within your body before it can be used effectively.
What Is Its Biological Role?
Vitamin D is a sort of side-kick in the vitamin world. Its purpose is to help your body properly absorb calcium. It also helps regulate calcium levels in the body once absorbed so that you have neither too little nor too much calcium.
Calcium is needed for the mending, growing, and maintaining of bones. It is, essentially, what makes them so strong. Without Vitamin D, your body would not be able to properly absorb calcium and use it to help keep you strong.
How Does It Help Bodybuilders and People Who Work Out?
It is especially important for anyone who spends a lot of time working out to ensure that they consume enough Vitamin D.
Any fitness regime is going to put some amount of stress on your bones and muscles--this is doubly true for weightlifters and bodybuilders. Normally that wouldn’t be a problem, because sufficient amounts of Vitamin D help your body properly utilize calcium to keep your bones strong and prevent injury.
With insufficient Vitamin D consumption, you greatly increase your risk of injury as a result of your fitness regime; without enough Vitamin D you lose calcium, and without enough calcium you end up with brittle bones that may break under the excess stresses of weight lifting or similar activities.
What Foods Contain It?
Vitamin D can be absorbed through skin during exposure to sunlight. Other than sunlight, the only other significant dietary sources are milk or other products that have been specifically fortified with Vitamin D, and oily fish such as swordfish, cod, or salmon.
How Much Of It Do You Need?
The recommended daily allowance of Vitamin D  is the same for all adults regardless of gender, or whether a new mother is pregnant or breastfeeding: 600 IU per day. For adults over 71 years of age, this recommended allowance is increased to 800 IU per day.
While it is not officially recommended for mothers to consume more Vitamin D when breastfeeding, increasing consumption may make the mother’s milk more rich in Vitamin D which can positively impact the child by helping to ensure proper bone formation as it grows.
Are There Risks Associated With Consuming Too Much Of It?
While unlikely due to its rarity from food sources, Vitamin D toxicity is possible when one consumes extreme doses of Vitamin D supplements. Vitamin D toxicity can result in hypercalcemia, which is an overabundance of calcium in the body that may start to negatively impact organs and veins.
It is worth noting that spending extended periods of time outside will not lead to Vitamin D toxicity, as the process that stimulates Vitamin D synthesis in reaction to sunlight is self-limiting. This means that after a certain threshold of production is reached, the sun starts to also break down the synthesized Vitamin D in a process called photo-degradation. This prevents your skin from producing harmful amount of Vitamin D while expose to direct sunlight.
Are There Risks Associated With Consuming Too Little Of It?
Without enough Vitamin D, your body cannot properly absorb and utilize calcium, which can results in rickets or osteomalacia in older adults. Rickets commonly affects children, and is a condition characterized by overly-soft bones as a result of Vitamin D deficiency which commonly results in skeletal deformities.
If rickets is caught soon enough, it is sometimes possible to reverse the effects with a therapeutically high dose of Vitamin D which can re-mineralize the bones since children are going through periods of near-constant growth for the first part of their life.
In modern times rickets is thankfully becoming increasingly rare, as is other conditions results from improper level of Vitamin D in the body. Still, it is important--especially as you age--to ensure you’re eating foods that contain Vitamin D when you can, and spending at least a bit of time outside without sunscreen so your body can do the rest.
That will allow you to live a long, full life without having to worry so much about whether your legs will always take you where you want to go.
 Office of Dietary Supplements, National Institute of Health. Vitamin D-Health Professional Fact Sheet. US Department of Health and Human Services, 2016.
 WebMD. Vitamin D Deficiency: Symptoms, Causes, and Health Risks. Webmd.com 2015.
 DeNoon, Daniel. Vitamin D FAQ: Vitamin D Recommendations, Deficiency, and More. Webmd.com, 2016.