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Vitamin D is an important nutrient that helps your body function properly. It isn't found naturally in many foods, but vitamin D is added to some foods to fortify them. Additionally, your body produces vitamin D when you go out in the sun.
How to tell if you’re getting enough vitamin D
The best way to find out if you are getting enough vitamin D through your lifestyle and diet is to take the 25-hydroxy vitamin D blood test. The ideal range is between 20 and 40 nanograms per milliliter. Some doctors prefer a result between 30 and 50 nanograms per milliliter. A result of fewer than 20 nanograms per milliliter means you are deficient.
Your doctor may recommend this test if you have symptoms of a vitamin deficiency. They might also recommend it if you have certain conditions that make it harder to absorb nutrients including:
- Cystic fibrosis
- Crohn's disease
- Celiac disease
- Bariatric surgery
- Kidney disease
- Liver disease
Some medications can also lower your ability to absorb vitamin D. If you take any of the following medications, your doctor may recommend a vitamin D test:
- Laxatives
- Drugs to lower cholesterol
- Prednisone and other steroids
- Phenobarbitol
- Phenytoin
- Rifampin
- Orlistat
Symptoms of vitamin D deficiency
If you have symptoms of a vitamin D deficiency, you may not be getting enough in your diet. Symptoms include:
- Tiredness
- Bone aches and pains
- Weak muscles
- Muscle cramps and pains
- Mood changes
More severe cases of vitamin D deficiency cause rickets in children. Rickets affects bone growth and causes deformities as a result. It also causes weaker bones, so fractures are more likely.
Adults and older children can get a similar condition called osteomalacia (soft bones). It causes bones to bend and break easily.
Luckily, both of these conditions are easy to treat with a diet high in vitamin D, or vitamin D supplements. Some people who have trouble absorbing nutrients through food may need to receive vitamin D injections to prevent these conditions.
Why is vitamin D important?
There are many ways that vitamin D helps your body to function properly.
Strong bones
No matter how much calcium you get in your diet, it can only be absorbed when you also have enough vitamin D. This combination of nutrients keeps your bones strong and helps to prevent bone fractures and osteoporosis as you get older. It also contributes to muscle health and strength.
Researchers have not found that vitamin D reduces the risk of getting cancer. However, studies do suggest that supplementing with vitamin D during cancer treatment can improve the likelihood of a positive outcome.
Immune function
Studies show that supplementing with vitamin D may reduce your likelihood of catching a cold or the flu. Researchers are also trying to determine if it can reduce your risk of getting a severe case of COVID-19. However, since it is such a new virus, more research is needed.
Foods that are high in vitamin D
There are only a few natural sources of vitamin D in the diet, including:
- Fish oils
- Salmon
- Swordfish
- Tuna
- Sardines
- Beef liver
- Egg yolks
Additionally, many orange juices, plant-based milks, and cereals are fortified with vitamin D to help people get more in their diet.
Vitamin D and sun exposure
You can also get vitamin D from the sun. However, it's very difficult to get the full amount of vitamin D that you need solely from the sun.
- Wearing sunscreen and clothing that covers your body prevents you from absorbing vitamin D.
- People with more melanin often absorb less vitamin D, because melanin is a natural sunscreen.
- If you stay inside most of the time, you will not get much sun exposure and will lack vitamin D.
- You also absorb less vitamin D as you age due to changes in your skin.
- People who live further from the equator don't get enough sun exposure to make the proper amount of vitamin D in the winter months.
Should you take vitamin D supplements?
If your vitamin D levels are too low, your doctor might recommend vitamin D supplements. Most people take between 600 and 800 international units of vitamin D each day. However, you can safely take up to 4,000 international units daily. You should only take more than that if your doctor recommends it.
If you take a high dose, you may be at risk for vitamin D toxicity. Symptoms include:
- Nausea
- Constipation
- Lack of appetite
- More thirst than usual
- Urinating more frequently
- Confusion
- Slurring words
If you have these symptoms and take a high dose of vitamin D, let your doctor know immediately and stop taking the supplement.
