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Nutrient in Focus: Vitamin D
As the sun starts to shine again, it’s time to get those vitamin D levels up again after a cold and wet winter!
What is vitamin D?
Vitamin D is a hormone made from sunshine, but there are some food sources that also provide the body with vitamin D. The body creates pre-vitamin D3 in the skin, which then turns into vitamin D3 with exposure to sunshine and is taken to the liver. Vitamin D3 is then taken from the liver to the kidneys, where it’s converted to an active form of vitamin D that the body can use. Vitamin D2, which behaves similarly to vitamin D3, can be found in some foods, although this is in low amounts. The conversion process is greatly influenced by the season, time of day, latitude, altitude, air pollution, skin pigmentation, sunscreen use, passing through glass and plastic, and aging.
Vitamin D is required for keeping bones healthy as it assists in the absorption of calcium from the digestive system. Absorption of calcium can increase by 25% with adequate vitamin D! Almost all cells in the immune system have vitamin D receptors as vitamin D helps the immune system to function normally. When the immune system is functioning incorrectly, there can be increased inflammation in the body which leads to fatigue and pain. Therefore, vitamin D has an indirect impact on energy levels. Recent research indicates a connection between depression and inflammation which would also suggest there is a connection to vitamin D as well, but more research is needed in this area. There are also vitamin D receptors on the lining of the digestive system, which help keep the lining strong and support the absorption of nutrients.
Both male and female fertility is impacted by vitamin D. It affects semen quality due to its role in separating and organising the DNA so the parent’s DNA can merge (also known as DNA fragmentation) and women with optimal levels of vitamin D are more likely to have a successful pregnancy. A study found pregnant women with morning sickness were twice as likely to have a vitamin D deficiency compared to pregnant women without morning sickness. Vitamin D supplementation during the preconception period and pregnancy can reduce the risk of adverse pregnancy outcomes such as low birth weight, pre-eclampsia, neonatal mortality, and wheezing/asthma in infants.
Sources of vitamin D
The best source of vitamin D is exposure to sunlight! The recommendation is to aim for 10-30 minutes of mid-day sun exposure a few times per week. As vitamin D is fat-soluble, it is better to have areas of the body with higher fat levels, such as the stomach and thighs, exposed to the sun for increased vitamin D production. However, if you’re uncomfortable with this, arms and legs are also acceptable.
There are some food sources of vitamin D2 as mentioned above however it is very hard to reach the recommended amount of vitamin D from dietary sources. Dietary sources include fatty fish such as salmon and eggs or cereals that have vitamin D added to them. Mushrooms can also create vitamin D2 when left in the sun for more than 15 minutes, so letting your mushroom sunbake before you eat them can be a great idea! The levels are higher than most food sources of vitamin D2 and remain stable when kept in the fridge for up to a week. However, the level will decrease with storage at room temperature and cooking.
Signs of deficiency
Signs and symptoms of vitamin D deficiency include:
- Frequent illness or infection
- Fatigue and tiredness
- Bone and muscle pain
- Chronic pain
- Depression and anxiety
- Slow wound healing
- Weight gain
When to take vitamin D
It is recommended to take vitamin D if your vitamin D levels are low on a blood test. The optimal range for vitamin D is about 100 nmol/L depending on the time of year that the test is done, if you’re looking to conceive and if you have any chronic health issues. This is a blood test that can be ordered by your GP.
Some practitioners will recommend everyone takes a vitamin D supplement in winter. However, this can depend on where you’re living and how high your vitamin D levels are at the end of summer.
The dosage of vitamin D is dependent on your blood test results, the time of year you’re taking it, your weight and the form being taken. Vitamin D is available as a liquid supplement or as a capsule. It is best to take vitamin D with a fat source such as avocado, cheese, or peanut butter to increase absorption.
If you’re concerned about your vitamin D levels, please book a consultation.