Up to 50% of the world’s population might not be getting enough sun, leaving many people deficient in vitamin D, the only nutrient your body produces when exposed to sunlight.
This is partly because people are spending more time indoors, wear sunscreen outside, and eat a diet low in quality sources of vitamin D.
With world-wide attention focused on the importance of vitamin D, here’s what you need to know.
What is Vitamin D?
Vitamin D is a micronutrient that is needed for optimal health throughout your whole life.
It is a fat-soluble vitamin, meaning that it dissolves in fat/oil and can be stored in the body for long periods of time. There are two main forms, D2 and D3; D3 being more effective.
Vitamin D is also unique, because it is both a nutrient we eat, and a hormone that our body makes from exposure to sunlight, which is why it is often named the ‘sunshine’ vitamin.
While vitamin D affects various cells related to bone health – like telling the cells in the gut to absorb calcium and phosphorus – but scientists have now generated a strong body of evidence supporting vitamin D as an indispensable hormone, required for regulation of many physiologic functions.
Research shows that vitamin D receptors are present in nearly every tissue and cell in the body, and adequate vitamin D is essential for optimal function of these tissues and cells to carry out important roles, including: reduction of inflammation, modulation of cell growth, immune function and glucose metabolism.
Simply put: Sufficient levels of vitamin D are essential for disease prevention, longevity, and optimizing human health.
How To Get Your Dose
The major source of vitamin D is direct sunlight exposure. Unveiling bare arms and legs for 5 to 30 minutes between 10:00 AM and 3:00 PM is often adequate to meet vitamin D requirements. But this can vary depending on skin pigmentation and other factors.
Vitamin D obtained from summer sunlight can be stored in our bodies for a long period, however many people cannot store enough to see them through the winter months.
Variables such as age can also affect the amount of vitamin D converted in the skin. The cholesterol precursor in the skin (7-dehydrocholesterol) for vitamin D2 and vitamin D3, decreases as we age. In fact, it decreases at a rate of 50% between the ages of 20-80. This inhibits the amount of vitamin D3 older people can make.
Thankfully, you don’t have to rely solely on the sun. Vitamin D dietary supplements are safe and inexpensive, and are becoming widely available. But ideally exploring whole-foods like oily fish and mushrooms can deliver a good source of vitamin D.
What should be on my shoppinglist?
According to the European Food Safety Authority, the Panel on Dietetic Products, Nutrition and Allergies (NDA) defined an adequate intake (AI) of 15 µg per day for healthy individuals over one year of age. This includes pregnant and lactating women. The DRVs for infants aged 7-11 months have been set at 10 µg per day.
Below you’ll find an indication of Vitamin D contents in foods available in Ireland.
- Salmon 100 g (palm of hand size) 2.9–18.5 µg *
- Trout 100 g (palm of hand size) 10 µg
- Mackerel 100 g (palm of hand size) 8.6 µg
- Tuna 100 g (palm of hand size) 3 µg
- Sardines 100 g (palm of hand size) 5 µg
- Eggs 2 eggs 4 µg
Vitamin D-fortified foods**
- Milk with added vitamin D 200 mL (a glass) 2–4 µg
- Cereal with added vitamin D 30–40 g (a bowl) 1.5–2.9 µg
- Yogurt with added vitamin D 125 g (a pot) 0.8–5.0 µg
- Cheese with added vitamin D One cheese string 1.3 µg
*The vitamin D content of wild salmon (9.4–18.5 μg) ) is higher than that of farmed salmon (2.9–9.5 μg) (Jakobsen et al., 2019); most of the salmon consumed in Ireland is farmed salmon.
**Nutrition labelling must be checked, as the types of foods fortified, and the amounts of vitamin D added to such foods, change continuously.
Source: Food Safety Authority of Ireland. Vitamin D, Scientific Recommendations for Food-Based Dietary Guidelines for Older Adults in Ireland (2020)
In addition to the Vitamin D sources listed above, we also should not forget the humble mushroom. Mushrooms are the only source of vitamin D in the produce aisle and one of the few non-fortified food sources. All mushrooms contain some vitamin D, but mushrooms have the unique ability to increase vitamin D amounts due to UV-light or sunlight exposure. Similar to humans, mushrooms naturally produce vitamin D following exposure to sunlight or a sunlamp: mushrooms’ plant sterol – ergosterol – converts to vitamin D when exposed to light. So keep them on your windowsill, not in the fridge
Get outside as often as you can. Even sitting in your garden for 10-15 minutes in the mid-day sun will help. If you work in an office, take your lunch break outside.
Starting a new outdoor hobby can also help you spend time in the sun, like running, bike riding, surfing, or simply walking daily. These are all great ways to get your daily dose of vitamin D.
Remember: Eating plenty of vitamin D-rich foods will help you keep on top of this essential micronutrient.
And finally, during the periods of low sun hours from October to March and if you find yourself more housebound you should take some Vitamin D supplements. Check with your health professional.