All about Vitamin D functions and food sources!

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Today’s topic is learning a few facts about Vitamin D & reliable food sources!

You can find information for UK supplementation guidelines in the NHS website and SACN vitamin D report . Especially now due to the “stay-in situation”, it is important to check any updates on your country’s supplementation guidelines!

It has recently been suggested that maintaining a normal Vitamin D status is important to protect our health during these difficult times and that vitamin D deficiency risk is increased due to staying inside . Let’s keeping in mind some important information about this nutrient.

A few facts about vitamin D

• It can be produced after skin exposure to sunlight when the time of the day, latitude and wavelength (290-315nm) are appropriate. In the UK and most north hemisphere countries, these factors are met between March and September. In this aspect, since it is produced by skin cells, Vitamin D acts as a pre-hormone .
• Vitamin D is a fat soluble vitamin. It meets the criteria to be a vitamin, since it is an organic substance found in small amounts in food, it is nessecary to maintain our health and its deficiency can cause diseases.
• It can be recieved from food in the form of Vitamin D3 and Vitamin D2.
• During winter, or in presense of other factors that prevent adequate exposure to sunlight, dietary intake of Vitamin D is nessecary to achieve adequate intake ^, .
• In the UK, the recommended dietary intake for adults and children older than 1 years old is 10μg (400 IU)/day .
• Vitamin D intake greater than 4000 IU/day (100 μg) could be harmful .

Vitamin D functions

• Maintain normal calcium blood levels: When calcium blood levels are low, Vitamin D induces calcium absorption in the small intestine, calcium reabsorption in the kidneys and calcium release from bones. The goal is to increase calcium concentration in the blood .
• Has a role in regulating phosphorus absorption .
• Role in immune system regulation: The active form of vitamin D (1,25 (OH)2 D3) enhances the production of substances with anti- microbial properties by macrophages and monocytes keratinocytes. Also, 1,25 (OH)2 D3 production by immune cells is increased in presence of inflammatory signals .
• Possible role in depression treatment: Brain areas that have a role in the pathophysiology of depression have Vitamin D receptors. Also, it is possible that by regulating calcium homeostasis, the signaling of the neurotransmitters GABA and glumate is positively affected. However, evidence is still inadequate .
• Vitamin D active metabolites participate in the expression of genes important for cell apoptosis, differentiation and prolifration . Due to this role in cell apoptosis, it is possible that a healthy vitamin D status could decrease the risk for some forms of cancer .

Rich Vitamin D food sources :

Food	μg Vitamin D (D2 + D3)/100g
Trout, steamed	20
Salmon, smoked	17.1
Mackerel, raw	13.8
Salmon, raw	10.9
Sardines, dry	10.1
Seabass, steamed	7
Pork spareribs, cooked	2.5
Egg, whole, raw	2
Veal patty,cooked	1.8
Pork sausages	1.4
Milk, whole	1.3
Oatmeal maked with milk	1.2
Beef liver, braised or fried	1.2
Milk, reduced fat (2%)	1.2
Low fat plain yogurt	1.2
Soy milk	1.1
Kefir	1
Almond milk, unsweetened	1
Coconut milk yogurt	0.9
Mushrooms, raw	0.2

In the UK, margarine fortification with Vitamin D is mandatory. Other foods that could be fortified include :

• Infant and follow-on formula milks which are fortified
• and some cereal and yogurt brands
• Fortified milks

To sum up, good dietary vitamin D sources are quite rare and consuming the amount we need exclusively from food could be hard. Sunlight is normally the main vitamin D source during spring and summer.

This year though, our safety is the priority. Please check your area’s guidelines regarding social distancing or isolation. If it is unsafe for you to go outside, paying more attention to your nutrition and consulting with a healthcare professional about the possibility of supplementation is definitely worth it!

References