Optimal immune function requires optimal vitamin D sources. This fat-soluble vitamin plays a crucial role in regulating the immune system, helping the body fight off infections and reducing the risk of chronic diseases. During winter months, vitamin D levels can easily drop below ideal levels. This is primarily because our bodies produce vitamin D when skin is exposed to sunlight, and shorter days combined with spending more time indoors means we get far less of this natural source. People living in northern latitudes are particularly vulnerable to this seasonal dip. Supplementing vitamin D intake can therefore be a helpful strategy to maintain adequate levels year-round.
Standard recommendation
The typical recommended daily intake is 400–800 International Units (IU) for most adults, though some health authorities suggest that higher amounts may be beneficial for certain groups, such as older adults or those with limited sun exposure. Personal requirements can differ. Therefore professional guidance for supplement is import when taking supplements.
Vitamin D: Food resources
Fortunately, several foods are naturally rich in vitamin D or are fortified with it, making it possible to boost your levels through diet. Here are some of the best nutritional sources of vitamin D.
| Source | Concentration | IU (40 IU = 1 g) |
| Fish | ||
| Cod liver oil | 10 g per 5 ml | 400 IU per 5 ml |
| Salmon | 11 g per 100g | 441 IU per 100g |
| Canned sardines | 4.8 g per 100g | 193 IU per 100g |
| Milk and egg products | ||
| Almond milk | 2.5-3.6g per 250 ml | 100 – 140 IU per 250 ml |
| Egg | 1.7 g per egg | 68 IU per egg |
| Cheddar | 0.6 g per 100g | 24 IU per 100g |
| Mushrooms | ||
| Dried Shiitake | 240 g per 100 g | 9680 IU per 100g |
| Chanterelles | 20 g per 100 g | 800 IU per 100g |