The calcium and vitamin D combination is one of the most important vitamin and mineral duos for teenage nutrition. All teens need a good supply of calcium as their bones increase in density long after they have stopped growing in length. Vitamin D plays its part by regulating the absorption of calcium from the gut. Functioning similarly to a hormone, vitamin D receives information about how much bone is needed and determines how much calcium to deliver to the skeleton to make bone. This happens for existing bone, making it stronger and denser with the additional calcium, and also for new bone as existing bones lengthen during pubertal growth spurts.
Dietary sources of vitamin D only contribute about 5% of overall needs; the rest being manufactured on the skin’s surface by the action of UV light from the sun. Vitamin D is then absorbed through the skin, stored in the liver, and then converted into an active form of Vitamin D by the kidney, ready for action in the gut.
Boys generally need more calcium than girls and are also more likely to have lower circulating levels of vitamin D. Calcium needs for girls are around 800mg and boys around 1000mg. Habitual lower intakes of calcium cause the intestine to up-regulate its absorption, provided there is enough vitamin D, and so calcium is only half the picture to promote strong bones. In the UK , where the sunlight is low for at least half the year, the general population is at risk of vitamin D deficiency. A supplement of 25ug/micrograms (or 1000 international units) of Vitamin D for 6 months of the year – during late autumn/winter/early-spring – helps to ensure bones continue to mineralise during this super-growth period. Teens who eat a poorly planned vegan diet may consider a calcium and vitamin D supplement.
Calcium needs can be met by 4 – 5 servings of dairy products each day. For kids who don’t eat dairy, fortified soya products, nuts and seeds are good choices. For well-rounded nutrition, a mix of different types of calcium rich foods is best.
Good Sources of Calcium
| Portion | Food | Calcium (mg) |
| 200mls | cow’s milk | 230 |
| 200mls | soya milk | 240 |
| 150g | natural yoghurt | 300 |
| 150g | fruit yoghurt | 240 |
| 30g | cheddar cheese | 200 |
| 30g | soya cheese | 125 |
| 2 | tinned pilchards | 330 |
| 4 | tinned sardines | 460 |
| 120g | tinned salmon | 105 |
| 1 tsp | tahini (sesame seeds) | 135 |
| 30g | almonds | 65 |
| 10 | apricots | 75 |
| 1 | dried fig | 50 |
| 90g | spinach | 145 |
| 3 tbls | baked beans | 70 |
| portion | broccoli | 35 |
| portion | spring greens | 65 |
| 1 slice | white bread | 30 |
| 1 slice | wholemeal bread | 20 |
Source “The Composition of Foods” 5th Ed; McCance & Widdowson; Royal Society of Chemistry