| In addition to its well known role in maintaining | | | | in latitudes which provide very limited sunlight for six |
| healthy bones,vitamin D is also vital for the health of | | | | months of the year. People commonly work indoors |
| the nervous and immune systems and may help | | | | and tend to use high factor sunblocks on the rare |
| protect against cancer. | | | | occasions on which they might expose significant |
| Vitamin D's importance in maintaining strong, healthy | | | | areas of skin to the sun. |
| bones through its interaction with the essential | | | | It is a cruel irony that this concern about skin cancer |
| mineral, calcium, is well known. But the vitamin is also | | | | may lead to the ill-health associated with vitamin D |
| vital for the health of the nervous and immune | | | | deficiency and may even increase the risk of other |
| systems, in regulating insulin levels and blood pressure, | | | | cancers. But in these circumstances the usual |
| and even as a possible protector against certain | | | | assumptions about vitamin D production in the body |
| common cancers. | | | | appear questionable at best, if not downright |
| The best known and most serious disease associated | | | | complacent. And the situation is even worse for the |
| with vitamin D deficiency is rickets, which arises when | | | | elderly, who may not only enjoy even less exposure |
| the deficiency causes blood calcium levels to fall too | | | | to the sun than the young, but are less able to make |
| low, and the body to respond by stripping the bones | | | | use of that which they do obtain. |
| of calcium leading to loss of bone density and | | | | Moreover, there are relatively few good natural food |
| malformation. | | | | sources of vitamin D, and the best source, oily fish |
| Interestingly, studies have shown that the | | | | such as sardines, mackerel and salmon is one which |
| geographical pattern of the incidence of rickets is | | | | many people, and perhaps children in particular, often |
| very similar to those for both breast and colon | | | | find unpalatable. The situation has improved |
| cancer, suggesting a possible (though not fully | | | | somewhat with the fortification of milk, orange juice, |
| understood) link between vitamin D deficiency and | | | | bread and some cereal products, but it may still be |
| these diseases. One 5 year study which grouped | | | | difficult for individuals to ensure they obtain a |
| 120,000 people by levels of vitamin D intake reported | | | | sufficient intake of the vitamin, particularly because |
| that men in the highest intake group had a 29% | | | | the amounts added to different foods and drinks are |
| lower incidence of colon cancer than those in the | | | | very variable. |
| lowest intake group and similar results have been | | | | Since the amount of vitamin D required from food |
| observed in breast cancer research. Relatively high | | | | will vary greatly depending on the amount of |
| blood levels of active form vitamin D have also been | | | | exposure to sunlight enjoyed by the individual, it has |
| associated with a lower risk of pre-cancerous | | | | not been deemed possible to determine a |
| growths (polyps) in the colon whereas lower levels of | | | | Recommended Dietary Allowance (RDA) for vitamin |
| vitamin in the blood have been associated with an | | | | D. But the Food and Nutrition Board has suggested |
| increased risk of prostate cancer. | | | | 200 IU (5mcg) for infants, children, and adults up to |
| Vitamin D is known to be essential for a healthy | | | | 50, rising to 400 IU for the 50-70s, and 600 IU for |
| immune system and has been shown to be | | | | the over 70s, as an "Adequate Intake" of the vitamin |
| particularly important in helping prevent auto-immune | | | | from food on the assumption that none is being |
| diseases - those in which the body's immune system | | | | obtained from sunlight. |
| attacks and destroys its own cells, wrongly having | | | | Orthodox opinion, however, seems to regard these |
| identified them as invaders. Type 1 (insulin | | | | suggestions as too conservative. And even for those |
| dependent) diabetes, rheumatoid arthritis and multiple | | | | individuals fortunate enough to enjoy regular |
| sclerosis are examples of serious diseases which fall | | | | exposure to good quality sunlight, the intake of 400 |
| into this category and a number of research studies | | | | IU (10 mcg) of vitamin D as part of a multi-vitamin |
| suggest that a generous intake of vitamin D may be | | | | and multi-mineral supplement is recommended. For the |
| a significant mitigating factor. | | | | over 65s, those with less than optimal liver or |
| Blood levels of vitamin D have also been shown to | | | | digestive health, those living in less advantageous |
| be inversely correlated with blood pressure, and | | | | climates and those who spend the majority of their |
| some research suggests that high dose supplements | | | | time in indoor occupations a supplementary dose of a |
| of vitamin D of (1,600 IU per day) may help this, | | | | further 400 IU, for a total of 800 IU is strongly |
| although orthodox medicine, as ever, is cautious | | | | advised. |
| about definitively acknowledging any direct causal link. | | | | For maximum effect, however, vitamin D |
| The traditional view was that adequate supplies of | | | | supplementation should be always be combined with |
| vitamin D can be synthesised in the skin upon its | | | | adequate dietary calcium - supplemented if necessary |
| exposure to sunlight. But the problem is that a large | | | | to achieve an intake of 1,000 - 1,200 mg per day of |
| proportion of the population in the affluent world lives | | | | this essential mineral. |