I have reading about vitamins. I read this extract:
Low vitamin D intakes and low serum vitamin D levels are associated with increased risk of colon cancer and other cancers; adequate vitamin D seems to protect against breast cancer recurrence. A distinguished medical researcher - Edward Giovanucci of the Department of Medicine, Harvard School of Public Health - said, "I would challenge anyone to find an area or nutrient or factor that has such consistent anticancer benefits as vitamin D." He added that vitamin D may prevent thirty deaths for every death caused by skin cancer.
Then the book lists factors that affect the body's production of vitamin D from sun exposure, which include:
- latitude and time of year
- time of day
- cloud cover, fog or smog
- materials that block UVB rays
- UVB sun lamp
- skin colour
- area of skin exposure
- age
- body weight
I also read about B12. This appears to be the one vitamin vegans cannot source naturally. It's a book about veganism, and the authors stress that, strictly, the vitamin comes from micro-organisms, not animal flesh, but that since you would normally get vitamin B12 by eating meat, I don't see the distinction. Interestingly, I thought vegans tended to look pale because they were not getting enough iron, but the book says iron is not a problem. They do say that a symptom of B12 deficiency is megaloblastic aneamia:
Without proper cell division, facilitated by vitamin B12, abnormally large red blood cells appear in the blood, because the cells have failed to divide properly. This condition is called megaloblastic aneamia. The blood has decreased ability to carry oxygen, which results in fatigue, weakness, decreased stamina, shortness of breath, palpitations and skin pallor. Note that this condition can be masked in diets rich in folate (as many vegan diets are), because dietary folate is part of the process of red blood cell division.