Thursday, May 24, 2007

Sun tans are REALLY bad for you

Leave the brownness to people who are born that way. The differences noted below do seem to be unusually strong. Non-Hodgkin's Lymphoma is a type of cancer and no fun at all. The incidence of the disease concerned is however not high so may be of limited concern unless there is a family history of it. Note: "A person's risk of developing non-Hodgkin lymphoma during their lifetime is about 1 in 50. The average age at diagnosis is 60 - the elderly have the highest risk of getting NHL". About 20,000 Americans die of it each year.

The study below does of course suffer from the usual epidemiological ambiguities. It could for instance be argued that tanning is just a proxy for a more outdoorsy lifestyle and that it is that lifestyle which conduces towards NHL rather than tanning as such. So you may be OK if you get your tan in a studio. If I were a frequent tanner, however, I would look into the matter in more depth. For instance, Californians and Australians are big on tanning. Do they therefore get more NHL? I have not had time to look.

Ultraviolet Radiation Exposure and Risk of Non-Hodgkin's Lymphoma

By Yawei Zhang et al.

Sun exposure has been suggested to increase the risk of non-Hodgkin's lymphoma. The authors analyzed data from a population-based, case-control study of Connecticut women between 1996 and 2000 to study the hypothesis. Women who reported having had a suntan experienced an increased risk of non-Hodgkin's lymphoma with increasing duration (ptrend = 0.0062) compared with women who reported never having had a suntan. An almost threefold increased risk of non-Hodgkin's lymphoma was observed among women who reported having had a suntan for less than 3 months per year and a suntan history of more than 60 years (odds ratio = 2.8, 95% confidence interval: 1.6, 4.9) compared with those who reported never having had a suntan. For women who reported having spent time in strong sunlight between 9 a.m. and 3 p.m. during the summer, a 70% increased risk of non-Hodgkin's lymphoma was observed for the highest tertile of duration compared with the lowest (odds ratio = 1.7, 95% confidence interval: 1.2, 2.4). The risk increased with increasing duration of time spent in strong sunlight in summer (ptrend = 0.0051). The risk appears to vary by non-Hodgkin's lymphoma subtypes. Further investigations of the role of ultraviolet radiation on the risk of non-Hodgkin's lymphoma are warranted

The easy way to get pregnant

I was unable to find the article referred to below in its alleged source but generalizing from people on a Chinese diet to Western women seems strange. I think the underlying message must be that all Western women get enough of the vitamin as it is. The last sentence would certainly indicate that

A bowl of cereal for breakfast or a baked potato for lunch could help a woman conceive. Research has found that eating foods rich in vitamin B6 can more than double the chances of becoming pregnant. Women who have plenty of the vitamin in their diet are also only half as likely to miscarry their baby in the critical first weeks of pregnancy. With millions of women already taking vitamin B6 supplements to combat premenstrual syndrome and alleviate morning sickness, the study adds to the evidence of the vitamin's role in reproductive health. It is thought that B6 - which is found in high levels in potatoes, fortified cereals, bananas, milk, eggs, and poultry - plays a key role in the development of the placenta.

The U.S. researchers looked at how levels of vitamin B6 affected the reproductive health of more than 300 healthy young women in south-western China who were trying for a baby. Scientists measured levels of vitamin in the women's blood and checked their hormone levels every day for a year. The results revealed a clear link between vitamin B6 and conception. Those with the highest levels of the vitamin were 2.2 times more likely to conceive than those with the lowest levels. The women were also half as likely to miscarry in the first six weeks of pregnancy, the American Journal of Epidemiology reported.

Earlier work by the same researchers showed that the vitamin appeared to ward off miscarriages later in pregnancy and halve the risk of premature birth. The University of Massachusetts researchers said: "Taken in their entirety, these observations suggest that maternal vitamin B6 status may influence reproductive events through the entire course of pregnancy, from conception through delivery."

The researchers did not recommend how much vitamin B6 prospective mothers-to-be should take. However, the Food Standard Agency advises women to take 1.2mg of the vitamin a day, and says this is possible with a balanced diet. It advises against taking daily supplements of more than 10mg, as high levels of the vitamin have been linked to loss of feeling in the arms and legs.

Other recent research has shown that a low-fat diet can dramatically cut the chances of pregnancy.

The study, carried out at the Harvard School of Public Health, showed that drinking a pint of semi-skimmed or skimmed milk or eating two pots of yoghurt a day almost doubles the risk of anovulatory infertility. Anovulatory infertility is an increasingly common condition in which women stop ovulating. Eating full-fat dairy products has the opposite effect. A bowl of ice cream a day was found to be enough to boost the chance of having a child.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

Trans fats:

For one summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and the evidence of lasting harm from them is dubious. By taking extreme groups in trans fats intake, some weak association with coronary heart disease has at times been shown in some sub-populations but extreme group studies are inherently at risk of confounding with other factors and are intrinsically of little interest to the average person.



Anonymous said...

Sun exposure and non-Hodgkin lymphoma.
It was initially hypothesized that sun exposure might cause non-Hodgkin lymphoma (NHL) on the following grounds: its incidence was increasing in parallel with that of cutaneous melanoma; its risk was increased in those with a history of melanoma or other skin cancer; sun exposure causes immune suppression; and immunosuppression for other reasons is associated with an increased risk of NHL. The association of NHL with prior skin cancer has been found consistently in subsequent studies, but results of ecological analyses have only partially supported this hypothesis. Contrary to it, three recent studies of NHL in individuals found that risk decreased, generally by 25% to 40%, across categories of increasing total or recreational, but not occupational, sun exposure. One study, thus far reported only in abstract, showed the opposite. Production of vitamin D from sun exposure offers a plausible mechanism for protection against NHL by sun exposure. A recent study has found a reduced risk of NHL in people with a high dietary intake of vitamin D. Results of additional studies in individuals and a planned original-data meta-analysis of case-control studies should help to resolve the present conflicting results on sun exposure and NHL.

jonjayray said...

That's a useful comment. I wish I got more of the same. Would have been even better with references though!