it's kind of increasingly thought that taking vitamin supplements is useless. that you can and should get all the vitamins and minerals you need from the food that you eat (and sunshine), and that vitamins in a supplement, especially a cheap low quality supplement can't really be adequately absorbed by the body. so i wouldn't think it matters whether you decrease the dosage. fish oil, the jury is still out. it's thought to be very beneficial for older people, and to a certain extent for younger people, for example, taken in the right quantities can help with depression, particularly post-natal depression.

but i'd be interested to know if vitamin supplements were particularly advised for people living in really polluted cities because pollution decreases your vitamin and mineral levels (along with drinking, smoking and certain food additives). so basically if you don't have a healthy enough lifestyle and you live in a polluted place, should you take vitamins even though they aren't that valuable, because they are more valuable than what your lifestyle is giving you?

Fish oils have recently been found to be at high risk of containing contaminants (heavy metals and PCBs). And, this is in the West, where food standards are typically better.

For drinking, B complex vitamins are a really good idea as you need extra. Vitamin D, if you do not get much sun. For women, calcium, though there may be some long term cardiac risks (new data, so would want to see replicated and weight bearing exercize is most important here). Vitamins in pregnancy, especially folic acid BEFORE you get pregnant (while you are trying) as it is most important for neural tubes in the first trimester. Iron tends to be low, and more so in women, as we use less iron in food production and cooking (a cast iron pan helps here).

Other than those, I have never seen much consistency in benefits for vitamins. But the above all have very good public health data.

The rest of the debates rests on how well balanced your diet is. For most of us, the main problem is too many calories from fat and not enough fiber. For the poorest on the planet, not enough protein.

And, for most, too sedentary a lifestyle and too many environmental exposures to carcinogens.

That pretty much sums up my learning from having done a postdoc in the area a long time ago and being an avid reader.

I started going back to the gym as "avid reader" derives from the Latin for "couch potato."

Sorry for the double (had to refresh).

You should check out MyHealthBeijing.com by a doctor here in Beijing. It's all about staying healthy and focuses on our lovely polluted Beijing.

I personally take a multi-vitamin and fish oils. Multi-vitamins give me what I don't get from eating the food. Yes, you can get certain vitamins and minerals from food, but there'll be no way you can get all the vitamins/minerals in one day (unless you want to eat and eat and eat). The fish oil is to lower the risk of heart diseases.

IF you decide to take any supplements, always make sure to get them from a reputable place (not taobao). And make sure the brand you get is highly reputable. In China, that'll be as safe as you can get in making sure you're getting great quality products. I never take chances with things that I'll be ingesting.