These pages are invaluable:

http://www.iherb.com/store/ProductsL...rbs&cid=health has links to all types of information.

http://healthlibrary.epnet.com/GetCo...chunkiid=33802 is for herbs and supplements

The B6 article is at http://healthlibrary.epnet.com/GetCo...chunkiid=21852 . The maximum safe dose for adults is 100 mg, but I wouldn't get near that. The theraputic dose is about 30 mg and the RDA is under 2 mg.

The vitamin D article is at http://healthlibrary.epnet.com/GetCo...chunkiid=21657
The recommended dosage depends on what for and in combination with what. The RDA is about 400 iu ( 10 mcg ). The upper limit is about 2,000 mcg. I'd try to stay about with the RDA, or maybe a little higher if you take supplemental calcium. Vitamin D can be toxic and can interfere with drugs. The entire article is well worth reading.

As a general thing, we don't digest and process food as efficiently as we age. Also, disease states (like PN) often respond well to supplemental vitamins, mineral, amino acids, herbs, and plant extracts. That being said, anything in excess is toxic, and a balance is important. Also, interactions are important.

As an interaction example, there is a lot of research supporting the beneficial effects of fish oil for inflamation, neuropathy, arthritis, and skin and hair condition. However, fish oil slows down blood clotting time. if you take prescription blood thinners or supplemental daily aspirin, too much fish oil could just be enough blood thinning to cause a stoke or other hemmorage.

For a co-factor example, if you take supplemental calcium without having enough vitamin D, the calcium cannot be integrated into bone and nerve tissue, and is so excreted by the kidneys. Depending on amounts, this would increase the risk of painful kidney stones. If you take supplemental calcium, you MUST supplement with the proper amount of vitamin D, or go out in the sun daily, to the point of increasing the risk of skin cancer.

In summary, before taking any supplement, learn about it, about interactions with it, optimal doses, etc. Then procede by all means, but cautiously.

I hope this helps.