There is a nice chart in the Down syndrome Nutrition Handbook that shows many of the common alternative remedies and possible risks.
My rule of thumb with my child is roughly this:
• I learn about a supplement and its potential benefit for people with DS.
• I research the supplement and any evidence based research that it works.
• I research the supplement and how it impacts individuals with DS.
• I research the supplement with the words "scam" after it on google.
• I look up the person who recommends it with the word "quack" after the name on google.
• I consider if I would feel comfortable taking it personally or if I would have my 5 year old take it.
• If I still think it looks like something I would consider giving her, I ask her pediatrician about it.
• If he says no problem to try, I'll give it to her and see how she responds.
That has lead me to DHA (ped's daughter does brain research and told him from the research she has seen, he needed to start taking fish oil, so HE does.) It is basically cod liver oil and both my younger girls take it. We buy this brand: http://www.amazon.com/Nordic-Naturals-Childrens-Dha-liquid/dp/B000ORY45G
That led me to a chewable Methyl B12 (we use this one - http://www.amazon.com/Foods-Methyl-B-12-5000mcg-Lozenges/dp/B003O1R73U)
That led me to occasional caffeine in food (more so when she was nursing through my breastmilk than now)
That led me to CoQ10 through my breastmilk, and I'll start that up again when she can chew a full CoQ10 pill (I didn't like the liquid method.) I used and will use this brand - and may just go ahead and order this one sooner rather than later http://www.epic4health.com/ch60chhidoco.html
I'm still on the fence about Ginkgo - I don't like the potential conflicts for heart/blood if she needed sudden surgery (though I have heard they can do things if they know she is taking it to contradict the issues). I do like the anecdotal reports parents using it give in terms of how it impacts speech. I've gone as far as knowing which brand I would order if I ever do order it - but just haven't pulled the trigger yet - it would be this one! http://www.amazon.com/HoneyCombs-Industries-Liquid-Ginkgo-Extract/dp/B0001ITV42
When Violette was constipated early on, I tried probiotics. She was so sick to her stomach. I stopped those right away. Conventional Miralax for her after that and it worked like a charm! In many cases, the researched medical option is the best!
I think every parent has to make the decisions they feel are best for their child. I know when Violette was first born I checked out every single possible therapy for her. I know parents who use various natural/alternative remedies with their kids and who are quite happy with the results. More power to them for their kids, I say. For me, I take what I consider a more conservative approach, and that is good for me. Who really knows though, if another parents more aggressive approach might not be better for my child?
There have been instances where parents have, through trial and error, and research found non-conventional remedies that have positively changed the reality for all children with certain issues. Will that happen with individuals with DS? Hard to say, but I can't blame them, particularly the ones with medical backgrounds, for trying.
Most of the focus of legitimate, medical research seems to be on treatments that would show small improvements in cognitive skills that would make a big difference for individuals with DS in their day to day lives.
DSRFT has a program called +15 that you can read about here: http://www.dsrtf.org/ They are affiliated with the Stanford DS Research Center where quite a bit of research with Down syndrome mice is taking place.
I'm warming up quite a bit to the push that is going on toward encouraging more National Institute of Health money and research being spent on DS. So much has changed with medicine in the last decade, and so little has been spent on Down syndrome.
This new push will lead to many interesting findings about individuals with Down syndrome, benefits to those of us without DS, and likely some very challenging ethical issues for us as parents about which treatments to give our kids and what the long term value/challenges of the treatments might be.
Also edited to add the work of DS Achieves - they have some great things in the works!
Should continue to be an interesting subject!