This is a follow-up to my last question http://paleohacks.com/questions/138905/recommended-a-vegan-diet-because-of-high-oxalate-levels#axzz224KSnwbr. I was instructed to put my paleo son on a vegan diet due to a very rare genetic disease (Primary Hyperoxaluria Type III). So I need help. I need to take my son off all animal products (milk and butter excepted) and introduce grains and legumes to his diet (I'm afraid he won't thrive otherwise). But which ones?
Your doctors are giving you partially incorrect information.
The theory is that people with primary Hyperoxaluria Type III, like your son, have a problem metabolizing the non-protein amino acid hydroxyproline. This is probably true. However, the idea that it is therefore necessary or beneficial to go vegan is not true.
The reason is simple: not all animal products contain significant amounts of hydroxyproline! Collagen (e.g. connective tissue, of which skin and tendons are made) is very high in hydroxyproline, but few other animal proteins contain any significant amount.
For instance, eggs don't contain hydroxyproline, so there is absolutely no reason for your son to avoid eating them. Milk and cheese don't contain any, either. (At least not in any detectable amount.) And butter won't, either, since it's just milkfat and has no protein anyway.
Unfortunately, muscle meat does contain some hydroxyproline (though not much...anywhere from 0.04% to 0.07% by weight), so you should still probably avoid that. However, animal fat is still fine...
...and liver, not being a muscle, is extremely low in hydroxyproline! It has only 46 mg HYP per 100 grams, which is less than a "low-oxalate" food like apples has oxalate!
Conclusion: there is absolutely no reason for you to feed your son a vegan diet of grains! You'll have to avoid muscle meat, but you can still feed him the best sources of animal nutrition: pastured eggs and butter, and beef liver. (And cheese for a treat.)
I would go with no gluten, soak all nuts and legumes (or if you have the budget, you can buy pre-soaked, sprouted and dehydrated flours, like at the Blue Mountain Organics website). I would buy Sally Fallon's Nourishing Traditions book. She has a lot of info on the proper preparation of grains, since that is what you have to work with. I know others have told you to get a second opinion, which I would recommend as well, but right now, I understand that you just need to feed your child.
Can he even have eggs? I am glad he can have butter at least. Wishing you and your son the best.
For grains, I think soaked or fermented oats are pretty good. Wild rice is decent. Properly prepared millet and amaranth are not bad either. Yeah, white rice is fine, but it has almost no nutrients except carbs so it shouldn't be a common thing. I still prefer things like potatoes and fruit over grains.
As far as legumes, I think chickpeas/garbonzos and green beans are some of the better ones. If properly prepared, I think lentils can be worthwhile (for more on preparation see this link). I don't really like peanuts, though they're not a terrible thing to eat. I'm less of a fan of soybeans, they're worth avoiding. In general, I'd recommend legumes over grains for nutrition, but all legumes should probably be prepared in some way. Soaking and cooking at least.
Is your son allowed all dairy? If you're getting a lot of protein from legumes, you'll often end up short on methionine, so I'd look for sources of that (a good one is diary protein).
I think you might be asking this question in the wrong place. Those on the Paleo diet pretty much avoid all grains and legumes -- as I have for about 18 months. They both cause me lots of problems including digestive distress, systemic inflammation, huge peaks and valleys in energy, sore muscles and joints, poor sleep and mood, etc. My answer to your question about which ones to introduce would be "none".
Paleo and vegan diets also differ in how much animal protein and fat they recommend (a lot and none, respectively). I don't think you're going to get anyone here giving advice about a vegan diet.
If you gave more background on your son's condition and what other doctors or health practitioners recommended, you might get a paleo perspective on his situation. Many "genetic" "diseases" have been completely cured via paleo diet.
So one MD suggest your son go vegan and you hop on the bandwagon. MDs have less than 10 hours in the area of nutrition at that is from the perspective of the USDA food plan. Please do not risk it. What issues are you experiencing with your son specifically? I went vegan and it nearly killed me. Our bodies need b12 and all the protein and nutrition from whole animal sources. Grains and legumes provide nothing unless they are enriched with things because they are devoid of nutrients. Your best bet is to do a gaps or pure paleo diet. No dairy whatsoever. Get him on the ketogenic diet and it will cure all health issues. There are many sources of reputable information on how to follow it, maintaing a very high fat diet. Don't ever put blindfaith into mainstream medicine.
I myself have done a vegetarian form of the lifestyle, and am just now adding meat. I think while difficult it is totally possible to eat a vegetarian form of the diet simply including plenty of nuts and eggs. The vegetarian form of the diet has greatly improved my arthritis and is worth a shot.