@Annie Sye keep in mind that the kidneys are one of the main detoxification organs, so if any of his other detox organs are struggling, the kidneys will pick up the slack.
The liver is a main player when it comes to blood sugar regulation so not taking his medication and eating high glycemic foods will definitely put more strain on both his liver and kidneys as a result.
Since he’s willing to make changes, following a low-glycemic diet will make the biggest difference for him overall. Teach him about my VPF principle; vegetables, proteins, and healthy fats. Here are some tips on dealing with cravings.
Obviously avoid any lifestyle choices that strain the liver like alcohol and smoking.
Make sure he hydrates well to help the kidneys function properly and flush out toxins. Sometimes adding in an electrolyte can help with hydration.
In terms of nutrients and supplements, there are many different herbs and nutrients to consider. For example:
Omega-3 fatty acids. Here’s a study that shows how it can reduce proteinuria
Astragalus is a known herb for its kidney-protective properties, particularly in reducing proteinuria and improving renal function in patients with chronic kidney disease. Here’s a study.
Cordyceps is also used in improving kidney function and reducing proteinuria, largely due to its anti-inflammatory and antioxidant properties. Here’s a review.
Curcumin (turmeric) has also shown benefits in improving urinary protein excretion. Here’s the study.
And there are many more…
There are supplements that offer a blend of all of these and more like Kidney Care by QuickSilver.
In terms of teas to consider, nettle leaf, dandelion root, ginger, and marshmallow root can all be helpful. In the US, I like Mountain Rose Herbs for sourcing herbs in bulk.
And as a food, parsley is wonderful for the kidneys. So if he likes Tabouli salad, encourage him to eat it regularly.
Hope this helps.