Kefir is a useful probiotic because it is rich in lactobacillus, which keeps the lower gut slightly acidic, displaces unfriendly bacteria, is directly toxic to yeast and is anti-inflammatory to the gut.
The joy of using Kefir is that one sachet can last a lifetime. Furthermore, the best results for probiotics come from using live cultures. I have been growing Kefir and it grows well at room temperature. Because dairy products are not evolutionarily correct foods, Kefir should be grown on non-dairy foods such as soya milk, rice milk or coconut milk and who knows what else! Start off with one litre of soya milk in a jug, add the Kefir sachet and within about 12-24 hours it should have semi-solid, junket like consistency. Do not expect it to look like commercial yoghurt, which has often been thickened artificially. Then keep the culture in the fridge, where it ferments further. This slower fermentation seems to improve the texture and flavour. However, it can be used at once as a substitute in any situation where you would otherwise use cream or custard. I often add a lump of creamed coconut which further feeds the Kefir, imparts a delicious coconut flavour and thickens the culture. Once the jug is nearly empty, add another litre of soya milk, stir it in, keep it at room temperature and away you go again. I don’t even bother to wash up the jug – the slightly hard yellow bits on the edge I just stir in to restart the brew. This way a sachet of Kefir lasts for life! One idea I am playing with is the possibility of adding vitamins and minerals to the culture. The idea here is that they may be incorporated into the bacteria and thereby enhance the absorption of micronutrients. You could try this if you do not tolerate supplements well.
Stir in grounds almonds or other such grounds nuts or seeds to thicken the culture.
A comment from Margot Ridler I have done this successfully: I live in Mexico and make my own Kefir from fresh coconut milk. Once I have extracted the milk, I add 1 teaspoon each of Spirulina, Barely grass and Kamut grass powder and 1/4 tsp. Kelp per 8 oz glass. I blend it well in the blender and then add Kefir grains.. Then I let this mixture ferment (here it only takes 6 hours because it is so warm) as it is understood that fermenting makes all vitamins and minerals more bioavailable, plus the sugars from those powders (otherwise sweet) is broken down. The drink is delicious.