Hi Garry,
Goji berries (Lycium barbarum, also known as wolfberries) are predominantly grown in China (around 90%), with the rest coming from Tibet and Mongolia. All the berries we get in the UK come from China. Many health claim have been made about them over the years, but scientific testing has found that all the claims are completely false. They don't appear to have any medicinal value whatsoever. Incidentally the ability to lower blood sugar is not a claim that is listed in any official sources.
If you are health food conscious then one thing to beware of is that the berries are all treated with organophosphates, which are banned throughout the western world. Under pressure from the US, who import huge quantities because they are currently a fashion fad, China is apparently considering whether to encourage organic growing, but has not yet made any decision on this. Also when you see them on sale they are usually a vivid red and quite dry to the touch. This is because after drying they have been treated with sulphites - in their normal dried state they are dark red and sticky, rather like raisins. You often see them on sale in health food shops and labelled as organic - they are not - no Chinese gojis are grown organically and we don't import them from Mongolia or Tibet where some are organic.
