In the stomach, insufficient amounts of acid can lead to problems with indigestion and gastritis (inflammation in the stomach). Zinc is one nutrient which can cause nausea or digestive discomfort, and this is almost certainly more likely to be the case if stomach acid levels are low. Your symptoms do suggest that you are not digesting food well, and this may well be related to low levels of stomach acid. Interestingly, the Hay diet (separating protein and carbohydrate at each meal) is thought to aid digestion, which is why eating to this pattern may be helping you.
Another thing which points to low stomach acid secretion in you is the fact that Losec (an acid-reducing medication) has not worked for you. In fact, the reality is that if your stomach acid levels were low to begin with, Losec may actually be worsening your underlying condition. Chronic (long-standing) gastritis does seem to increase the risk of stomach cancer, and I do think it is important for you to have your stomach function properly assessed. There are two tests which would be useful in your case:
First of all, if you haven't been tested already, I suggest you be assessed for the organism Helicobacter pylori. This bacterium can live in the stomach and is known to give rise to problems with gastritis and/or ulcers. Research suggests that individuals with rosacea seem to be prone to this infection. If you do have a Helicobacter infection, then appropriate treatment may really help to reduce your symptoms and normalise your stomach function. You will need to speak to your doctor about this.
Secondly, I think it would be worthwhile for you to have the level of acid in your stomach formerly assessed. The best test I know of for this is something called 'gastric acid analysis by radiotelemetry'. This entails swallowing a capsule which measures acid content of the acid and sends a signal with this reading to a device help over the stomach. The only laboratory I know of in the UK that offers this test is BioLab in London's West End (020 7636 5959). You will need to see a practitioner to have this test, and the laboratory can advise you about how you can go about doing this.
If your stomach acid secretion does indeed turn out to be low, then, certain natural approaches may help you. One strategy that may work for you in the long term is to supplement with digestive acid prior to meals. I have seen this approach work very well in many individuals with rosacea. However, I have to stress it is important for you to have your stomach acid properly assessed before you embark on such a treatment.
One natural supplement which may help you in the meantime is deglycyrrhizinated liquorice (DGL). DGL helps stimulate the production of a mucus-like lining which protects the stomach from acid and other irritants. Taking DGL often helps to reduce the symptoms of gastritis by helping the healing process in the stomach. Chew and swallow one or two DGL tablets about 20 minutes prior to meals.