- Dietary studies have a relatively low priority within the field of medical research.
- The main problem with epidemiological (observational) studies consists of factors that are associated with the dietary factor being examined but are not causal factors, as they are only statistically related to the disease in question.
- Unlike drugs, lifestyle changes cannot be studied in a double-blind manner.
- Publication bias: over 7,000 articles related to nutrition are published annually, which makes it difficult for anyone to get a complete overview.
- An important source of inspiration for researchers themselves is the hope that their own hypotheses will be confirmed.
- A recent study analysing financial sponsorship showed that 100% of industry-sponsored studies came to the conclusion that the beverage under investigation was beneficial to health.
- One common effect of preconceived ideas is their tendency to direct the scientist’s focus towards those dietary aspect that are considered interesting in a trial, such as the proportion of fat/protein/carbohydrate or the amount of some other nutrient.
- The uncertainty in nutritional science is considerable and the low grade of evidence behind dietary advice is obvious.
It's a bit more tricky situation with dietary supplements. There is always a nutritional blog, article or book saying you need this or that supplement. In his magnum opus 'Food and Western Disease' Staffan Lindeberg writes: "Consumption well exceeds the recommended levels for all known vitamins with one exception: vitamin D." However, "Vegans have a very high risk of vitamin B12 deficiency and generally need supplements... early humans must have had access to animal foods in order to avoid B12 deficiency."
It's funny that studies often claim that more studies are necessary, apparently because all the previous studies have failed to make complete sense of the mess we are in. The fact that people were doing pretty fine healthwise long before there were any nutritional studies is usually ignored. Perhaps all that we need to do is come back to our senses and stop thinking more studies will somehow help us out.
Perhaps nutritional studies are only required to sell us something we don't need and help someone make money. If you keep it simple and do what you know is right, there's no urgent need for any additional nutritional studies.
Just eat well, re-activate your lifestyle with daily exercise, and you can easily achieve great health and fitness.