Answer to a Reader's Question:
Question: I have been troubled recently by a number of articles claiming that DHA is nutritionally essential. The posters often promote the taking of fish oils. To their credit there do seem to be a number of papers suggesting clinical benefits for fish oils, and also that vegetarians have lower levels of DHA. There is also research linking these low levels to Alzheimers, and poorer performance in school children.
On the other size I am reminded that there are 3rd generation vegans who seem to be okay, and I also note that the founder of the vegan society is still alive and well after over 50 years as a vegan.
It is my belief that this topic is still controversial, but there is no RDA, so this nutrient must be considered non-essential. There seem to be certain cases, when ingesting excessive omega 6 oils, where DHA supplements are useful, but that is not a case for them being essential. What is your take on this?
Answer: Your question is not only interesting for the question of DHA itself but also is an interesting in reference to the definition of nutrition in general.
The meaning of nutrients has tended to be reserved for those food chemicals that are required (or essential) for life because we, as mammals, cannot make them. Thus we have determined minimum intakes and recommended allowances (about 2 standard deviations above the minimum intakes) for these essential chemicals.
However, this meaning (history) was--and still is--a very superficial, narrowly focused view. It was based on choosing which endpoint is used to decide what is "essential". It tended to be life itself, but not always. In my view, when a broader view is taken--as exemplified by Nature herself--we discover that there are thousands, hundreds of thousands, even millions of food chemicals that contribute to important life events/reactions that can be regarded as health. We only know an extremely small number of such chemicals and an even smaller number of these 'known' nutrients have RDAs.
Most importantly, however, we need to understand that these chemicals (nutrients) work in a highly integrated, virtually symphonic manner to produce their health effect. Thus it is a matter of thinking about the collection of such chemicals in large groups of foods. I hold that we need to discard the traditional view of nutrition, based on the effects of single nutrients, and take seriously the symphonic nature of food chemicals working together. In effect, the 'whole' nutritional effect is greater than the sum of its parts.
If I must answer the DHA question, I would only say that we can get plenty of that type of chemical from the consumption of the omega-3 fatty acids that are found in certain plants--certain nuts, flaxseed, etc. Indeed, it also is related to a dietary balance of omega-3 to omega-6 fatty acids and this balance can be readily met with a good quality diet of wholesome vegetables, fruits, grains and nuts.
Vegans do just fine when eating in this way. Indeed, there are new findings that for those who have even gone only part of the way toward that goal, they live 10 years longer and have much less of the chronic degenerative diseases than those who still consume regular American fare.