General consensus where? On this board or in the real world? People in my daily contact have little belief that multi-vitamins work to correct deficiencies or to meet adequate RDA for all nutrients found within the capsule, so in that case your viewpoint goes against general consensus.
In the real world. Most of my collegues believe multivitamins are a waste because you end up pissing the excess out anyway. I have yet to meet a person that claim multivitamins are bogus or "sugar pills". But i get your point though.
I checked, for the hell of it, FDA and ods.od.nih.gov/factsheets/MVMS-HealthProfessional/. Both are more concerned with MVs causing excess levels and poisoning from regular consumption in the HUGE chunk of population consuming them. This is not proof of anything other than the general consensus is indeed that multivitamins are believed to be sufficiently absorbed, at least sufficiently enough to cause an excess level.
Im not even going to cite whatever statements they claim because they probably dont weigh anything here. Instead i refer to this paper discussing bioequivalency and bioavailability of multivitamins and multiminerals: ajcn.nutrition.org/content/85/1/269S.full.pdf+html
To summarize states that a definite bioavailability is hard to determine due to the many regulatory mechanisms.
Vitamin and mineral bioavailability in MVMs is affected not
only by product but also by host factors. Host factors include
homeostatic mechanisms that regulate absorption or excretion
depending on the nutrient status of the host (eg, the iron status of
the host affects iron absorption) (27, 29). These factors vary by
age, sex, and physiologic state (eg, pregnancy) (29, 30, 37).
Homeostatic mechanisms may regulate circulating concentra-
tions of nutrients within a tight range and are therefore insensitive
to changes in ingested amounts or to utilization at the site of
action (27). The size of the ingested load may affect bioavail-
ability [eg, the absorption load of calcium varies inversely as the
logarithm of the load size(27), and single high doses of folic acid
exceed the metabolic capacity for reduction and methylation
(38)].
Table 3 gives an example of the bioavailability of a couple of vitamins and minerals.
Vitamin A DRI expressed as retinol activity equivalents (RAE):
2 ug supplemental all-trans -carotene = 12 ug dietary all-trans -carotene = 24 ug other dietary provitamin A carotenoids
Iron Algorithm for estimating dietary iron bioavailability:
18% bioavailability from a total diet based on
differences in absorption from heme- and nonheme-
iron sources in a mixed US diet
Folate DRI expressed as dietary folate equivalents (DFEs):
1 ug DFE = 0.6 ug folic acid from fortified food or as a supplement taken with meals = 1 ug food folate = 0.5 ug supplement taken on an empty stomach
Vitamin B-12 An assumed absorption from foods of 50% is included in the DRI, advise adults aged 51 y that foods fortified with vitamin B-12 or supplements containing vitamin B-12 be used to meet the DRI because of reduced absorption of food forms
The vitamin A and folate paragraph state that supplemental folate and vitamin A have higher bioavailability than the ones found in food forms. Folate is even best absorbed on empty stomach.
Although i dont believe in that you are completely wrong in stating that MVs may not treat deficiencies, and this is be cause i believe the deficiency originated from the inability to absorb or proper utilize the said nutrient to begin with. For the general population that do not suffer from vitamin malabsorption are able to absorb and untilize vitamins in MV form, although they probably do not "need" it.
