Can we survive on liquid diet?

Question

What if I am getting all my nutrition from fluids that includes vegetable and fruit juices, milk etc. Will it effect my body, metabolism, or digestive system in any way?

Answer 1

What if I am getting all my nutrition from fluids that includes vegetable and fruit juices, milk etc. Will it effect my body, metabolism, or digestive system in any way?

What you're describing is something that I did for a several years. I went to all these dieticians because I wanted to make sure I was not killing myself slowly and none of them could give me an adequate reason.

I will note two things that you may wish to consider:

1. The GI tract may require some coarse material from time to time so that the cells lining it can be sloughed off. This was suggested to me by a professor of anatomy and it's by far the best suggestion. Things like nuts might act as abrasive material to help facilitate this process.

2. If you decide to revert back to solids, you might want to consider doing so very slowly. I base this on having lived off a liquid diet for several years, only to lose a good 10 kg of muscle while traveling overseas and being forced onto solids.

It's a matter of use it or lose it: if there is no need for enzymes to be excreted, then production will be downregulated. Likewise the histology of the cells lining the epithelium of the GI tract will be modified. If you switch to solids overnight, it will take time for your body to adapt, and in the interim, you may have issues will malabsorption.

EDIT

The following reference is quite old but a good overview of adaptive response to changes in diet.

Some excerpts from The adaptation of digestive enzymes to the diet: its physiological significance

Dietary changes instantiate robust adjustment to digestive enzyme secretion and/or production:

From the above analysis, it is clear that any alteration in the amount of protein, carbohydrate or lipid intake causes an adjustment in the enzymes hydrolyzing those substances. For example, increasing starch intake causes pancreatic amylase activity to augment, which in turn induces an increase in the quantity of disaccharides releas- ed. It was seen that the latter increase stimulates disaccharidase enzyme activity ; this is also true for protein and lipid digestion. The enzymes adapt to the diet within 2 to 3 days and this adaptation is stabilized after 5 to 7 days (Ben Abdeljlil and Des- nuelle, 1964 ; Corring and Saucier, 1972 ; Corring, 1975). However, recent studies have shown that quantitatively changing a substrate has a very rapid effect on the corresponding enzyme activity.

And the following may be of relevance to chronic utilisation of liquid diet:

To explain why it takes a relatively long time for enzymatic adaptation to be established, Corring (1977) suggested that it depends on the adjustment of other digestive processes such as gastric emptying or intestinal motility. The presence of a stable amount of substrate in the intestinal lumen, leading to a new enzyme activity, would thus necessitate the previous adaptation of digestive motor processes. The stimulus of changing the diet composition would cause a very short-term digestive response which must be repeated (intake of several meals of the new diet) in order to establish a new enzyme activity. In studies on digestive enzyme adaptation to the diet, the values of enzyme activities are usually the daily means which do not show the immediate effects of intake. Moreover, the adaptation time may vary with the synthesis site, depending on the enzyme.

The adaptiveness is an attempt to accommodate temporary deficiencies, and modifications to diet:

The first part of this paper showed that the organism has a complete digestive equipment which can adapt to any alteration in the amount of substrate intake. In the second part of the paper, it was seen that this increase seemed to have no apparent advantage in the development of the normal, well fed animal. On the contrary, it would be useful when all the nutritional requirements are not covered by the diet. Dietary deficiency, particularly protein deficiency, if it is not too severe, is compen- sated for by digestive secretion supply ; this compensation is only possible because of the adaptive capacity of the enzymes. In man, in which malnutrition or undernourish- ment are well known, it would seem that such cases would be rapidly and inevitably fatal, if there was no process of enzyme adaptation. Dietary deficiency could also be the result of a lack of substrate due to enzymatic deficiency ; in some cases, enzyme adaptation limits its effects owing to digestive compensation. Although it cannot be considered as an endogenous digestive secretion, the intestinal microflora plays a crucial role which it is necessary to define, if the microflora is to be used as a digestive enzyme source in humans suffering from enzyme insufficiency or deficiency.