I have no idea what the volume of psyllium in capsules would be, but I
would imagine that it would be measured in milligrams. Most of the
studies on fibers that I have read mention a dose dependent effect
and the volume is in quite a few grams. Soluble fiber has a different
effect than insoluble (nondigestible) fiber.

"Results: Soluble fiber, 2–10 g/d, was associated with small but
significant decreases in total cholesterol ... and LDL cholesterol ... .
The effects on plasma lipids of soluble fiber from oat, psyllium, or
pectin were not significantly different. We were unable to compare
effects of guar because of the limited number of studies using 2–10 g/d.
Triacylglycerols and HDL cholesterol were not significantly influenced
by soluble fiber. Lipid changes were independent of study design,
treatment length, and background dietary fat content.

Conclusions: Various soluble fibers reduce total and LDL cholesterol by
similar amounts. The effect is small within the practical range of
intake. For example, 3 g soluble fiber from oats (3 servings of oatmeal,
28 g each) can decrease total and LDL cholesterol by <0.13 mmol/L.
Increasing soluble fiber can make only a small contribution to dietary
therapy to lower cholesterol." Source: Cholesterol-lowering effects of
dietary fiber: a meta-analysis -
http://www.ajcn.org/cgi/content/full/69/1/30

"Design: After a 2-wk dietary stabilization phase, 34 men with type 2
diabetes and mild-to-moderate hypercholesterolemia were randomly
assigned to receive 5.1 g psyllium or cellulose placebo twice daily for
8 wk. Serum lipid and glycemic indexes were evaluated biweekly on an
outpatient basis and at weeks 0 and 8 in a metabolic ward.

Results: In the metabolic ward, the psyllium group showed significant
improvements in glucose and lipid values compared with the placebo
group. Serum total and LDL-cholesterol concentrations were 8.9% (P <
0.05) and 13.0% (P = 0.07) lower, respectively, in the psyllium than in
the placebo group. All-day and postlunch postprandial glucose
concentrations were 11.0% (P < 0.05) and 19.2% (P < 0.01) lower in the
psyllium than in the placebo group. Both products were well tolerated,
with no serious adverse events related to treatment reported in either
group.

Conclusion: The addition of psyllium to a traditional diet for persons
with diabetes is safe, is well tolerated, and improves glycemic and
lipid control in men with type 2 diabetes and hypercholesterolemia."
Effects of psyllium on glucose and serum lipid responses in men with
type 2 diabetes and hypercholesterolemia -
http://www.ajcn.org/cgi/content/full/70/4/466

Also a study has shown a time-dependent effect.  The volume of a high
fiber diet was about 50 gram of fiber per day (table 3).  Results from
this study did not support the high fiber diet for lipid control (table 5).

"Conclusions: In subjects with type 2 diabetes, changes in serum
SCFAs in response to changes in carbohydrate and fiber intakes
took many months to occur, and the changes in serum acetate
were significantly related to the long-term adaptive changes in
blood lipids. ... Over the first 3 mo, the ratio of total to HDL
cholesterol increased significantly more with the LF diet than with the
MUFA diet, but this difference disappeared by 6 mo. Unexpectedly,
fasting triacylglycerol and cholesterol concentrations tended to rise
between 3 and 6 mo with the HF diet, and postprandial triacylglycerols
were significantly higher after 6 mo of the HF diet than after
6 mo of the LF diet (See table 5). ... Subjects were randomly assigned
to 1 of 3 treatments: ... ; high-fiber, low–glycemic index breakfast
cereal (HF diet); or ... .  The high-fiber cereals were Bran Buds with
Psyllium (Kellogg Co, Battle Creek, MI) and a prototype oat-loop cereal
enriched with psyllium." Source: Do colonic short-chain fatty acids
contribute to the long-term adaptation of blood lipids in subjects with
type 2 diabetes consuming a high-fiber diet? -
http://www.ajcn.org/cgi/reprint/75/6/1023.pdf

The only benefit that a high nondigestible fiber diet may contribute is
that it can be a prebiotic for the probiotic bacteria that cause
increases in the tissues of the colon (hypertrophic effect) which may
also produce more GLP-1 or GLP-2 [such as occur with longer life GLP-1
mimics such as Byetta or DPP IV inhibitors such as LAF237 (Vildagliptin)
that extend the life of incretin hormones (GLP-1, GLP-2; GIP)].

A scholar.google.com search for dietary+fiber+lipids+long+term resulted
in 5,570 finds - http://tinyurl.com/9n94k.  The first few pages give
enough results for further review.

Frank