If a conflict of interest is not literally declared, is it safe to assume there is a conflict of interest? What does this imply about the findings? For the first example below, a conflict of interest (CoI) isn't literally declared, but seems to be implied in the funding section. Additionally, the majority of the studies included have a similar CoI. For the second example, again with funding there seems to be partial CoI. Is there any credence to studies funded from food industry sources not be tolerated?
Example 1
2009 Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis
forty-seven studies (11 of pre-, 35 of post- and 1 of perimenopausal women)
isoflavones – soy phytoestrogen (which mimics estrogen in the body, beneficial in combating symptoms and conditions caused by estrogen deficiency)

To our knowledge, this is the first systematic review and
meta-analysis to compare the endocrine effects of different soy
products on hormonal status in women at different lifecycle stages. It
provides weak evidence that soy and isoflavones decrease FSH and LH in
premenopausal women, and a suggestion that they may increase estradiol
[estrogen steroid hormone and the major female sex hormone] in
post-menopausal women.

Results

Twenty studies declared a funding source with a commercial interest in the study results; 25 did not report industry funding; and 2 were
unclear.

Funding

This work was partially funded by the Soy Nutrition Institute, Inc., St Louis, MO, USA. M.J.M. consults for companies that manufacture
and/or sell soyfoods, soy protein and isoflavone supplements and is a
Scientific Advisory Board Member of the Soy Nutrition Institute.

ncbi.nlm.nih.gov/pmc/articles/PMC2691652
Extra for 1
Letters to the Editor

These estrone levels are important because in the meta-analysis of
Hooper et al. (2009) […] evidence indicates that isoflavones will not
increase breast cancer risk in healthy women or worsen the survival of
breast cancer patients.

academic.oup.com/humupd/article/16/1/110/709455

Example 2
2010 Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis
36 studies

The results of this meta-analysis indicate that neither soy protein
nor isoflavones affect reproductive hormone concentrations in men
regardless of age or cancer status. Although the duration of most
trials was &lt;6 months, soy protein and isoflavone intake greatly
exceeded typical dietary Japanese intake 2. These results suggest
that consumption of soy foods or isoflavone supplements would not
result in the adverse effects associated with lower T levels
[31][32][33].


J.H.-R while a doctoral student at the University of Minnesota
received some minor funding from the Soy Nutrition Institute for work on this manuscript. G.V. has nothing to disclose. S.J.D. has
nothing to disclose. W.R.P. has nothing to disclose. M.S.K.
occasionally consults for the Solae Company. M.J.M. regularly consults
for companies in the soy food industry.

ncbi.nlm.nih.gov/pubmed/19524224/doi.org/10.1016/j.fertnstert.2009.04.038
Supplement for 2
2011 Re: Clinical Studies Show No Effects of Soy Protein or Isoflavones on Reproductive Hormones in Men: Results of a Meta-Analysis
Editorial comment

The authors performed a meta-analysis of the available literature, and
conclude that soy protein or isoflavone intake had no detectable
effect on free or total testosterone, sex hormone binding globulin or
free androgen index. While the study does not include measurements of
semen or paternity, and androgenic status does not tell the whole
story of male fertility, this meta-analysis is a step in the direction
that soy products are unlikely to be harmful to male reproduction.

sci-hub.se/10.1016/S0022-5347(11)60138-9
Conflicts of interest on their own do not imply poor results is the blanket answer to this question.  It is true that in several high-profile (and most likely lower profile) research projects funded by industry that muzzling or cherry picking has happened (here is an interesting analysis of one particular industry and its issues).  Industry obviously has an interest in funding research that will give them favorable results.  However, just because industry has funded the research does not mean that it is automatically untrustworthy.
Unless there is good reason not to, we have to trust in the peer review process and acknowledge that it is our job as readers of research to interpret and contextualize studies regardless of conflicts of interest.   For instance, we should always be sure to thoroughly read and understand the methods used in the research and to determine if they are up to acceptable scientific standards.
It is similarly important to understand that a single study or suite of studies does not imply scientific truth.  For instance, if a paper shows that they were able to observe a particular thing in a particular population, that implies only that the observation is possible under certain conditions, not that it is universal.
Conflicts of interest are also sometimes unavoidable.  A drug company trying to do trials of a specific, proprietary drug must fund those trials.  That's a conflict and they obviously have an interest in favorable results, but just because that interest exists does not automatically imply that the results will be untrustworthy.
Finally, just because something is not declared does not mean that you should automatically reject it.  Of course be critical, but don't assume that just because something is unclear the authors are being evasive.  At the end of the day you can always try to send an email to the corresponding author and ask.  Worst thing that happens is you are ignored.