Issue with conda update anaconda

Question

I am trying to update anaconda on my Mac. When I run the command conda update anaconda, I get the following output

The following packages will be downloaded:

package                    |            build
---------------------------|-----------------
conda-env-2.6.0            |                0          601 B
conda-4.2.13               |           py27_0         375 KB
------------------------------------------------------------
                                       Total:         375 KB

The following packages will be SUPERCEDED by a higher-priority channel:

conda:        4.2.13-py27_0      conda-forge --> 4.2.13-py27_0
conda-env:    2.6.0-0            conda-forge --> 2.6.0-0
hdf5:         1.8.17-8           conda-forge --> 1.8.15.1-1
jpeg:         9b-0               conda-forge --> 8d-1
libpng:       1.6.26-0           conda-forge --> 1.6.17-0
libtiff:      4.0.6-5            conda-forge --> 4.0.2-1
numexpr:      2.6.1-np111py27_0  conda-forge --> 2.4.3-np19py27_0

The following packages will be DOWNGRADED due to dependency conflicts:

numpy:        1.11.0-py27_0                  --> 1.9.2-py27_0
pip:          8.1.2-py27_0                   --> 7.0.3-py27_0
scikit-learn: 0.17.1-np111py27_0             --> 0.16.1-np19py27_0
scipy:        0.17.0-np111py27_0             --> 0.15.1-np19py27_0

Proceed ([y]/n)?

My question is why the packages will be DOWNGRADED? Or if there is any better way to keep the system up to date.

EDIT 1

When I do conda update --all, I get the following output:

Fetching package metadata .......
Solving package specifications: ....


UnsatisfiableError: The following specifications were found to be in conflict:
  - jasper -> jpeg 9*
  - sockjs-tornado
Use "conda info <package>" to see the dependencies for each package.

Answer 1

Anaconda is a distribution. It includes many packages with a specific version. The latest Anaconda package has not necessarily the very latest version of each packages. So, if you installed a newer version of package and the anaconda package itself has not been updated yet, it will downgrade these packages.

As an alternative you can use:

conda update --all

to update all installed packages in your current environment.

Answer 2

The Continuum blog may have the answer you need:

From https://www.continuum.io/blog/developer/advanced-features-conda-part-1#conda-update-all

"The anaconda metapackage is designed for people who want to keep a stable set of packages, which have been tested together. It is updated every few months. If you want to do this, you should keep anaconda installed and use conda update anaconda to update things. If you want to update packages individually to the latest versions as they come out, you should conda remove anaconda and use conda update --all to keep packages up-to-date."

So yeah, if you don't mind the downgrade of the packages in the end you get a coherent environment. Personally I would go for that option, unless I need some specific feature of those to-downgrade libraries versions.