Which sources do you use to learn more about health & nutrition (anything from podcasts to papers will do)?
When in doubt, try to think what humans evolved to do and to process, and try to mimic that.
For nutrition, did we evolve with enormous servings of fast food, donuts, and spend millions of years eating highly refined highly concentrated packaged garbage packed full of preservatives, chemicals, and mystery substances, all consumed in absurd quantities? Or did we evolve to eat a diverse range of plants with occasional proteins and meats?
For health and exercise, did we spend millions of years sitting around watching TV and being screen sloths? Or did we spend millions of years walking dozens of miles every day, with near constant physical activity in some form or another?
As for studies and raw data, NIH pubmed https://www.ncbi.nlm.nih.gov/pmc/, NHS, EU, all have interesting raw largely non-opinionated information to scan through.
You mean die at age 30? Sorry for being sarcastic, but that's actually really horrible advice, and exactly the type of advice OP is trying to avoid. Please back up your claims with scientific evidence, not conjecture.
I think part of the reason that there is so little reliable and definitive science is that people living long enough for nutrition to be a problem is a relatively new thing. Just 100 years ago the average person in the US died in their early 50's. And during that time our medical knowledge has been increasing rapidly. So it's really hard to isolate a person's diet from everything else that's changing.
I dare say the diabetes and heart disease epidemic is the start of natural selection weeding out the genes less tolerant of high carb, high fat diets.
As a part of it, we're also making something similar to SpamAssassin for articles. "A friend of mine" is co-hosting SciHub mirror, so we parse and index an extensive collection of papers.
We ban for any "toxins", "detox.+", "mycotoxin", juicing, for anything "leaky gut"-related, any "meso-/ecto-/whatever-"-morph (somehow this stuff is popular here in China), any trademark mention, all Bulletproof® Coffee™ and such; ban most "doctors" mentioned on quackwatch.org + our own blacklist (Mercola, Osprey, Taubes etc).
Generally, we don't trust anything from the Internet, double-check the books, and re-check the scientific papers. Many papers study very small cohorts (N=10-20) or miss important correlation issues (like the famous Blue Zones study or China study).
Learn to recognize that ~30% of current proven knowledge will be disproven in the future, like cholesterol.
Personally, I trust Dr. David Katz, examine.com, to less degree consumerlab.com, healthnewsreview.org, sciencebasedmedicine.org, nutritionfacts.org.
I switched my diet over to something more closely to what diet doctor advocates, and have gotten slighly more strict with every year, becauase I _feel_ a little better. To me, the "proof" that the information is accurate is that I feel good.
I have the impression, though this may be dated information, that a lot of science on the topic has been primarily focused on measuring the number of calories in/out, because that's easy to measure. When you try to measure _quality_ of your calories, everything becomes magnitudes more complicated to prove, so there's far less reliable science on the topic.
The health articles are written for the layperson and go to the source of the research - explaining the methodology and limitations of a particular study.
It's an excellent resource and one that deserves a wider audience in my view:
Here's how they reported on a recent story about bread: Is white bread just as healthy as brown?
And here's one from 2015: Sugar intake should be drastically reduced, says report
I read directly from scientific articles. And I'm also trying to come up with a methodology to select the best and most useful ones, that can provide actionable guidance in terms of which lifestyle changes to adopt.
You can find more about my habits and the papers I've selected in one of my answers on reddit  or you can also check a prototype I created to help me find which lifestyle changes would most improve my health/longevity 
Let me know if I can help in any other way
How do you choose which papers to follow? Any rules of thumb/red flags for assessing a paper?
First, I start with a clear goal/question in mind: e.g. which lifestyle changes could help me live longer? Then there are several things I look for when assessing a specific paper:
a) Sample size is key. Small samples are not very reliable as you can reach almost any conclusion you want. I also prefer looking at meta-analysis (this is when scientists look at all the studies that analysed a given topic). This means more data (larger samples) and less risk of biases.
b) Low P-value (below 5% is what you're looking for). This is the probability that the effect found was due to randomness. If this is too high, then you cannot rely on your conclusions.
c) Adjusting for other variables that could explain the effect that was found in the study. E.g. if you want to find if eating more vegetables is healthy, you should adjust for exercise, so you can compare people that do the same amount of exercise but eat different amounts of vegetables. Otherwise the effect found could be explained by other variables not adjusted for.
d) No funding bias. Is this a study stating that eating X is good but funded by the Association of X Producers? Avoid those :)
e) No publication bias (this only applies to meta-analysis). This is when scientists don't publish their findings (e.g. because they did a small study, or found an insignificant effect, or found an effect they or their funders "didn't like"). Most good meta-analysis will comment on this (it's also called Funnel test/analysis).
f) Human studies. I tend to ignore studies that aren't done with humans as the probability the conclusions will hold in humans is actually very low (probably less than 10%). It's also preferable to have intervention studies (when you get two groups of people that receive two different interventions - e.g. eating beets juice and placebo - and compare outcomes; they generally don't know which intervention they're getting) vs. observational studies (when you study a group of people and try to assess if differences in what they say they do lead to different health outcomes). But in this field, most studies are actually observational, hence the importance of all the other things I've mentioned.
Hope this helps!
The Harvard School of Public Health are behind 2 of the biggest ongoing studies on diet, the Health Professionals Follow-Up Study, which has followed 50,000 men for over 30 years, and the Nurses' Health Study which has included 275,000 people over 40 years.
I find the information they provide so valuable that I developed and currently maintain their Daily Dozen Android app that helps you track that you're eating the correct foods for good health. Check it out here: https://play.google.com/store/apps/details?id=org.nutritionf...
Then there is Greger's work mentioned already somewhere above. And McDougall and Fuhrmann are worth your time.
If you "supplement" this information with Graham (811rv is the keyword) you'll get a pretty broad picture which includes discussion of all fashion diets like Paleo etc.
Bottom line is that for over thirty years it's pretty clear that animal protein is a problem fur the human body. Whole foods plant based it's the answer. Or the alternative is Western diet plus drugs. Pretty much the "truth" you can see all around you these days. If you dare to look objectively..
Old knowledge is better than new when it comes to health - statistically too it has "survived" longer without being debunked.
Forget fads and realize there are always economic incentives at play to promote information on health.
Excessive attention to health could be called stress, which itself is horribly bad for health.
Your best bet is do do N=1 experiments on yourself. Find what works, and do that.
The deeper analytical stuff by NYTimes and NHS is strong too.