The Core

^{related to LM's recent nutrition/diet thread}

TL;DR: Caveat Emptor

IIRC, food companies in the US are allowed to misstate food label nutrient data by 25%.  I assume this wide margin for error was lobbied in when food production methods were less precise to give manufacturers a hedge against product liability lawsuits.  Today, it seems far too wide but we're stuck with it.  Companies are definitely using that margin and math to make their products appear healthier.  Again IIRC, they are allowed to round down if the value is <1. So look for very small 'servings' portions to get that 0 carb (probably .8 carb) and the magic of letting you multiply by zero. Larger values, such as calories, are going to be manipulated to the low side plus the error margin.  In short, you probably need to add 15-20% to your tracked nutrition values in order to approximate what you're actually taking in.

http://nutritiondata.self.com/tools/nutrient-search  

Single item search is on the upper right. In terms of modern search capabilities, it's very weak; requires a very literal, precise match with a kw in their title to find something.  Still, it's the best I can find that has even a semblance of trustworthy data.

<added>
Green Beans serp:
http://nutritiondata.self.com/foods-green%20bean000000000000000000000.html

select Beans, snap, green, cooked, boiled, drained, without salt
http://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2342/2

Source: Nutrient data for this listing was provided by USDA SR-21

<added>
Chasing the USDA database turns up these search pages:

https://ndb.nal.usda.gov/ndb/nutrients/index

https://ndb.nal.usda.gov/ndb/search/list

I've not used these.

Great links, just what i was looking for but couldn't find one with so much detail.

>IIRC, food companies in the US are allowed to misstate food label nutrient data by 25%.

Correction: 20%

Unfortunately, Nutrition Facts labels are not always factual. For starters, the law allows a pretty lax margin of error—up to 20 percent—for the stated value versus actual value of nutrients. In reality, that means a 100-calorie pack could, theoretically, contain up to 120 calories and still not be violating the law. The same margin of error goes for other nutrients as well, which doesn't bode well for diabetic carb counters, folks with high blood pressure who are watching sodium intake, or moms looking to boost the iron content of their babies' diets. The FDA has never established a systematic, random label-auditing process, and compliance with the law is expected to be self-enforced by food manufacturers.

When Nutrition Labels Lie

https://health.usnews.com/health-news/blogs/eat-run/2012/08/21/when-nutrition-labels-lie

<added>
Rounding rule for vitamins & minerals are changing (assuming the FDA doesn't roll back these Obama-era regulations). See line-item chart:

http://www.sgs.com/en/news/2017/01/safeguards-00917-us-fda-issues-two-draft-guidance-documents-for-the-new-nutrition-facts-panel

<added 2>
Potassium become mandatory

https://www.esha.com/labeling-compliance/potassium-rounding-rules-on-the-2016-nutrition-facts-panel/