We all want healthier foods, but reading labels won't always help you spot them. Many terms are defined and regulated by the Food and Drug Administration or the Depart­ment of Agriculture, depending on the type of food. But similar-sounding terms might not be.

And even when a term has a clear definition, ­using it on a package can give the impression that a food is healthy overall when it might not be. For example, a study in the Journal of the Academy of Nutrition and Dietetics found that shoppers gravitate toward labels such as "low sodium," "low fat," and "reduced sugar," but foods and drinks with these claims weren't significantly healthier than similar products without the claims and in some cases were less healthy. How can that be? ­Because a low-sodium soup may well fall within the FDA guidelines of 140 mg or less per serving but could still be high in calories, fat, or sugars.

Here, then, are pairs of terms to keep distinct in your mind:

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'Organic' vs. 'Natural'
Organic: This term is strictly regulated and can be on a label only when farmers and processors adhere to federal standards designed to promote a more sustainable food system. To be called organic, a food must contain at least 95 percent organic ingredients, which means crops are grown with fewer pesticides and no synthetic fertilizers or genetically modified organisms, and farm animals are fed organic feed and raised without the routine use of drugs such as antibiotics. Processed foods labeled "organic" also cannot contain arti­ficial ingredients unless they go through a rigorous review process, and have no artificial preservatives, colors, or flavors.

Natural: A 2015 nationally representative Consumer Reports survey found that 62 percent of consumers seek out foods with the "natural" label, and roughly as many of them think this term means no pesticides, no antibiotics, and other attributes of organic. But it doesn't. There is little government regulation of this term. CR has petitioned the FDA to ban it because it is so misleading. ­Recently the agency called for public comments on the use of the word on labels, and it is currently reviewing them. Meanwhile, manufacturers continue to use it.

'Pasture Raised' vs. 'Free Range'
Pasture Raised: This term alone on your egg carton does not have any meaning. Look for it in combination with the "American Humane Certified" or the "Certified Humane" seal. Together they mean that the hens must be outside every day and have lots of space to roam.

Free Range: This claim on egg cartons implies that the hens get to move freely outdoors. But the label has no meaning alone. Look for it in combination with the "American Humane Certified" seal to ensure that the hens have sufficient outdoor space to roam.

'100% Whole Grain' vs. 'Made With Whole Grains'
100% Whole Grain: A product with this label should contain exclusively whole grains and should have whole-wheat flour (or another whole grain) listed as the first ingredient.

Made With Whole Grains: This means a product might contain only a small amount of whole grain—the rest of the grains can be refined.

'Low Sodium' vs. 'Reduced Sodium'
Low Sodium: Because it guarantees no more than 140 mg of sodium per serving, a product with this term is the right choice for anyone trying to keep his or her salt intake in check.

Reduced Sodium: For this designation, a product has to have at least 25 percent less sodium than the full-sodium version of the same product. It could still ­deliver a big sodium punch.

'Sugar Free' vs. 'Unsweetened'
Sugar Free: Such a product contains less than 0.5 gram of sugar per serving—including naturally occurring fruit and milk sugars. But it can (and often does) contain artificial sweeteners.

Unsweetened: No sugars—or artificial sweeteners—have been added to the product. It may still contain sugars that occur naturally.

Editor's Note: This article also appeared in the July 2017 issue of Consumer Reports magazine.