DEAR DR. BLONZ: I was at a large dinner party where they served sea salt with the meal. However, I have been avoiding modern sea salt if its source is evaporated seawater.

I have traveled extensively to islands in the Caribbean where seawater is channeled into successive ponds on land, where it is evaporated to salt crystals and harvested for market. These islands typically have limited sewage treatment facilities, and waste with toxic components is discharged directly into the sea. This makes me suspect of salt made this way. -- B.T., Scottsdale, Arizona

DEAR B.T.: The FDA has a strict "good manufacturing practice," or GMP, for sea salt, and products adhering to the guidelines earn GRAS status: generally regarded as safe. While there can be trace amounts of heavy metals such as lead and arsenic in evaporated sea salt, they tend to be below the level of concern.

In recent years, though, science has discovered a different potential issue with sea salts: the presence of microplastics. Check out this article in National Geographic, which found microplastics in 90% of the evaporated salts it checked from around the world (visit b.link/4xzzx).

This all makes the case for doing your homework before you buy. If considering a particular sea salt, read the product label about the purity of the water from which it was harvested. Get more answers by contacting the company, or checking online, to see if the brand has had purity issues in the past.

DEAR DR. BLONZ: You often mention epidemiology when describing research, but I am not sure what that is. Could you give me a brief explanation? -- S.F., Seattle

DEAR S.F.: Epidemiology is the science that investigates connections between specific events, such as the occurrence of a disease, and a particular behavior pattern. In matters of nutrition, this could be an association between diet, exercise and a pattern of health or disease. Epidemiological research can help suggest what's going on, but it cannot tell you what's causing what with any precision. Some findings can be informative and on target, while others may only be coincidental.

For example, one study had found that inner-city children suffering from iron-deficiency anemia were more likely to have lead poisoning. The study showed that these items were connected, but it couldn't say what was causing what. Inner-city residents often have a greater exposure to lead, which could be present in peeling lead-based paints. So, did the lead causing the anemia, or was it the other way around?

Additional studies filled in the blanks by providing a plausible mechanism behind the relationship. In this case, it was discovered that that low blood iron (anemia) facilitates lead absorption.

This is an example of epidemiology at work, but studies can also uncover strange relationships. One of my favorites, uncovered while in graduate school, came from a list of statistically "connected" phenomena. There was a finding that physicians who eat more meat and consume more alcohol have one-third the risk of dying in a plane crash. So, does that indicate that it's legitimate science to encourage doctors to grab a burger and a beer before they board their flight? Hardly.

In that case, as in all others, we need to understand a plausible mechanism before giving full credence to results from epidemiology. For more, check out the Centers for Disease Control and Prevention's lesson on epidemiology at b.link/cmx954.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I keep seeing the word "hydrolyzed" on ingredient labels, but I am not sure what it means. Is it anything like "partially hydrogenated"? -- H.S., Anderson, South Carolina

DEAR H.S.: "Hydrolyzed" refers to a chemical process in which a large compound is broken down after reacting with water (hence the "hydro").

An example of its use in the world of food is the splitting apart of proteins, which are composed of long chains of amino acid building blocks. Proteins are large, complex molecules, and get broken into their individual building blocks before absorption by our bodies. Our digestive system is designed to perform this action.

The "hydrolyzed" you spotted on a label was likely associated with an ingredient called "hydrolyzed vegetable protein" (HVP). But if digestion will accomplish the goal, why break apart a protein before it enters the body? Food scientists discovered that certain individual amino acids could enhance flavor. Small amounts of hydrolyzed proteins began being used as additives in processed foods after tests revealed it helped bring out the natural flavor of some foods.

A related issue deserves mention here. There has been, in the past, some concern about HVP due to its association with monosodium glutamate (MSG), which tends to form in hydrolyzed proteins. Some people claimed an extreme sensitivity to MSG, including symptoms like headaches and discomfort. The resulting polarizing uproar led to the phrase "No MSG" appearing on countless menus and labels. Blinded studies, however, in which individuals did not know whether they were consuming MSG or a placebo, failed to support the effect -- even with many who claimed sensitivity. The discussion was further complicated given that MSG is naturally present in the body, it forms naturally in foods, and it has been in use as an additive for over 100 years.

The conclusion reached by researchers was that MSG is generally regarded as safe at the levels found in foods. It is used as an additive in snacks, fast foods, soups, seasonings and dressings. A small number of people can react to MSG in certain circumstances, especially with elevated levels of intake. (Read about the sensitivity angle at b.link/ywsqat, and more big-picture stuff at b.link/2jdyrc.)

Back to your ingredient label question: The phrase "partially hydrogenated" refers to a different process altogether. Hydrogenation refers to adding hydrogen; in this case, it can be used to modify a liquid vegetable oil into a solid block of fat. Partial hydrogenation takes this process part of the way and creates a semisolid fat, the characteristics of which depend on its intended use.

Partial hydrogenation has been widely used in food processing because it allows inexpensive vegetable oils to be used in many different food applications -- from margarine and shortening to cookies, crackers, fries and pastries.

However, further research revealed a significant downside to partially hydrogenated fats: Hydrogenation produced the trans fatty acids associated with an increased risk of health issues, including heart disease and certain cancers. The consistent refrain, as research progressed, was that trans fats must be avoided. In 2003, the FDA began requiring manufacturers to declare the level of trans fats present in a serving of their products.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: A recent blood test showed that my cholesterol levels were fine, but my triglycerides were slightly elevated. You mention them periodically, but please explain what triglycerides are and the role my diet might be playing. -- F.L., Oakland, California

DEAR F.L.: The role of triglycerides often confuses people. That's not surprising, given the speed with which complex health terms have encroached upon our daily lives.

Think of triglycerides as the body's most concentrated form of stored energy. (For this discussion, think of the terms "fats" and "triglycerides" as compatible.) The human body is designed to be mobile and to conserve energy. Triglycerides are the form into which excess energy is converted, and also the way they get packaged for transport and storage.

Contrast this with plants, where the mission is to grow rapidly; energy in plants gets made into carbohydrates, which serve as a building material. (If we stored energy as carbohydrates, we would be too bulky to move.) The fascinating shift in plant life is with their seeds, where their light weight allows them to travel on the wind or with animals to land -- and grow -- in a new area. In seeds, energy is stored as fat.

A list of triglycerides would include the fats in our diet (butter, cooking oils, etc.), those in our bloodstream, and the fat that eventually makes its way to the body's energy storage depots. All triglycerides are built like a squat version of the letter "E," where the three prongs are individual saturated or unsaturated fatty acids attached to a glycerol backbone.

There is a big difference between triglycerides and cholesterol. Cholesterol is a waxy, fatlike substance with a complex structure that looks a small piece of honeycomb. Cholesterol is not used for energy; it is a structural element in all cells and serves as a raw material in making many hormones.

Both triglycerides and cholesterol are members of the lipid family. In addition, both travel through the body in packages known as lipoproteins. And finally, both share the dubious distinction of having their elevated blood levels associated with an increased risk of heart disease.

The blood triglyceride level usually goes up after eating, even if there's a limited amount of fat in the meal. This occurs because the body is programmed to convert excess protein or carbohydrate into triglycerides, the form of energy best suited for transport and storage. Consuming alcohol or excess sugars such as fructose, sucrose or glucose will also increase triglycerides.

Should you be concerned about your triglyceride level? As blood tests for triglycerides are typically taken after a fast, any effects from your last meal should be over. Given this, if you still have an elevated triglyceride level, it would be something to be discussed with your health professional. Much will depend on your health profile and history. You and your doctor will decide whether this is something to be monitored or if additional tests may be needed to rule out any ongoing problems.

Read more about conditions that can elevate triglycerides at b.link/r34n7r.

Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.