This is our 600th “Health Options” column. So it seems like a good time to summarize a few of our “take home” messages shared over nearly 20 years of columns.

>> Errors of fact are common in popular nutrition information. Whether motivated by profit or personal philosophy, people commonly ignore facts well established in the science of nutrition. In 2002, we first used the term “infoterrorism” to stress how people often use misinformation to promote their causes. If repeated enough, fiction can take on the cloak of truth.

>> Step one in good nutrition is meeting essential nutrient needs. This is “no-brainer” nutrition 101. If just one of the 40 or so essential nutrients is absent in your diet, you are guaranteed to have health problems over time, with the worst-case scenario being death.

>> The benefits of good nutrition and damage from bad nutrition both take time to show their impact. Consequently, linking a dietary change you made five or 10 years ago with a current health problem is difficult.

>> Major considerations for those trying to eat healthfully include a number of challenges related to getting too little of some food groups and too much of others. Of course, this balance needs to be achieved without consuming excessive calories.

>> Homeostasis (keeping a stable equilibrium within the body) is critical for maintenance of healthy tissue along with repair when necessary. For example, intestinal tract cells are replaced about every three days and skeletal calcium turns over about every seven years. An adequate supply of essential nutrients is required for homeostasis.

>> Blood volume is critical for delivering oxygen and nutrients to cells and removing metabolic waste products. Maintaining adequate quality blood requires many essential nutrients, but the dietary nutrients most commonly in short supply are protein, iron, zinc, and vitamins B12 and folate. Animal protein foods are good sources of these nutrients, with the exception of folate, which can be found in fruits and green leafy vegetables.

>> “Bioavailability” of dietary nutrients affects how much of a nutrient consumed in food actually gets absorbed into and used by the body. This concept is one of the most important, yet most commonly misunderstood, in nutrition. It is not how much of a nutrient that goes into the mouth that matters, but how much is absorbed into the blood and goes to the cells.

>> Iron is the most common nutrient deficiency, especially for women during their child-bearing years. Women’s iron needs are more than double those of men. Due to low bioavailability of iron in plant foods, vegetarians require almost twice and vegans almost triple what is recommended for an omnivore. Spinach, for example, contains plenty of iron, but due to very low bioavailability, spinach is a poor source of iron compared to foods like red meat or dark-meat poultry.

>> Adequate food digestion requires chloride that comes primarily from salt (sodium and chloride). Too much salt reduction can impair stomach acid production and decrease absorption of various nutrients.

>> Too many “healthy” foods can make an unhealthy diet. Trace minerals, such as manganese and aluminum, are found in high concentrations in many foods considered “healthy.” For example, whole grains, some nuts, seeds and berries, and soy products are high in manganese. Whole-grain foods like pancakes, muffins and scones made with aluminum-based baking powder can be very high in aluminum. In excess, these minerals damage the nervous system over time. Both of these minerals are more readily absorbed by people who are iron deficient.

All in all, essential nutrients should follow the Goldilocks rule: Not too much, not too little, but just right!

Alan Titchenal, Ph.D., C.N.S., and Joannie Dobbs, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Dobbs also works with University Health Services.