Vitamin A can become toxic when taken in large amounts (over 100,000 International Units) on a daily basis over time, as can vitamin D. Substituting beta-carotene for vitamin A can alleviate this risk. Very large doses of minerals taken over long periods may have toxic effects in the body. Dosages far exceeding RDA's of vitamins are not recommended, nor are large doses of other supplements.
What is moderation? In essence, it means eating only as much food as your body needs. You should feel satisfied at the end of a meal, but not stuffed. For many of us, moderation means eating less than we do now. But it doesn’t mean eliminating the foods you love. Eating bacon for breakfast once a week, for example, could be considered moderation if you follow it with a healthy lunch and dinner—but not if you follow it with a box of donuts and a sausage pizza.
Dynamic contrast. Dynamic contrast refers to a combination of different sensations in the same food. In the words of Witherly, foods with dynamic contrast have “an edible shell that goes crunch followed by something soft or creamy and full of taste-active compounds. This rule applies to a variety of our favorite food structures — the caramelized top of a creme brulee, a slice of pizza, or an Oreo cookie — the brain finds crunching through something like this very novel and thrilling.”
In humans, the large intestine is host to more than 1,000 species of microorganisms, mostly bacteria, numbering in the tens of trillions. "Probiotic" in the context of dietary supplements is the theory that by orally consuming specific live bacteria (or yeast) species, it is possible to influence the large intestine microbiota, with consequent health benefits. Although there are numerous claimed benefits of using probiotic supplements, such as maintaining gastrointestinal health, in part by lowering risk of and severity of constipation or diarrhea, and improving immune health, including lower risk of and severity of acute upper respiratory tract infections, i.e., the common cold, such claims are not all supported by sufficient clinical evidence. A review based on interviews with dozens of experts in microbiome research expressed concern about "...how biomedical research is co-opted by commercial entities that place profit over health." The concern is timely, as through 2021, probiotic supplements are expected to be the fastest growing segment of the dietary supplement market worldwide, while at the same time, the global health benefits market for probiotic-containing yogurt (a food, not a dietary supplement) is declining.
Sodium. Sodium is found in salt, but most of the sodium we eat does not come from salt that we add while cooking or at the table. Most of our sodium comes from breads and rolls, cold cuts, pizza, hot dogs, cheese, pasta dishes, and condiments (like ketchup and mustard). Limit your daily sodium to less than 2,300 milligrams (equal to a teaspoon), unless your doctor says something else. Check the Nutrition Facts label for sodium. Foods with 20% or more of the “Daily Value” of sodium are high in sodium.
Your doctor may also be able to notify you of any other potential risks a supplement might pose to your health (especially if you're pregnant, have other medical conditions or are planning to have surgery), as well as offer guidance on the best dosage to take. If your doctor isn't comfortable with advising you on supplement use, ask if he or she can refer you to a qualified supplement-savvy health practitioner. But keep in mind that because of a lack of research on side effects, just how a supplement may interact with a medication isn't known.
Nutritional supplements may be designed to provide specialized support for athletes. Some of these consist of high-protein products, such as amino acid supplements, while other products contain nutrients that support metabolism, energy, and athletic performance and recovery. People engaging in intense athletic activity may have increased needs for water-soluble vitamins, antioxidants, and certain minerals, including chromium. Sports drinks contain blends of electrolytes (salts) that the body loses during exertion and sweating, as well as vitamins, minerals, and performance-supporting herbs.