

Fish oil is a commonly used fatty acid supplement because it is a source of omega-3 fatty acids.[43] Fatty acids are strings of carbon atoms, having a range of lengths. If links are all single (C-C), then the fatty acid is called saturated; with one double bond (C=C), it is called monounsaturated; if there are two or more double bonds (C=C=C), it is called polyunsaturated. Only two fatty acids, both polyunsaturated, are considered essential to be obtained from the diet, as the others are synthesized in the body. The "essential" fatty acids are alpha-linolenic acid (ALA), an omega-3 fatty acid, and linoleic acid (LA), an omega-6 fatty acid.[43][44] ALA can be elongated in the body to create other omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Look for supplements certified by the United States Pharmacopeia (USP), NSF International, or the United Natural Products Alliance, as it indicates a higher standard of quality assessment. (The USP's screening process, for instance, ensures that a product will break down properly and effectively release its ingredients into the body.) These organizations have a certification seal that is typically shown on the product packaging.
Scientific evidence shows that some dietary supplements are beneficial for overall health and for managing some health conditions. For example, calcium and vitamin D are important for keeping bones strong and reducing bone loss; folic acid decreases the risk of certain birth defects; and omega-3 fatty acids from fish oils might help some people with heart disease. Other supplements need more study to determine their value. The U.S. Food and Drug Administration (FDA) does not determine whether dietary supplements are effective before they are marketed.



Watch your portion sizes: Check to see what the recommended portion sizes of foods you eat looks like in the bowls, plates, and glasses you use at home. When dining out avoid "supersizing" your meal or buying "combo" meal deals that often include large-size menu items. Choose small-size items instead or ask for a take home bag and wrap up half of your meal to take home before you even start to eat.
In the United States, the National Health and Nutrition Examination Survey (NHANES) has investigated habits of using dietary supplements in context of total nutrient intakes from the diet in adults and children.[101] Over the period of 1999 to 2012, use of multivitamins decreased, and there was wide variability in the use of individual supplements among subgroups by age, sex, race/ethnicity, and educational status.[115] Particular attention has been given to use of folate supplements by young women to reduce the risk of fetal neural tube defects.[116][117]

A review of clinical trials registered at clinicaltrials.gov, which would include both drugs and supplements, reported that nearly half of completed trials were sponsored wholly or partially by industry.[125] This does not automatically imply bias, but there is evidence that because of selective non-reporting, results in support of a potential drug or supplement ingredient are more likely to be published than results that do not demonstrate a statistically significant benefit.[125][126] One review reported that fewer than half of the registered clinical trials resulted in publication in peer-reviewed journals.[127]
FDA regulations for nutritional supplements differ in important ways from those for prescription or over-the-counter drugs. For one thing, pharmaceutical companies have to gather data showing that a new drug is safe and effective in order to get the FDA's approval to market the drug. Makers of dietary supplements don't have to show that sort of proof. Be sure to let your doctor know about any nutritional supplement you plan on taking so you can discuss whether it's right for you and the appropriate dose.



Although as a general rule, dietary supplement labeling and marketing are not allowed to make disease prevention or treatment claims, the U.S. FDA has for some foods and dietary supplements reviewed the science, concluded that there is significant scientific agreement, and published specifically worded allowed health claims. An initial ruling allowing a health claim for calcium dietary supplements and osteoporosis was later amended to include calcium supplements with or without vitamin D, effective January 1, 2010. Examples of allowed wording are shown below. In order to qualify for the calcium health claim, a dietary supplement much contain at least 20% of the Reference Dietary Intake, which for calcium means at least 260 mg/serving.[16]

Among general reasons for the possible harmful effects of dietary supplements are: a) absorption in a short time, b) manufacturing quality and contamination, and c) enhancing both positive and negative effects at the same time.[56] The incidence of liver injury from herbal and dietary supplements is about 16–20% of all supplement products causing injury, with the occurrence growing globally over the early 21st century.[41] The most common liver injuries from weight loss and bodybuilding supplements involve hepatocellular damage with resulting jaundice, and the most common supplement ingredients attributed to these injuries are green tea catechins, anabolic steroids, and the herbal extract, aegeline.[41] Weight loss supplements have also had adverse psychiatric effects.[84]




In the United States, manufacturers of dietary supplements are required to demonstrate safety of their products before approval is granted for commerce.[83] Despite this caution, numerous adverse effects have been reported,[72] including muscle cramps, hair loss, joint pain, liver disease, and allergic reactions, with 29% of the adverse effects resulting in hospitalization, and 20% in serious injuries or illnesses.[72] By more than five-fold, the highest incidence of health problems derived from "combination products", whereas supplements for vitamins and minerals, lipid products, and herbal products were less likely to cause adverse effects.[72]
Compared to pharmaceutical drugs, supplements of most essential nutrients are quite harmless. However, some supplements may have poor quality, or contain toxic metals such as lead or cadmium. Therefore, it is the duty of our authorities to ensure that potentially hazardous products or supplements of poor quality are not sold, and that consumers are offered fair prices in a free market. An example where the Norwegian authorities do not follow up such basic duties is that pharmacies demand more than 1,600 Norwegian Kroner (about $190) per kg of vitamin C in powder form, which would cost less than $20 with free competition and no restrictions in permitted doses or outlets.