However, the Norwegian authorities do admit that vitamin D supplements are needed during part of the year.  Only part of the year? One third of Norway is within the Arctic Circle. Norway has far too little sunshine (especially during winter months) to get adequate levels of vitamin D from UVB radiation on the skin. The authorities also recommend that pregnant women take folic acid to prevent birth defects, and omega-3-fatty acids may be advisable for those who do not eat fish regularly. Norwegians have a long tradition of giving children cod liver oil, which in a daily tablespoon provides enough vitamin A and D and essential fatty acids to cover basic needs.
Prepare more of your own meals. Cooking more meals at home can help you take charge of what you’re eating and better monitor exactly what goes into your food. You’ll eat fewer calories and avoid the chemical additives, added sugar, and unhealthy fats of packaged and takeout foods that can leave you feeling tired, bloated, and irritable, and exacerbate symptoms of depression, stress, and anxiety.
There are thousands of dietary supplements on the market, including 40+ essential nutrients alone and in various combinations, i.e. vitamins, minerals, trace elements and fatty acids. However, a number of other nutrients are "conditionally essential", meaning that the body normally can make these molecules, but some people do not make optimal amounts. Examples are L-carnitine, alpha-lipoic acid, the methyl donor betaine,  chondroitin sulfate, coenzyme Q10, choline, amino acids such as tyrosine or arginine, and "essential" sugars normally formed in the body. 
The daily calcium recommendations are 1,000 milligrams a day for women under 50, and 1,500 milligrams a day for women 51 and older. Oddly enough, these are the same requirements for men, who are much less prone to osteoporosis than women. But the recommendation takes into account the fact that women are smaller than men. Thus the amount of daily calcium is greater for women on a proportional basis.
Studies link high sodium intake to higher blood pressure, and evidence suggests that many people at risk for high blood pressure can reduce their risk by consuming less salt or sodium, as well as following a healthy diet. Most Americans consume more sodium than they need. The recommended amount is less than 2,300 mg per day for children and adults to age 50. The limit drops to 1,500 mg per day for those 51 and older or those of any age who are African American or have hypertension, diabetes or chronic kidney disease. You get 2,300 mg in just one teaspoon of salt. One good way to reduce your sodium intake is to eat fewer prepared and packaged foods.
Animal products, such as meat, fish and poultry are good and important sources of iron. Iron from plant sources are found in peas and beans, spinach and other green leafy vegetables, potatoes, and whole-grain and iron-fortified cereal products. The addition of even relatively small amounts of meat or foods containing vitamin C substantially increases the total amount of iron absorbed from the entire meal.
After menopause. Lower levels of estrogen after menopause raise your risk for chronic diseases such as heart disease, stroke, and diabetes, and osteoporosis, a condition that causes your bones to become weak and break easily. What you eat also affects these chronic diseases. Talk to your doctor about healthy eating plans and whether you need more calcium and vitamin D to protect your bones. Read more about how very low estrogen levels affect your health in our Menopause section. Most women also need fewer calories as they age, because of less muscle and less physical activity. Find out how many calories you need based on your level of activity.
Make the right changes. When cutting back on unhealthy foods in your diet, it’s important to replace them with healthy alternatives. Replacing dangerous trans fats with healthy fats (such as switching fried chicken for grilled salmon) will make a positive difference to your health. Switching animal fats for refined carbohydrates, though (such as switching your breakfast bacon for a donut), won’t lower your risk for heart disease or improve your mood.
A person's caloric requirement depends on his body size and exercise level. Sedentary people of both genders will keep their weight stable by taking in about 13 calories per pound of body weight each day. Moderate physical activity boosts this requirement to 16 calories a pound, and vigorous exercise calls for about 18 calories a pound. On average, a moderately active 125-pound woman needs 2,000 calories a day; a 175-pound guy with a similar exercise pattern needs 2,800 calories. And like women, men will lose weight only if they burn more calories than they take in.
Do you wonder if you need a dietary supplement? Maybe you do, but usually not. Ask yourself why you think you might want to take a dietary supplement. Are you concerned about getting enough nutrients? Is a friend, a neighbor, or someone on a commercial suggesting you take one? Some ads for dietary supplements in magazines, online, or on TV seem to promise that these supplements will make you feel better, keep you from getting sick, or even help you live longer. Often, there is little, if any, good scientific research supporting these claims. Supplements may cost a lot, could be harmful, or simply might not be helpful. Talk to your doctor or a registered dietitian for advice.
Iodine is needed for normal mental development of the baby, but it can be difficult to get enough from food. Ways of increasing iodine intake include using iodised salt, eating fish and seafood weekly (see your health professional for advice about safe types and amounts of fish), or using a multivitamin supplement that contains iodine and is safe for pregnancy.
^ Fortmann, SP; Burda, BU; Senger, CA; Lin, JS; Whitlock, EP (Nov 12, 2013). "Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force". Annals of Internal Medicine. 159 (12): 824–834. doi:10.7326/0003-4819-159-12-201312170-00729. PMID 24217421.
For example, while increased consumption of fruits and vegetables are related to decreases in mortality, cardiovascular diseases and cancers, supplementation with key factors found in fruits and vegetable, like antioxidants, vitamins, or minerals, do not help and some have been found to be harmful in some cases. In general as of 2016, robust clinical data is lacking, that shows that any kind of dietary supplementation does more good than harm for people who are healthy and eating a reasonable diet but there is clear data showing that dietary pattern and lifestyle choices are associated with health outcomes.