We've heard a lot of encouraging news about supplements. A series of studies hailed vitamin D as a possible defense against a long list of diseases, including cancer, diabetes, depression, and even the common cold. Omega-3 fatty acids have been touted for warding off strokes and other cardiovascular events. And antioxidants such as vitamins C and E and beta carotene were seen as promising silver bullets against heart disease, cancer, and even Alzheimer's disease.
Nutritional density varies considerably geographically between different regions, even with the same agricultural methods. This was documented in the United States in 1948 by a researcher at Rutgers University in the so-called Firman Bear report.  At that time agriculture was little mechanized, and artificial fertilizers and pesticides were hardly used. The analysis found large differences in the content of minerals in the same food. The largest variations were found for potassium, sodium, boron and iron in spinach, while the greatest differences in calcium, magnesium and copper content were found in tomatoes.
According to US & Canadian Dietary Reference Intake guidelines, the protein Recommended Dietary Allowance (RDA) for adults is based on 0.8 grams protein per kilogram body weight. The recommendation is for sedentary and lightly active people. Scientific reviews can conclude that a high protein diet, when combined with exercise, will increase muscle mass and strength, or conclude the opposite. The International Olympic Committee recommends protein intake targets for both strength and endurance athletes at about 1.2-1.8 g/kg body mass per day. One review proposed a maximum daily protein intake of approximately 25% of energy requirements, i.e., approximately 2.0 to 2.5 g/kg.
^ Jump up to: a b Coghlan, M. L.; Haile, J; Houston, J; Murray, D. C.; White, N. E.; Moolhuijzen, P; Bellgard, M. I.; Bunce, M (2012). "Deep Sequencing of Plant and Animal DNA Contained within Traditional Chinese Medicines Reveals Legality Issues and Health Safety Concerns". PLoS Genetics. 8 (4): e1002657. doi:10.1371/journal.pgen.1002657. PMC 3325194. PMID 22511890.
Low-fat diets also can help you lose weight.16 But the amount of weight lost is usually small. You can lose weight and lower your risk for heart disease and stroke if you follow an overall healthy pattern of eating that includes more fruits, vegetables, whole grains and beans that are high in fiber, nuts, low-fat dairy and fish, in addition to staying away from trans fat and saturated fat.
The average woman should get 10 to 35 percent of her daily calories from protein. Protein helps prevent muscle tissue from breaking down and repairs body tissues. Sources of animal proteins include meat, fish, poultry, eggs, milk and cheese. Vegetable proteins include dried beans and peas, peanut butter, nuts, bread and cereal. (A three-ounce serving of cooked chicken contains about 21 grams of protein.)
Try the “Outer Ring” technique while buying food. Author James Clear suggests using this smart strategy while grocery shopping. “Only shop on the outer perimeter of the store. This is usually where the healthy food lives: fruits, vegetables, lean meats, fish, eggs, and nuts. If you only shop on the outer ring, then you’re more likely to buy healthy foods,” he explains.
Something else to remember: an estimated 90 to 95 percent of dieters who lose weight regain all or part of it within five years, and the consequences can be even worse than simply being overweight. Those who exercise regularly as part of a weight loss diet and maintenance program are more likely to keep the weight off. Also note that an overly restrictive diet can lead to more overeating, a natural reaction to food deprivation.
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.
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.
Research has found that certain foods are protective against cancer, while others are associated with higher cancer risk. Fruits and vegetables might be among those that reduce risk, while processed meats and fast food are among those to avoid. In addition, maintaining a healthy weight and getting regular physical activity might help a person avoid cancer. (Locked) More »
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.
The FDA does not have authority over dietary supplements in the same way it does prescription medicines. The Federal Government does not regularly test what is in dietary supplements, and companies are not required to share information on the safety of a dietary supplement with the FDA before they sell it. The companies are responsible for making sure the supplement is safe, but the FDA does not evaluate the safety of the product before the supplement is sold. So, just because you see a dietary supplement on a store shelf does not mean it is safe, that it does what the label says it will, or that it contains what the label says it contains.
The European Union's (EU) Food Supplements Directive of 2002 requires that supplements be demonstrated to be safe, both in dosages and in purity. Only those supplements that have been proven to be safe may be sold in the EU without prescription. As a category of food, food supplements cannot be labeled with drug claims but can bear health claims and nutrition claims.
Eat a balance of carbohydrates, proteins and fats at each meal and choose foods rich in fiber, vitamins and minerals. A good way to do this is to fill your plate with 3–4 food groups at each meal. Eat a combination of protein-rich foods, whole grains, dairy, fruits and vegetables, and incorporate the groups you miss into other meals and snacks throughout the day. Stick to healthy portions — see our Essential Guide to Portion Sizes for tips.
Higher dosages may be given after having consulted a therapist who has measured the ratio of omega-6 to omega-3 fatty acids in relevant cell membranes (red blood cells). In most industrialized countries, many people get too much of the omega-6 fatty acids, and would therefore benefit from eating more seafood or taking supplements with omega-3 fatty acids derived from organisms low in the food chain (algae, krill). Flax seeds contain a high level of the essential omega-3 fatty acid alpha-linolenic acid, and freshly ground flaxseed meal or flax oil can be mixed with breakfast cereals or smoothies. Note that it may be advisable to limit eating farmed fish to once per week, since their fodder contains less omega-3 fatty acids than the food eaten by wild fish, and possibly also contains more contaminants.  Some researchers even warn against letting children eat too much fish because of the content of environmental toxins. [13,14]
Go nuts for nuts (and seeds). From protein and healthy fats to vitamins and minerals, these superfoods pack a serious nutritional punch. Similarly, seeds like chia, flaxseed and pumpkin seeds are nutritional powerhouses too. They are an excellent source of vitamins, antioxidants, and minerals like calcium, zinc, and magnesium. You can add them to your favorite baking recipe, sprinkle them over your cereal or simply munch on them instead of a candy bar.
The majority of adults in the United States take one or more dietary supplements either every day or occasionally. Today's dietary supplements include vitamins, minerals, herbals and botanicals, amino acids, enzymes, and many other products. Dietary supplements come in a variety of forms: traditional tablets, capsules, and powders, as well as drinks and energy bars. Popular supplements include vitamins D and E; minerals like calcium and iron; herbs such as echinacea and garlic; and specialty products like glucosamine, probiotics, and fish oils.
In addition to diet, exercise and other lifestyle factors can also play an important role in bone health. Smoking and drinking too much alcohol can increase your chances of developing osteoporosis, while weight-bearing exercise (such as walking, dancing, yoga, or lifting weights) can lower your risk. Strength or resistance training—using machines, free weights, elastic bands, or your own body weight—can be especially effective in helping to prevent loss of bone mass as you age.