What you eat is even more important as you enter your 40s. Women need protein (meat, fish, dairy, beans, and nuts), carbohydrates (whole grains), fats (healthy oils), vitamins, minerals, and water. These foods have been linked to some disease prevention, such as osteoporosis, high blood pressure, heart disease, diabetes, and certain cancers. The American Academy of Family Physicians supports the development of healthy food supply chains in supplemental nutrition programs so as to broaden the availability of healthy food.
Good sources of iron include liver, kidneys, red meat, poultry, eggs, peas, legumes, dried fruits and dark, green leafy vegetables. Three ounces of cooked chicken liver contains 7.2 mg of iron; a cup of cooked spinach contains 6.4 mg. Your health care professional will probably recommend iron supplements during pregnancy (probably starting at 30 mg per day).
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.
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 need for efficient detoxification and excretion is greatly increased by environmental pollution from the chemical industry, herbicides and pesticides used by industrial agriculture, antibiotic treatment of animals, transport, and plastic packaging.  In our polluted world, the increased toxic load may be compensated for by an increase in nutrients to promote detoxification. One can respond by taking large doses of supplements of essential nutrients, for example, antioxidants vitamin C and E, and an adequate dose of selenium, which help the body detoxify harmful chemicals. Also helpful is regularly taking sauna baths, fasting periodically, and eating an excellent diet that includes generous portions of dark green leafy vegetables and colorful vegetables and fruits. 
2. Eat a variety of foods. As we covered earlier, the brain craves novelty. While you may not be able to replicate the crunchy/creamy contrast of an Oreo, you can vary your diet enough to keep things interesting. For example, you could dip a carrot (crunchy) in some hummus (creamy) and get a novel sensation. Similarly, finding ways to add new spices and flavors to your dishes can make eating healthy foods a more desirable experience.
Don't take dramatic steps alone. You need to work closely with an experienced health care professional to lose weight, particularly if you have other medical problems, plan to lose more than 15 to 20 pounds or take medication on a regular basis. An initial checkup can identify conditions that might be affected by dieting and weight loss. Make sure you find out how much experience your health care professional has dealing with nutrition. It's not always well covered in medical schools. You may want to talk to a registered dietitian before embarking on a diet.
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.
One exception, he says, is seniors, who may need additional B-12 because as we get older, we absorb less of it. Most of us should skip the supplements and get our Bs from grains, dark green vegetables, orange juice, and enriched foods. People with certain medical conditions or who take drugs that interfere with vitamin absorption may also require supplementation.
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.
Nutritional supplements are exactly that, supplements to a healthy, nutritious diet. One should not take nutritional supplements in the hope that they will make up for a poor diet and lack of exercise, they will not! There are some nutritional supplements including some vitamins and minerals, as well as other nutrients/cofactors that one can use in conjunction with a healthy diet to promote optimal health. For example, to consume the amount of vitamin E that has been shown to protect the body against free radical damage, one would have to consume a very significant amount of fat calories as vitamin E is found in foods that are high in fat such as vegetable oils, nuts and seeds. it makes sense to take a supplement of vitamin E rather than consuming lots of fat. The same goes for vitamin D. It's very difficult to get vitamin D in your diet as it isn't found in many foods and studies show that most people do not get enough vitamin D.
In 1994, the United States Congress passed a law defining nutritional supplements, and requiring them to be labeled as dietary supplements and identified as not intended to be a substitute for certain foods. A nutritional supplement can be defined as a product intended for consumption in tablet, capsule, powder, soft gel, gel cap, or liquid form, and containing vitamin(s), mineral(s), herb(s), other botanicals, amino acids, or any combination thereof.
Brimming with vitamins! Bursting with energy! Store shelves are exploding with colorful, cleverly named drinks that sound healthy but are actually just sweetened water. Don't let the labels fool you, Berman says. If it's not plain H2O or regular coffee or tea, it's a treat. For a healthier sip, try lemon or mint iced tea or sparkling water with a splash of juice.
Substances which the FDA regulates as food are subdivided into various categories, including foods, food additives, added substances (man-made substances which are not intentionally introduced into food, but nevertheless end up in it), and dietary supplements. The specific standards which the FDA exercises differ from one category to the next. Furthermore, the FDA has been granted a variety of means by which it can address violations of the standards for a given category of substances.