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. 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. 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. Weight loss supplements have also had adverse psychiatric effects.
Calcium may even be harmful for men, at least in large amounts. The worry is prostate cancer, and two Harvard studies have raised the alarm. In 1998, the Health Professionals Follow-up Study found that a high consumption of calcium from food or supplements was linked to an increased risk of advanced prostate cancer. The risk was greatest in men who got more than 2,000 mg a day. More recently, the U.S. Physicians' Health Study reported that a high consumption of calcium from dairy products appeared to increase a man's risk of prostate cancer by up to 37%. A study from the Fred Hutchinson Cancer Research Center in Seattle also found a link between calcium and advanced prostate cancer.
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. 
Calories. Most times, women need fewer calories. That’s because women naturally have less muscle, more body fat, and are usually smaller. On average, adult women need between 1,600 and 2,400 calories a day. Women who are more physically active may need more calories. Find out how many calories you need each day, based on your age, height, weight, and activity level.
Eat healthy fats. According to the American Heart Association, women should get at least five to 10 percent of total daily calories from omega-6 fatty acids (equal to 12 to 20 grams), and between 0.5 and 3 grams of omega-3 fatty acids, depending on individual risk for heart disease. Good sources of omega-6 fatty acids include sunflower, safflower, corn, cottonseed and soybean oils. And good sources of omega-3 fatty acids include fatty fish, tofu and other forms of soybeans, canola, walnuts, flaxseed, and their oils. Talk with your health care professional about how much of these beneficial oils you should be getting, how you can best incorporate them into your diet and whether or not you should be taking them in supplement form.
Purchasing organic local produce is better for both the environment and your health, but when the nearest farm is hours away, don't default to a package of Oreos. "Frozen, canned and fresh fruit all have comparable amounts of nutrients," says Christine M. Bruhm, Ph.D., director of the Center for Consumer Research at the University of California at Davis.
As the science of nutrition continually evolves, researchers recognize that nutrients needed to maintain a healthy lifestyle must be tailored to the individual for maximum effectiveness. Recognizing that people are not all alike and that one size does not fit all when it comes to planning and achieving a healthful diet, the Institute of Medicine's dietary guidelines, titled "Dietary Reference Intakes for Macronutrients," stress the importance of balancing diet with exercise and recommends total calories based on an individual's height, weight and gender for each of four different levels of physical activity.
It is possible to ingest too much of certain vitamins and minerals (vitamin A, calcium, iron, copper, selenium) which may exacerbate an existing imbalance or lack of another mineral (magnesium, zinc). It is also important to balance intake of fatty acids in the omega-6 and omega-3 series, as most people get too much omega-6 and not enough omega-3. Small children can be overdosed with adult doses of for example vitamin A or iron, and pills may be dangerous for babies or young children because they can get stuck in the throat. Therefore, I recommend consulting a doctor or nutritionist educated in orthomolecular medicine. Most people are likely to benefit from taking a broad-spectrum multivitamin/mineral supplement as a basic insurance against deficiencies.
According to the American Heart Association, it's better to eat more complex carbohydrates (vegetables, fruits and whole grains) than simple carbohydrates found in sugars. Complex carbohydrates add more fiber, vitamins and minerals to the diet than foods high in refined sugars and flour. Foods high in complex carbohydrates are usually low in calories, saturated fat and cholesterol.
During adolescence and early adulthood, women need to consume foods rich in calcium to build peak (maximum) bone mass. This will reduce the risk of developing osteoporosis, a progressive condition where there is a loss of bone that leaves those affected more susceptible to fractures. Women also need an adequate iron intake because they lose iron through menstruation. Women also need an adequate intake of calories to support energy and nutritional needs in order for the body to function properly. The amount of calories that an individual needs varies for each person and is based on age, gender and activity level. As a general recommendation, women between 23 and 50 years of age generally need between 1,700 and 2,200 calories per day to maintain their current energy needs and body weight. Older women generally require fewer calories to support and sustain energy needs. Consuming fewer than 1,500 calories per day, even in attempts to lose weight, can put women at nutritional risk and can result in malnutrition and poor health. For more information on how to calculate one’s nutritional needs, go to www.choosemyplate.gov and insert your personal information. The 2005 Dietary Guidelines for Americans is another reference or guide to assist you in learning to eat a balanced and nutritious diet for good health.
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.