Q: How important is organic food to my overall health?

A: The Environmental Working Group released a study that identified 232 chemicals in the cord blood of babies, which showed that even before we're born, we're bombarded with toxins from our environment. Buying organic is a key way to reduce exposure to pollutants. 

Organic fruits and vegetables are grown without pesticides, which are poisons designed to keep pests away from produce. At low levels, some have no proven dangerous effects on humans, but there aren't studies on the lifelong cumulative effect of exposure. When choosing to buy organic focus on most vegetables, and thin-skinned fruits like apples, cherries, and berries (the thicker the skin the less pesticides inside). Wash any non-organic produce you buy in a citrus-based fruit and vegetable wash, which helps to lift pesticides from the skin. 

When you're shopping for meat, also consider organic. In non-organic poultry, cattle, and fish farms, chemical additives are used heavily -- including growth hormones, antibiotics, and grains grown with pesticides -- which are then passed on to you when you eat them. In contrast, organic animals eat whole foods and consequently, cattle and pigs that forage have higher omega-3 health fats.

Q: Do I need to take a vitamin D supplement?

A: It's likely -- 70 to 75 percent of women are deficient in vitamin D. To know for sure, request a simple blood test (called 25-hydroxy-vitamin D) from your doctor; your levels should be between 40 and 100. Vitamin D is critical: Its deficiency is linked to osteoporosis, low immunity, and coronary artery disease. It's also an important nutrient in the prevention of several cancers (including breast and prostate).

So many people are deficient because the only way that our bodies can produce vitamin D is by exposure to the sun. But if you live north of the 35th parallel (which runs from southern California through North Carolina), the sun's rays are not strong enough during the winter months for vitamin D production, and even below that latitude, it takes much longer in the winter to get the amount you need. During the summer, we necessarily wear sunscreen to prevent skin cancer, but this also prohibits vitamin D production.

For people who are deficient, I start them off at 2,000 units a day, and often two days of the week I give them 20,000 units. Once they're back up to the optimal range, I recommend a minimum daily supplement of 1,000 units, which is the equivalent of 10 to 15 minutes of exposure to strong sunlight.

Note: People with calcium and kidney stone problems need to be taking extra vitamin D, and it's always important to clear any new supplement with your doctor before taking it.

Q: I eat a lot of canned beans. How worried should I be about BPA in the lining of food cans?

A: The FDA has now recognized that BPA (or bisphenol A, a chemical commonly found in plastics) in the food supply is a potential health hazard, but there's no regulatory structure set up to enforce a ban. Canned food is one of the many places (along with some baby bottles, water bottles, and reusable plastic containers) that you find BPA.

My recommendation is to strictly limit canned foods for children, whose developing bodies are most susceptible to the hazards of BPA. For adults, try to reduce your consumption to one or two cans per week, and when possible, rinse off food. To avoid cans, consider buying uncooked beans and preparing them in a pressure cooker.

Woodson Merrell, M.D., is Chairman of the Department of Integrative Medicine, Beth Israel Medical Center, and coauthor of "Power Up: Unleash Your Natural Energy, Power Up Your Health, and Feel 10 Years Younger."

Do you have a medical concern or a question about leading a healthy and active lifestyle? Email drmerrell@bodyandsoulmag.com and your question may be answered online or in a future issue of Body+Soul. Please include your first and last name, city, and state.

Check back every month for new advice from Dr. Merrell.