Most of us are lucky enough to have access to food that meets our general daily vitamin and mineral requirements.

But things get more complicated if, for example, you're a vegetarian, pregnant, or lactose or gluten intolerant. There are a number of situations in which, even given the abundance of choices the United States, vitamin supplements can be crucial to peak health.

Harvard University

When I walk into a pharmacy and face a whole wall of vitamins and supplements, it can make me want to turn around, buy a pack of gum, and run out of the store otherwise empty handed. The average physician isn't that much more help, robotically intoning, "If you are worried, take a multivitamin," or "You might want to start taking calcium." Given the dizzying range of costs and dosages, this kind of advice leads to more questions than answers. It can feel like your only choice is to just close your eyes, point to a random bottle, and hope you don't end up throwing your money away if the supplement you chose isn't effective—or worse, if it contains contaminants like heavy metals.

Like many mothers, I didn't get serious about my research until I decided my own kid might need a boost of supplemental vitamins and minerals. She's still growing, an athlete, and over the past couple of years has gone from shunning red meat, to being a pescatarian, to eating a plant-based diet with the occasional egg but (no dairy). Her diet and lifestyle combo seemed like a vitamin and mineral deficit waiting to happen.

General Guidelines

If it seems like the recommendations about which vitamins to take are always changing, it's because they are. One year vitamin C is all the rage, the next we should all be taking vitamin E, and then we're told it's better to avoid supplements all together.

Getting good study results is a challenge, in part because control groups can skew results. For example, people who take supplements tend to be wealthier and more active—is it the vitamin or is the money and the exercise that's promoting health? Another issue is that studies might not continue long enough to measure rates of chronic disease, such as cancer, that can develop over years.

However, Dr. Walter Willett, a professor at the Harvard T.H. Chan School of Public Health, says it's not a bad idea to take a daily multivitamin "for insurance." What experts do agree on is that you don't want to megadose on vitamins and minerals. Some, like vitamin C, are simply excreted when you take more than you need, but others, such as too much beta carotene (from vitamin A) have been shown to actually increase cancer rates.

An excellent source of information on all forms of supplements and foods with popularly touted health benefits (such as olive oil, dark chocolate, and apple cider vinegar) is the subscription website ConsumerLab, an independent organization that tests and rates products based on purity, efficacy, and value. We analyzed their data to provide the most up to date recommendations.

Adult multivitamin: If you are looking for the "insurance" suggested by Dr Willett, Kirkland's Daily Multi has you covered with the recommended daily allowance for most vitamins and minerals without risky megadoses, for only three cents a pill. For those of you who like gummy vitamins, I'm sorry to be the bearer of bad news but gummies tested the least reliably of all forms of vitamin and mineral supplements, often containing "far too much or two little of listed ingredients."

Women's multivitamin: Target's Up and Up Women's Daily Multivitamin provides extra iron and calcium for an affordable price.

Prenatal multivitamin: Pregnant woman want to look for a supplement that contains 400 mcg of folate, a B vitamin, which prevents certain birth defects. A regular multivitamin can do the trick for a lower cost than special prenatal brands, but check with your OB/GYN or midwife. According to the Mayo Clinic, Omega-3's are also beneficial for brain development. 21st Century Fish Oil lozenges are relatively inexpensive and coated to prevent the dreaded "fish burp."

Calcium: What most people don't know is that you can't absorb more than 500 mg of calcium at one time, so don't bother with larger doses. GNC Calcium Citrate is a good choice that is taken twice a day for a total of the recommended 1000 mgs (some doctors say 500-700 mg total is adequate).

Organic Facts

Vitamin D: The body produces its own vitamin D when your skin is exposed to sunlight, but most people in the Northern Hemisphere don't get enough sun exposure during winter months. You may have heard it's healthy to take high doses of vitamin D—don't buy it. There are studies that show excess vitamin D can lead to more stress fractures and weakened leg muscles. If you aren't taking a multivitamin look for a source that contains 800-1000 IUs in a daily dose. Inexpensive sources that have been tested for purity and absorption rate are Thorne Naturals Vitamin D drops and GNC D3.

Vegetarians and Vegans: If you are a vegetarian and regularly eat eggs and dairy as well as a varied diet of whole foods, you probably don't need a supplement at all as long as your doctor hasn't identified deficiencies during your annual physical or through blood tests.

Vegetarians with a more limited diet and people who don't consume any animal products at all are probably good candidates for supplements—especially if they have athletic lifestyles. You should consider taking calcium, magnesium, B vitamins, vitamin K, and Omega 3s. Jarrow Bone-Up up contains a calcium, magnesium, vitamin K, and vitamin D and you can take two tablets a day instead of three and save money because it contains high doses of its active ingredients. Kirkland Signature Super B-complex covers those essentials vitamins without mega-dosing. Source Naturals has a fish-free Omega-3 supplement made from algae. If you are eating lots of fruits, veggies, beans, and grains you don't need to take a multi on top of these supplements.

For vegans and others taking more than one product, compare the labels to make sure you aren't double dosing.

While taking a supplement may be appropriate for some, it's important to remember that, in most cases, the ideal way to get your body what it needs is through food. Unlike a pill, whole foods contain fiber, micronutrients, and antioxidants—and they are delicious, satisfying, and a central part of a balanced life. As the saying goes,"eat your vitamins."