How do you choose the right vitamin brand? Let’s back up: How do you even know which vitamins you should be taking? Holistic pharmacist Sherry Torkos has been asked these questions hundreds of times throughout her career. She’s come up with a clever response: Remember the first five letters of the alphabet.

A: Analyze why you want to take this vitamin. “Understand what to expect from taking this supplement,” says Torkos. “For example, a good-quality fish oilsupplement may help to lower your triglyceride levels, but will have no impact on your HDL cholesterol.”

B: Beware of interactions and side effects. “Some vitamins, such as vitamin K, may not be recommended if you are also taking a blood-thinning medication. St. John’s wort may reduce the effectiveness of anti-depressants and birth control pills.”

1. Vitamin A

This is best known for its importance for vision, skin health, and immune function. Prescription vitamin A derivatives are used to treat acne, wrinkles, and other skin conditions. Dosages greater than 5000 IU may increase the risk of osteoporosis and are not recommended for pregnant women due to risk of birth defects. “Choose a supplement that contains beta-carotene, which is converted to vitamin A in the liver but is not associated with the health risks seen with vitamin A.”

2. B-Vitamins

Important for the health of the nervous system, energy production, and many enzyme reactions in the body. The B-vitamins work in conjunction with each other to support numerous body processes. B12 absorption requires proper functioning of the stomach, pancreas, and intestines, and a deficiency is common especially among the elderly, those with poor diets, vegetarians, and those with digestive problems such as Crohn’s, colitis, IBS, and celiac disease. “If you’re over 50, or have low stomach acid or digestive disease, look for sublingual forms of vitamin B12, which are absorbed under the tongue directly into the circulation.

3. Vitamin C

Popularly known as the vitamin for immune support, vitamin C is also important for skin health (synthesis of collagen), wound healing, and gum health. Many drugs, such as birth control pills and aspirin, can deplete vitamin C, as can stress and smoking. “If you have a sensitive stomach, look for a buffered vitamin C, such as calcium ascorbate. This form is less acidic, and less likely to cause upset stomach.

4. Vitamin D

Once thought of as primarily important for bone health, the use of vitamin D for other health conditions is greatly expanding. Recent research has found that vitamin D plays a key role in immune function, cancer prevention, regulating blood pressure, and it may help to prevent autoimmune diseases such as multiple sclerosis. Supplements are particularly important for those without adequate sun exposure, those with dark skin, the elderly, and those with celiac disease and liver disease. “Look for a supplement that provides vitamin D3 (not D2). The Institute of Medicine recommends 600 IU for those ages one through 70, and 800 IU for those older than 70.”

5. Vitamin E

Long touted for its heart health and skin health benefits, research on some forms of vitamin E is yielding exciting results. Most people think of vitamin E as a single nutrient but there are actually eight different forms of vitamin E: four tocopherols and four tocotrienols. Tocopherols and tocotrienols have entirely different health benefits. Recent research has found that certain tocotrienols may possibly limit the neurological damage if you have a stroke. Tocotrienols are also good for the heart. Look for tocotrienol supplements derived from Malaysian palm fruit oil, which is non-GMO. Palm fruit oil has a neutral effect on cholesterol, and red palm fruit cooking oil can tolerate high-heat cooking better than olive oil.