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.
The transition from an existence as hunter and gatherers to urban agriculture around 10,000 years ago began an epoch when foods were mass-produced but had lower nutritional density, compared with the previous food eaten by our ancestors. The nutritional density in many foods has fallen significantly since human societies transformed from hunter-gatherers into resident farmers. This is especially true in the last 60-70 years after agriculture was changed from small, versatile ecologically driven family farms to large, chemical-based, industrial agriculture.  The reduction of nutritional content in modern crops, compared with older varieties, is well documented.  It is a consequence of soil erosion, loss of essential minerals from continual heavy use, combined with breeding of new varieties, which has increased the size and growth rate of plants by increasing the content of sugar and water and decreasing their mineral content compared to ancient species. At the same time, the relative content of other macronutrients (fat, protein/amino acids) and antioxidants may have been reduced.
For instance, foods rich in vitamin E and beta-carotene are healthy and can help reduce cancer risk. However, the U.S. Preventive Services Task Force (USPSTF) and the American Academy of Family Physicians (AAFP) recommend against taking vitamin E or beta-carotene for the prevention of cardiovascular disease. People who smoke or are at risk for lung cancer also should avoid beta-carotene. It can increase their risk of lung cancer.