By Karen Collins, RD, MS, CDN
American Institute for Cancer Research

Q: Can you get enough vitamin A from milk, cereal and other sources without eating vegetables?

A: Although you could obtain adequate amounts of vitamin A solely from animal sources, you would miss out on important antioxidant properties provided by beta-carotene-rich vegetables and fruits.

Vitamin A, most notable for its role in immune function, eye and skin health, is an essential nutrient. There are three major dietary sources of vitamin A:

• Animal foods, such as milk, cheese, eggs and liver;

• Plant sources, like dark green and orange vegetables, which supply the nutrient as its precursor beta carotene.

• Fortified grains and cereals.

Antioxidants protect our cells from highly reactive “free radicals” that could otherwise damage cells and lead to cancer, heart disease and other health problems.

In addition, people who don’t eat enough vegetables and fruits are likely to be low in other vitamins and minerals, including folate and potassium, and disease-fighting phytochemicals that occur naturally in plant foods. Emerging laboratory science suggests that phytochemicals may block several steps in the cancer development process.

Regardless of the non-plant-based sources of vitamin A in your diet, aim for at least five servings of a variety of vegetables and fruits every day to obtain a wide range of health benefits.

Q: My grocery store is now carrying more and more gluten-free foods. Are they healthier than others?

A: Gluten-free food products are intended for use by consumers who suffer from celiac disease, a condition that triggers an autoimmune response to the protein gluten. Gluten is a natural component of grains like wheat, rye and barley, and many food companies also add gluten protein as a thickening agent to processed foods like soups and salad dressings.

Exposure to even trace amounts of gluten is dangerous for people with celiac disease, resulting in damage to the digestive tract and causing both immediate symptoms and long-term health risks.

Although the increased availability of gluten-free foods is wonderful for people diagnosed with celiac disease, if you don’t have the disease, there’s no reason to spend additional money on gluten-free products as they offer no advantage to the average consumer.

If you think you may have a digestive problem related to wheat or gluten, see your doctor before you try a gluten-free diet. Your doctor can order a blood test to check for gluten sensitivity, but if you’ve already omitted gluten from your diet, the test won’t tell you anything.

Q: Is it true that celery supplies “negative calories?”

A: The whole concept of negative calories—that a food supplies fewer calories than you burn chewing and digesting it—is illogical as a weight control strategy, whether you’re talking about celery or any other food.

In theory, the concept is true: two stalks of celery, which are roughly 12 calories, will require approximately 13 calories worth of energy to chew, digest, absorb and metabolize the food. Although you could technically say that eating celery burns more calories than it contains, that one-calorie difference is very approximate.

More importantly, a deficit of one, even 10, calories, is completely insignificant when looking at total energy requirements.

To put things in perspective, consider that you need to burn roughly 3500 calories more than you take in each week to lose just one pound of body fat. Banking a handful of negative calories from foods like celery will have no impact on the (or your) bottom line.

On the other hand, substituting low-energy-dense vegetables and fruits, like celery, for other high-calorie foods will affect total energy intake; this is the primary role such foods play in weight control.

Karen Collins is a nationally known dietitian and nutrition expert whose work appears on Nubella News, MSNBC.com and other major Web sites. She is nutrition advisor with the American Institute for Cancer Research.