DEAR DR. BLONZ: At times during the previous year, I took St. John’s wort for periodic bouts of mild depression. I have had little success with the prescription antidepressants I have tried. Does the fact that I have not had any problems with my St. John’s wort indicate that I can continue taking it? -- S.C., Tulsa, Oklahoma

DEAR S.C.: We all need to appreciate that the human body has sophisticated systems designed to protect it from potential dangers posed by unfamiliar substances. These systems try to detoxify, break down or eliminate “foreign” compounds that enter the body. Foreign compounds can include everything from herbal products and prescription or over-the-counter (OTC) drugs to pesticides and environmental pollutants. It doesn’t matter that some of these might be thought of as beneficial; foreign compounds get identified as such, and processed for elimination.

The complexity starts because there can be multiple compounds processed at any given time. This gives rise to interactions between medications and herbs that can affect the way they work and the rate they get eliminated from the body. Our liver is the focus of this process. The method typically involves a reaction with the substance that’s tantamount to putting metabolic handcuffs on it, preventing it from being active while it’s in queue for elimination.

A specific family of enzymes plays a key role in metabolizing, or breaking down, unknown substances. Compounds broken down via this enzymatic system include herbs; drugs used to treat heart disease, HIV infections, seizures, depression and cancer; drugs used to prevent the rejection of transplanted organs; and oral contraceptives. Different substances can either compete with each other for enzyme attention -- resulting in slower decreases in their respective blood levels -- or they can stimulate the enzymes, which results in a more rapid decline. This is significant for health conditions where reliable medication blood levels are a key part of the treatment.

St. John’s wort is metabolized by this enzyme system, and it acts as a stimulant. That means that if St. John’s wort is being taken, the blood levels of other drugs can be lower than expected -- lower, even, than needed to achieve that drug’s therapeutic effect.

I don’t know if you are taking other medications or substances, but this is definitely a discussion you should have with your physician or pharmacist without delay.

Before prescription drugs are approved by the Food and Drug Administration, they have to undergo rigorous testing for safety and efficacy. Tests are also done to determine how a drug works, the effective dose, any potential side effects or adverse reactions, how long the drug lasts, and how it is eventually eliminated from the body. All this helps to provide the information used by health professionals when dispensing the drugs. For OTC drugs, this info is available for you either on the package or in the package insert.

Herbs have been in use for centuries, and some may have health-boosting potential. Our knowledge, however, about side effects and interactions with other medications -- even with other herbs -- is still in its infancy. That is one of the reasons why people should approach the use of herbs with caution, especially when also using other medications. There are websites providing interaction information, including drugs.com and rxlist.com, but these should not be considered a substitute for that talk with your health professional.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I have been a vegetarian for about 10 years. Lately I have been having problems with muscle discomfort in my shoulder, and some people have been telling me that it might not be healing correctly because I do not eat red meat. I don’t buy this at all, but was wondering: Is there anything I should supplement my diet with, since I no longer eat red meat? -- K., San Diego

DEAR K.: A plant-based, whole-foods diet is the way to go, and good nutrition is good nutrition, whether or not there’s ever meat on the plate. You did not mention whether you consume other animal products, but if you eat vegetarian, there are some nutrients you should be mindful of. These include vitamin B12, calcium, iron, zinc and vitamin D.

In most cases, getting adequate protein doesn’t represent any problem for vegetarians. Amino acids are the building blocks of protein, and of the 22 different amino acids, our body can manufacture all but nine. These nine, referred to as the essential amino acids (EAAs), need to be supplied by our diet. Most foods contain some amino acids. Animal proteins, such as meat, poultry, fish, eggs and dairy are considered “complete” proteins because they contain all the EAAs.

Except for soybeans, vegetable proteins such as grains and legumes are incomplete proteins because they lack one or more of the EAAs. Vegetarians easily meet their daily protein requirement by combining different foods so that sufficient amounts of all the EAAs are consumed over the course of the day.

Vitamin B12 is needed for red blood cells and nerve tissue, and it is only found in bacteria and animal foods. Vegetarians can use specially fermented soy products, such as tempeh or miso, as a dietary source for B12, or rely on foods fortified with it.

If you consume dairy products, there shouldn’t be a problem getting enough calcium. If not, you will have to rely on calcium-rich foods such as broccoli, dark green leafy vegetables (such as kale and turnip greens), calcium-set tofu, almonds, figs and some legumes. There is also the growing variety of calcium-fortified non-dairy milks, and fortified orange juice.

Red meat is an excellent source of iron, but it is also found in dark green leafy vegetables, legumes, raisins and prunes. Iron absorption is facilitated by acidic foods, such as citrus juices. Zinc, which can also be in short supply for vegetarians, can be found in nuts, seeds, whole grains and legumes.

Vitamin D, needed for calcium absorption and bone formation, is another nutrient that’s not widely available in vegetarian cuisine. Besides food sources such as fish and fortified milk products, the body produces this nutrient upon exposure to direct sunlight. An alternative is to rely on a supplement.

Back to your question about that muscle problem that is not healing: Your physician or health professional may have done routine blood work, and this can help verify if there are indications of a nutritional deficiency. You might also consider getting a referral to a physical therapist, who might help with specific strategies and exercises to help strengthen the affected muscle and get that discomfort into the history books.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: Our reading group was discussing milk, and one of the long-standing members argued that milk, especially homogenized milk, is a bad and even dangerous food for seniors. How can this be? I remember it being called “nature’s most perfect food.” I was hoping you could explain if things have changed, and whether milk is a food to avoid. -- L.I., San Jose, California

DEAR L.I.: One valid reason to avoid milk and milk products would be if you had been tested and found to be allergic to milk protein. Another motivation might be lactose intolerance: a dislike of side effects experienced due to an inability to digest the lactose carbohydrate that milk typically contains. Common lactose intolerance produces intestinal gas or other digestive upset. Some don’t experience symptoms unless milk is consumed on an empty stomach, or if more than a certain volume is involved. Many with lactose intolerance have no problems with yogurt and cheese.

Concerns about homogenization often come from a paper that suggested that an enzyme naturally present in milk (xanthine oxidase) might contribute to the risk of inflammation and several chronic ailments. It was nothing more than a hypothesis, but it was adopted by what became an “anti-milk” crowd. The human body produces its own xanthine oxidase, and it is associated with inflammation, but there is no solid evidence that consuming it in milk has negative health effects. It’s helpful to remember that proteins -- and enzymes are proteins -- are disassembled during digestion, before absorption.

There is now a growing variety of nondairy milk, and new twists on the dairy version. Lactose-free milk products represent an option for those with the intolerance issue, and some milk products are now offered that contain a slightly different protein. The protein in milk is beta casein, and cows can produce two versions: A1 and A2. Most cows’ milk contains a mix, but there are now milk and dairy products from cows that only make A2. The argument is that negative health effects and discomfort from milk might be related to the A1 protein specifically, not lactose. This is an emerging theory, and the evidence is far from solid. Those who have a milk protein allergy, of course, should avoid either kind.

Assuming you are not eating vegan, and absent an allergy or intolerance to one or more of its components, there are few health reasons to avoid milk. I wouldn’t call milk “nature’s most perfect food,” and it’s certainly not “essential,” but it does have much to offer nutritionally. There are many spreading twists on the “milk is bad” message, but the negative allegations, thus far, have failed to stand up to the light of science. For more on milk, check out b.link/milk27.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.