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Dear Dr. Roach: I have been reading a lot about the cardiovascular and general health benefits of supplemental vitamin C and lysine given that human beings are the only animal that does not produce vitamin C. I also read that otherwise healthy adults should be taking 4,000 milligrams of vitamin C and 2,400 milligrams of lysine, with adults suffering from cardiovascular disease taking up to 6,000 milligrams of vitamin C daily. What do you think about this?

B.S.

Dear B.S.: I disagree with the sources you have been reading. Humans and primates do need dietary vitamin C, but so do some birds, fruit bats, guinea pigs, coho salmon and other species, which also are unable to make it. More importantly, large trials — such as the Physician’s Health Study II, which randomly assigned nearly 15,000 men to vitamin C versus placebo — found no significant difference in heart disease, cancer or death rates. Foods high in vitamin C, including many fruits and vegetables, help reduce heart disease risk, but supplements have not been proven to do so.

Lysine (along with arginine, another amino acid) reduced anxiety levels in one study, but there is no good evidence that it reduces heart disease risk.

When reading medical sources, be sure to look for any potential conflicts of interest. Some of the online sources I found on this subject were selling the very same supplements they were recommending. It’s also important to look for current evidence; some cited studies from the 1950s.

Dear Dr. Roach: You recently discussed monoclonal gammopathy in relation to multiple myeloma. “IgA,” “IgG” and “IgM” are terms medical professionals use as if they were common abbreviations.

I was diagnosed with kidney failure in 2015 (my GFR is 7) caused by “IgM nephropathy.” Otherwise, I am perfectly healthy. As good as my nephrologist is, I don’t understand the cause of my kidney failure. Please explain in layman’s terms “IgA,” “IgG” and “IgM,” and how they affect the body. How can the apparently same condition cause cancer of the plasma cells and kidney failure?

G.D.L.

Dear G.D.L.: Immunoglobulins, also called antibodies, are one of the two pillars of the immune system (the other is T-cells). There are five families of immunoglobulins: IgA, IgG, IgM, IgE and IgD. They all have different functions in health.

Seventy-five percent of the immunoglobulins we have are IgG, which is the type that usually provides long-lasting immunity. IgM is the first antibody produced in a new infection, so IgM in the blood usually indicates acute infection. IgA is found in secretions, like breast milk. IgD is a regulator, and IgE is important in allergic reactions. Immunoglobulins are made by plasma cells, which are found mostly in the bone marrow.

In disease, immunoglobulins are part of the mechanism through which the body attacks itself. IgM nephropathy is a variant of a disease called “minimal change disease,” an autoimmune disease of the kidney. IgM nephropathy is a cause of nephrotic syndrome, which involves the loss of large amounts of protein from the kidney. The IgM may represent the body attacking the kidney, and it is damage to the kidney that allows protein to escape.

In multiple myeloma, the plasma cell itself is the cancer cell. A plasma cell making any kind of immunoglobulin can turn cancerous, and make variable amounts of immunoglobulin, which can be found in the blood. Unfortunately, those immunoglobulins don’t help the immune system, and infections are a serious risk in people with myeloma — the plasma cells crowd out the other immune cells in the bone marrow. High amounts of IgM in myeloma also may damage the kidney.

Email questions to ToYourGoodHealth@med.cornell.edu.

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