October 2011

Better nutrition boosts diabetic foot outcomes

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The evidence documenting the role of nutrition in improving wound healing and neuropathy symptoms hasn’t been widely publicized, particularly among lower extremity healthcare practitioners. But getting that information to your diabetic patients could help save their feet.

By Larry Hand          

Practitioners who care for diabetic patients with neuropathy and an elevated risk of foot ulcers tend to agree on one thing: there is no one-treatment-fits-all solution. It takes a team of specialists working together, assessing patients one by one, to arrive at an effective treatment plan. And what lower extremity practitioners may not realize is that nutrition is a key part of that multidisciplinary equation.

“What we don’t do well in medicine is evaluate nutritional status,” said David Armstrong, DPM, MD, PhD, professor of surgery and director of the Southern Arizona Limb Salvage Alliance at the University of Arizona in Tucson. “It is to our patients’ detriment that we don’t focus on this. If we ignore our feet, they’re going to go away. And by ignoring our nutrition, maybe we’re ignoring our feet. Whether we’ve taken it seriously in medical or nursing school, I think it’s important that we focus on it as we practice and in the research we do.”

For patients with diabetes, evaluating nutritional status starts with evaluating blood glucose levels, which can affect both peripheral neuropathy and wound healing. But even blood sugar management requires more than a cookie-cutter approach, according to Wanda Howell, PhD, RD, university distinguished professor of nutrition science at the University of Arizona.

“The emphasis for everybody on a team is to work with people, and follow up over the course of their management of diabetes to try to bring blood sugar within a reasonable range,” Howell said. “Notice I did not use ‘normal’ range, because for some people it turns out that the peaks and valleys of blood sugar become far more dangerous relative to the microvascular neuropathy damage that can be done. So you truly do have to work with each patient individually, so each maintains a relatively narrow range of blood sugar levels, even if the levels are a little high.”

Previous research has found some evidence supporting the use of vitamin supplements in the management of diabetic peripheral neuropathy and neuropathic pain (see “Nutritional management of diabetic neuropathy”). More recent research provides additional clues as to how nutrition can help improve neuropathic symptoms and heal wounds.

Neuropathy symptoms and vitamin D

In a study published in the July issue of Diabetes Medicine, researchers at the Medical University of South Carolina in Charleston concluded that vitamin D insufficiency is associated with peripheral neuropathy symptoms in people with diabetes even after adjusting for confounding factors. Senior authors Vanessa Diaz, MD, MS, and Arch Mainous, PhD, said their study is apparently the first to make such a connection using a nationally representative sample of adults.

They and their coauthors analyzed data from the National Health and Nutrition Examination Survey (NHANES), 2001-2004, limiting their study population to adults 40 years and older who were diagnosed with diabetes and whose vitamin D levels were included in the NHANES database. More than 80% of the participants had vitamin D deficiency, using 30 ng/mL as the level of sufficient vitamin D serum level. Half of the participants reported experiencing paresthesia in their hands or feet within three months preceding the survey, almost 40% reported numbness or loss of feeling in their hands or feet, and 8% reported four to six insensate areas on their feet. However, the database did not distinguish between type 1 and type 2 diabetes.

“We know that adequate vitamin D levels help prevent development of diabetes and with glycemic control, which is very important for neuropathy,” Diaz said. “We recommend that practitioners check their neuropathy patients’ serum vitamin D levels to determine whether there is a deficiency. We’ve looked at data around our own clinic, and 80 to 90 percent of our patients are deficient in vitamin D.”

What is problematic, however, is determining the optimal way to take in vitamin D and how much supplementation is beneficial.

“We have vitamin D receptors throughout the body,” Mainous said. “The question is whether you limit intake to foods, add supplements, or get it from sunlight. If I get an extra hour of sun exposure, do I need to take less of a supplement? We really don’t know at this point.”

The current Recommended Daily Allowance (RDA) for vitamin D is 600 IU/day for children and adults up to 70 years and 800 IU/day for older individuals. However, in November 2010, the Institute of Medicine (IOM), citing public confusion over the vitamin’s benefits and the risks of overconsumption, issued an update on Dietary Reference Intakes (DRIs) that specified 2000 to 4000 IU/day for most people as the upper limit for vitamin D intake.

No direct correlation exists between serum levels of vitamin D and the intake levels of supplements, Diaz said, which is why she and her colleagues recommend using the serum level as a guide for patients on an individual basis.

“Research now needs to move more toward how supplementation works and what level of supplementation works. Now 2000 to 4000 IU seems to be adequate. However, more than 4000 IU could be risky,” she said.

More on vitamin B complex

In a study published in the winter-spring 2011 issue of Reviews in Neurological Diseases, researchers at Allen M. Jacobs and Associates in St. Louis described how nerve fiber density was affected by vitamin supplement therapy in 11 patients with diabetic peripheral neuropathy. The therapy, a combination of oral forms of vitamins L-methlylfolate (B9, 3 mg), methylcobalamin (B12, 2 mg), and pyridoxal 5’-phosphate (B6, 35 mg), has been previously associated with reductions in neuropathic pain and improvement in two-point discrimination (see “Nutritional management of diabetic neuropathy,” March, page 63).

Eleven patients with DPN and type 2 diabetes took the treatment for six months, and epidermal nerve fiber density was measured by biopsy from the calf of the leg at the beginning and end of the period. Eight of the patients showed an increase in nerve fiber density after treatment, and nine patients experienced fewer and less intense paresthesias compared to baseline.

“The key with the diabetic patient is to make sure they are adhering to their diabetic diet and controlling their diabetes. That alone will reverse neuropathy symptoms in many patients,” said Allen Jacobs, DPM, a podiatric surgeon. “I don’t know if practitioners can help patients alleviate neuropathy symptoms, other than the obvious, which is to screen patients for nutritional deficiencies.”

In the fall 2010 issue of the same journal, researchers from the Carolina Musculoskeletal Institute in Aiken, SC, described how the same dietary supplement led to statistically significant improvements in cutaneous sensation in the feet of type 2 diabetic patients with peripheral neuropathy. Twenty participants took the therapy twice daily for four weeks, then once daily for 48 more weeks. They were tested at baseline and at six-month and one-year intervals. The greatest improvement took place over the course of the year.

Despite the evidence supporting B vitamin supplementation for neuropathy symptoms, Jacobs emphasized that it represents only one aspect of patient care.

“You can’t reduce treatment to just one or two things. Effective treatment, based on each individual patient, takes at a minimum good vitamin and protein intake, good general nutrition, and sometimes pharmaceutical therapy. Patients might not always require supplementation,” Jacobs said.

‘Pay me now…’

Those sentiments were echoed by Dennis Frisch, DPM, a podiatrist in Boca Raton, FL, and a member of the committee that develops content for the National Diabetes Education Program at the National Institutes of Health. That program offers publications and other educational materials to individuals and professionals.

“Unfortunately, there is not a be-all, end-all for neuropathy,” Frisch said. “What I tell my patients is ‘pay me now or pay me later.’ Take better care of your diabetes up front to try and decrease the chance of getting neuropathy.”

Neuropathy onset can be delayed and possibly avoided if blood sugar stays within a reasonably controlled range over time, Howell explained.

“Keeping a reasonably consistent blood sugar is the best approach for most people when you’re working with individuals trying to prevent complications like neuropathies,” she said.

The most difficult neuropathies to manage often are those associated with type 1 diabetes, Howell said.

“(Those patients) have been trying to control their disease with insulin injections for many years, and they start to get these vascular complications,” she added. “Working with them is the most challenging, because you just can’t say, ‘Well, gee, if you’d just lose a few pounds your blood sugar might come under control. People with type 1 diabetes have devastating consequences and they are who I think of when I think of the challenge of telling someone, ‘It’s not so much what you eat as it is when and how much and the fact that you are consistent about it.’”

Howell recommends a nutrition program based on scheduling, frequency of eating, and amount of food intake rather than counting teaspoons of sugar.

“Just as you manage the disease with pharmaceuticals, you manage it with food. The scheduling and coordination of food intake with medication seems to work best for everybody,” she said.

But not everybody will have the same—or even similar—schedules.

“Anybody who has been told they have high blood sugar absolutely has to have follow-up care with a multidisciplinary team, and part of that follow-up has to be finding out what can work for that particular person in that particular lifestyle doing that particular everyday living and working at that particular job,” Howell said.

Using the glycemic index—a ranking of carbohydrates according to the extent to which they raise blood sugar levels after eating—to guide food choices is one option that could help with control, she suggested. The American Diabetes Association website offers a number of dietary recommendations, as does the National Diabetes Education Program.

Howell also agrees that, rather than a single nutritional supplement or extra nutrient from food, control of neuropathic symptoms requires a comprehensive approach.

“There’s no way on earth including any one vitamin is going to affect diabetic neuropathy to the point that someone might not need to follow dietary or prescription approaches,” she said.

Youth and obesity

Although much of the neuropathy burden is borne by older people, younger people are being increasingly affected—a trend that has been developing worldwide, according to Armstrong.

“We’re seeing a lot more people getting diabetes sooner,” he said, adding that it’s actually a two-headed trend. “We have older folks living longer with complications, and we have younger people getting diseases earlier and coming in at relatively young ages, such as the late twenties or early forties.”

Whereas older patients may have any number of comorbidities that can increase their risk of diabetes, research suggests that in younger patients, obesity is a primary contributing factor—and therefore a major target for nutritional intervention.

A University of Michigan study published in the November 2006 issue of Diabetes Care found that more than half of obese adolescents were insulin resistant and at significantly increased risk of developing diabetes. In that study, weight status was by far the most important determinant of insulin resistance. Even more alarming are the findings of a February 2010 Pediatric Diabetes study that found an obesity prevalence of 79.4% among youths with type 2 diabetes.

Wound healing and nutrition

While it is difficult to arrive at a nutritional approach to improve neuropathy symptoms, it is a bit more straightforward when it comes to nutrition and wound healing, Frisch said.

“A proper diet to maintain glucose control also helps to promote better wound healing,” he said.

In the March 2006 issue of Ostomy & Wound Management, researchers from the University of North Carolina at Chapel Hill found that chronic diabetic foot ulcers were less likely to have healed after 12 weeks in patients whose glucose levels increased during that time period than those whose glucose levels decreased or remained stable.

But glucose isn’t the only factor to consider, Howell said.

“Wound healing is more a question of appropriate protein intake relative to total calorie intake,” she said. “Wounds do not heal without tissue synthesis, which doesn’t occur without adequate protein substrate, which is what we derive when we eat high-protein foods broken down into amino acids. We need those amino acids to synthesize new tissue. You have to have enough protein and enough calories in a decent distribution so that you spare that protein for actual lean-body synthesis rather than it being used for energy.”

Howell said other nutrients are involved in wound healing, but there have been conflicting results from studies on the effects of zinc and vitamin C. Although a review in the November 2009 issue of Current Opinion in Clinical Nutrition & Metabolic Care suggested that combinations of vitamin C and zinc could be useful for healing pressure ulcers and possibly surgical wounds, another review published three months later in the Annals of Long Term Care: Clinical Care and Aging found insufficient evidence to support this type of combination therapy.

Jacobs believes it is past time to start talking more about nutrition and wound healing.

“Realistically diabetic patients, particularly older diabetic patients, frequently have nutritional deficiencies that can contribute to impaired wound healing,” Jacobs said. “The issue is whether practitioners are screening patients and looking for these things—and my sense is that this seldom actually occurs.”

Most people interviewed for this article blamed medical education for a lack of interest in blending nutritional and lifestyle approaches with pharmaceutical methods of preventing or controlling diabetes and neuropathy and expediting wound healing.

“The nutritional aspects of wound healing have been very much ignored by almost everyone in wound healing. It’s a topic you rarely see discussed even at wound healing meetings,” Jacobs said. “Many diabetic patients are deficient in cofactors that are required for wound healing, such as vitamin A, vitamin C, zinc, and arginine. Some studies have shown that supplementation with active forms of vitamin B, such as L-methylfolate, are helpful in increasing vascular wound healing.”

Larry Hand is a writer based in Massachusetts.

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