The role of diet in TB

Tuberculosis (TB) is estimated to infect approximately one third of the world's population, with South Africa being one of the hardest-hit countries.

Caused by Mycobacterium tuberculosis, TB is one of the most prevalent and serious diseases that threatens the health and survival of thousands of South Africans. The emergence of drug-resistant TB and the association of TB and HIV/Aids complicate both treatment and the chances that patients will survive.

While TB drugs are the first line of defence against this age-old killer disease, a healthy diet rich in protective nutrients can also play an important role in improving the outcome.

Nutrients and TB: the link
The two most recent editions of the Arbor Clinical Nutrition Updates (2009A & B) give an update on research findings related to the link between nutrients and TB, with special emphasis on vitamin D.

Basically, researchers found the following:

• TB patients in India had suppressed blood zinc levels compared to healthy control subjects. The low zinc status of the Indian subjects improved as their treatment with anti-TB drugs progressed. Previous studies have also identified zinc and selenium as nutrients that are depleted in patients with TB, particularly if they also suffer from HIV.
• Another study investigated the use of vitamin E (alpha-tocopherol, 140mg/day) and selenium (200ug/day) supplementation for two months in newly diagnosed TB patients receiving standard anti-TB therapy. Significant improvements in antioxidant status of up to 40% were found in the patients receiving the two supplements.
• Tanzanian patients who were given a multivitamin and mineral supplement containing vitamins A, B1, B2, B6, B12, E, niacin, folic acid and selenium for up to 43 months had a significantly lower risk of developing neurological fallout (peripheral neuropathy) and had a 73% reduction in the risk of the TB spreading from the lungs into other organs. In addition, the HIV-negative TB patients had fewer genital ulcers and higher lymphocyte counts, while the HIV-positive patients were less likely to suffer from recurrent TB infections.
  (Arbor, 2009A)

The role of iron
Iron fulfils a significant and complex role in TB. Understandably, low blood iron values and iron-deficiency anaemia are often found in TB patients. This may be due to the generally poor nutrition of these patients, or inaccurate iron-detection methods in developing countries where TB is rife (Arbor, 2009A).

According to the Arbor publication (2009A), iron is important "because of the genetically influenced interaction between iron status, host immunity and infecting agents such as the mycobacterium and HIV. Iron is needed by both the host's immune system and by the microorganisms, so iron status plays a key role in mediating the battle between them."

High body iron stores are often linked to poor clinical outcomes in TB patients, as was recently demonstrated in a study conducted in Zimbabwe.

What we don't yet know is what iron level in the human body will "starve" the TB organism, but help the patient to fight back. Researchers should concentrate on determining optimum iron intake and blood levels of TB patients, but because of the complex nature of the relationship between iron, the mycobacterium and patient health, this represents a significant challenge to the scientific community (Arbor, 2009A).

TB and vitamin D
Vitamin D is the flavour of the month and year when it comes to scientific research at present. Not a week goes by without a paper being published that indicates another new role for vitamin D or pinpoints vitamin D deficiencies in populations that were hitherto believed to have adequate intakes or to produce sufficient vitamin D due to sun exposure of the skin.

The role of vitamin D in TB is thus also under the spotlight. The second Arbor publication (2009B), has highlighted some of the most recent research in this field:

• The results of seven studies were combined to see if low vitamin D levels are linked to TB susceptibility. All seven of these studies found that TB patients had lower vitamin D levels than healthy control subjects.
• However, a study conducted in Guinea-Bissau where TB patients were randomly given placebo (dummy treatment) or 100,000IU of vitamin D three times during their TB treatment, found no improvement in the group that received vitamin D supplementation.
• An English study investigated if a single dose of 100,000IU of vitamin D, given to 192 healthy adults who had come into contact with patients suffering from active TB, would improve resistance to the disease. After six weeks, the test subjects who had been treated with the single dose of vitamin D were 25% more resistant to developing TB after exposure than the subjects who had been given placebo treatment.
  (Arbor, 2009B)

The conflicting results reported above (two trials found positive results, one trial found no effect with vitamin D supplementation), indicate that we need more in-depth research into the effect of vitamin D on TB before we can draw firm conclusions.

What does this mean?
In terms of patients suffering from TB (and HIV/Aids), the results of these new studies indicate that the use of a well-balanced diet that's rich in protective nutrients, such as vitamins, antioxidants, zinc and selenium, is essential for patients to be able to combat the ravages of this disease.

With regards to vitamin D, the traditional treatment of TB patients who were hospitalised in places where they could bask in the sunshine every day (the Alps in Europe and the Karoo in South Africa), was a good idea because this gave the patients the chance to produce a maximum amount of vitamin D. This is probably still one of the best treatments for TB patients.

In previous centuries, the traditional use of cod liver oil, which is rich in vitamins D and A, was also beneficial. However, nowadays when many TB patients also suffer from HIV/Aids, the use of supplements containing high levels of vitamins and minerals needs to be balanced against the effect such supplements may have on the effectiveness of antiretroviral drugs. Some of these drugs are less effective if patients take vitamin supplements and/or herbal medications.

At this point in time, patients suffering from TB (and HIV/Aids) should ensure that they eat as healthy a diet as possible and spend time exposing their skin to sunlight to enable their bodies to produce vitamin D. Don't start taking vitamins, minerals, herbal mixtures or any other supplement without discussing their use with the doctor who is treating your TB and/or HIV/Aids.

The SA Sugar Association has published a Booklet on 'Food Choices for People Living with HIV', which also applies to TB or combined infections. You can order the booklet from The Nutrition Department, SA Sugar Association, P O Box 700, Mount Edgecombe, 4300, or phone: (031) 508 7000, or send an e mail to nutrition@sasa.org.za for excellent information on diets for TB/HIV.

(Dr I.V. van Heerden, DietDoc, November 2009)

Any questions? Ask DietDoc

References:
(Arbor (2009A). TB and nutrition: what’s new? Arbor Clinical Nutrition Updates, Issue 312, October, 1-3; Arbor (2009B). TB and vitamin D. Arbor Clinical Nutrition Updates, Issue 313, October, 1-3.)