5. Dietary Supplements and Cancer

What does dietary reference values (DRV) consist of?

• Average requirements (used for research)

• Population reference intakes (used for recommendations)

• Adequate intakes

How is average requirement intake defined?

Intake level meeting personal requirement of 50% of the population

Population reference intake

Intake level sufficient for almost entire population (~97.5%)

This is the value found under RI% on vitamin bottles

Adequate intake

Intake level assumed to meet the needs of virtually everyone in the population (derived if average requirement and population reference intake cannot be determined)

Tolerable upper intake level

= highest intake level at which no harmful overdosage effects are to be expected from long-term exposure, this is NOT ideal intake level

Vitamin B6

• Important for >150 reactions

• Deficiency can cause nerve damage

Why is there a strict tolerable upper intake for vit B6

Too much can cause peripheral neuropathy

• In a study it was found that when there is too much synthetic B6 (PN), there is 40% cell death

• Additionally, inactive PN inhibits active PLP processes (PLP is activate form of vitamin B6)

What are ABC and D

Link between beta carotene and lung cancer

It was found that there was a 20% increase in the risk of lung cancer in people who take beta carotene and 16% in smokers who took beta carotene.

• This was against the hypothesis because beta-carotene is a precursor of vitamin A and vit A is an antioxidant

• Therefore, supplements should not be used for cancer prevention as no beneficial effects have been found.

Folic acid fortification

Some countries add folic acid to their food.

Folic acid vs. folate

Folate = natural (vegetables & fruits)

Folic acid = Synthetic version

Benefit of folic acid

• Folic acid use reduces the risk of neural tube defects in babies

• When you want to get pregnant, it is beneficial to take 400 mg until you are 12 weeks pregnant

Effect of folic acid on cancer patients

• Folic acid can help with the efficiency of chemo therapy

• However, too much may also affect the healthy parts of your body if chemo works too well

Antioxidants and cancer

• Caused fewer toxicities + less side effects

• However, if the antioxidants help repair, then they might also repair the cancerous cells

• Therefore, balance: you want antioxidants but not too many so that it prevents the effectiveness of the treatment.

Multivitamin use after cancer

• At 3-5 tablets per week, the mortality risk was lower

• However, more than 10 tablets increased the mortality risk

Why is population reference intake used on supplement packaging rather than adequate intake?

Population Reference Intake (PRI) is used on supplement packaging instead of Adequate Intake (AI) because PRI is designed to meet the nutritional needs of nearly all (97.5%) healthy individuals in a population, whereas AI is only an approximation based on observed intake when precise scientific data to calculate individual requirements are missing