6.13 Nutrition, Natural Health Products, and Complementary Medicine
Key Takeaways
- Natural health products sold in Canada carry an eight-digit Natural Product Number or Homeopathic Medicine Number issued by Health Canada under the Natural Health Products Regulations.
- St. John's wort induces CYP3A4 and P-glycoprotein and can cause failure of contraceptives, transplant immunosuppressants, direct oral anticoagulants, and antiretrovirals.
- Vitamin K in green vegetables and in some supplements antagonises warfarin; the counselling message is dietary consistency rather than avoidance.
- Adults over 50 should obtain 400 to 1,000 IU of vitamin D daily, and adults over 50 need a vitamin B12 supplement or fortified foods because food-bound B12 absorption declines with age.
- Refeeding syndrome causes a rapid fall in phosphate, potassium, and magnesium when nutrition is restarted in a severely malnourished patient and requires slow initiation with thiamine.
6.13 Nutrition, Natural Health Products, and Complementary Medicine
Exam Focus: The PEBC syllabus lists complementary and alternative medicine, natural health products, and the application of nutrition and supplements explicitly under Pharmacotherapeutics. Items test regulatory recognition, interaction screening, and the ability to give an evidence-based answer without dismissing the patient.
Nutrition Assessment in Pharmacy Practice
Nutrition status is assessed from unintended weight change, dietary intake, physical signs, and biochemistry. A loss of more than 5% of body weight in one month, or 10% in six months, is clinically significant.
Canada's Food Guide replaced the older serving-based model with a plate proportion — roughly half vegetables and fruit, one quarter whole grain foods, one quarter protein foods — alongside water as the drink of choice and guidance to limit highly processed foods.
Populations needing targeted supplementation:
| Population | Recommendation |
|---|---|
| People who could become pregnant | Folic acid 0.4 to 1 mg daily, higher with risk factors |
| Exclusively breastfed infants | Vitamin D 400 IU daily |
| Adults over 50 | Vitamin D 400 to 1,000 IU daily; vitamin B12 from supplements or fortified foods |
| Vegans | Vitamin B12, and attention to iron, zinc, calcium, iodine, and omega-3 fatty acids |
| Post-bariatric surgery | Lifelong multivitamin plus iron, calcium citrate, vitamin D, and vitamin B12 |
Refeeding syndrome occurs when nutrition is reintroduced to a severely malnourished patient: the insulin surge drives phosphate, potassium, and magnesium into cells, producing cardiac and neurological complications. Prevention requires slow reintroduction of energy, thiamine before or with the first feed, and close electrolyte monitoring.
Vitamins and Minerals: Practical Points
- Vitamin D is measured as 25-hydroxyvitamin D. Deficiency is common in Canada because of latitude. Toxicity from prolonged very high doses causes hypercalcemia, nausea, and kidney injury.
- Calcium absorption is best in doses of 500 mg or less at a time. Calcium carbonate needs gastric acid and is taken with food; calcium citrate does not and is preferred with proton pump inhibitor therapy or after bariatric surgery.
- Iron is discussed in the hematology section; the key interaction set is calcium, antacids, proton pump inhibitors, tetracyclines, quinolones, and levothyroxine.
- Potassium and magnesium supplements interact with renin-angiotensin blockers and potassium-sparing diuretics.
- Fat-soluble vitamins (A, D, E, K) accumulate. High-dose vitamin A is teratogenic; vitamin E at high doses increases bleeding risk with anticoagulants.
The Canadian Regulatory Framework
Natural health products are regulated under the Natural Health Products Regulations made under the Food and Drugs Act. A product legally sold in Canada carries a Natural Product Number (NPN) or, for homeopathic preparations, a Homeopathic Medicine Number (DIN-HM) — an eight-digit identifier confirming that Health Canada has reviewed the product for safety, efficacy, and quality, and has authorised its label claims.
This is a genuine but limited assurance. It does not mean the product has been tested against a prescription therapy, and product-to-product variability in botanical content remains a real problem. Adverse reactions to natural health products are reported to Health Canada through the Canada Vigilance Program, exactly as for drugs.
Pharmacists must ask about natural health product use directly, because patients frequently do not volunteer it and do not classify these products as medicines. Record them on the medication profile.
Commonly Used Products, Evidence, and Interactions
| Product | Common use | Evidence | Interaction and safety concerns |
|---|---|---|---|
| St. John's wort | Mild to moderate depression | Some benefit in mild depression | Potent CYP3A4 and P-glycoprotein inducer: contraceptive failure, transplant rejection, reduced direct oral anticoagulant, antiretroviral, and cyclosporine levels; serotonin syndrome with serotonergic drugs |
| Ginkgo biloba | Cognition, claudication | Weak and inconsistent | Bleeding risk with anticoagulants and antiplatelets; seizure risk |
| Garlic, ginger, ginseng, feverfew | Various | Limited | Additive antiplatelet or anticoagulant effect |
| Echinacea | Cold prevention | Inconsistent | Caution in autoimmune disease |
| Glucosamine and chondroitin | Osteoarthritis | Not consistently better than placebo | Shellfish-derived products; glucose monitoring in diabetes |
| Saw palmetto | Benign prostatic hyperplasia | Not better than placebo in good trials | May confound prostate-specific antigen interpretation |
| Melatonin | Insomnia, jet lag | Modest, best for circadian phase shift | Sedation; interacts with fluvoxamine |
| Fish oil (omega-3) | Triglyceride lowering | Effective at high doses for hypertriglyceridemia | Bleeding risk at high doses; atrial fibrillation signal |
| Valerian, kava | Anxiety, insomnia | Weak | Kava is associated with severe hepatotoxicity |
| Probiotics | Antibiotic-associated diarrhea | Modest benefit for some strains | Avoid in severe immunosuppression and central venous catheters |
Warfarin and vitamin K deserve a separate note. Leafy green vegetables, and some multivitamins and nutritional supplement drinks, contain vitamin K that antagonises warfarin. The correct counselling is consistency, not avoidance: keep intake stable week to week so the international normalized ratio stays stable, and tell the anticoagulation clinic when diet changes substantially.
Answering the Complementary Medicine Question Well
A dismissive answer ends the conversation and drives the use underground, where interactions go undetected. A professional response has four parts:
- Ask openly what the patient is taking and what outcome they hope for.
- Screen for interactions and contraindications against the full medication profile, including the specific inducer, bleeding, and serotonergic risks above.
- Give the evidence honestly, distinguishing "no good evidence of benefit" from "evidence of harm".
- Agree on monitoring and a decision point — how the patient will judge whether it is working, and when to stop.
Never recommend that a patient replace an effective prescription therapy with a natural health product, and never endorse a product for a serious condition on testimonial evidence alone.
A patient taking a combined oral contraceptive begins St. John's wort for low mood. What is the most important consequence to address?
Which identifier confirms that a natural health product has been authorised for sale in Canada?
A patient on warfarin says a friend told her to stop eating all green vegetables. What is the best counselling?
A severely malnourished patient is admitted and nutritional support is about to begin. Which complication must be anticipated?