In part one of this two-part series, we reviewed why taking multivitamins is likely only beneficial to those of us with known nutritional deficiencies. And that if taking multivitamins, it is best to avoid those containing iron and copper. For those of us eating a whole-food plant-based diet, I covered all we need to know about vitamin B12 in part one, and will continue here with the only remaining nutrients that we need to keep in mind in terms of supplementation.

Vitamin D

Michael Greger, MD recommends in his book How Not to Die taking one 2,000 IU vitamin D3 supplement daily (ideally with the largest meal of the day) if we are unable to get sufficient sun. What constitutes enough sun you ask?

    • Northern hemisphere (below 30° latitude) 15 minutes each day on forearms and face without sunblock should produce enough vitamin D for Caucasians under 65. Those who have darker skin or who are older may require 30 minutes or more.
    • Moving north, at 40° latitude, from November through February it is unlikely that we’ll make any vitamin D
    • Above 50° latitude, there is likely a 6-month winter stretch during which we cannot make vitamin D
    • He recommends supplements for people at the higher altitudes during winter months and year-round for those not getting enough midday sun, regardless of location.

You can have your serum vitamin D tested to ensure your approach is effective.

Essential Fatty Acids

One of the reasons Michael Greger recommends one tablespoon per day of ground flaxseeds is that our bodies take from it the short-chain omega 3 ALA and convert it to the long chain omega 3s EPA and DHA (which are found in fish fat). The one tablespoon would do the trick to meet the requirements set by the World Health Organization, but Dr. Greger is concerned it may not be sufficient for optimal brain health (see more on this here). Until we know more, in addition to the one tablespoon of flaxseed, he recommends 250 mg per day of contaminant-free EPA and DHA. The source of the fatty acids is algae, which is where the fish get it.

Why not just take the fish oil supplements? Due to contamination with PCBs and pollutants. More on the issues with fish another time.


Iodine is added to table salt in Canada and the US because it is essential for thyroid function. People who avoid common sources of iodine (seafood and dairy products) do not appear to have impaired thyroid function. However, iodine intakes of people on vegan diets may be insufficient unless they use iodized salt, sea vegetables, or a supplement that contains iodine. Iodine deficiency is particularly risky during pregnancy.

The recommended daily intake is 150 mcg. Too much can be toxic and may cause excessive thyroid gland activity. The upper limit is 1,100 mcg/day.

If you use salt, use iodized salt instead of sea salt, which is usually not iodized. With iodized salt, we’ll get the recommended daily intake about a 1/2 tsp. Keep in mind in Canada and the US, the vast majority of salt used in food processing and fast foods, isn’t iodized (see here).

A natural source of iodine that is better than salt is seaweed. To achieve the 150 mcg/day use one of these options:

  • Two sheets of nori /day (used to make sushi)
  • ½ tsp per day dulse or arame (purchase flaked and sprinkle on your food)

Kelp is tricky because it contains a lot of iodine and so may take us over the limit.